The effects of seasonal, sex and size on digestive enzyme activities of Astacus leptodactylus in natural habitat were investigated in the present study. The freshwater crayfish were sampled 584 individual as seasonally from Egirdir Lake. Ten male and 10 female individuals were sampled randomly from caught crayfish in each two different size ranges (4.5–7.0, 7.1–9.9 cm) and each season. The gastrointestinal tract, gastric, intestine and midgut gland were individually dissected on ice for enzyme analysis and stomach contents. At the end of the study, amylase activities were affected by interaction of season × sex × size in intestinal, season × sex in midgut gland. However, any interaction was not determined in amylase activities of the gastric. Lipase activities were affected by interaction of season × sex × size in intestinal and gastric, season × sex in midgut gland. The protease activities in each organ were affected by interaction of season, sex and size (p ˂ .05). In all organs, amylase and lipase activities were similar. However, the highest protease activity was in stomach while the lowest protease activity was the intestine. The protease activities were higher than amylase and lipase activities. There is a positive correlation between protease enzyme activities in gastric with gonad maturation and active feeding period. It can be said based on data of digestive system and high protease activity that A. leptodactylus is an omnivore species in need high protein. In addition, the reason for the low levels of lipase activity may be A. leptodactylus not prefer high fat foods or not fed high fat foods.
Bu çalışma, Eğirdir Gölü'nde yaşayan Astacus leptodactylus türünde mide sindirim enzim aktiviteleri üzerine (proteaz α-amilaz ve lipaz) mevsim ve eşeyin etkisini araştırmak amacıyla oluşturulmuştur. Bu amaçla kerevitler 1 yılda 4 mevsim olarak Eğirdir Gölü'nden avlandı. İlkbahar mevsiminde, kerevitlerin pinterlere girmemesi nedeniyle örnekleme yapılamadı. Bu nedenle, sonuçlar üç mevsim (sonbahar, kış, yaz) ve eşeyler üzerinden faktöriyel düzeyinde varyans analizi ile değerlendirildi. Bulgular, eşey ve mevsim faktörlerinin kerevitlerin midesindeki proteaz ve lipaz aktivitesini önemli düzeyde etkilediğini (p<0,05), α-amilaz aktivitesinde ise istatistiksel olarak önemli düzeyde etkili olmadığını gösterdi (p>0,05). Bulgular ayrıca, kerevitlerin, proteaz enzim aktivitesinin sonbahar ve kışın, lipaz enzim aktivitesinin ise kışın eşeyler arası önemli değişim gösterdiğini ortaya çıkardı (p<0,05). Bununla birlikte, proteaz enzimin en yüksek aktiviteyi (524,73 U/mg protein) sonbahar mevsiminde dişilerde, lipaz enzimin (0,022 U/mg protein) ise kışın erkek bireylerde olduğu belirlendi (p<0,05). Sonuç olarak, bu çalışma araştırılan enzimlerin varlığı ve değişkenliğinin belirlenmesiyle, bu türün geniş besin çeşitliliğine ve sindirme yeteneğine sahip olduğunu gösterdi.
The present study determined changes in protease, α-amylase and lipase activities during embryonic and post-embryonic developmental stages of the freshwater crayfish <em>Astacus leptodactylus</em> Eschscholtz, 1823. The embryonic stages studied comprised Phase III (blastula formation), Phase X (embryos with anlagen of masticatory) and Phase XIV (embryos with strongly developed posterior hepatopancreas lobes). The post-embryonic stages comprised Stage I (no feeding) and Stage II (prior to the onset of feeding). Protease and α-amylase activities were relatively high as compared with lipase activity. Protease activity values showed a steady increase from Phase III to Stage I. α-amylase and lipase activities were low in Phase XIV. The activities of these two enzymes tended to increase just before hatching and reached the highest levels in Stage II. Digestive enzyme activities increased in accordance with maturation of the hepatopancreas and prior to the onset of external feeding. Protease activity was high in the early stage of embryonic development and continued to increase in later stages. On the other hand, α-amylase and lipase activities were low until maturation of the hepatopancreas and then remained high. The results of the present study provide important information on changes in digestive enzyme levels during different developmental stages of <em>A. leptodactylus</em>.
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