Masculinization of silver perch (bidyanus bidyanus mitchell 1838) by dietarysupplementation of 17 a-methyltestosterone

The aim of this research was to assess the possible use of dietary supplementation of 17a-methyltestosterone (MT), to produce all-male population of silver perch, Bidyanus bidyanus Mitchell 1838, as a step forward in producing neomales, which later can be used to produce an all-female population. Larvae were fed 17a-MT at various concentrations, viz. 0 (control), 9 and 18 mg/kg diet for the period of 30 days from 31 to 60 days post hatching (dph). Phenotypic sex ratios at 225 dph identified through histological examination revealed that MT significantly (P < 0.05) increases the male percentage from 59% to 100%. Testes of MT-fed fish were well developed, had a normal appearance at the same developmental stages to that of the control group. No significant differences (P > 0.05) in gonad weight (GW), gonad length (GL) and gonadosomatic index (GSI) among treatments which may indicate that the resulting neomales were viable. The MT supplementation did not influence the mortality rate, but significantly (P < 0.05) increased the final weight and specific growth rate (SGR). The study suggests that the dietary supplementation of MT at 9–18 mg/kg of the diet from 31 to 60 dph larvae is effectively in inducing masculinization in silver perch

Fish sperm motility assessment as a tool for aquaculture research, a historical approach

[EN] Fish sperm motility is nowadays considered the best biomarker for the quality of fish spermatozoa, and sperm motion parameters from more than 300 fish species have been reported in more than 1500 scientific articles covering a wide range of topics, from molecular biology to ecology. The most studied topics have been (i) the sperm storage (involving both the use of chilled¿storage protocols for short¿term periods and sperm cryopreservation techniques for long¿term storage), (ii) the sperm physiology (fathom in the spermatozoa activation process and the whole propulsion machinery of the sperm cells) and (iii) the broodstock management (covering aspects such as rearing conditions, dietary requirements or hormonal induction treatments). In addition, other aquaculture and ecological topics, such as (iv) the knowledge of the breeding cycle of the species, (v) the phenomenon of the sperm competition and (vi) ecotoxicological studies for the evaluation of aquatic environments, have also been approached from the evaluation of sperm motion performance. Therefore, fish sperm motility assessment can serve as a potential tool for aquaculture and ecological purposes, covering key topics of fundamental and applied research. This review gives an overview of the major research areas in which fish sperm motility has been applied successfully.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 642893 (IMPRESS). VG has a postdoc grant from the UPV (PAID-10-16).Gallego Albiach, V.; Asturiano Nemesio, JF. (2018). Fish sperm motility assessment as a tool for aquaculture research, a historical approach. Reviews in Aquaculture (Online). 1-28. https://doi.org/10.1111/raq.12253S12

Hybridization and its application in aquaculture

Inter‐specific hybrids are usually formed by mating two different species in the same genus. They have been produced to increase growth rate, improve production performance, transfer desirable traits, reduce unwanted reproduction, combine other valuable traits such as good flesh quality, disease resistance and increase environmental tolerances, better feed conversion, and increase harvesting rate in culture systems. Hybrids play a significant role in helping to increase aquaculture production of several species of freshwater and marine fishes – for example, hybrid catfish in Thailand, hybrid striped bass in the USA, hybrid tilapia in Israel, and hybrid characids in Venezuela. As the domestication of fish species increases, the possibilities to increase production through appropriate hybridization techniques are ongoing, with a view to produce new hybrid fishes, especially in culture systems where sterile fish may be preferred because of the concern that fish may escape into the open freshwater, marine and coastal environment. Intentional or accidental hybridization can lead to unexpected results in hybrid progeny, such as reduced viability and growth performances, loss of color pattern and flesh quality, and it also raises risks for maintenance of genetic integrity. Appropriate knowledge on the genetic constitution of the brood stock, proper brood stock management, and monitoring of the viability and fertility of the progeny of brood fishes, is thus very crucial before initiating hybridization experiments. In addition, some non‐generic factors, such as weather conditions, culture systems, seasons, and stresses associated with selecting, collecting, handling, breeding and rearing of brood stock and progeny, may influence hybridization success in a wide variety of freshwater and marine fin fishes to a greater extent

Induced gynogenesis in the silver barb (Puntius gonionotus Bleeker) and evidence for female homogamety

Diploid gynogenesis was induced experimentally in the silver barb (Puntius gonionotus) as the first step in a programme aimed at monosex female production. Sperm was exposed to ultraviolet light at a dose rate of 196 μWcm-2 for 0-32 min (0-376.3 mJcm-2), using a standard sperm concentration of 8 × 108ml-1. The optimal UV dose for producing haploid gynogenetics when such irradiated sperm was used to fertilise eggs was 1 min (11.8 mJcm-2). Diploidisation of the gynogenetic genome was achieved via temperature shocks. Cold shocks of 2 ± 0.1 °C for 10, 20 or 30 min or a heat shock of 40 ± 0.1 °C for 1.0 min were applied at various times after fertilisation (pre-shock incubation temperature 29 ± 1 °C). A maximum survival rate of 61.3% viable diploid gynogenetic offspring (relative to control) was obtained using a cold shock of 2 ± 0.1 °C for 10 min starting 1.5 min after fertilisation. A total of 268 diploid gynogenetic fry from ten different females were reared and sexed by histological examination of the gonads. With the exception of four undifferentiated fish, all of the gynogenetic fish were female, in contrast to the controls, which had a mean sex ratio of 54.6% female (which was not significantly different from 50% female). The implications of these results for monosex female production are discussed

Monosex female production in the silver barb (Puntius gonionotus Bleeker)

This paper describes hormonal masculinisation of genetically female, gynogenetic silver barbs (Puntius gonionotus) and the results of crosses between such neomales and ordinary females. Gynogenetic fish (previously shown to be all females) were used in trials on hormonal masculinisation to simplify assessment of the results. Treatment with 25 mg kg-1 17α-methyltestosterone in the diet for 4 or 5 weeks, starting at two weeks post-hatch, produced 33.9% and 29.8% males, respectively. The majority of crosses between such males and ordinary females gave all-female progeny, which supports the hypothesis of female homogamety and establishes that large-scale production of monosex females is feasible in this species. A growth trial comparing monosex female groups to mixed-sex groups in pond culture showed an increase in yield from the monosex groups. The implications of the results for commercial production of monosex female silver barbs are discussed