Aynur Lök

Interspecies comparison of the mechanical properties and biochemical composition of byssal threads

ABSTRACT Several bivalve species produce byssus threads to provide attachment to substrates, with mechanical properties highly variable among species. Here, we examined the distal section of byssal threads produced by a range of bivalve species (Mytilus edulis, Mytilus trossulus, Mytilus galloprovincialis, Mytilus californianus, Pinna nobilis, Perna perna, Xenostrobus securis, Brachidontes solisianus and Isognomon bicolor) collected from different nearshore environments. Morphological and mechanical properties were measured, and biochemical analyses were performed. Multivariate redundancy analyses on mechanical properties revealed that byssal threads of M. californianus, M. galloprovincialis and P. nobilis have very distinct mechanical behaviours compared with the remaining species. Extensibility, strength and force were the main variables separating these species groups, which were highest for M. californianus and lowest for P. nobilis. Furthermore, the analysis of the amino acid composition revealed that I. bicolor and P. nobilis threads are significantly different from the other species, suggesting a different underlying structural strategy. Determination of metal contents showed that the individual concentration of inorganic elements varies, but that the dominant elements are conserved between species. Altogether, this bivalve species comparison suggests some molecular bases for the biomechanical characteristics of byssal fibres that may reflect phylogenetic limitations. Summary: An interspecies comparison of byssus produced by nine species in different natural environments shows that mechanical properties depends on the interrelationship between morphometric characteristics and their biochemical contents.

An investigation on ovarian development of grooved shrimp Melicertus kerathurus in Izmir Bay, Turkey

In the current study, commercially valuable penaeid shrimp, Melicertus kerathurus, were attained approximately monthly in the Izmir Bay, southern Aegean Sea from May 2004 to April 2005 . For each specimen, we measured body length, body weight and ovarian weight, and calculated gonadosomatic indices (GSI). GSI values results pointed out that the GSI in Melicertus kerathurus increased during vitellogenesis (2.03 ± 0 . 24 %) but sharply decreased after spawning ( 0 . 53 ± 0 . 35 %) to reach levels similar to those in immature females. We also examined oogenesis in Melicertus kerathurus by histological observation of the ovary to determine reproductive cycle for future domestication. The observation on the gonads leads us to conclude that there are five stages of development for the females: (I) previtellogenic; (II) early vitellogenic; (III) late vitellogenic; (IV) mature; and (V) spent. Histological characteristics showed that the best time to capture adult shrimps for breeding purposes was between the months of April and June. The numbers of each oocyte type that were present were also counted, measured, and used to evaluate the following traits: total oocyte number; mean oocytes diameter; and maximum oocyte diameter. Oocyte diameter was significantly different at all stages (P < 0 . 05 ) and the largest diameter was observed as 1 6 3 . 92 ± 4.51 μm at stage IV.

Foraging Behaviors of Hexaplex trunculus (Gastropoda: Muricidae) Juveniles

ABSTRACT Foraging behaviors of juvenile Hexaplex trunculus (Linnaeus, 1758), a predatory snail, preying on the Mediterranean mussel Mytilus galloprovincialis were investigated. To understand the mechanisms of the prey-predator relationship between young forms of these species and assess the foraging capabilities of the snails, size selection and attacktype experiments were set up. Furthermore, the predation signatures, which are used as a valuable tool for ecology and paleoecology studies, were measured with an alternative method; their locations were classified and related with the predator-prey sizes to make some descriptions. Snails (as two size categories, about 2–6 and 6–11 mm shell length (SL) during the experimental period) typically accessed the mussel (as four size categories up to 20 mm SL) flesh by drilling and/or marginal chipping. About 90% of the shell samples had at least one attack signature from each attack type. By the end of the experimental period, 74% of all of the attacks with the visible predation signature were made by drilling and 26% by chipping; attack type did not differ according to predator or prey size. Group-attacking events were observed frequently during the experiments as well as solitary attacks; 48% of the mussel shells that had at least one attack signature had multiple attack signatures. Positions of the drill holes were dense over anterior-dorsal areas and their distributions did not differ according to snail size. Drill hole diameters were found to be related with snail and also mussel sizes by linear regression. Even though both small and large juvenile snails were capable of foraging on mussels that were three or four times larger than themselves, they showed size preference for particular mussel size classes. The ratio of the prey size/predator size did not have any effect on the attack type of the snails. After reaching 9 mm (auxiliary experiments), snails started to consume larger mussels (more than 40 mm) as well as the individuals from smaller groups.

