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51.
This paper explores the plasticity of sexually dimorphic characters in subadult female Brevimyrus niger, an African weakly electric mormyrid species. Thirty-five fish were exposed in a staggered fashion (five fish a week) to aromatizable 17α-methyltestosterone over a period of 7 weeks; 18 fish served as untreated controls. 17α-MT induced precocious vitellogenesis that mirrored the natural maturational process during seasonal ovarian recrudescence. At the same time, 17α-MT exposure resulted in complete masculinization of the females’ anal fin support structure normally observed during rainy season in adult males. We discuss possible hormonal mechanisms acting along the brain-pituitary-gonad axis that would explain the occurrence of precocious vitellogenesis and the male-typical transformation of the female’s anal fin ray bases. Our findings are relevant to commercial aquaculture as the use of 17α-MT in fish hatcheries can pose serious environmental issues. 相似文献
52.
Fumitaka Kondo Takashi Ohta Toshiharu Iwai Atsushi Ido Chiemi Miura Takeshi Miura 《Fish physiology and biochemistry》2017,43(6):1543-1555
The improvement in feed efficiency is one of the most important subjects in fish culture. The development of feed, in terms of good intake, high growth performance, and high feed efficiency is needed. Squid viscera are one of the candidates for alternative material in improving feed efficiency in fish culture. In the present study, we described the dietary effect of the squid viscera hydrolysate (SVH) on the growth performance of the red sea bream. The addition of SVH to feed caused significant increases in feed intake, fork length, and body weight and produced a marked improvement in feed conversion after 4 weeks of feeding. Furthermore, the results of this feeding revealed that low dietary levels of SVH promote growth performance in the red sea bream. We physiologically analyzed digestion and appetite in fish fed diet containing SVH. SVH promoted the activity of hepatic trypsin and lipase, gene expression of stomach pepsin, hepatic lipase, and pyloric caeca trypsin, thereby improving the nutrient availability in red sea bream. Moreover, the mRNA expression of appetite regulating factor, such as brain NPY and stomach ghrelin was significantly improved by dietary SVH. Our current results indicate that dietary SVH as alternative material produced excellent effects on growth performance, which is dependent on the promoting effect on digestion and appetite in red sea bream. 相似文献
53.
Suzu Sakao Takafumi Fujimoto Terumasa Kobayashi Goro Yoshizaki Etsuro Yamaha Katsutoshi Arai 《Fisheries Science》2009,75(4):993-1000
Diploid gametes generated with tetraploid animals are a stepping stone to improving chromosome manipulation techniques. However,
artificially induced tetraploid individuals generally die soon after hatching. Diploid gametes could be induced by in vivo
cultures of tetraploid primordial germ cells (PGCs) through germ-line chimera. In the present study, characteristics of PGCs
were studied in inviable tetraploid masu salmon, Oncorhynchus masou. Histological observation of tetraploid embryos revealed that the same or smaller numbers of PGCs were observed and they
migrate into the genital ridges as did diploid PGCs during gonadogenesis. By whole-mount in situ hybridization using vasa messenger RNA (mRNA), 4–35 vasa-positive signals were detected in a pair of genital ridges of tetraploids. By cytological
observation of genital ridge cell suspensions, several large round cells were observed, some of which extended pseudopodia.
They also contained large nuclei and round granules in their cytoplasm, characteristics of PGCs. As the results suggest that
inviable artificial tetraploids have PGCs, we expect to achieve diploid gamete production through surrogate propagation and
tetraploid fish production. 相似文献
54.
