Aquaculture and Fisheries最新文献

Sex control techniques are in great demand for aquaculture because of the huge benefits of mono-sex production. In a previous study on yellow catfish (Tachysurus fulvidraco), intersex individuals were produced by administrating 17α-methyltestosterone (MT) or aromatase inhibitor letrozole (LZ). The ovarian and testicular portions of intersexual gonads developed well and were completely separated, arousing our interest in producing self-fertilizable fish and clone-like fish populations. In this study, yellow catfish fry were treated with a combination of MT and LZ at a low dose (5 mg kg⁻¹ MT, 300 mg kg⁻¹ LZ) at a low water temperature (27.0 °C, mixed sex-producing temperature, LL group) and a high temperature (33.5 °C, male-producing temperature, HL group), and with a high dose (10 mg kg⁻¹ MT, 600 mg kg⁻¹ LZ) at a low water temperature (LH group), during 12–65 days post-hatching, the critical period of sex differentiation. Both XX and XY intersex were produced with different percentages at the same time through co-treatment with MT and LZ, with or without the help of male-producing temperature. The highest percentage of XY intersex (53% in XY, 36% in XX and XY) and XX intersex (47% in XX, 25% in XX and XY) was produced in LH and HL groups, respectively. Results of gonadal morphology, histology, and sperm dynamic analysis indicate that some XX and XY intersex individuals were capable of self-fertilization through artificial insemination. The reproductive performance of these intersex individuals was then investigated by injecting spawning agents, dissecting gonads, and artificially fertilizing eggs with their own sperm. The XX, XY, and YY genotypic individuals were produced by the self-fertilization of XY intersex individuals. The present study successfully produced high percentages of XX and XY intersex and conducted self-fertilization by mating the eggs and sperm of a single intersex individual. Self-fertilization in fish will show great potential in aquaculture genetics and breeding, for example, generating highly homozygous (or ‘‘clonal’’) genetic material, producing mono-sex populations, and identifying unknown sex determination modes. In particular, the cloning method of producing genetic materials will be greatly beneficial for maintaining advantageous traits through self-fertilization generation after generation.

Occurrence of neurotoxic chemicals in the aquatic environment is on the rise posing a potential threat to aquatic biota including fish. In teleosts, zebrafish has become a popular model organism for toxicological studies and testing strategies. However, over the decade, siluriformes (catfish) are also finding ever increasing application being robust as well as their adaptability to adverse ecological conditions, surgical interventions, and tolerant models for toxicity studies and manipulations. Such information can infer potential effects occurring to other species exposed to neurotoxins in their aquatic environment and predicting potential risks of a chemical for the aquatic ecosystem. The aim of this review is to compare and interpret recent results published concerning neuro-behavioral and morphological disturbances caused by toxicants/pollutants providing a holistic view of potential neurotoxic outcomes in catfish. Overall, this review summarizes various effects of toxicants/pollutants in terms of neurotoxicity and neurodegeneration associated with behavioral phenotypes.

This review highlights the recent developments regarding neuroendocrine mechanisms controlling teleost reproduction. In teleosts, the pituitary gland receives major neuronal innervations from Gnrh neurons as well as minor innervations from small population of neurons that will secrete neurotransmitters and/or neuropeptides. The diversity of Kiss/Kissr system in various teleost species and their actions in the context of HPG axis and reproduction has been extensively covered. In teleost model systems, zebrafish and medaka, mutant lines for key components of the HPG axis have been generated through targeted mutagenesis but surprisingly most of the mutants developed normally without major defects in reproduction; these mutant phenotypes are described. In the last decade, complex role of diverse neuropeptides in teleost reproduction is being revealed. A brief overview about the reproductive functions of neuropeptides is presented. Finally, the effects of environmental factors namely photoperiodism and temperature on the functions of HPG axis is summarised.