Gamogenetic cycle, condition index and meat yield of the Noah’s Ark shell (Arca noae Linnaeus, 1758) from Gerence Bay, Aegean Sea Turkey

Bu calismada Gerence Korfezi’nde (Ege Denizi, Turkiye) Arca noae Linnaeus, 1758 turunun (Nuhun gemisi) gametogenik dongusu, kondisyon indeksi ve et verimi Agustos 2009 ve Temmuz 2010 tarihleri arasinda takip edilmistir. Her ornekleme doneminde sicaklik, tuzluluk, klorofil-a, partikul organik ve partikul inorganik madde icerigi belirlenmistir. Yapilan histolojik calismalara gore dinlenme safhasi Eylul ayinda %100 olarak tespit edilmistir. Eylul ayinin disinda, dol atimi tum yil boyunca gozlenmis ve Nisan ile Haziran aylari arasinda yuksek degerlerde oldugu belirlenmistir. Cinsiyet orani esit olarak tespit edilmemistir ve disiler populasyonda baskindir (2:1). Et verimi, kondisyon indeksi ve gonadindeksi arasinda pozitif iliski tespit edilmistir (P≤0.05). Cevresel parametreler icerisinde sadece partikul inorganik madde ile ureme arasinda ters iliski oldugu tespit edilmistir (P≤0.05).

Farklı istiridye türlerinin tespitinde RAPD-PZR kullanımı

Bu calismada, Ege Denizi’nde gozlemlenen ve istilaci tur oldugu dusunulen bazi istiridye ornekleriyle, yerli istiridye turu olan Ostrea edulis (Linnaeus 1758) ornekleri arasindaki genetik farkliliklarin tespitinin, RAPD (Rastgele Cogaltilmis Polimorfik DNA)-PCR (Polimeraz Zincir Reaksiyonu) yardimiyla hizli bir sekilde belirlenmesi amaclanmistir. Bu baglamda, denizlerimizin yaygin turu olan Ostrea genusundan morfolojik olarak farkli oldugu gozlenen ve Crassostrea genusuna ait ozellikler gosteren istiridye bireyleriyle, yerli tur 8 adet RAPD profili kullanilarak genetik olarak ayirt edilmistir. Calismada toplam 343 bant elde edilmistir. Polimorfizm orani Crassostrea sp.’ye ait orneklerde daha yuksek bulunmustur. Ele alinan lokuslardan 6 tanesinin ayrim gucu yuksek cikmistir. Istilaci ture ait 11, yerli ture ait 5 adet toplamda 16 adet ture-ozgu diagnostik bant belirlenmistir.

Işınlı inci istiridyesi (Pinctada radiata) spatlarının toplanması üzerine Türkiye’deki ilk sonuçlar

Bu calisma torba ve kabuk kolektor tipleriyle isinli inci istiridyesi ( Pinctada radiata , Leach 1814) spatlarinin toplama verimliligini bulmak icin Karantina Adasi’nda gerceklestirildi. Kolektorler alti grup olarak hazirlandi ve uzun halat sistemi uzerine yerlestirildi. Sicaklik, tuzluluk, klorofil-a ve toplam partikul madde miktari gibi cevresel parametreler calisma periyodu boyunca izlendi. P. radiata spati ilk olarak Agustos ayinda torba kolektorlerde 11,66±2,08 birey/0,91 m 2 , kabuk kolektorlerde ise 2,33±1,52 birey/0,91 m 2 olarak tespit edildi. Ayni ayda en yuksek sicaklik ve tuzluluk degerleri sirasiyla 27 °C ve ‰ 36,5 olarak kayit edildi. Calisma boyunca, torba kolektorlerde en iyi spat toplama performansini Grup 2 (G2-25 Haziran’da yerlestirildi) gosterirken, kabuk kolektorde G4 (29 Agustos’ta yerlestirildi) daha basarili olmustur. Toplamda 172±34,39 spat toplandi. 119±22,60 (69.18%) spat torba kolektorlerle toplanirken, 53±11.78 (30.82%) spat kabuk kolektorlerle toplandi. Ortlama 7,26 birey/m 2 Pinctada spati torba kolektorlerde, 3,23 birey/m 2 kabuk kolektorde belirlenmistir. Kolektor gruplari arasinda toplam spat bulunma farkinin onemli derecede anlamli ciktigi gorulmustur (p<0,05). Torba kolektorler uzerinde bulunan Pinctada spatlarinin boy araligi 4,47-33,9 mm arasinda degisirken, kabuk kolektorler uzerinde bulunan spatlarin boy araligi 4,66-18 mm arasinda degisim gosterdi. Fouling organizmalar (Balanus, Poliket, Bryozoa) ve predator turler de (yengec ve gastropod) kolektor gruplarinda bulundu. Calisma sonucunda torba kolektorlerin kabuk kolektorlere oranla daha verimli oldugu belirlenmistir.