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31.
Human ribosomal protein (RP) gene sequences with respect to intron/exon structures and corresponding cDNA or genomic data of fish species were obtained from the GenBank database. Based on conserved exon sequences, 128 primer pairs for 41 genes were designed for exon-primed intron-crossing (EPIC) polymerase chain reaction (PCR). In reference to the draft genome sequences of the Pacific bluefin tuna (Thunnus orientalis), 12 primer pairs expected to amplify introns of the bluefin tuna with lengths of 500–1000 bp were selected and applied to six distantly related fish species belonging to the Orders Clupeiformes, Tetraodontiformes, Pleuronectiformes, Perciformes, Scorpaeniformes, and Anguilliformes. PCR amplification was observed for at least four species in each primer pair, and all fragments were larger than those expected for intronless amplification. Single fragment amplification was observed for at least seven primer pairs per species. Fragment sizes of the bluefin tuna for nine primer pairs corresponded to those expected from the genomic data. Thus, our primer pairs are potentially applicable to a wide variety of fish species and serve as an initial step for isolating single-copy nuclear DNA sequences. 相似文献
32.
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
33.
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
34.
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
35.
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
36.
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
37.
Xiaowu LI Zhongjie LI Jiashou LIU Tanglin Zhang Chaowen Zhang 《Aquaculture International》2011,19(2):301-311
A 74-day growth trial was carried out to investigate the effects of light intensity on the juvenile Chinese mitten crab, Eriocheir sinensis, under semi-natural conditions. The experiment had three light intensity treatment groups, natural light (NL), middle light
(ML), and low light (LL), as light intensity became weaker. The results indicated that light intensity had no significant
effect on molting interval and molting frequency but did have a significant effect on the molting weight gain of the crab.
Molting weight gain in group NL was significantly higher than that in group LL (P < 0.05). Specific growth rate in weight (SGRw) and in carapace width (SGRcw), weight gain, and final body weight were significantly
affected by light intensity (P < 0.05). No significant difference was detected in survival between groups (P > 0.05). The precocious rate in groups NL, ML, and LL was 26.14, 15.48, and 17.14%, respectively. The precocious rate in
group NL was significantly higher than that in groups ML and LL (P < 0.05). Chemical composition of the crab body was significantly affected by light intensity, but the activity of alkaline
phosphatase, trypsin, and pancreatic lipase was not significantly affected by light intensity. The results indicated that
the submitted light intensity was useful in reducing the precocious rate without affecting the normal growth of juvenile E. sinensis. 相似文献
38.
Monosex male culture of C. quadricarinatus is proposed for increasing yields because males reach a larger size at harvest than females. An experiment was done to evaluate
the effects of androgenic gland extract and temperature on sex reversal and somatic growth in early juvenile females. Females
were exposed to the following experimental conditions: C: control food and temperature maintained at 26 ± 1°C; HT (high temperature):
control food and temperature maintained at 28.5 ± 1°C; VHT (very high temperature): control food and temperature maintained
at 31 ± 1°C; AG: food with enriched with androgenic gland (1/10 dose for each juvenile per day) and temperature maintained
at (26 ± 1)°C. The juveniles were weighed, sexed, and growth increment (GI) and growth rate (GR) were calculated twice a month.
The HT and AG groups differed from the C group in GI and GR indicating a greater somatic growth. At the end of the experiment,
the HT and AG groups had similar weight but only the HT group had enhanced oocyte diameter, with some vitellogenic oocytes
compared to the C group. In the HT group, there was significant sex reversal, as indicated by development of male and intersex
male characteristics in different individuals. Both temperature and AG diet have a high potential for culture of this species
because of their enhancement of somatic growth; higher temperature increases the proportion of males, a desirable characteristic
of cultured populations. 相似文献
39.
The ontogenetic development of the digestive enzymes amylase, lipase, trypsin, and alkaline phosphatase and the effect of
starvation in miiuy croaker Miichthys miiuy larvae were studied. The activities of these enzymes were detected prior to exogenous feeding, but their developmental patterns
differed remarkably. Trypsin activity continuously increased from 2 days after hatching (dah), peaked on 20 dah, and decreased
to 25 dah at weaning. Alkaline phosphatase activity oscillated at low levels within a small range after the first feeding
on 3 dah. In contrast, amylase and lipase activities followed the general developmental pattern that has been characterized
in fish larvae, with a succession of increases or decreases. Amylase, lipase, and trypsin activities generally started to
increase or decrease at transitions from endogenous to exogenous feeding or diet changes, suggesting that these enzymatic
activities can be modulated by feeding modes. The activities of all the enzymes remained stable from 25 dah onwards, coinciding
with the formation of gastric glands and pyloric caecum. These results imply that specific activities of these enzymes underwent
changes due to morphological and physiological modifications or diet shift during larval development but that they became
stable after the development of the digestive organs and associated glands was fully completed and the organs/glands functioned.
Trypsin and alkaline phosphatase were more sensitive to starvation than amylase and lipase because delayed feeding up to 2 days
after mouth opening was able to adversely affect their activities. Enzyme activities did not significantly differ among feeding
groups during endogenous feeding; however, all activities were remarkably reduced when delayed feeding was within 3 days
after mouth opening. Initiation of larvae feeding should occur within 2 days after mouth opening so that good growth and survival
can be obtained in the culture. 相似文献
40.