Bivalviya - Bivalvia

Bivalviya Vaqtinchalik diapazon: Erta Kembriy - yaqinda[1][2] PreꞒ Ꞓ O S D. C P T J K Pg N
"Acephala", dan Ernst Gekkel "s Kunstformen der Natur (1904)
Ilmiy tasnif
Qirollik:	Animalia
Filum:	Molluska
Sinf:	Bivalviya Linney, 1758
Subklasslar
Heterodonta Paleoheterodonta Protobranxiya Pteriomorfiya Va matnni ko'ring

Ning bo'sh qobig'i ulkan mollyuska
(Tridacna gigas)

Bo'sh qobiq qilich ustara
(Ensis ensis)

Bivalviya (/baɪˈvælvmenə/), oldingi asrlarda Lamellibranchiata va Pelecypoda, a sinf dengiz va chuchuk suvlardan iborat mollyuskalar Ikkita menteşeli qismdan iborat qobiq bilan o'ralgan lateral siqilgan jismlarga ega. Ikki pog'onali guruh sifatida boshi yo'q va ular kabi odatdagi mollyuskan organlari yo'q radula va odontofor. Ular tarkibiga quyidagilar kiradi mollyuskalar, istiridye, xo'rozlar, Midiya, taroqlar va boshqa ko'plab narsalar oilalar sho'r suvda yashovchi, shuningdek, chuchuk suvda yashovchi bir qator oilalar. Ko'pchilik filtrli oziqlantiruvchi vositalar. The gilzalar ga aylangan ctenidia, ovqatlanish va nafas olish uchun ixtisoslashgan organlar. Aksariyat ikki qavatli hayvonlar o'zlarini nisbatan xavfsiz bo'lgan joylarda cho'kindilarga ko'mishadi yirtqichlik. Boshqalari dengiz tubida yotishadi yoki o'zlarini toshlarga yoki boshqa qattiq sirtlarga yopishtiradilar. Ba'zi bivalves, masalan, taroqsimon va chig'anoqlar, mumkin suzish. The kema qurtlari yog'och, loy yoki toshga singib, shu moddalar ichida yashaydi.

The qobiq ikki pallali kaltsiy karbonat, va odatda o'xshash bo'lgan ikkita qismdan iborat vanalar. Ular bir chekka bo'ylab birlashtiriladi (The menteşe chizig'i ) moslashuvchan tomonidan ligament odatda, har bir klapanning bir-biriga bog'langan "tishlari" bilan birgalikda menteşe. Ushbu tartib qobiqni ikkala yarmini ajratmasdan ochish va yopish imkonini beradi. Qobiq odatda ikki tomonlama nosimmetrik, ichida joylashgan menteşe bilan sagittal tekislik. Voyaga etganlarning ikki qavatli qobig'ining kattaligi millimetrning fraksiyalaridan uzunligi bir metrgacha o'zgarib turadi, ammo aksariyat turlar 10 sm (4 dyuym) dan oshmaydi.

Ikki qavatli suyaklar uzoq vaqtdan beri qirg'oq bo'yi va qirg'oq bo'ylab yashovchilar populyatsiyasining ovqatlanish qismiga aylangan. Istiridye edi madaniyatli Rimliklar tomonidan suv havzalarida va marikultur yaqinda oziq-ovqat uchun ikki tomonlama hayotning muhim manbaiga aylandi. Mollyuskalarning reproduktiv tsikllari haqidagi zamonaviy bilimlar inkubatsiya va yangi madaniyat usullarini rivojlanishiga olib keldi. Imkoniyatlarni yaxshiroq tushunish xavf xom yoki pishmagan holda iste'mol qilish qisqichbaqalar saqlash va qayta ishlashni yaxshilashga olib keldi. Pearl istiridyalari (sho'r suv va chuchuk suvda bir-biridan juda farq qiladigan ikkita oilaning umumiy nomi) eng keng tarqalgan tabiiy manba hisoblanadi marvaridlar. Ikki qavatli chig'anoqlar hunarmandchilikda, zargarlik buyumlari va tugmachalarni tayyorlashda ishlatiladi. Bivalves shuningdek ifloslanishni biokontrol qilishda ishlatilgan.

Ikki qavatli suyaklar paydo bo'ladi fotoalbomlar birinchi navbatda Kembriy 500 million yildan ko'proq vaqt oldin. Ma'lum yashovchilarning umumiy soni turlari 9,200 atrofida. Ushbu turlar 1260 avlod va 106 turkumga joylashtirilgan. Dengiz bivalves (shu jumladan sho'r suv va daryo suvi turlari) taxminan 8000 turni ifodalaydi, to'rtta sinfda va 1100 naslga ega 99 oilada birlashtirilgan. Eng kattasi yaqinda dengiz oilalari Veneridae, 680 dan ortiq turlari va Tellinidae va Lucinidae, ularning har biri 500 dan ortiq turga ega. Chuchuk suv bivalvesiga etti oilani o'z ichiga oladi, ularning eng kattalari Unionidae, taxminan 700 tur bilan.

Etimologiya

The taksonomik Bivalvia termini birinchi marta ishlatilgan Linney ichida 10-nashr uning Systema Naturae 1758 yilda ikkitadan iborat chig'anoqlari bo'lgan hayvonlarni nazarda tutadi vanalar.^[3] Yaqinda sinf Pelecypoda nomi bilan tanilgan, ya'ni "bolta -foot "(hayvonning oyog'i uzaytirilganda shakliga asoslanib).

"Ikki tomonlama" nomi Lotin bis, "ikki" ma'nosini anglatadi va qopqoq, "eshik barglari" ma'nosini anglatadi.^[4] Juft qobiqlar ikki tomonlama bo'lmagan hayvonlar orasida bir necha bor mustaqil ravishda rivojlanib bordi; juft klapanlari bo'lgan boshqa hayvonlar ma'lumlarni o'z ichiga oladi gastropodlar (kichik dengiz salyangozlari oilada Juliidae ),^[5] filum a'zolari Brachiopoda ^[6] va ma'lum bo'lgan daqiqali qisqichbaqasimonlar ostrakodlar^[7] va konstruktorlar.^[8]

Anatomiya

Chizish marvarid midiya chuchuk suvi (Margaritifera margaritifera) anatomiya: 1: orqa adductor, 2: old adduktor, 3: chap chap gill demibranch, 4: chap chap gill demibranch, 5: eksurent sifon, 6: chiqadigan sifon, 7: oyoq, 8: tishlar, 9: menteşe, 10 : mantiya, 11: umbo

A chap valfining ichki qismi venerid

Ikki qavatli qobiqning asosiy qismlari: 1: sagittal tekislik, 2: o'sish chiziqlari, 3: ligament, 4: umbo

Ikkita juftlar umumiy shaklda juda farq qiladi. Ba'zilar, masalan xo'rozlar, deyarli sharsimon kabuklara ega; xo'rozlar oyoqlarini bukish va to'g'rilash bilan sakrashlari mumkin. Boshqalar, masalan ustaralar, cho'zilgan chig'anoqlari va tez qazish uchun moslashtirilgan kuchli oyoqlari bo'lgan mutaxassislarni qazishmoqda. The kema qurtlari, oilada Teredinidae juda cho'zilgan tanalarga ega, ammo ularning qopqoq klapanlari ancha kamaygan va tananing oldingi uchi bilan chegaralangan, bu erda ular hayvonga o'tin orqali tunnel qazishga imkon beradigan qirib tashlovchi organlar sifatida ishlaydi.^[9]

Mantiya va qobiq

Qobiqning menteşasi yaqinida umbo, odatda dumaloq, tugmachaga o'xshash protuberans odatda atrofni o'rab oladi tumshuq. Umbo - umuman va tumshuq - aniqrog'i, qobiqning eng qadimgi qismini aks ettiradi, qo'shimcha materiallar asta-sekin qarama-qarshi tomonlarning chekkalari bo'ylab yotqiziladi. Menteşe nuqtasi yoki chizig'i qobiqning dorsal mintaqasi bo'lib, pastki, egri chiziq esa ventral mintaqadir. Qobiqning old yoki old tomoni bu erda byssus (mavjud bo'lganda) va oyoq joylashgan bo'lib, qobiqning orqa tomoni sifonlar joylashgan joy. Umbons / menteşe eng yuqori qismida va hayvonning old tomoni tomoshabinning chap tomoniga qarab, tomoshabinga qaragan qopqoq chap valf, qarama-qarshi valf esa o'ngdir.^[10]

Barcha mollyuskalarda mantiya ingichka hosil qiladi membrana hayvon tanasini qoplaydigan va undan qopqoq yoki loblarda tarqaladigan. Ikki pog'onali suyaklarda mantiya bo'laklari klapanlarni, mantiya tepasi esa butun menteşe mexanizmini chiqaradi. ligament, byssus iplari (mavjud bo'lgan joyda) va tish.^[11]

