RESUMO
The ability of the anesthetics metomidate hydrochloride and tricaine methanesulfonate (MS-222) to mitigate the cortisol stress response of Channel Catfish Ictalurus punctatus was evaluated during a 10-min confinement stress. The cortisol concentrations of Channel Catfish anesthetized in metomidate hydrochloride remained consistent throughout the 10-min exposure; however, for fish anesthetized with MS-222 and nonanesthetized fish, cortisol concentrations were approximately 7- and 22-fold higher, respectively, than the baseline concentrations. While both anesthetics reduced cortisol concentrations relative to those of nonanesthetized fish, these results suggest that MS-222 is an appropriate anesthetic to use during the initial 5 min of sedation and that metomidate hydrochloride is appropriate for longer periods of sedation.
Assuntos
Aminobenzoatos/farmacologia , Etomidato/análogos & derivados , Hidrocortisona/sangue , Ictaluridae/metabolismo , Estresse Fisiológico/efeitos dos fármacos , Aminobenzoatos/efeitos adversos , Anestésicos/efeitos adversos , Anestésicos/farmacologia , Animais , Etomidato/efeitos adversos , Etomidato/farmacologia , Ictaluridae/sangueRESUMO
Sex-linkage of glucosephosphate isomerase-B (GPI-B) was observed in five experimental matings between heterozygous male and homozygous female channel catfish (Ictalurus punctatus). Offspring phenotypes for GPI-B were 40.8% heterozygous male and 43.0% homozygous female, while recombinant offspring were 7.4% homozygous male and 8.8% heterozygous female. Thus, GPI-B and the sex-determining gene (SDG) were linked and had a recombination rate of 16.2%. This linkage was designated I. punctatus linkage group XXIX. The gene-centromere distance (1.66 cM) of SDG, estimated in six gynogenetic families derived from XY females, indicated that SDG resides very close to the centromere. Based on estimates of these genetic distances, a chromosomal order of GPI-B-centromere-SDG was proposed. Additionally, joint segregation of GPI-A and SDG in two experimental matings indicated no genetic linkage between GPI-A and sex. These genetic relationships were compared to those reported in other teleost taxa with regard to evolutionary conservation of ancestral gene arrangements.
Assuntos
Genes Reguladores , Genes , Glucose-6-Fosfato Isomerase/genética , Ictaluridae/genética , Isoenzimas/genética , Análise para Determinação do Sexo , Cromossomo X/genética , Animais , Mapeamento Cromossômico/veterinária , Troca Genética , Transtornos do Desenvolvimento Sexual , Feminino , MasculinoRESUMO
In amniotes, the banded krait minor (Bkm) minisatellite (GATA), the human telometric sequence (TTAGGG)7, and the Y-specific genes, ZFY and SRY, are associated with a particular sex. These sequences were studied in the channel catfish, Ictalurus punctatus. However, none was sex-specific in catfish; homologs of each were present in males and females. Our data suggest that components of mammalian sex-determining systems may be widespread and shared among the vertebrates in general. Whether those components are involved in sex determination in lower vertebrates or merely represent evolutionary precursors of sex-determining factors in amniotes remains to be determined.
Assuntos
DNA/análise , DNA/genética , Ictaluridae/genética , Família Multigênica/genética , Análise para Determinação do Sexo , Telômero/química , Animais , Sequência de Bases , Evolução Biológica , Southern Blotting , Feminino , Masculino , Dados de Sequência Molecular , Reação em Cadeia da Polimerase , Homologia de Sequência do Ácido NucleicoRESUMO
Treatment of channel catfish with 0.2, 20, or 200 mg/liter of dihydrotestosterone (DHT) in the water during the egg stage or during egg and sac-fry stages did not alter the expected 1:1 sex ratio of the progeny. Feeding DHT at 200 mg/kg of feed for the first 21 days after yolk sac absorption resulted in 80% females; this proportion was increased by combining feeding with treatment of 200 mg DHT/liter in the sac-fry stage (90%) or in the egg and sac-fry stage (97%). In contrast, treatment of blue catfish sac-fry with 200 mg DHT/liter, with or without the combination of feeding DHT at 200 mg/kg food, resulted in 100% female populations. Neither clomiphene citrate, an estrogen-receptor blocking agent, nor clofibrate, an inhibitor of hepatic synthesis of cholesterol, affected the sex ratio of channel catfish, and neither of these compounds altered the feminizing effect of 200 mg DHT/kg when fed in combination with DHT. The nonaromatizable androgen DHT is not as effective as many other androgens in producing paradoxical female populations of channel catfish. However, feminization of blue catfish by treatment of sac-fry indicates that this species is more susceptible to hormonal manipulation and that the period of sex determination may occur earlier in development than in channel catfish.
Assuntos
Di-Hidrotestosterona/farmacologia , Ictaluridae/embriologia , Análise para Determinação do Sexo , Animais , Clomifeno/farmacologia , Feminino , Masculino , Ovário/embriologia , Razão de Masculinidade , Testículo/embriologiaRESUMO
The mechanism of sex determination in channel catfish Ictalurus punctatus was evaluated by hormonal and genetic methods. Aromatizable and nonaromatizable androgens, as well as an estrogen, caused feminization in fish fed steroids for 21 days after yolk-sac absorption. The effectiveness of 60 micrograms of ethynyltestosterone/g food decreased markedly when the experimental feeding period was shortened and was ineffective when the treatment lasted less than 12 days. Females from all-female populations produced by treatment with sex hormones were mated with normal males resulting in nine spawns with a sex ratio different from 1:1. The sex ratios were statistically similar to 3 male: 1 female in five spawns, both 2:1 and 3:1 in two spawns, and 2:1 in two spawns. These data are consistent with a model for female homogametic sex determination in channel catfish and suggest that the YY equivalent genotype is viable.