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1.
Abstract  Methods for improving spawning habitat for lakeshore spawning kokanee, Oncorhynchus nerka (Walbaum), were explored by quantifying incubation success of embryos exposed to three substrate treatments in Lake Pend Oreille, Idaho, USA. Substrate treatments included no modification that used existing gravels in the lake (EXISTING), a cleaned substrate treatment where existing gravels were sifted in the water column to remove silt (CLEANED) and the addition of new, silt-free gravel (ADDED). Incubation success was evaluated using Whitlock–Vibert incubation boxes buried within each substrate treatment that contained recently fertilised embryos. Upon retrieval, live and dead sac fry and eyed eggs were enumerated to determine incubation success (sac fry and eyed eggs × 100/number of fertilised embryos). Incubation success varied significantly among locations and redd treatments. In general, incubation success among ADDED redds (0.0–13.0%) was significantly lower than that for EXISTING (1.4–61.0%) and CLEANED (0.4–62.5%) redds. Adding new gravel to spawning areas changed the morphometry of the gravel-water interface and probably exposed embryos to disturbance from wave action and reduced embryo survival. Moreover, efforts to improve spawning habitat for lakeshore spawning kokanee should consider water depth and location (e.g. protected shorelines) as important variables. Adding clean gravel to existing spawning areas may provide little benefit if water depth or lake-bottom morphometry are altered.  相似文献   

2.
Highly ploidy polymorphism was detected in embryos of inter-subfamily hybridization by a cross of Megalobrama amblycephala ♀ × Tinca tinca ♂. It produced an average of 23% haploids, 46.4% aneuploids, 24.6% 2n hybrid, 2.8% 3n hybrid, 3.2% hypo-4n, which are all inviable, and also a small number of viable 2n gynogens. However, different results were found in the reciprocal hybridization by T. tinca ♀ × M. amblycephala ♂. An average of 89.1% embryos were 2n hybrids with 48 chromosomes and 6% and 2.8% of embryos were aneuploids and allo-triploids, respectively. Additionally, a proper ratio of spontaneously complete tetraploidy embryos (about 2%) was able to be induced in the reciprocal hybridization. 50% of reciprocal hybrid embryos developed normally and 30% of the normal fry survived. Ploidy polymorphism (2n, 3n, 4n or 4n mosaics) and morphological variation were identified in 120-day survival of juveniles in the reciprocal hybridization.  相似文献   

3.
Triploid hybrid saugeyes may be a desirable stocking alternative because diploid saugeyes are fertile and can compromise the genetic integrity of parental stocks. Four groups of saugeye eggs were heat-shocked 5 min after fertilization for 15 min at 31 °C, which resulted in an 86.7 ± 9.4% triploidy rate and 57.8 ± 24.3% survival to the eyed-stage. Heat shocked and control saugeyes were stocked in two ponds for 40 days at 395 000 ind. ha–1. Mean length and weight of triploid and heat-shocked diploid saugeyes were greater ( P  < 0.01) than unshocked diploid saugeyes. Survival of heat-shocked saugeyes (22.4%) was lower than unshocked saugeyes (94.7%). Heat-shocked fish ( n =25 851) harvested from ponds were stocked for 153 days in O'Shaughnessy Reservoir, Ohio, USA. Triploids were 34 mm shorter and weighed 41 g less than heat-shocked diploids ( P  < 0.01). Mean length and weight of triploids were comparable with unshocked diploids elsewhere in Ohio.  相似文献   

4.
ABSTRACT:   Mottled amago salmon Oncorhynchus masou ishikawe with both yellow- and dark-pigmented skin occurred together with typical albino individuals in a commercial farm. Out of 12 mottled fish examined by DNA content flow-cytometry and erythrocytic nucleus size, three were diploid, eight were haploid-diploid mosaic and one was diploid-triploid mosaic. This fact indicates that the mottled coloration might link to polyploid mosaicism. Genotype of diploid and non-diploid cells at the albino locus was estimated in nine mature mottled fish by observing the frequency of wild-type and albino progeny when mating to homozygous albino ( aa ). One diploid and three haploid-diploid mosaic mottled fish were presumed to have mosaic genotype with both hemizygous ' a ' and heterozygous ' Aa ' cells ( a/Aa ), because the segregation ratio between two phenotypes was 1 : 1. Three other haploid-diploid mosaic fish were presumed to have mosaic genotype with both hemizygous ' a ' and homozygous ' AA ' cells ( a/AA ), because of exclusive occurrence of wild-type phenotype in the progeny. The diploid-triploid mosaic mottled fish was presumed to have mosaic genotypes ' aa / AAA ', ' aa/AAa ' or ' aa / Aaa ', because this fish yielded only albino progeny. One diploid mottled fish produced both two phenotypes but albino embryos appeared with much more frequency than the expectation, when assuming the genotype ' Aa '. Thus, this fish was considered to have mosaic genotype ' Aa/aa '.  相似文献   

