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¹ Department of Zoology, Kurukshetra University, Kurukshetra 136119, India
² Central Inland Fisheries Research Institute, Regional Centre, Prayagraj 211002, India
³ Department of Veterinary Science, Polo Universitario dell'Annunziata, University of Messina, 98168 Messina, Italy
⁴ Department of Chemical, Biological, Pharmaceutical, and Environmental Sciences, University of Messina, 98168 Messina, Italy
⁵ Department of Animal Nutrition and Nutritional Diseases, Veterinary Medicine Faculty, Kastamonu University, 37150, Kastamonu, Türkiye DOI : 10.4194/TRJFAS25504 Viewed : 432 - Downloaded : 382 This study aimed to investigate the reproductive biology of female rainbow trout (Oncorhynchus mykiss). Mature female (n.80) rainbow trout from different reproductive phases were collected. Through a transmission electron microscope (TEM), it was feasible to examine the oocyte at several developmental stages, namely the perinucleolus stage, cortical alveoli stage, vitellogenic stage, mature stage, and postovulatory stage. Progesterone and estradiol levels were measured at their lowest during the immature and spent phases, while reaching their highest levels during the maturing and mature stages. The total amount of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA) was greater in mature ovaries compared to immature and maturing ovaries. Gene transcripts related to the production of steroids, specifically star, cyp11a1, cyp17a1 and hsd3b were expressed at low levels during the immature stage and showed a significant rise during the mature stage. The ovarian gene expression patterns during oogenesis exhibited distinct dissimilarities. The fatty acid content, essential for the development of fish ovaries, and the sex steroid hormonal profile, which play a key role in regulating oogenesis, are particularly significant. These results will enhance our comprehension of the reproductive biology and sustainable management of rainbow trout in their natural environment. Keywords : Rainbow trout Progesterone Estrogen Fatty acids Gene expression