Ko'p bo'sh valfli klapanlarning ichki qismida ko'rinib turibdiki, qobiqning tashqi chetiga ozmi-ko'p parallel o'tadigan va ko'pincha ikkalasini bir-biriga bog'laydigan porloq egri chiziq adduktor mushak chandiqlar (agar hayvonda ikkita aduktor mushaklari bo'lsa). Ushbu chiziq (. Nomi bilan tanilgan pallial chiziq ) mavjud, chunki, ikki qavatli qobiqning ochilish chetiga parallel ravishda, mantiya qobiqqa uzluksiz tor qatorli daqiqali mantiya retraktor mushaklari bilan biriktirilgan. Ushbu kichik mushaklarning vazifasi - bu yirtqichlarning kichik urinishlari tufayli kerak bo'lganda mantiyaning bo'sh chekkasini zararli yo'ldan tortib olish. Ko'p ikki qavatli oyoqlarda mantiya qirralari qobiqning orqa uchida birlashib, ikkitasini hosil qiladi sifonlar, ulardan biri orqali nafas olinadi, ikkinchisi esa nafas olinadi va suspenziyali oziqlantirish.^[10] Ko'pincha, cho'ntakka o'xshash bo'shliq paydo bo'ladi, unda sifonlar orqaga tortilganda ularga mos keladi. Bu valfning ichki qismida pallial chiziqdagi chuqurchaga o'xshab ko'rinadi pallial sinus.^[10]

Qobiq ikkitadan iborat ohakli bir-biriga bog'lab turadigan valflar. Vanalar ikkalasidan ham tayyorlangan kaltsit, istiridyalarda bo'lgani kabi, yoki ikkalasi ham kalsit va aragonit. Ba'zan aragonit ichki, nafratli tartibda bo'lgani kabi qatlam Pteriida. Boshqasida taksonlar, kalsit va aragonitning muqobil qatlamlari yotqizilgan.^[12] Bog' va bussus, agar kalsifikatsiya qilingan bo'lsa, aragonitdan iborat.^[12] Qobiqning eng tashqi qatlami bu periostrakum, a dan tashkil topgan teriga o'xshash qatlam konchiolin. Periostrakum mantiyaning tashqi va o'rta qatlamlari orasidagi yivda ajralib chiqadi va odatda zaytun yoki jigarrang rangga ega va osonlikcha ishqalanadi.^[13] Klapanlarning tashqi yuzasi ko'pincha haykaltaroshlik qiladi, qisqichbaqalar ko'pincha kontsentrik chiziqlar bilan, taroqlar radiusli qovurg'alar va ustritsalar tartibsiz belgilar bilan ishlangan.^[14]

Qobiq ikki usul bilan qo'shiladi; Qopqoqning chetida mantiya tomonidan ko'proq moddalar ajralib chiqqanda klapanlar kattalashadi va klapanlarning o'zi hayvonning butun hayoti davomida asta-sekin qalinlashadi, chunki mantiya loblari tomonidan ko'proq kalkerli moddalar ajralib chiqadi. Vana tashqi qismidagi (ba'zida zaif) kontsentrik halqalarni odatda "o'sish halqalari" yoki "o'sish chiziqlari" deb ta'riflagan bo'lsada, qobiqning yoshini aniqlashning aniq usuli bu orqali kesma kesib o'tib, o'sib boruvchi o'sish bantlari. Ushbu texnikadan foydalanish ko'plab bivalveslarning uzoq umr ko'rish nuqtai nazarini o'zgartirdi. Masalan, yumshoq qobiq (Mya arenariya) qisqa umr ko'rishgan, ammo hozirda kamida 28 yil umr ko'rishi isbotlangan.^[15]

Ikki qavatli qobiqning ikkita klapani a tomonidan menteşada ushlab turiladi ligament ikkitadan iborat keratinlangan oqsillar, tensilium va resilium. Ikkita ikki tomonlama guruhlarda ligament ichki yoki tashqi holatda bo'lishi mumkin. Bog'ning asosiy vazifasi (shuningdek, klapanlarni birlashtirish) passiv ravishda qobiqning ochilishiga olib keladi. Ikkala klapanning ichki yuzasiga bog'langan adduktor mushak yoki mushaklar yordamida qobiq faol ravishda yopiladi. Mushaklarning holati ko'pincha bo'sh klapanlarning ichki qismida aylana yoki oval mushak izlari sifatida aniq ko'rinadi. Qobiqning menteşe chizig'i bo'ylab, aksariyat hollarda, klapanlarning bir-biriga nisbatan lateral harakatlanishiga to'sqinlik qiladigan bir qator menteşe tishlari mavjud. Ushbu tishlarning joylashishi ko'pincha ikki tomonlama juftlarni aniqlashda muhim ahamiyatga ega.^[16]

Asab tizimi

Ikki tomonlama suyaklarning harakatsiz odatlari, umuman olganda asab tizimi aksariyat boshqa mollyuskalarga qaraganda unchalik murakkab emas. Hayvonlarda yo'q miya; asab tizimi a dan iborat asab tarmog'i va bir qator juft ganglionlar. Eng ibtidoiy bivalvalardan tashqari, ikkala serebroplevral ganglionning ikkala tomonida joylashgan qizilo'ngach. Miya ganglionlari sezgi organlarini boshqaradi, plevra ganglionlari mantiya bo'shlig'ini asab bilan ta'minlaydi. Oyoqni boshqaradigan pedal ganglionlari uning tagida joylashgan va suzish bivalvallarida ancha katta bo'lishi mumkin bo'lgan visseral ganglionlar orqa aduktor mushaklari ostida.^[17] Ushbu ganglionlar serebroplevral ganglionlar bilan bog'langan asab tolalari. Uzoq sifonli ikkilamchi suyaklarda ularni boshqarish uchun sifonal ganglionlar ham bo'lishi mumkin.^[17]

Sezgilar

Ikki tomonlama suyaklarning sezgi organlari yaxshi rivojlanmagan va asosan orqa mantiya chekkalarida joylashgan. Organlar odatda mexanoreseptorlar yoki xoreseptorlar, ba'zi hollarda qisqa joylashgan chodirlar. Xemoreseptor hujayralari suvni tatib ko'radi va teginishga sezgir. Ular odatda sifonlar yaqinida uchraydi, ammo ba'zi turlarda ular butun mantiya bo'shlig'ini chetlab o'tishadi.^[18] The osfradiy bu suvni tatib ko'rishga yoki uni o'lchashga xizmat qilishi mumkin bo'lgan orqa adductor mushagi ostida joylashgan sezgir hujayralar qismidir loyqalik, lekin ehtimol emas gomologik salyangoz va salyangozlarda topilgan bir xil nomdagi tuzilishga ega.^[19] Statotsistlar organizm ichida bivalvega yo'nalishini sezish va to'g'rilashga yordam beradi. Har bir statotsist, tortishish kuchi ostida mineral massa, statolit harakatini aniqlaydigan sezgir kipriklar bilan o'ralgan kichik sumkadan iborat.^[20][21] In buyurtma Anomalodezma, nafas oluvchi sifon o'ljani aniqlash uchun tebranishga sezgir tentaklar bilan o'ralgan.^[22]

Ko'p ikki qavatli oyoqlarning ko'zlari yo'q, lekin Arcoidea, Limopsoidea, Mytiloidea, Anomioidea, Ostreoidea va Limoidea a'zolarining bir nechtasi mantiya chetida oddiy ko'zlarga ega. Ular fotosensor hujayralari chuquridan va a ob'ektiv.^[23] Taroq ikki qavatli, ob'ektiv bilan yanada murakkab ko'zlarga ega bo'ling retina va konkav oyna.^[24] Barcha ikki pog'onali bor nurga sezgir hujayralar hayvon ustiga tushgan soyani aniqlay oladigan.^[17]

Mushaklar

Ikki qavatli mushaklarning asosiy mushak tizimi bu orqa va oldingi oldingi mushaklari qisqarishi yoki ba'zi turlarda yo'qolishi mumkin bo'lsa-da, aduktor mushaklari. Ushbu kuchli mushaklar ikkita klapanni bir-biriga bog'lab, qisqaradi va qobiqni yopadi. Ular klapanlarni ajratib turadigan ligamentga qarama-qarshi ishlaydi.^[16] Bir klapan ustida joylashgan harakatsiz yoki yotgan ikki qavatli suyaklarda, masalan, ustritsalar va taroqsimonlarda oldingi qo'shimchali mushak yo'qolgan va orqa mushak markazlashgan holda joylashtirilgan. Yilda chig'anoqlar ularning klapanlarini silkitib suzish mumkin, bitta, markaziy aduktor mushak paydo bo'ladi.^[13] Ushbu muskullar ikki turdagi mushak tolalari, tezkor harakatlar uchun chiziqli mushak to'plamlari va barqaror tortishish uchun silliq mushak to'plamlaridan iborat.^[13]

Mantiya suspenziyasi mushaklari mantiyani qobiq bilan biriktirib, qopqoqning ichki qismida kamon shaklida chandiq qoldiradi, pallial chiziq. Juftlangan pedal protraktori va retraktor mushaklari hayvonning oyog'ini boshqaradi. Ba'zi ikkilik suyaklari, masalan, istiridyalar va ko'pgina taroqlar, oyoqlarini cho'zolmaydilar va ularda bu mushaklar yo'q. Boshqa juft muskullar sifonlar va byussni boshqaradi.^[10][13]

Qon aylanishi va nafas olish

Moviy midiya gillalarining to'rtta tolasi (Mytilus edulisa) to'rtta filamanning kirpikli interfaamentar birikmalarini ko'rsatadigan qismi (cj) b) ikkitasini ko'rsatadigan bitta filamaning diagrammasi lamellar interlamellar birikmalari (ilj) va kirpiklararo birikmalarning pozitsiyasi (cp) oralig'ida bog'langan

