Effects of GnRH and the dual regulatory actions of GnIH in the pituitary explants and brain slices of Astyanax altiparanae males.

The pituitary gonadotropins, Fsh (follicle-stimulating hormone) and Lh (luteinizing hormone), regulate testicular development and functions in all vertebrates. At the pituitary, different signaling systems regulate the synthesis and secretion of the gonadotropins, such as the hypothalamic neuropeptides GnRH (gonadotropin-releasing hormone) and GnIH (gonadotropin-inhibitory hormone). While GnRH exerts stimulatory roles, the actions of GnIH remain controversial for many teleost species. Therefore, the aim of this study was to evaluate the in vitro effects of chicken GnRH2 (cGnRH2) and zebrafish GnIH-3 (zGnIH-3) on the male gonadotropin and GnRH system expression using pituitary explants and brain slices from a neotropical species with economical and ecological relevance, Astyanax altiparanae. Our results showed that in males, cGnRH2 increased fshb and lhb mRNA levels in the pituitary explants. Interestingly, zGnIH-3 has no effect on basal gonadotropin expression, however zGnIH-3 decreased the cGnRH2-induced fshb and lhb transcripts in male pituitary explants. In the male brain slices, zGnIH-3 showed stimulatory effects, increasing gnrh2 mRNA levels. Overall, our results suggested that GnIH seems to have dual regulatory actions on gonadotropin and GnRH2 expression of A. altiparanae males. This study provided basic information on endocrine regulation of A. altiparanae reproduction, and the obtained results will expand our knowledge, improving the reproductive management of this economically important freshwater species.

Time-efficient germ cell transplantation from goldfish (Carassius auratus) into adult common carp (Cyprinus carpio).

Germ cell transplantation in fish is a promising technique for surrogate broodstock parents with broader application in aquaculture and conserving endangered and valuable genetic resources. Herein, we describe the establishment of an intrapapillary xenogeneic transplant of germ cells from sexually mature goldfish (C. auratus) males into common carp (C. carpio) males cytoablated with a thermochemical treatment (two doses of busulfan at 40 mg/kg at 35°C). To analyze the presence and development of donor germ cells in recipient testes, donor germ cells were labeled with PKH26, a fluorescent cell membrane dye, before transplantation. Our results demonstrated that thermochemical treatment caused effective spermatogenesis suppression and pronounced germ cell loss. Moreover, transplanted spermatogonial cells were able to colonize the recipients' testes, resume spermatogenesis, and generate spermatozoa within eight weeks after germ cell transplantation. These findings suggested that recipient testes provided suitable conditions for the survival, colonization, proliferation, and differentiation of donor spermatogonia from a related species. This study indicated that recipients' testes exhibited a high degree of plasticity to accept and support xenogeneic donor germ cells, which were able to form sperm in a short time frame. This approach has significant implications for assisted animal reproduction, biotechnology, conservation, and the production of valuable genetic resources and endangered fish species.

Cooling of pacu (Piaractus mesopotamicus) embryos at various stages of development for 6 or 10 hours.

The objective of this research was to verify the effects of cooling embryos of pacu, Piaractus mesopotamicus, in four stages of development during two stocking periods. The stages of embryo development were at: blastoderm, ∼ 64 cells-1.4 h after fertilization (haf); 25% of the epiboly movement--5.2 haf; blastoporous closing--8.0 haf; and optical vesicle appearing--13.3 haf. Embryos were exposed to a cryoprotectant solution containing methanol (10%) and sucrose (0.5 M). Thereafter, embryos were submitted to a cooling curve until they reached -8 °C, and then kept cooled for 6 or 10 h. In addition, for each stage of embryonic development, a control group with uncooled embryos was used to compare hatching rates. The total number of larvae from the first two stages of ontogenetic development (1.4 and 5.2 haf) was lower compared to the other stages (0.0 and 8.0 haf). There was no significant difference between stages 8.0 and 13.3 haf for the total number of larvae (49.9 ± 6.7% and 55.2 ± 6.7%, respectively). Embryo diameter varied according to embryonic stage, providing evidence of differences in membrane permeability. There was a negative correlation between embryo diameter and the total number of larvae (r = -0.372). In conclusion, use of embryonic stages 8.0 and 13.3 haf were recommended for maintaining cooled pacu embryos at -8 °C for 6 or 10 h.