5.
Suppression of cell division causes chromosome set doubling. Some chemical agents or physical shocks such as temperature or hydrostatic pressure are effective tools for suppression of cell division. As spindles are obviously inactivated or disorganized by these treatments, it has been supposed that inactivation or disassembly of spindles blocks the anaphase movement of chromosomes and a duplicated nucleus is formed without cell division. The present study demonstrated that hydrostatic pressure treatment (650 kg/cm2 for 6 min) around the time of metaphase of the first cell cycle of the rainbow trout embryos did not suppress the first cleavage but the second one. Spindles disassembled by the hydrostatic pressure or heat shock regenerated soon after treatment, resulting in the occurrence of the first mitosis. Interestingly, a monopolar spindle was assembled in each blastomere in the second cell cycle, and disjunction of duplicated chromosomes and the cleavage was prevented, leading to the chromosome set doubling. From the third cell cycle, normal cell division resumed. No significant difference was found between the area of the nucleus plate of the treated embryos and twice the area of the nucleus plate of control embryos in the third cell cycle, meaning that the chromosome sets had been doubled at the end of the second cell cycle. The process of chromosome set doubling caused by heat shock seemed to be fundamentally the same as that caused by hydrostatic pressure. To the best of our knowledge, this is the first time that the mechanism of chromosome set doubling in animal eggs treated with hydrostatic-pressure or heat shock has been clarified.

Haploid–diploid or diploid–tetraploid mosaics sometimes occur among individuals treated for cleavage inhibition. The mechanism of such occurrence of mosaicism is, however, not clear. In this study, we found interesting two-cell stage embryos, which had a monopolar spindle in one blastomere and a bipolar spindle in the other during the second mitosis in a batch subjected to tetraploidization treatment. These embryos have a high potential of developing diploid–tetraploid mosaics. This paper also discusses the mechanism of occurrence of these aberrant embryos and discusses their relationship to diploid–tetraploid mosaicism.  相似文献   


6.
To evaluate the effect of salinity on the hatching rate, hatching time, survival percentage, osmoregulation pattern and the incidence of abnormalities in newly hatched larvae, embryos of Sphoeroides annulatus (Jenyns 1842) were exposed to 5, 12, 19, 26, 33, 35 and 40 psu. The hatching percentage (HP), survival percentage (PS), normal larvae (PN), deformed larvae (PD) and hatching time (HT) were significantly affected by salinity (P < 0.05). The embryos exposure to 5 psu caused that HP, PS, and PN had lower values (2.6 ± 0.32, 7.78 ± 0.88 and 70.37 ± 7.75% respectively), PD and HT had the highest values 26.67 ± 7.54% and 55.53 ± 0.59 h respectively. However, the survival of newly hatched larvae was not possible in 5 ups, though it was in 40 ups. Osmotic pressure (OP) remained constant in each salinity, whereas isosmotic points changed from 435.5 mOsm kg?1 in 21 h post fertilization to 342.8 mOsm kg?1 at 47 h post fertilization, obtaining a pattern of hyper‐osmoregulation at lower salinities and hypo‐osmoregulation in higher salinities. This study is the first carried out on embryos of this species; therefore, the obtained information is essential to improve strategies and growing conditions in their initial development.  相似文献   

7.
Triploid fish are increasingly used in aquaculture because they are generally unable to reproduce successfully. Energy is channeled into somatic growth rather than gonadal development, and in the event of escape, the animals are unlikely to breed successfully among themselves or with wild conspecifics. This study tested the ability of recently matured triploid African catfish (Clarias gariepinus) to produce and fertilize eggs with and without ovaprim treatment. Triploid females did not show the increase in ovary size observed in diploid members of the same cohort between 8 and 9 months of age, or the coincident decrease in visceral fat deposits, and this was unaffected by up to 5 weekly i.m. injections of 0.5 ml kg−1 Ovaprim. However, we observed advanced vitellogenin (Vtg) sequestration in oocytes of triploid females, albeit to a lesser degree and with lesser cortical alveoli, compared to oocytes from diploid cohort members. Histological sections revealed a positive trend of oocyte development up to the third weekly ovaprim injection followed by a negative gonadal development in weeks four and five. Milt from triploid males injected 9–12 h earlier with 0.25 ml kg−1 ovaprim i.m. fertilized more diploid eggs than milt from untreated triploid males (30 vs. 20%), but none of the developing embryos of triploid paternity survived to hatch. In contrast, milt of diploid males fertilized 49% of eggs, and 20% of the developing embryos hatched successfully. These rates were improved in ovaprim-injected diploid males to 70% fertilization and 33% hatch. This study demonstrates potential of overcoming non-viability of eggs from triploid female African catfish, and enhancing the ability of triploid milt to fertilize eggs.  相似文献   