Ikkita juftlik ochiq qon aylanish tizimi a'zolarni yuvadigan gemolimf. The yurak uchta kameradan iborat: ikkita quloqchalar gildan qon olish va bitta qorincha. Qorincha mushak bo'lib, gemolimfani ichkariga pompalaydi aorta, so'ngra tananing qolgan qismiga. Ba'zi ikki yonbosh suyaklarning bitta aortasi bor, lekin ko'pchiligida hayvonning orqa qismlariga xizmat qiladigan ikkinchi, odatda kichikroq aortasi mavjud.^[25]

Kislorod gemolimfaga birlamchi nafas olish sirtini ta'minlovchi gilzalarda so'riladi. Gilllar pastga osilgan mantiya bo'shlig'i, uning devori ikkinchi darajali nafas olish yuzasi bilan yaxshi ta'minlanadi kapillyarlar. Gomellari bo'lmagan turlarda, masalan, Anomalodesmata subklassi, mantiya bo'shlig'ining devori nafas olish bilan shug'ullanadigan yagona organdir. Gelgit muhitiga moslashgan ikkilamchi suyaklar qobig'ini mahkam yopib suvdan bir necha soat yashab turishi mumkin. Ba'zi chuchuk suv turlari, havoga ta'sir qilganda, qobiqni ozgina teginishi va gaz almashinuvi amalga oshishi mumkin.^[26]

Odatda gemolimfada nafas olish organlari etishmaydi pigment, garchi oila a'zolari Arcidae va Limidae egalik qilishlari ma'lum gemoglobin to'g'ridan-to'g'ri erigan sarum.^[20] Yirtqichlarga Poromya, gemolimfa qizil rangga ega amebotsitlar tarkibida gemoglobin pigmenti mavjud.^[27]

Ovqat hazm qilish tizimi

Ovqatlanish usullari

Ko'p qavatli juftlar filtrli oziqlantiruvchi vositalar kabi zarrachali ovqatni olish uchun ularning gillari yordamida fitoplankton suvdan. The protobranchlar detritusni dengiz tubidan qirib tashlab, boshqa yo'l bilan boqing va bu gilllarni filtrlash uchun moslashtirilgunga qadar barcha ikki pog'onali suyaklar tomonidan ishlatiladigan oziqlantirishning asl usuli bo'lishi mumkin. Ushbu ibtidoiy bivalvatlar pastki qavatni og'iz chetida juft tentakl bilan ushlab turadi, ularning har biri bitta palp yoki qopqoq. Tentaklar yopilgan mukus, oziq-ovqatni ushlab turuvchi va zarrachalarni palpaga qaytaradigan siliya. Keyinchalik ular zarrachalarni saralashadi, yaroqsiz yoki juda katta bo'lganlarini hazm qilishdan bosh tortadilar va boshqalarni og'ziga etkazadilar.^[20]

In Filibranxiya va Eulamellibranxiya, orqa tomondan suv qobiqga tortiladi ventral hayvonning yuzasi, gilladan yuqoriga qarab o'tadi va qabul qilishdan bir oz yuqoriga chiqarib yuborish uchun ikki baravar ortadi. Burrowing turlarida dengiz tubiga etib boradigan ikkita cho'zilgan, tortib olinadigan sifonlar bo'lishi mumkin, ularning har biri nafas olish va ekshalant suv oqimlari uchun. Filtr bilan oziqlanadigan ikki pog'onali gillalar ktenidiya deb nomlanadi va ularning oziq-ovqat olish qobiliyatini oshirish uchun juda o'zgartirilgan. Masalan, siliya dastlab kiruvchi cho'kindilarni olib tashlashga xizmat qilgan gilzalarda oziq-ovqat zarralarini ushlab qolish va ularni shilimshiq oqim bilan og'izga etkazish uchun moslashgan. Gilllarning iplari ham ibtidoiy bivalvallarga qaraganda ancha uzunroq va buklangan holda oziq-ovqat tashish mumkin bo'lgan chuqurchaga aylanadi. Gilllarning tuzilishi sezilarli darajada o'zgarib turadi va ikki pog'onali suyaklarni guruhlarga ajratish uchun foydali vosita bo'lib xizmat qilishi mumkin.^[28]

Bir nechta bivalves, masalan, donador poromya (Poromya granulata), bor yirtqich, juda katta ovqatlanish o'lja boshqa bivalves tomonidan iste'mol qilinadigan mayda mikroalglarga qaraganda. Ushbu hayvonlarda gilzalar nisbatan kichik bo'lib, asosiy mantiya bo'shlig'ini suv chiqaradigan kichik xonadan ajratib turadigan teshikli to'siq hosil qiladi. Mushaklar, bir vaqtning o'zida kichik qisqichbaqasimonlar va qurtlarni emizadigan, sigir shaklidagi organga o'zgartirilgan inhalant sifon orqali suv oladi. Sifonni tezda tortib olish va teskari burish mumkin, bu o'ljani og'ziga etib boradi. Ichak katta miqdordagi oziq-ovqat zarralarini hazm qilish uchun o'zgartirilgan.^[27]

G'ayrioddiy nasl, Entovalva, bo'ladi endosimbiyotik, faqat qizilo'ngachda topilgan dengiz bodringlari. Kichkina klapanlarini to'liq o'rab turgan mantiya burmalariga ega. Dengiz bodringi cho'kindini so'rib olganda, ikki pallali suv uning gillasi ustidan o'tib, mayda organik zarralarni ajratib oladi. O'zini supurib yubormaslik uchun, u o'zlariga bissal iplar bilan bog'lanadi mezbon tomoq. Dengiz bodringi zarar ko'rmaydi.^[29]

Ovqat hazm qilish trakti

Odatda ikki yon suyaklarning ovqat hazm qilish trakti an qizilo'ngach, oshqozon va ichak. Bir qator ovqat hazm qilish bezlari oshqozonga ochiladi, ko'pincha juftlik orqali divertikulalar; bu oshqozonda ovqat hazm qilish uchun fermentlarni ajratadi, shuningdek, hujayralarni ham o'z ichiga oladi fagotsitoza oziq-ovqat zarralari va ularni hujayra ichidagi hazm qilish. Filtr bilan oziqlanadigan ikki qavatli suyaklarda qotib qolgan balg'amning cho'zilgan tayog'i "kristalli uslub "biriktirilgan xaltadan oshqozonga chiqadi. Xaltadagi kilyalar uslubning aylanishiga, og'izdan oziq-ovqat tarkibidagi shilimshiq oqimiga o'ralishiga va oshqozon tarkibini chayqashga olib keladi. Bunday doimiy harakat oziq-ovqat zarralarini saralash hududiga aylantiradi. kichikroq zarrachalarni ovqat hazm qilish bezlariga, og'irroq zarralarni esa ichakka tarqatadigan oshqozon orqa qismi.^[30] Chiqindilar rektumda birlashtirilib, granulalar shaklida anal teshik orqali ekshalatsiyali suv oqimiga bo'shatiladi. Ovqatlanish va ovqat hazm qilish kunlik va gelgit tsikllari bilan sinxronlashtiriladi.^[31]

Yirtqich hayvonlarning ikki tomonlama uslublari juda qisqartirilgan va a xitinli g'ilof bu ovqatni hazm qilishdan oldin maydalashga yordam beradi. Boshqa yo'llar bilan, ularning ichaklari filtr bilan oziqlanadigan bivalvalalarga o'xshaydi.^[20]

Ekskretator tizimi

Ko'pgina boshqa mollyuskalar singari, ikki yonbosh suyaklarning chiqaruvchi organlari juft nefridiya. Ularning har biri uzun, ilmoqli, glandular naychadan iborat bo'lib, ular yurak ostidagi tana bo'shlig'iga ochiladi va siydik pufagi siydikni saqlash. Perikardial bezlar yo yurak aurikulalarini qoplaydi yoki perikardga yopishadi va qo'shimcha filtratsiya organlari bo'lib xizmat qiladi. Metabolik chiqindilar mantiya bo'shlig'ining yuqori qismining old qismiga yaqin er-xotin teshiklari orqali siydik pufagidan bo'shatiladi, u erdan ekshalant suv oqimiga qo'shiladi.^[32]

Ko'paytirish va rivojlantirish

Jinslar odatda ikki qavatli, lekin ba'zilari alohida germafroditizm ma'lum. The jinsiy bezlar ichaklarga yaqin joylashgan bo'lib, yoki nefridiyaga, yoki alohida teshik orqali mantiya bo'shlig'iga ochiladi.^[33] Erkak va urg'ochi ayollarning pishgan jinsiy bezlari spermatozoid va tuxumlarni ichkariga chiqaradi suv ustuni. Urug'lantirish doimiy ravishda sodir bo'lishi yoki kun davomiyligi, suv harorati yoki suvda sperma borligi kabi atrof-muhit omillari tomonidan qo'zg'atilishi mumkin. Ba'zi turlar "dribling yumurtalari", ammo boshqalari o'z jinsiy hujayralarini birdaniga yoki birdaniga chiqarib yuboradilar. Ommaviy yumurtlama hodisalari, ba'zida mintaqadagi barcha ikki qavatli juftlar ularning bo'shashishini sinxronlashtirganda sodir bo'ladi.^[34]