[Ectoparasites of the Nile tilapia (Oreochromis niloticus) bred in net-tanks in the Corvo and Guairacá rivers, state of Paraná, Brazil]. / Ectoparasitos de tilápia do Nilo (Oreochromis niloticus) cultivados em tanques-rede nos rios do corvo e Guairacá, Paraná, Brasil.

Current experiment estimates the prevalence of ectoparasites of the Nile s tilapia (Oreochromis niloticus), strain Chitralada, bred in net-tanks during 130 days, from April to August 2006, and reports on the water's physical and chemical parameters. Three hundred and eighty-seven samples of tegumentary scrapes and branchia of post-reversed males were analyzed. Experiment was conducted in thirty 6.8 m-3 net-tanks (2.0m x 2.0m x 1.7m), filled with 6.0 m-3 water, of which 15 were placed in the Corvo river and 15 in the Guairacá river, with three stocking densities (100, 150, 200 fish per m-3) and five repetitions each. At the start of experiment, total ectoparasites prevalence in 105 fish, average weight 35.4 +/- 19.3g and total length 11.7 +/- 2.1cm, was 87.6%. Prevalence was higher for Monogenoidea (40.0%), followed by mixed parasitism (33.3%) and Tricodinids (14.3%). Whereas in the Corvo river total ectoparasites prevalence in the four collections reached 38.2%, with predominance for Monogenoidea (19.4%), in the Guairacá river prevalence reached 44.2%, with predominance for Tricodinids (17.4%). Water's physical and chemical parameters, with the exception of temperature, fitted conditions for Nile s tilapia breeding.

Características qualitativas do sêmen de pacu (Piaractus mesopotamicus) após indução hormonal / The semen qualitative characteristics and spermatozoa life time ofo pacu (Piaractus mesopotamicus) after hormonal induction

Parâmetros qualitativos do sêmen de 44 Piaractus mesopotamicus foram analisados com e sem a indução reprodutiva com extrato de hipófise de carpa. Não ocorreu diferença (P>0,05) para a motilidade progressiva e vigor espermático entre os tratamentos, muito embora tenha ocorrido uma tendência de médias maior para o sêmen oriundo de animais induzidos, 79,5 por cento e 3,7 pontos contra 73,5 por cento e 3,5 pontos respectivamente. O tempo de vida dos espermatozóides também não apresentou diferença (P>0,05) para o sêmen analisado com e sem indução hormonal 50,3 e 52,4 segundos, respectivamente. Não houve diferença (P>0,05) no sêmen analisado de pacus induzidos e não induzidos, para porcentagem de espermatozóides normais (58,2 e 62,6) com patologias leves (12,9 e 12,1) e graves (28,9 e 25,3). Os tipos de patologias mais incidentes, tanto no sêmen de animais induzidos e não induzidos, foram cauda quebrada e enrolada, sendo os dois tipos graves. Através dos resultados conclui-se que a indução hormonal com extrato de hipófise de carpa, não causou alterações significativas para os parâmetros qualitativos avaliados. Porém, ficou constatado a incidência elevada de patologias graves no sêmen de pacu, especialmente, cauda enrolada, quebrada e corrugada.

Qualitative parameters of 44 Piaractus mesopotamicus semen were analyzed with and without reproductive induction using hypophysis extract obtained from carp. There was no difference (P>0.05) in what concerns both the progressive motility and the spermatic vigor between the treatments, although there was a tendency of greater medians for the semen of induced animals, 79.5 per cent and 3.7 points against 73.5 per cent and 3.5 points, respectively. The spermatozoa’s life time did not show any difference as well (P>0.05) for the semen analyzed with and without hormonal induction during 50.3 and 52.3 seconds, respectively. There was no difference (P>0.05) in the analyzed semen of either the induced or not induced pacu fish, considering the percentage of normal spermatozoa (58.2 and 62.6) with secondary pathologies (12.9 and 12.1) and with primary pathologies (28.9 and 25.3). The most incident primary types of pathologies in the semen of both the induced and not induced animals were broken and coiled tail. Based on the results it can be concluded that the hormonal induction with hypophysis extract obtained from carp did not cause any significant changes for the qualitative parameters evaluated. However, a high incidence of primary pathologies was observed in the pacu’s semen, mainly crooked, bent and coiled tail.