8.
Gynogenetic diploids were induced in the loach, Misgurnus anguillicaudatus, by applying cold shock to the egg after fertilization with spermatozoa genetically inactivated by ultraviolet-ray irradiation, to examine their survival, growth and fertility. Eggs were obtained from orange phenotype loach (homozygous for a recessive demelanogenesis gene). Spermatozoa were obtained from black phenotype loach (homozygous for a dominant melanogenesis gene), and from common carp, Cyprinus carpio. All hybrids between loach and carp were inviably abnormal.Eggs fertilized with loach or carp spermatozoa irradiated at doses of 6000 and 12000 erg/mm 2 and then treated with cold water (1°C for one hour 4 and 5 min after fertilization developed into embryos with 61–78% survival. About 70–87% of newly-hatched fry were normal in appearance. Gynogenetic fish induced by both loach and carp spermatozoa showed lower rates of survival and growth than did the normal diploid controls. All gynogenetic fish from carp spermatozoa were female and 94.9% of the gynogenetic fish from loach spermatozoa were female. The second gynogenetic offsprings were produced from females selected from both gynogenetic groups.  相似文献   

9.
Abstract – In past dietary studies kokanee Oncorhynchus nerka were prominent in the diet of Pend Oreille Lake's large piscivores: native bull trout Salvelinus confluentus, cutthroat trout O. clarki and northern pikeminnow Ptychocheilus oregonensis, and introduced lake trout S. namaycush and Kamloops rainbow trout O. mykiss gairdneri. However, kokanee have declined to 10–20% of their former abundance. We therefore initiated this study to understand current predation demands on kokanee and diet overlap among piscivores, using gut content samples and analysis of stable nitrogen (δ15N) and carbon (δ13C) isotopes from the lake's fish and invertebrate community. In gut content samples, kokanee were the main prey item of large [i.e., ≥400 mm total length (TL)] bull and lake trout; a conclusion that was affirmed by stable isotope analysis. Rainbow trout >500 mm TL consumed mostly kokanee, thus there was a high degree of diet overlap among large bull, lake and rainbow trout. Small (i.e., <400 mm TL) rainbow and cutthroat trout diets overlapped, and were composed mostly of littoral benthic invertebrates. However, gut content and stable isotope analysis did not accord for 400–500 mm TL rainbow trout, small lake trout, and large cutthroat trout. In these instances, a linear mixing model using stable isotope results predicted kokanee consumption for each species, but no kokanee were identified in rainbow or lake trout gut content. Gut content and stable isotope analysis of native northern pikeminnow indicated a diet of mostly littoral benthic invertebrates at smaller (100–150 mm TL) lengths, with kokanee becoming more prominent in the diet of individuals >300 mm TL. Percent of kokanee in the diet of northern pikeminnow has declined from a prior study; otherwise piscivore diets have apparently remained unchanged. In this study, judgments as to the feeding of some piscvores, based on gut content alone, would be tenuous because of small sample sizes, but stable isotope analysis provided an efficient means for confirming diets.  相似文献   

10.
ABSTRACT:   To elucidate the utilization of the major yolk nutrient stocks in eggs and larvae of walleye pollock Theragra chalcogramma , the contents of free amino acids (FAA), the major yolk protein (180 kDa lipovitellin originated from vitellogenin B in ovulated eggs: oLv B), and lipids were measured. Most eggs hatched 18 days after fertilization at 5°C, and all larvae absorbed almost all their yolk mass by 28 days. The total FAA content showed no change during the first 6 days, and then decreased to 28% of the initial level by 18 days. The oLv B contents, measured by an enzyme-linked immunosorbent assay using a specific antiserum against oLv B, gradually decreased from 6 to 18 days, followed by a rapid decline. The content of phospholipids (PL) and triacylglycerols (TG) showed no marked change until hatching, and then decreased until disappearance of yolk sac. From these results, it is proposed that there are two main periods for nutrient utilization in embryos and larvae of walleye pollock. In the first period, FAA was mainly utilized until 18 days after fertilization. Active utilization of oLv B and lipids (PL and TG) instead of FAA occurred during the second period from 18 to 28 days.  相似文献   