Urug'lantirish odatda tashqi hisoblanadi. Odatda, tuxum qo'yilishidan oldin qisqa bosqich bir necha soat yoki kun davom etadi troxofora lichinkalar. Keyinchalik ular rivojlanadi veliger dengiz tubiga tushib, o'tib ketadigan lichinkalar metamorfoz ba'zan (masalan, istiridyada) "tupurish" deb nomlanadigan balog'atga etmagan bolalarga.^[33] Ba'zi turlarda, masalan, turkumda bo'lganlar Lasaea, urg'ochilar sperma o'z ichiga olgan suvni nafas olish sifonlari orqali ichkariga kiritadilar va urug'lanish urg'ochi ayol ichida bo'ladi. Keyin bu turlar mantiyani bo'shliqlari ichida yoshlarni boqishadi va oxir-oqibat ularni vener lichinkalari yoki sudralib yuradigan balog'at yoshidagi suv ustuniga qo'yib yuboradilar.^[35]

Suv ustunidagi tuxumlardan chiqqan ikki tomonlama lichinkalarning ko'p qismi ovqatlanadi diatomlar yoki boshqa fitoplankton. Yilda mo''tadil turlari, taxminan 25% lesitotrofik, asosiy energiya manbai bo'lgan tuxum sarig'ida saqlanadigan ozuqalarga bog'liq lipidlar. Lichinka birinchi ovqatlanishidan oldin davr qancha ko'p bo'lsa, tuxum va sarig'i shunchalik katta bo'lishi kerak. Ushbu energiyaga boy tuxumlarni ishlab chiqarish uchun reproduktiv xarajatlar yuqori va ular soni odatda kichikroq. Masalan, Boltiq bo'yidagi tellin (Macoma baltica ) ozgina, yuqori energiyali tuxum ishlab chiqaradi. Ulardan chiqqan lichinkalar energiya zaxiralariga tayanadi va ovqatlanmaydi. Taxminan to'rt kundan so'ng, ular D-bosqichli lichinkalarga aylanadi, ular birinchi navbatda mentli, D shaklidagi klapanlarni rivojlantiradilar. Ushbu lichinkalar joylashishdan oldin nisbatan kichik tarqalish qobiliyatiga ega. Oddiy midiya (Mytilus edulis ) lichinkalarga tushadigan va tez orada tirik qolish va o'sishi uchun ovqatlanish kerak bo'lgan 10 baravar ko'p tuxum ishlab chiqaradi. Ular ancha keng tarqalishi mumkin, chunki ular uzoq vaqt planktonik bo'lib qoladilar.^[36]

Tartib bo'yicha chuchuk suvli bivalvallar Unionoida boshqa hayot tsikliga ega bo'lish. Spermatozoidlar suv bilan urg'ochi gilosiga tortiladi va ichki urug'lantirish jarayoni amalga oshiriladi. Tuxum ichiga kirib boradi gloxidiya urg'ochi qobig'ida rivojlanadigan lichinkalar. Keyinchalik ular ozod qilinadi va o'zlarini biriktiradilar parazitik uchun gilzalar yoki baliq egasining suyaklari. Bir necha hafta o'tgach, ular uy egasini tashlab, metamorfozga uchraydi va balog'atga etmagan bolalarga aylanadi substrat. Buning mollyuskalarga afzalligi shundaki, ular doimo suv oqimi ostida pastga siljib ketishdan ko'ra, o'zlarining vaqtinchalik xostlari bilan birga yuqori oqimga tarqalib ketishlari mumkin.^[37]

Chuchuk suvli midiya oilasining ba'zi turlari, Unionidae Odatda cho'ntak daftarlari deb nomlanuvchi odatiy bo'lmagan reproduktiv strategiyani ishlab chiqdi. Ayolning mantiyasi qobiqdan chiqib, taqlid qiluvchi mayda baliqlarga aylanadi, baliqlarga o'xshash belgilar va soxta ko'zlar bilan to'ldiriladi. Ushbu aldov oqimda harakat qiladi va haqiqiy baliqlarning e'tiborini tortadi. Ba'zi baliqlar aldovni o'lja, boshqalari esa a o'ziga xos. Ular yaqindan ko'rish uchun yaqinlashadi va midiya gilzalaridan juda ko'p sonli lichinkalarni chiqaradi, qiziquvchan baliqlarni mitti, parazit yoshlari bilan yuvadi. Ushbu gloxidiya lichinkalari baliq gilosiga tortilib, u erda birikadi va to'qima reaktsiyasini keltirib chiqaradi, bu kichik kist har bir lichinka atrofida. Keyin lichinkalar kistalar ichidagi baliq to'qimalarini parchalash va hazm qilish orqali oziqlanadi. Bir necha hafta o'tgach, ular o'zlarini kistadan ozod qilishadi va balog'at yoshiga etmagan mollyuskalar sifatida oqim oqimiga tushadilar. Baliqlar nisbatan zararsizdir.^[38]

Brakiyopodlar bilan taqqoslash

Anadara, bilan ikki qavatli taxodont tishi dan Plyotsen ning Kipr

Yura davri brakiyopodi lofofora butunligini qo'llab-quvvatlash

Brakiyopodlar yuzma-yuz ikki qavatli mushaklarga o'xshash dengiz qobig'i, ular o'xshash kattaligi va ikki qismdan iborat menteşeli qobig'i bor. Biroq, brakiyopodlar ajdodlarimizning nasl-nasabidan kelib chiqqan holda rivojlangan va bivalvlarga o'xshashlik faqat shu kabi turmush tarzi tufayli paydo bo'lgan. Ikki guruh o'rtasidagi farqlar ajdodlarning kelib chiqishi bilan bog'liq. Turli xil boshlang'ich tuzilmalar bir xil muammolarni hal qilish uchun moslashtirilgan, masalan konvergent evolyutsiyasi. Zamonaviy davrda brakiyopodlar ikki pog'onali suyak kabi keng tarqalgan emas.^[39]

Ikkala guruhda ikkita valfdan tashkil topgan qobiq bor, lekin ikki guruhda qobiqning tashkil etilishi mutlaqo boshqacha. Brakiyopodlarda ikkala klapanlar tananing dorsal va ventral yuzalarida joylashgan bo'lsa, bivalvallarda klapanlar tananing chap va o'ng tomonlarida joylashgan bo'lib, aksariyat hollarda bir-birining ko'zgu tasviridir. Brakiyopodlarda a lofofora, filtrni oziqlantirish uchun moslashtirilgan, o'ralgan, qattiq xaftaga tushadigan ichki apparat, bu xususiyat dengiz umurtqasiz hayvonlarning boshqa ikkita asosiy guruhi bilan birgalikda bryozoyanlar va fronidlar. Ba'zi brakiyopod chig'anoqlari yasalgan kaltsiy fosfat lekin ko'plari kaltsiy karbonat biomineral shaklida kaltsit, ikki qavatli chig'anoqlar har doim butunlay kaltsiy karbonatidan iborat bo'lib, ko'pincha biomineral shaklida bo'ladi aragonit.^[40]

Evolyutsion tarix

The Kembriya portlashi taxminan 540 dan 520 million yil oldin sodir bo'lgan (Mya). Ushbu geologik qisqa davrda barcha asosiy hayvonlar fitna ikkiga bo'lingan va ular tarkibiga mineralizatsiyalangan skeletlari bo'lgan birinchi jonzotlar kiritilgan. Brakiyopodlar va ikki yonboshlar bu vaqtda paydo bo'lib, toshbo'ron qilingan qoldiqlarini qoldirib ketishdi.^[41]

Mumkin bo'lgan erta bivalves Pojetiya va Fordilla; bular, ehtimol toj guruhiga emas, balki poyada yotadi. Watsonella va Anabarella ushbu taksilarning (ilgari) yaqin qarindoshlari sifatida qabul qilinadi.^[42] Kambriyalik taxmin qilingan "ikki tomonlama" larning atigi beshta nasli mavjud, boshqalari esa Tuarangiya, Kamya va Arhouriella va potentsial Buluniella.^[43] Ikkilamchi suyaklar shuningdek, evolyutsiyadan rivojlangan deb taklif qilingan rostrokonchlar.

