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    Melatonin Implantation in Preovulatory Rainbow Trout (Oncorhynchus mykiss) under Short Photoperiod Regime Reduces Egg Quality
    (Central Fisheries Research Inst, 2014) Sonmez, Adem Yavuz; Aydin, Ilhan; Hisar, Olcay; Kaya, Hasan; Hisar, Sukriye Aras
    As in other vertebrates, the pineal organ in salmonids receives photic information directly through specialized photoreceptor cells to synchronize both daily and seasonal behavioral and physiological events, including the reproductive. In this study, the effect of a melatonin implantation before the preovulatory period on egg quality was investigated in rainbow trout (Oncorhynchus mykiss) adults. Fish were exposed to two different lighting regimes [(constant short photoperiod (SP) of 6h light/18h dark) or natural photoperiod (NP) of 9h light/15h dark) with sub groups receiving a slow-release melatonin implant ((containing 9 mg melatonin hormone (MLT)) or sham implant. Melatonin implanted fish showed supraphysiological plasma MLT concentration during the 45 days after implantation. The spawning period started at the same time in all groups after implantation, although eggs were obtained from females exposed to SP lighting regimes only or SP lighting regimes plus implanted MLT exhibited significantly lower quality characterized by lower hatching rate and survival to first feeding than that of females expose to NP. In conclusion, it was determined that implantation of MLT in preovulatory rainbow trout females causes a decrease in egg quality. However, future investigations should be conducted to ascertain the MLT dose required for and time of implantation in rainbow trout.
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    The effects of elevated carbon dioxide and temperature levels on tilapia (Oreochromis mossambicus): Respiratory enzymes, blood pH and hematological parameters
    (Elsevier Science Bv, 2016) Kaya, Hasan; Hisar, Olcay; Yılmaz, Sevdan; Gurkan, Mert; Hisar, Sukriye Aras
    Oreochromis mossambicus were exposed to two different temperature and carbon dioxide partial pressure levels for about two weeks, as the ambient (Control; 25 degrees C, 3.3 mg/L CO2), high CO2 (25 degrees C, 14 mg/L CO2), high temperature (30 degrees C, 3 mg/L CO2) and combined (30 degrees C, 14.1 mg/L CO2) groups. No mortality was observed during the experiments. As a result of the study, elevated CO2 concentrations cause negative effects on the hematological parameters. At the end of the study, while the blood Carbonic Anhydrase (CA) activity, in the high CO2 group (25 degrees C, 14 mg/L CO2), statistically increased at the 7th day compared to the control group, it decreased at the 14th day (p<0.05). In addition, the blood CA activity, in the combined (30 degrees C, 14.1 mg/L CO2) group, showed a decrease at the 14th day compared to the control group (p<0.05). At the end of study, unlike the blood CA activity, gill, liver and kidney CA activity showed an increase in the tissues compared to the control groups (p<0.05). Furthermore, the Na+, K+-ATPase activities were stimulated significantly in the gills in both high CO2 and temperature groups at day 7, but it showed a significant amount of inhibition at the 14th day compared to the control groups. Overall, increasing carbon dioxide concentration in different temperatures has negative effects on the hematological parameters and respiratory enzyme of the tilapia fish. In addition, it is observed that the fish survive at negative conditions with adaptation mechanisms. (C) 2016 Elsevier B.V. All rights reserved.
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    The sexually dimorphic adipose fin is an androgen target tissue in the brown trout (Salmo trutta fario)
    (Springer, 2013) Hisar, Olcay; Sonmez, Adem Yavuz; Hisar, Sukriye Aras; Budak, Harun; Gultepe, Nejdet
    An investigation has been described on the relationship of body length, age and sex with adipose fin length and the number of androgen receptor (AR)-containing cells in the adipose fin as a secondary sexual characteristic for brown trout (Salmo trutta fario). Firstly, body and adipose fin lengths of 2- to 5-year-old brown trout were measured. Thereafter, these fish were killed by decapitation, then their sexes were determined, and adipose fins were excised. The cellular bases of AR binding activities in the adipose fins were analyzed with an antibody against human/rat AR peptide. Immunocytochemistry and western blotting techniques were performed with this antibody. Analysis of morphological measurements indicated that body length and age had a linear relationship with adipose fin length. The coefficients of determination for the body length and age were 0.92 and 0.85 in the male fish and 0.76 and 0.73 in the female fish against the adipose fin length, respectively. At 2 years of age, cells in the adipose fin did not exhibit AR immunoreactivity. However, AR-immunopositive cells were abundant in the adipose fin of 3- to 5-year-old fish. Moreover, the number of AR-immunopositive cells was significantly (P < 0.05) high in males and increased with age. These observations indicate that the adipose fin in the brown trout is a probable target for androgen action and that tissue function or development may to some extent be androgen dependent. In addition, it is likely that such an effect will be mediated by specific androgen receptors.