Thermal inactivation of Ca2+ ATPase of squid myofibrils was significantly suppressed in the presence of Ca2+. Monomeric myosin content decreased much faster than Ca2+ ATPase inactivation in Ca medium, which was well explained by fast rod denaturation. In contrast, rod denaturation was slower
than S-1 in EDTA medium. The decrease in monomeric myosin content was explained by faster S-1 denaturation. Comparing the
S-1 and rod denaturation rates at a fixed temperature, it was concluded that S-1 denaturation was suppressed by Ca2+ whereas the rod denaturation was not. An unfolding experiment with isolated myosin rod confirmed that there was no stabilizing
effect of Ca2+ on myosin rod. It was concluded that significant stabilization of the S-1 portion by Ca2+ generated the apparently different myosin denaturation patterns in the two media. 相似文献
55.
The relative efficacies of three natural estrogens viz., estrone (E1), estradiol-17β (E2) and estriol (E3) to induce synthesis of vitellogenin (Vg) and choriogenin (Chg) were assessed in primary hepatocyte cultures of the Indian
freshwater spotted snakehead, Channa punctata. Hepatocytes were isolated from the spotted snakehead liver by a non-enzymatic protocol. Optimum culture conditions were
standardized for ensuring their viability and functioning. Isolated hepatocytes were cultured for 48 h for monolayer formation
and then exposed to various concentrations (0.001–10 μM) of the three estrogens. Competitive homologous ELISAs, developed
and validated for spotted snakehead Vg and Chg were employed to determine the amounts of these two proteins secreted into
the culture medium after 48 h of incubation. The results reveal that although all the three estrogens were effective in inducing
the production of Vg and Chg in a dose-dependent manner, there were differences in their relative potencies. Of three estrogens,
E1 was the least potent and could induce synthesis of Vg and Chg only at a minimum concentration of 0.5 μM; whereas significant
levels of both the proteins were quantified in culture medium by exposing the hepatocytes to E2 or E3 even at a concentration of 0.001 μM. All three estrogens were effective in inducing synthesis of Vg and Chg in vivo also.
These results suggest the possibility of employing the above in vitro experimental design to monitor the presence of estrogens/estrogen-like
chemicals in natural waters, which could interfere with the estrogen receptor system of fish. This study further points to
the possibility of using Chg, in addition to Vg, as a parameter for screening various chemicals for their estrogenic activity. 相似文献
56.
ABSTRACT: Hermatypic (reef-building) corals harbor dinoflagellate endo-symbionts Symbiodinium spp. In studying gene expression in such symbiotic corals, problems arise regarding how to distinguish the coral and symbiont mRNA, and how to estimate their fractions in the mRNA population of the holobiont (symbiotic complex of the coral and Symbiodinium cells). In this study, these issues were addressed using juveniles of hermatypic coral Acropora tenuis in symbiosis with Symbiodinium cells of strain PL-TS-1. First, the guanine-cytosine (GC) contents were determined in expressed sequence tags (EST) from PL-TS-1 cells cultured in vitro and symbiont-free larvae of A. tenuis , and their average GC contents were found to be significantly different. The average GC content of the EST from the holobiont was much closer to that of A. tenuis larvae, suggesting that the majority (>90%) of mRNA isolated from the holobiont originated in the host. In protein-coding sequences, little overlap was observed between the GC-content distributions of PL-TS-1 cells and A. tenuis larvae. All of the coding sequences ( n = 59) found in the A. tenuis EST had GC contents below 0.5, whereas the GC content exceeded 0.5 in the majority (43/44) of coding sequences from the nuclear genome of PL-TS-1 cells. 相似文献
57.
Microsatellites have become the preferred molecular markers for strain selection and genetic breeding in fish. In this study
a total of 105 microsatellites were isolated and identified in gibel carp (Carassius auratus gibelio) by microsatellite sequence searches in GenBank and other databases and by screening and sequencing of positive clones from
the genomic library enriched for AG and GATA repeats. Moreover, nineteen microsatellites were randomly selected to design
locus-specific primer pairs, and these were successfully used to identify and discriminate different cultured strains of gibel
carp including strains A, D, L, and F. Three different types of microsatellite pattern were distinguished by the number and
length of fragments amplified from the 19 primer pairs, and some microsatellite primer pairs were found to produce different
microsatellite patterns among strains and strain-specific fragments. In addition, some duplicated alleles were also detected
in two microsatellite patterns. Therefore, the current study provides direct molecular markers to discriminate among different
cultured strains for selective breeding and aquaculture practice of gibel carp. 相似文献
58.