Chig'anoqlar ko'milgan cho'kindi jinsga qotib qolganida ikki qavatli toshqotganliklar paydo bo'lishi mumkin. Ko'pincha, klapanlar tomonidan yaratilgan taassurot klapanlar emas, balki fotoalbom bo'lib qoladi. Davomida Dastlabki ordovik, ikki qavatli turlarning xilma-xilligida katta o'sish yuz berdi va disodont, heterodont va taksodont tishlari rivojlandi. Tomonidan Erta silur, gilzalar filtr bilan oziqlantirish uchun moslangan bo'lib, va davomida Devoniy va Karbonli birinchi bo'lib sifonlar paydo bo'ldi, bu yangi rivojlangan mushak oyog'i bilan hayvonlarni cho'kindiga chuqur ko'mishga imkon berdi.^[44]

O'rtalarida Paleozoy, 400 Mya atrofida, brakiyopodlar okeandagi eng ko'p filtrlaydigan oziqlantiruvchilardan biri bo'lgan va 12000 dan ortiq qazilma turlari tan olingan.^[45] Tomonidan Permiy-trias davridagi yo'q bo'lib ketish hodisasi 250 Mya, ikkilamchi suyaklar juda katta tajribaga ega edi nurlanish xilma-xillik. Ikki qavatli mushuklar bu voqeadan qattiq zarba olishdi, lekin o'zlarini qayta tiklashdi va rivojlanishdi Trias keyingi davr. Aksincha, brakiyopodlar 95 foizini yo'qotdilar turlarning xilma-xilligi.^[40] Ba'zi ikki pog'onali suyaklarning yirtqichlardan yiroqlashi va shu bilan yirtqichlardan saqlanish qobiliyati ularning muvaffaqiyati uchun asosiy omil bo'lishi mumkin. Turli xil oilalardagi boshqa yangi moslashuvlar turlarga ilgari ishlatilmagan evolyutsiya nishlarini egallashga imkon berdi. Bunga nisbiy o'sish kiradi suzish qobiliyati yumshoq cho'kindilarda qobiqda tikanlar paydo bo'lib, suzish qobiliyatiga ega bo'ladi va bir necha hollarda yirtqich odatlarni qabul qiladi.^[44]

Uzoq vaqt davomida ikkilamchi suyaklar brakiyopodlarga qaraganda suv hayotiga yaxshiroq moslashgan deb o'ylashgan; raqobatbardosh va ularni voyaga etmaganlarga topshirish nişler keyingi asrlarda. Ushbu ikki takson darsliklarda raqobat bilan almashtirishning misoli sifatida paydo bo'ldi. Buning uchun berilgan dalillarga klapanlarni ochish va yopish uchun energetik jihatdan samarali bo'lgan ligament-mushak tizimi tufayli yashash uchun kam ovqatga ehtiyoj borligi kiradi. Bularning barchasi umuman rad etildi; brachiopodlardan zamonaviy ikki pog'onali suyaklarning ustunligi, ularning javobidagi tasodifiy nomutanosibliklarga o'xshaydi. yo'q bo'lib ketish hodisalari.^[46]

Mavjud bivalvlarning xilma-xilligi

Kattalarning maksimal hajmi yashash ikki qavatli turlari 0,52 mm dan (0,02 dyuym) gacha Kondilonukula mayasi,^[47] uzunligi 1532 millimetr (60,3 dyuym) gacha bo'lgan yong'oq qozig'i Kupus politalamiyasi, cho'zilgan, burmalangan kema qurti.^[48] Ammo, odatda, eng katta tirik jonzot deb qaraladigan tur - bu ulkan mollyuska Tridacna gigas uzunligi 1200 mm (47 dyuym) va og'irligi 200 kg (441 lb) dan oshishi mumkin.^[49] Eng katta ma'lum yo'q bo'lib ketgan bivalve - bu bir tur Platitseramus uning qoldiqlari uzunligi 3000 mm (118 dyuym) gacha.^[50]

2010 yilgi risolasida, Ikkita juftlik to'plami, Markus Xuber 106 oilada jami 9200 tirik tirik ikki tomonlama turlarning umumiy sonini beradi.^[51] Xuberning ta'kidlashicha, adabiyotda tez-tez uchraydigan 20000 tirik turlarning soni aniqlanmadi va ma'lum bo'lgan xilma-xillikni ko'rsatish uchun quyidagi jadvalni taqdim etdi:

Tarqatish

Michigan ko'lida suv tezligini hisoblagich bilan o'rab olgan zopak midiya

Ikki pog'onali suyaklar - bu butun dunyo bo'ylab suv muhitida joylashgan umurtqasizlarning juda muvaffaqiyatli sinfidir. Ko'pchilik nopok va dengiz tubidagi cho'kindilarga yoki chuchuk suvlar yashaydigan joylarda cho'kindilarga ko'milgan holda yashaydilar. Ikki pallali turlarning katta qismi okeanlarning intertidal va sublittoral zonalarida uchraydi. Qumli dengiz plyaji yuzaki ko'rinishda hayotdan mahrum bo'lib tuyulishi mumkin, lekin ko'pincha qum yuzasida juda ko'p sonli bivalves va boshqa umurtqasizlar yashaydi. Katta plyajda Janubiy Uels, ehtiyotkorlik bilan tanlab olish 1,44 million koklni tashkil etdi (Cerastoderma edulasi ) plyajning bir gektariga.^[52]

Ikkita ikkilamchilar tropik mintaqalarda, shuningdek mo''tadil va boreal suvlarda yashaydilar. Bir qator turlar o'ta og'ir sharoitlarda omon qolishi va hatto rivojlanishi mumkin. Ular Arktikada juda ko'p, bu zonadan 140 ga yaqin tur ma'lum.^[53] Antarktika taroq, Adamussium kolbekki, Yer sharining boshqa chekkasidagi dengiz muzlari ostida yashaydi, bu erda past darajadagi harorat o'sish sur'atlari juda sekin ekanligini anglatadi.^[54] Gigant midiya, Batimodiolus termofili va ulkan oq mollyuska, Calyptogena magnifica, ikkalasi ham atrofida to'planib yashaydi gidrotermal teshiklar da tubsiz Tinch okeanidagi chuqurliklar. Ularning gillarida oksidlanadigan xemosimbiyotik bakteriyalar mavjud vodorod sulfidi, va mollyuskalar ushbu bakteriyalar tomonidan sintez qilingan ozuqa moddalarini o'zlashtiradi.^[55] Egar istiridye, Enigmonia aenigmatica, ko'rib chiqilishi mumkin bo'lgan dengiz turlari amfibiya. Tropik Hind-Tinch okeanining pastki qismida yuqori oqim belgisidan yuqorida yashaydi mangrov barglari, mangrov shoxlarida va dengiz devorlarida splash zonasi.^[56]

Ba'zi chuchuk suvli bivalvlarning chegaralari juda cheklangan. Masalan, Ouachita daryosi midiya, Villosa arkansasensis, faqat oqimlaridan ma'lum Ouachita tog'lari Arkanzas va Oklaxomada va AQShning janubi-sharqidagi boshqa bir qancha chuchuk suvli midiya turlari singari u yo'q bo'lib ketish xavfi ostida.^[57] Aksincha, chuchuk suvning ikki tomonlama ikki xil turlari, shu jumladan oltin midiya (Limnoperna fortunei ), ularning diapazonlarini keskin oshirmoqda. Oltin midiya Janubi-Sharqiy Osiyodan Argentinaga tarqaldi, u erda u an invaziv turlar.^[58] Yaxshi sayohat qilingan yana bir chuchuk suvli ikki qavatli zebra midiya (Dreissena polimorfasi ) Rossiyaning janubi-sharqida paydo bo'lgan va tasodifan Shimoliy Amerika va Evropaning ichki suv yo'llariga kiritilgan, bu erda turlar suv inshootlariga zarar etkazadi va mahalliy ishlarni buzadi. ekotizimlar.^[59]

Xulq-atvor

Ko'p sonli jonli venerid bivalvlari suv ostida sifonlar ko'rinadigan

Tinch okeani istiridyesi uning kundalik xatti-harakatiga rioya qilish uchun faol elektrodlar bilan jihozlangan

Ikki pog'onali suyaklarning aksariyati harakatsiz yoki hatto o'tirib oladi o'tiradigan hayot tarzi, ko'pincha butun umrini ular voyaga etmaganlar sifatida birinchi bo'lib yashagan joyda o'tkazadilar. Ikki pog'onali suyaklarning ko'p qismi dengiz tubida yashaydigan, qum, loy, loy, shag'al yoki marjon parchalari kabi yumshoq substratlarga ko'milgan infaunaldir. Ularning aksariyati yashaydi intertidal zona bu erda to'lqin chiqqanda ham cho'kindi nam bo'lib qoladi. Cho'kindilarga ko'milganida, dumaloq bivalvilar to'lqinlarning urishidan, qurib qolishidan va past oqim paytida qizib ketishdan va yomg'ir suvi ta'sirida sho'rlanish o'zgarishidan himoyalangan. Ular, shuningdek, ko'plab yirtqichlarning qo'lidan kelgan.^[60] Ularning umumiy strategiyasi - to'lqinlanish paytida sifonlarni oziqlantirish va nafas olish uchun yuzaga ko'tarish, lekin to'lqin tugashi bilan chuqurroqqa tushish yoki qobig'ini mahkam yopish.^[60] Substratni qazish uchun ular mushak oyog'idan foydalanadilar. Buni amalga oshirish uchun, hayvon o'zining adduktor mushaklarini bo'shatadi va qobig'ini keng ochib, o'z joyiga o'rnatib qo'yadi, u oyog'ini pastki qatlamga uzatadi. Keyin u oyog'ining uchini kengaytiradi, qobiqni yopish uchun aduktor mushaklarini tortib oladi, oyog'ini qisqartiradi va o'zini pastga qaratadi. Ushbu qator harakatlar chuqurroq qazish uchun takrorlanadi.^[61]

