In this study, we examined whether a homolog of the master sex-determining gene amhy of Odontesthes hatcheri is present and plays any role in testis determination of pejerrey O. bonariensis, a species otherwise known for its strong temperature-dependent sex determination (TSD). Screening of wild and laboratory-reared pejerrey for amhy revealed a high, although not complete linkage with phenotypic sex. The sex ratio in an amhy +/−/amhy −/− full sibling progeny reared during the thermolabile period of sex determination at an intermediate temperature of 25°C was 68.7% male:31.3% female; all amhy +/− fish developed as males whereas about 2/3 and 1/3 of the amhy −/− were female and male, respectively. Expression analyses revealed that amhy transcription began during embryo stage and decreased by the end of sex determination period. The autosomal amha was present in all individuals regardless of amhy genotype; its expression increased significantly from the end of the same period in the gonads of all amhy+ /− but only in part of the amhy− /− animals. After histological gonadal differentiation, all gonads of amhy −/− animals with amha ISH signals were testes and those without it were ovaries. These results suggest that amhy is important for testicular differentiation in pejerrey, at least at intermediate temperatures. Thus, we hypothesize that amhy +/− animals differentiate as males by expression of either amhy alone or amhy and amha together whereas the amhy −/− probably rely solely on amha expression. These findings represent the first clear genomic evidence that genotypic and environmental sex determinants can coexist in species with marked TSD such as the pejerrey. The finding of amhy will make possible to monitor wild pejerrey populations for mismatches between genotypic and phenotypic sex and may prove instrumental for field studies addressing the effects of endocrine disruptors or abnormal temperatures on reproduction and the ecological relevance of TSD for this species.

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Sex determination in pejerrey is genetically prescribed by the Y chromosome-linked anti-müllerian hormone amhy but is also strongly influenced by water temperature during the critical period of sex determination. Its gonadal differentiation is characterized by a cephalocaudal and left-to-right histological gradient in both sexes that presumably helps prevent discrepant intersex development in different regions of the gonads in response to ambiguous thermal and genetic stimuli, but the relation of this gradient to molecular processes of sex differentiation is unknown. In this study, we investigated the spatiotemporal expression patterns of amh, gonadal aromatase (cyp19a1a), and apoptosis in relation to the histological gradient in ovaries and testes at an intermediate, sexually neutral temperature. The location and timing of expression of amh, cyp19a1a, and apoptosis seemed to be highly coordinated with the time of gonadal sex differentiation and the histological gradient of gonadal sex differentiation. Apoptosis occurred predominantly in the anterior region of the right gonads and is surmised to be a process to delay differentiation in this area compared to the left gonad, possibly as a means to ensure uniform development in both gonads. Aromatase expression early during development was noted even in putative XY males, supporting the notion of primacy of female development in pejerrey gonads. Thus, apoptosis may be particularly important to prevent discrepant gonadal differentiation in XY individuals where genetic pro-male (amhy), pro-female (cyp19a1a), and thermal stimuli may antagonize.

Some problems in catfish culture are the spawning circle, female catfish begin to mature gonad at 10 months, and after 1,5 months can spawn again. The purpose of this study was to evaluate the process of accelerating maturation female mutiara catfish with the addition Estradiol-17? by oral treatments. The study was design used 3 treatments : 0 ml/kg feed, 0,4 ml/kg feed, 0,6 ml/kg feed with three individual replications. The result showed that the addition of Estradiol-17? significantly affected on reproductive performance : Gonado Somatic Index (GSI) 102,3% and eggs diameter 16,4% in female mutiara catfish compared with 0 ml/kg feed. Key words : Clarias gariepinus, Eggs Diameter, Estradiol-17ß, Gonadosomatic Index (GSI), Reproductive Performance.

One of the problems in North African Catfish (Clarias gariepinus) breeding is the inability to spawn spontaneously due to a specific spawning season. This happens due to reproductive dysfunction resulting in a slow development of gonads in catfish broodstock. This research aimed to study the effect of injection of pituitary gland extract from Striped Catfish head waste on the spawning performance of North Africans Catfish. This study used a completely randomized design (CRD) with 4 treatments and 3 replications. The treatments were A (pituitary gland 0 mg/kg broodstock), B (pituitary gland 200 mg/kg broodstock), C (pituitary gland 300 mg/kg broodstock), and D (pituitary gland 400 mg/kg broodstock). The spawning process was performed with a ratio of 1:1 between male and female broodstock. The pituitary gland was injected into the head of female catfish at 07:30 pm and at 04:00 am. The research parameters observed were relative fecundity, fertilization rate (FR), hatching rate (HR), and survival rate (SR). The results showed that injection of the pituitary gland from Striped Catfish head waste could increase spawning performance with relative fecundity reaching of 31,357±12,265 eggs/ kg of female broodstock, FR 65±4%, HR 74±14%, and SR 81±10%. Therefore, hypophysation by utilizing Striped Catfish head waste is effectively increases the spawning performance of North African Catfish (Clarias gariepinus) seen from the high values of relative fecundity, FR, HR, and SR of larvae in treatment B (200 mg/kg broodstock).