Interannual variations in abundance, timing of outmigration from rivers, growth rate and condition of juvenile chum salmon
(Oncorhynchus keta) were studied in the Nemuro Strait (eastern Hokkaido, Japan) during 1999–2002 to establish a possible relationship to zooplankton
abundance. The otolith microstructure of juveniles was examined each year in late June to determine their time and size at
sea entry (i.e., outmigration), and to estimate the early marine growth rates. Salmon outmigration peaked in mid- or late
May, which coincided, in three of the four study years, with the peak release of juveniles into rivers within the study area.
Abundance, growth rate and condition of fish were higher in 2001, when—compared to other years—smaller fish experienced higher
growth rates, coinciding with greater zooplankton abundance for that year. Our results suggest that high zooplankton abundance
positively influenced juvenile chum salmon growth and the condition of the fish during their early marine life despite their
small size at sea entry. 相似文献
59.
To standardize conditions during the final maturation and ovulation of ovarian follicles from Japanese eel, we have developed
a culture system for the production of fertilizable eggs from post-vitellogenic ovarian follicles in vitro. Post-vitellogenic
ovarian follicles were incubated in culture medium supplemented with 17α,20β-dihydroxy-4-pregnen-3-one (DHP) with or without
bovine serum albumin (BSA) to assess the effects of protein concentration. Eggs that ovulated during incubation were fertilized,
and the remaining follicles were incubated in prostaglandin F2α (PGF2α) for a further 3 or 6 h before fertilization. Male eels were injected repeatedly with human chorionic gonadotropin. The quality
of eggs obtained under the different culture conditions was evaluated after artificial fertilization in terms of hatching
success. Hatching rates tended to decrease with increasing concentrations of BSA in the incubation medium in a dose-dependent
manner. The addition of PGF2α drastically increased the number of eggs that ovulated, but the rate of hatching was greatly decreased compared with eggs
obtained earlier by DHP incubation alone. The larvae obtained from artificially fertilized eggs produced in vitro survived
for 14 days without feeding. We conclude that in vitro culture systems thus have a great potential for the acquisition of
good quality eggs under tightly controlled artificial conditions, culminating in the production of eel larvae. 相似文献
60.
Shiwei Xie Lixia Tian Jin Niu Guiying Liang Yongjian Liu 《Fish physiology and biochemistry》2017,43(4):1011-1020
An 8-week feeding trial was conducted to evaluate the effect of N-acetyl cysteine (NAC) and glycine supplementation on growth performance, glutathione (GSH) synthesis, and antioxidative ability of grass carp, Ctenopharyngodon idella. Four practical diets were formulated: control, control + 0.2% NAC, control + 0.5% glycine, and control + 0.2% NAC + 0.5% glycine. Each diet was randomly assigned to quadruplicate groups of 30 fish (approximately 8.8 g). Weight gain and specific growth rate were significantly increased with the supplementation of NAC. Supplementation of NAC plus glycine significantly increased the feed efficiency. Glutathione peroxidase (GPx) and γ-glutamine cysteine synthase (γ-GCS) in plasma were significantly increased with the supplementation of NAC plus glycine. GSH in plasma increased and malondialdehyde (MDA) decreased in fish fed diets supplemented with NAC. Respiratory burst, superoxide dismutase (SOD), and catalase (CAT) activity were not affected by NAC or glycine. These results clearly indicated that NAC improved the growth performance and restored GSH of grass carp, supplemented NAC together with glycine enhanced GSH synthesis, and improved the antioxidative ability of grass carp. 相似文献