Kabi boshqa bivalves Midiya, keratin va oqsillardan tayyorlangan qattiq bussus iplari yordamida o'zlarini qattiq sirtlarga yopishtiring. Ular yirtqichlarning hujumiga duchor bo'lgan ikki pog'onali suyaklardan ko'ra ko'proq ta'sir ko'rsatadi. G'ildirak kabi ba'zi yirtqich gastropod salyangozlari (Buccinidae ) va murex salyangozlari (Muricidae ) ikki qavatli po'stlog'ini qobig'iga zeriktirib ovqatlantiradi, garchi ko'p Busikonin (masalan, Busycon carica, Sinistrofulgur sinistrum ) are "chipping-style" predators. The dog whelk (Nucella lamellosa ) drills a hole with its radula assisted by a shell-dissolving secretion. The dog whelk then inserts its extendible proboscis and sucks out the body contents of the victim, which is typically a blue mussel. The whelk needs a few hours to penetrate the shell and thus living in the littoral zone is an advantage to the bivalve because the gastropod can attempt to bore through the shell only when the tide is in.^[62]

Some bivalves, including the true oysters, the jewel boxes, jingle shells, thorny oysters va kitten's paws, cement themselves to stones, rock or larger dead shells.^[63] In oysters the lower valve may be almost flat while the upper valve develops layer upon layer of thin horny material reinforced with calcium carbonate. Oysters sometimes occur in dense beds in the neritic zone and, like most bivalves, are filter feeders.^[16]

Bivalves filter large amounts of water to feed and breathe but they are not permanently open. They regularly shut their valves to enter a resting state, even when they are permanently submerged. In oysters, for example, their behaviour follows very strict circatidal and circadian rhythms according to the relative positions of the moon and sun. During neap tides, they exhibit much longer closing periods than during spring tides.^[64]

Although many non-sessile bivalves use their muscular foot to move around, or to dig, members of the freshwater family Sphaeriidae are exceptional in that these small clams climb about quite nimbly on weeds using their long and flexible foot. The European fingernail clam (Sphaerium corneum ), for example, climbs around on water weeds at the edges of lakes and ponds; this enables the clam to find the best position for filter feeding.^[65]

Predators and defence

The thick shell and rounded shape of bivalves make them awkward for potential predators to tackle. Nevertheless, a number of different creatures include them in their diet. Ko'p turlari halokatli baliq feed on them including the oddiy karp (Cyprinus carpio), which is being used in the upper Mississippi River to try to control the invasive zebra mussel (Dreissena polymorpha).^[66] Birds such as the Evroosiyo istiridye (Haematopus ostralegus) have specially adapted beaks which can pry open their shells.^[67] The herring gull (Larus argentatus) sometimes drops heavy shells onto rocks in order to crack them open.^[68] Sea otters feed on a variety of bivalve species and have been observed to use stones balanced on their chests as anvils on which to crack open the shells.^[69] The Pacific walrus (Odobenus rosmarus divergens) is one of the main predators feeding on bivalves in Arctic waters.^[70] Shellfish have formed part of the human diet since prehistoric times, a fact evidenced by the remains of mollusc shells found in ancient middens. Examinations of these deposits in Peru has provided a means of dating long past El Niño events because of the disruption these caused to bivalve shell growth.^[71]

Invertebrate predators include crabs, starfish and octopuses. Crabs crack the shells with their pincers and starfish use their water vascular system to force the valves apart and then insert part of their stomach between the valves to digest the bivalve's body. It has been found experimentally that both crabs and starfish preferred molluscs that are attached by byssus threads to ones that are cemented to the substrate. This was probably because they could manipulate the shells and open them more easily when they could tackle them from different angles.^[63] Octopuses either pull bivalves apart by force, or they bore a hole into the shell and insert a digestive fluid before sucking out the liquified contents.^[72]

Razor shells can dig themselves into the sand with great speed to escape predation. Qachon Tinch okeanidagi jilet (Siliqua patula) is laid on the surface of the beach it can bury itself completely in seven seconds ^[73] va Atlantika jaket pichog'i, Ensis directus, can do the same within fifteen seconds.^[74] Scallops and file clams can swim by opening and closing their valves rapidly; water is ejected on either side of the hinge area and they move with the flapping valves in front.^[75] Scallops have simple eyes around the margin of the mantle and can clap their valves shut to move sharply, hinge first, to escape from danger.^[75] Cockles can use their foot to move across the seabed or leap away from threats. The foot is first extended before being contracted suddenly when it acts like a spring, projecting the animal forwards.^[76]

In many bivalves that have siphons, they can be retracted back into the safety of the shell. If the siphons inadvertently get attacked by a predator, they snap off. The animal can qayta tiklash them later, a process that starts when the cells close to the damaged site become activated and remodel the tissue back to its pre-existing form and size.^[77]

File shells such as Limaria fragilis can produce a noxious secretion when stressed. It has numerous tentacles which fringe its mantle and protrude some distance from the shell when it is feeding. If attacked, it sheds tentacles in a process known as avtotomiya. The toxin released by this is distasteful and the detached tentacles continue to writhe which may also serve to distract potential predators.^[78]

Mariculture

Oyster culture in Brittany, France

Istiridye, Midiya, clams, scallops and other bivalve species are grown with food materials that occur naturally in their culture environment in the sea and lagoons.^[79] One-third of the world's farmed food fish harvested in 2010 was achieved without the use of feed, through the production of bivalves and filter-feeding carps.^[79] European flat oysters (Ostrea edulis) were first farmed by the Romans in shallow ponds and similar techniques are still in use.^[80] Seed oysters are either raised in a hatchery or harvested from the wild. Hatchery production provides some control of the broodstock but remains problematic because disease-resistant strains of this oyster have not yet been developed. Yovvoyi spats are harvested either by broadcasting empty mussel shells on the seabed or by the use of long, small-mesh nets filled with mussel shells supported on steel frames. The oyster larvae preferentially settle out on the mussel shells. Juvenile oysters are then grown on in nursery trays and are transferred to open waters when they reach 5 to 6 millimetres (0.20 to 0.24 in) in length.^[80]

Many juveniles are further reared off the seabed in suspended rafts, on floating trays or cemented to ropes. Here they are largely free from bottom-dwelling predators such as starfish and crabs but more labour is required to tend them. They can be harvested by hand when they reach a suitable size. Other juveniles are laid directly on the seabed at the rate of 50 to 100 kilograms (110 to 220 lb) per hectare. They grow on for about two years before being harvested by chuqurlashtirish. Survival rates are low at about 5%.^[80]

The Pacific oyster (Crassostrea gigas) is cultivated by similar methods but in larger volumes and in many more regions of the world. This oyster originated in Japan where it has been cultivated for many centuries.^[81] It is an estuarine species and prefers sho'rlanish of 20 to 25 ming qism. Breeding programmes have produced improved stock that is available from hatcheries. A single female oyster can produce 50–80 million eggs in a batch so the selection of broodstock is of great importance. The larvae are grown on in tanks of static or moving water. They are fed high quality mikro suv o'tlari and diatoms and grow fast. At metamorphosis the juveniles may be allowed to settle on PVC sheets or pipes, or crushed shell. In some cases, they continue their development in "upwelling culture" in large tanks of moving water rather than being allowed to settle on the bottom. They then may be transferred to transitional, nursery beds before being moved to their final rearing quarters. Culture there takes place on the bottom, in plastic trays, in mesh bags, on rafts or on long lines, either in shallow water or in the intertidal zone. The oysters are ready for harvesting in 18 to 30 months depending on the size required.^[81]

Similar techniques are used in different parts of the world to cultivate other species including the Sidney toshbo'ron (Saccostrea commercialis), the northern quahog (Mercenaria mercenaria), the blue mussel (Mytilus edulis), the O'rta er dengizi midiyasi (Mytilus galloprovincialis), the New Zealand green-lipped mussel (Perna canaliculus), the grooved carpet shell (Ruditapes decussatus), the Yaponiya gilamchali qobig'i (Venerupis philippinarum), the pullet carpet shell (Venerupis pullastra) va Yesso taroq (Patinopecten yessoensis).^[82]

Production of bivalve molluscs by mariculture in 2010 was 12,913,199 tons, up from 8,320,724 tons in 2000. Culture of clams, cockles and ark shells more than doubled over this time period from 2,354,730 to 4,885,179 tons. Culture of mussels over the same period grew from 1,307,243 to 1,812,371 tons, of oysters from 3,610,867 to 4,488,544 tons and of scallops from 1,047,884 to 1,727,105 tons.^[83]

Use as food

Flat oysters (Ostrea edulis ) from France

Bivalves have been an important source of food for humans at least since Roman times^[84] and empty shells found in middens at archaeological sites are evidence of earlier consumption.^[71] Oysters, scallops, clams, ark clams, mussels and cockles are the most commonly consumed kinds of bivalve, and are eaten cooked or raw. In 1950, the year in which the Oziq-ovqat va qishloq xo'jaligi tashkiloti (FAO) started making such information available, world trade in bivalve molluscs was 1,007,419 tons.^[85] By 2010, world trade in bivalves had risen to 14,616,172 tons, up from 10,293,607 tons a decade earlier. The figures included 5,554,348 (3,152,826) tons of clams, cockles and ark shells, 1,901,314 (1,568,417) tons of mussels, 4,592,529 (3,858,911) tons of oysters and 2,567,981 (1,713,453) tons of scallops.^[85] China increased its consumption 400-fold during the period 1970 to 1997.^[86]

