Gediz Deltası, İzmir Körfezi (Ege Denizi, Türkiye)’ndeki Avrupa Yılan Balığının (Anguilla anguilla, Linnaeus, 1758) Gonad Gelişimi Üzerine Bir Ön Çalışma

Yıl 2025, Cilt: 8 Sayı: 1, 393 - 403, 17.01.2025

Burcu Taylan , Ertan Taşkavak , Şule Gürkan

https://doi.org/10.47495/okufbed.1516180

Öz

Katadrom bir tür olan Anguilla anguilla’nın tatlı sudaki yaşamlarının son aşamasında uzun bir göçe uyum sağlamak adına morfolojik ve fizyolojik olarak birçok değişime uğradığı, bu değişikliklerin de gonad gelişimi ile yakından ilişkili olduğu düşünülmektedir. Bu amaçla Gediz Deltası’nda dağılım gösteren yılan balığı popülasyonunda gonad gelişimini incelemek amacıyla 2020-2021 yılları arasında ticari balıkçılardan 89 adet ölü yılan balığı alınarak incelenmiştir. Laboratuvarda total boy ve ağırlıkları ölçülen balıklar disekte edilmiştir. Örneklerin total boy ve ağırlık değerleri sırasıyla; 19,2-72,5 (ort: 46,77) cm, 10,1-1002,4 (ort: 254,69) g’dır. Dişi:erkek oranı 1:1,28 olarak saptanmış olup ki kare testi sonucu dişi ve erkek bireyler arasında belirgin bir fark tespit edilmemiştir (χ²hesap0.625<χ²tablo3.841). Türün GSI değerinin 0,22-0,47 arasında olduğu ve maksimum değere sonbaharda (0,47) ulaştığı saptanmıştır. Dişilere ait ovaryumlar histolojik olarak incelendiğinde olgunlaşmamış ve olgunlaşmakta olmak üzere 2 safha tespit edilmiş olup ovaryum içerisindeki oositlerin pre-vitellogenik safha ve erken vitellogenik safhalardan oluştuğu gözlenmiştir. Pre-vitellogenik safhadaki oositlerde yoğun sitoplazma ile merkezde konumlanmış büyük bir çekirdek saptanmıştır. Bu safhadaki oositlerde çap; 90-200 µm olarak tespit edilmiştir. Erken vitellogenik evre, periferik bölgede bulunan daha büyük oositler ve yüksek miktarda yağ dokusu ile karakterize edilmiştir. Bu safhadaki oositlerde çap; 210-280 µm olarak tespit edilmiştir.

Anahtar Kelimeler

Anguilla anguilla, Avrupa yılan balığı, Gonadların olgunlaşması, Gediz Deltası

A Preliminary Study on Gonadal Development in the European Eel (Anguilla anguilla, Linnaeus, 1758) within the Gediz Delta, Izmir Bay (Aegean Sea, Türkiye)

Öz

Anguilla anguilla, a catadromous species, is believed to undergo significant morphological and physiological changes in the final stage of its freshwater life. These changes are closely associated with gonad development and enable adaptation for long migration. This study examined 89 eels from the Gediz Delta, caught by commercial fishermen between 2020-2021. The eels' total lengths and weights were measured in the laboratory before they were dissected to examine gonad development. The total length and weight values of the specimens ranged from 19.2-72.5 cm (average: 46.77 cm) and 10.1-1002.4 g (average: 254.69 g) respectively. The ratio of female to male eels was 1:1.28. The chi-square test revealed no significant difference between female and male individuals (χ² calculation: 0.625 < χ² table: 3.841). The Gonadosomatic Index (GSI) value of the species was found to be between 0.22-0.47, peaking in the fall (0.47). Upon histological examination of the females' ovaries, two phases were identified - immature and maturing. Oocytes in the ovary consisted of pre-vitellogenic and early vitellogenic phases. The pre-vitellogenic phase featured a large nucleus situated in the centre of dense cytoplasm. The diameter of oocytes in this stage was measured between 90-200 µm. The early vitellogenic stage was characterized by larger oocytes located primarily in the peripheral zone of the ovarian stroma, containing a high amount of adipose tissue. The oocytes in this stage had a diameter ranging from 210-280 µm.

Anahtar Kelimeler

European eel, Anguilla anguilla, Gonad maturation, Gediz Delta

Kaynakça

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