It has been known for more than a century that consumption of raw or insufficiently cooked shellfish can be associated with infectious diseases. These are caused either by bacteria naturally present in the sea such as Vibrio spp. or by viruses and bacteria from sewage oqava suv that sometimes contaminates coastal waters. As filter feeders, bivalves pass large quantities of water through their gills, filtering out the organic particles, including the microbial pathogens. These are retained in the animals' tissues and become concentrated in their liver-like digestive glands.^[86][87] Another possible source of contamination occurs when bivalves contain marine biotoksinlar as a result of ingesting numerous dinoflagellates. These microalgae are not associated with sewage but occur unpredictably as algal blooms. Large areas of a sea or lake may change colour as a result of the proliferation of millions of single-cell algae, and this condition is known as a red tide.^[86]

Viral and bacterial infections

In 1816 in France, a physician, J. P. A. Pasquier, described an outbreak of tifo linked to the consumption of raw oysters. The first report of this kind in the United States was in Konnektikut in 1894. As sewage treatment programmes became more prevalent in the late 19th century, more outbreaks took place. This may have been because sewage was released through outlets into the sea providing more food for bivalves in estuaries and coastal habitats. A causal link between the bivalves and the illness was not easy to demonstrate because the illness might come on days or even weeks after the ingestion of the contaminated shellfish. One viral pathogen is the Norvalk virus. This is resistant to treatment with chlorine-containing chemicals and may be present in the marine environment even when coliform bacteria have been killed by the treatment of sewage.^[86]

In 1975 in the United States, a serious outbreak of oyster-vectored disease was caused by Vibrio vulnificus. Although the number of victims was low, the mortality rate was high at 50%. About 10 cases have occurred annually since then and further research needs to be done to establish the epidemiologiya of the infections. The cases peak in mid-summer and autumn with no cases being reported in mid winter so there may be a link between the temperature at which the oysters are held between harvesting and consumption.^[86] In 1978, an oyster-associated gastrointestinal infection affecting more than 2,000 people occurred in Australia. The causative agent was found to be the Norvalk virus and the epidemic caused major economic difficulties to the oyster farming industry in the country.^[88] In 1988, an outbreak of gepatit A associated with the consumption of inadequately cooked clams (Anadara subcrenata ) sodir bo'ldi Shanxay Xitoyning maydoni. An estimated 290,000 people were infected and there were 47 deaths.^[89]

In the United States and the European Union, since the early 1990s regulations have been in place that are designed to prevent shellfish from contaminated waters entering the Oziq ovqat zanjiri. This has meant that there is sometimes a shortage of regulated shellfish, with consequent higher prices. This has led to illegal harvesting and sale of shellfish on the qora bozor, which can be a health hazard.^[86]

Paralitik qisqichbaqasimon zaharlanish

Paralitik qisqichbaqasimon zaharlanish (PSP) is primarily caused by the consumption of bivalves that have accumulated toxins by feeding on toxic dinoflagellates, single-celled protists found naturally in the sea and inland waters. Saksitoksin is the most virulent of these. In mild cases, PSP causes tingling, numbness, sickness and diarrhoea. In more severe cases, the muscles of the chest wall may be affected leading to paralysis and even death. In 1937, researchers in Kaliforniya established the connection between blooms of these phytoplankton and PSP.^[90] The biotoxin remains potent even when the shellfish are well-cooked.^[90] In the United States, there is a regulatory limit of 80 .g /g of saxitoxin equivalent in shellfish meat.^[90]

Qisqichbaqasimon amnezik zaharlanish

Qisqichbaqasimon amnezik zaharlanish (ASP) was first reported in eastern Canada in 1987. It is caused by the substance domoik kislota found in certain diatoms of the genus Pseudo-nitzschia. Bivalves can become toxic when they filter these microalgae out of the water. Domoic acid is a low-molecular weight aminokislota that is able to destroy brain cells causing memory loss, gastroenterit, long-term neurological problems or death. In an outbreak in the western United States in 1993, finfish were also implicated as vectors, and seabirds and mammals suffered neurological symptoms.^[90] In the United States and Canada, a regulatory limit of 20 µg/g of domoic acid in shellfish meat is set.^[91]

Ekotizim xizmatlari

Nutrient extraction services provided by bivalves. Blue mussels are used as examples but other bivalves like istiridye can also provide these nutrient extraction services.^[92]

Ekotizim xizmatlari provided by marine bivalves in relation to nutrient extraction from the coastal environment have gained increased attention to mitigate adverse effects of excess nutrient loading from human activities, such as agriculture and sewage discharge. These activities damage coastal ecosystems and require action from local, regional, and national environmental management. Marine bivalves filter particles like fitoplankton, thereby transforming particulate organic matter into bivalve tissue or larger faecal pellets that are transferred to the bentos. Nutrient extraction from the coastal environment takes place through two different pathways: (i) harvest/removal of the bivalves – thereby returning nutrients back to land; or (ii) through increased denitrifikatsiya in proximity to dense bivalve aggregations, leading to loss of nitrogen to the atmosphere. Active use of marine bivalves for nutrient extraction may include a number of secondary effects on the ecosystem, such as filtration of zarracha material. This leads to partial transformation of particulate-bound nutrients into dissolved nutrients via bivalve excretion or enhanced mineralization of faecal material.^[92]

When they live in polluted waters, bivalve molluscs have a tendency to accumulate substances such as og'ir metallar va doimiy organik ifloslantiruvchi moddalar in their tissues. This is because they ingest the chemicals as they feed but their enzyme systems are not capable of metabolising them and as a result, the levels build up. This may be a health hazard for the molluscs themselves, and is one for humans who eat them. It also has certain advantages in that bivalves can be used in monitoring the presence and quantity of pollutants in their environment.^[93]

Economic value of bivalve nutrient extraction, linking processes to services to economic values.^[92]

There are limitations to the use of bivalves as bioindicators. The level of pollutants found in the tissues varies with species, age, size, time of year and other factors. The quantities of pollutants in the water may vary and the molluscs may reflect past rather than present values. In a study near Vladivostok it was found that the level of pollutants in the bivalve tissues did not always reflect the high levels in the surrounding sediment in such places as harbours. The reason for this was thought to be that the bivalves in these locations did not need to filter so much water as elsewhere because of the water's high nutritional content.^[94]

A study of nine different bivalves with widespread distributions in tropical marine waters concluded that the mussel, Trichomya hirsuta, most nearly reflected in its tissues the level of heavy metals (Pb, Cd, Cu, Zn, Co, Ni, and Ag) in its environment. In this species there was a linear relationship between the sedimentary levels and the tissue concentration of all the metals except zinc.^[95] In Fors ko'rfazi, the Atlantic pearl-oyster (Pinctada radiata ) is considered to be a useful bioindicator of heavy metals.^[96]

Crushed shells, available as a by-product of the seafood canning industry, can be used to remove pollutants from water. It has been found that, as long as the water is maintained at an alkaline pH, crushed shells will remove cadmium, lead and other heavy metals from contaminated waters by swapping the calcium in their constituent aragonite for the heavy metal, and retaining these pollutants in a solid form.^[97] The rock oyster (Saccostrea cucullata ) has been shown to reduce the levels of mis and cadmium in contaminated waters in the Persian Gulf. The live animals acted as biofilters, selectively removing these metals, and the dead shells also had the ability to reduce their concentration.^[98]

Boshqa maqsadlar

Carved shell miniatures

Conchology is the scientific study of mollusc shells, but the term conchologist is also sometimes used to describe a collector of shells. Many people pick up shells on the beach or purchase them and display them in their homes. There are many private and public collections of mollusc shells, but the largest one in the world is at the Smitson instituti, which houses in excess of 20 million specimens.^[99]

1885 wampum belt

Freshwater mussel shell used for making buttons

Carved nacre in a 16th-century qurbongoh

Shells are used decoratively in many ways. They can be pressed into concrete or plaster to make decorative paths, steps or walls and can be used to embellish picture frames, mirrors or other craft items. They can be stacked up and glued together to make ornaments. They can be pierced and threaded onto necklaces or made into other forms of jewellery. Shells have had various uses in the past as body decorations, utensils, scrapers and cutting implements. Carefully cut and shaped shell tools dating back 32,000 years have been found in a cave in Indonesia. In this region, shell technology may have been developed in preference to the use of stone or bone implements, perhaps because of the scarcity of suitable rock materials.^[100]

The Amerika qit'asining tub aholisi living near the east coast used pieces of shell as wampum. The channeled whelk (Busycotypus canaliculatus) va quahog (Mercenaria mercenaria) were used to make white and purple traditional patterns. The shells were cut, rolled, polished and drilled before being strung together and woven into belts. These were used for personal, social and ceremonial purposes and also, at a later date, for currency.^[101] The Winnebago Tribe from Wisconsin had numerous uses for freshwater mussels including using them as spoons, cups, ladles and utensils. They notched them to provide knives, graters and saws. They carved them into fish hooks and lures. They incorporated powdered shell into clay to temper their pottery vessels. They used them as scrapers for removing flesh from hides and for separating the scalps of their victims. They used shells as scoops for gouging out fired logs when building canoes and they drilled holes in them and fitted wooden handles for tilling the ground.^[102]

Tugmalar have traditionally been made from a variety of freshwater and marine chig'anoqlar.^[103] At first they were used decoratively rather than as fasteners and the earliest known example dates back five thousand years and was found at Mohenjo-daro ichida Hind vodiysi.^[104]

Dengiz ipagi is a fine fabric woven from the byssus threads of bivalves, particularly the pen shell (Pinna nobilis ). It used to be produced in the Mediterranean region where these shells are endemik. It was an expensive fabric and ortiqcha baliq ovlash has much reduced populations of the pen shell.^[105] There is mention in the Greek text on the Rozetta tosh (196 BCE) of this cloth being used to pay taxes.^[106]

Crushed shells are added as a calcareous supplement to the diet of laying poultry. Oyster shell and cockle shell are often used for this purpose and are obtained as a by-product from other industries.^[107]

Pearls and mother-of-pearl

Mother-of-pearl or nacre is the naturally occurring lustrous layer that lines some mollusc shells. It is used to make pearl buttons and in artisan craftwork to make organic jewellery. It has traditionally been naqshli into furniture and boxes, particularly in China. It has been used to decorate musical instruments, watches, pistols, fans and other products. The import and export of goods made with nacre are controlled in many countries under the International Convention of Trade in Endangered Species of Wild Fauna and Flora.^[108]

A dur is created in the mantle of a mollusk when an irritant particle is surrounded by layers of nacre. Although most bivalves can create pearls, istiridye oilada Pteriidae and freshwater mussels in the families Unionidae va Margaritiferidae are the main source of commercially available pearls because the calcareous concretions produced by most other species have no lustre. Finding pearls inside oysters is a very chancy business as hundreds of shells may need to be pried open before a single pearl can be found. Most pearls are now obtained from cultured shells where an irritant substance has been purposefully introduced to induce the formation of a pearl. A "mabe" (irregular) pearl can be grown by the insertion of an implant, usually made of plastic, under a flap of the mantle and next to the mother-of-pearl interior of the shell. A more difficult procedure is the grafting of a piece of oyster mantle into the gonad of an adult specimen together with the insertion of a shell bead nucleus. This produces a superior, spherical pearl. The animal can be opened to extract the pearl after about two years and reseeded so that it produces another pearl. Pearl oyster farming and pearl culture is an important industry in Japan and many other countries bordering the Indian and Pacific Oceans.^[109]

Simvolik

The scallop is the symbol of Sent-Jeyms and is called Coquille Saint-Jacques yilda Frantsuz. It is an emblem carried by pilgrims on their yo'l to the shrine of Santyago de Kompostela in Galicia. The shell became associated with the pilgrimage and came to be used as a symbol showing hostelries along the route and later as a sign of hospitality, food and lodging elsewhere.^[110]

Rim myth has it that Venera, the goddess of love, was born in the sea and emerged accompanied by fish and dolphins, with Botticelli depicting her as arriving in a scallop shell. The Romans revered her and erected shrines in her honour in their gardens, praying to her to provide water and verdant growth.^[111] From this, the scallop and other bivalve shells came to be used as a symbol for fertility.^[112] Its depiction is used in architecture, furniture and fabric design and it is the logo of Dutch Dutch Shell, the global oil and gas company.^[113]

Bivalvian taxonomies

Mussels in the intertidal zone in Kornuol, Angliya

Mytilarca is a distant relative of the mussels; o'rtadan Devoniy ning Viskonsin.

Fotoalbom gastropod and attached mytilid bivalves in a Jurassic ohaktosh (Matmor Formation ) in southern Isroil

Aviculopecten subcardiformis; a fotoalbom of an extinct scallop dan Logan Formation ning Wooster, Ohio (external mold)

For the past two centuries no consensus has existed on bivalve filogeniya from the many classifications developed. In earlier taxonomic systems, experts used a single characteristic feature for their classifications, choosing among shell morphology, hinge type or gill type. Conflicting naming schemes proliferated due to these taxonomies based on single organ systems. One of the most widely accepted systems was that put forward by Norman D. Newell in Part N of the Treatise on Invertebrate Paleontology,^[114] which employed a classification system based on general shell shape, microstructures and hinge configuration.^[115] Because features such as hinge morphology, dentition, mineralogy, shell morphology and shell composition change slowly over time, these characteristics can be used to define major taxonomic groups.

Since the year 2000, taxonomic studies using cladistical analyses of multiple organ systems, shell morphology (including fossil species) and modern molekulyar filogenetik have resulted in the drawing up of what experts believe is a more accurate phylogeny of the Bivalvia.^{[116][117][118][119][120]} Based upon these studies, a new proposed classification system for the Bivalvia was published in 2010 by Bieler, Carter & Coan.^[121] In 2012, this new system was adopted by the Dunyo dengiz turlari turlarining reestri (WoRMS) for the classification of the Bivalvia. Some experts still maintain that Anomalodesmacea should be considered a separate subclass, whereas the new system treats it as the order Anomalodesmata, within the subclass Heterodonta. Molecular phylogenetic work continues, further clarifying which Bivalvia are most closely related and thus refining the classification.^[122][123]

Practical taxonomy of R.C. Mur

R.C. Moore, in Moore, Lalicker, and Fischer, 1952, Invertebrate Fossils, gives a practical and useful classification of pelecypods (Bivalvia) even if somewhat antiquated, based on shell structure, gill type, and hinge teeth configuration. Subclasses and orders given are:

Subklass:Prionodesmacea

Buyurtma

Paleoconcha

Taxodonta: Many teeth (e.g. order Nuculida )

Schizodonta: Big bifurcating teeth (e.g. Trigoniya spp.)

Isodonta: Equal teeth (e.g. Spondilus spp.)

Dysodonta: Absent teeth and ligaments joins the valves.

Subklass:Teleodesmacea

Buyurtma

Heterodonta: Different teeth (e.g. family Cardiidae ). [ Quyi Ordovik  – Yaqinda ]

Pachydonta: Large, different, deformed teeth (e.g. Rudist spp.). [ Kech yura  – Yuqori bo'r ]

Desmodonta: Hinge-teeth absent or irregular with ligaments (e.g. family Anatinidae ).

Prionodesmacea have a prismatic and nacreous shell structure, separated mantle lobes, poorly developed siphons, and hinge teeth that are lacking or unspecialized. Gills range from protobranch to eulamellibranch. Teleodesmacea on the other hand have a porcelanous and partly nacreous shell structure; Mantle lobes that are generally connected, well developed siphons, and specialized hinge teeth. In most, gills are eulamellibranch.

1935 taxonomy

In his 1935 work Handbuch der systematischen Weichtierkunde (Handbook of Systematic Malacology), Johannes Thiele introduced a mollusc taxonomy based upon the 1909 work by Cossmann and Peyrot. Thiele's system divided the bivalves into three orders. Taxodonta consisted of forms that had taxodont dentition, with a series of small parallel teeth perpendicular to the hinge line. Anisomyaria consisted of forms that had either a single adductor muscle or one adductor muscle much smaller than the other. Eulamellibranchiata consisted of forms with ctenidial gills. The Eulamellibranchiata was further divided into four suborders: Schizodonta, Heterodonta, Adapedonta va Anomalodezma.^[124][125]

Taxonomy based upon hinge tooth morphology

The systematic layout presented here follows Newell's 1965 classification based on hinge tooth morfologiya (all taxa marked † are extinct) :^[115]

The monofil of the subclass Anomalodesmata is disputed. The standard view now is that it resides within the subclass Heterodonta.^{[116][119][126]}

Taxonomy based upon gill morphology

An alternative systematic scheme exists using gill morphology.^[127] This distinguishes between Protobranchia, Filibranchia and Eulamellibranchia. The first corresponds to Newell's Palaeotaxodonta and Cryptodonta, the second to his Pteriomorphia, with the last corresponding to all other groups. In addition, Franc separated the Septibranchia from his eulamellibranchs because of the morphological differences between them. The septibranchs belong to the superfamily Poromyoidea and are carnivorous, having a muscular septum instead of filamentous gills.^[128]

2010 taxonomy

In May 2010, a new taxonomy of the Bivalvia was published in the journal Malakologiya. In compiling this, the authors used a variety of phylogenetic information including molecular analysis, anatomical analysis, shell morphology and shell microstructure as well as bio-geographic, paleobiogeographic and stratigrafik ma `lumot. In this classification 324 families are recognized as valid, 214 of which are known exclusively from fossils and 110 of which occur in the recent past, with or without a fossil record.^[121] This classification has since been adopted by WoRMS.^[129]

Proposed classification of Class Bivalvia (under the redaction of Rüdiger Bieler, Joseph G. Carter and Eugene V. Coan) (all taxa marked † are extinct) :^[130]

Adabiyotlar

Qo'shimcha o'qish

• Shnayder, Jey A. (2001). "20-asr davomida ikki qavatli sistematika". Paleontologiya jurnali. 75 (6): 1119–1127. doi:10.1666 / 0022-3360 (2001) 075 <1119: BSDTC> 2.0.CO; 2. ISSN  0022-3360.
• Poutiers, J.-M .; Bernard, F. R. (1995). "Tropik g'arbiy Tinch okeanidan yirtqich ikki tomonlama mollyuskalar (Anomalodesmata), tavsiya etilgan tasnifi va so'nggi turlarining katalogi bilan". Bouchetda P. (tahrir). Résultats des Campagnes Musorstom. Mémoires Muséum National d'Histoire Naturelle. 167. 107-188 betlar.
• Vaught, K. C. (1989). Tirik mollyuskaning tasnifi. Amerikalik malakologlar. ISBN  978-0-915826-22-3.