11.
Broodstock of Atlantic cod were fed with three diets; astaxanthin supplemented (100 ppm kg?1) hydrated diet (30% water) (HWHAs), no additional astaxanthin supplemented (50 ppm kg?1) hydrated diet (30% water) (HWLAs) and a control diet (50 ppm kg?1 astaxanthin and 10% water). Throughout the spawning period, eggs were collected daily and fertilization success and proportion of embryos with normal cleavage were recorded. Larvae were reared using standard culture methods. Larval growth was recorded every 10 days and larval survival was recorded at 50 days post hatch. In general, broodstock fed with diets containing higher water content (HWHAs and HWLAs) and higher astaxanthin (HWHAs) had higher egg production and efficiency of egg output, lower egg incubation mortality and higher larval growth and survival. Broodstock fed with higher water content diets consumed less feed compared to control group. Also, broodstock fed with HWHAs and HWLAs recovered faster in terms of body condition than the control group. The egg bound mortality of female fish was significantly higher in control broodstock compared to broodstock fed with HWHAs and HWLAs. Broodstock fed with higher astaxanthin (HWHAs) had significantly higher fertilization success than other two groups however; no differences were found in proportion embryos with normal cleavage among different groups. Larval survival was significantly higher in HWHAs broodstock compared to other two groups. Our results showed that increased water content and astaxanthin levels in the diet could improve the condition and fecundity of Atlantic cod broodstock.  相似文献   

12.
去除卵膜及受精膜是成功制备棘皮动物染色体的关键步骤。为找到高效去除海胆卵膜与受精膜的方法,使用三氮唑（2 g/L）、盐酸海水溶液（pH 4.75）、二硫苏糖醇（3×10-3 mol/L）和对氨基苯甲酸（3×10-3 mol/L）等4种化学试剂分别对中间球海胆（）卵子及各时期胚胎进行处理,比较了不同试剂、处理时间或处理时期的去膜率、去膜后受精率和胚胎畸形率等指标的差异;利用常规空气干燥法对经去膜处理的囊胚期胚胎制备染色体,并进行核型分析。结果表明,三氮唑、盐酸海水溶液、二硫苏糖醇和对氨基苯甲酸等4种试剂对中间球海胆的卵膜和受精膜均有去除效果,其中2 g/L三氮唑处理未受精卵30 min的去膜率为85.50%,去膜后受精率为97.25%,畸形率为1.75%,去膜效果优于其余处理组。利用经该方法去膜后的早期囊胚进行染色体制备效果较好,获得了61个分散良好、形态完整的染色体中期分裂相。核型分析表明,中间球海胆的二倍体染色体数为2n=42,核型公式为：2n=20m+20sm+2st,NF=84,即有10对中部着丝粒染色体,10对亚中部着丝粒染色体,1对亚端部着丝粒染色体,染色体臂数为NF=84。本研究可为海胆染色体制备及染色体操作育种提供技术参考。  相似文献   

13.
NORIYUKI  HORIE  TOMOKO  UTOH  YOSHIAKI  YAMADA  AKIHIRO  OKAMURA  HUAN  ZHANG  NAOMI  MIKAWA  ATSUSHI  AKAZAWA  SATORU  TANAKA  HIDEO P  OKA 《Fisheries Science》2002,68(5):972-983
Development of embryos and larvae in the common Japanese conger Conger myriaster was observed after artificial fertilization. Eggs were obtained from females matured artificially by hormone injections and milt was obtained from males matured naturally. Fertilized eggs were kept in seawater at 12–14°C. The first cleavage occurred at 4 h, epiboly began at 24 h, the embryonic body was formed at 38 h and hatching occurred at 84 h after insemination. Newly hatched larvae were approximately 2.5 mm (total length) and similar to those of Anguilla japonica in terms of external features. The mouth and anus opened on the 7th day after hatching. Pigments began to appear at the tip of the tail on the 10th day. The total length of the larvae reached approximately 8 mm on the 11th day. Eye pigmentation began on the 14th day. One larva lived for 19 days without food.  相似文献   

14.
用钼蓝比色法和紫外分光光度法分别测定栉孔扇贝（Chlamys farrPri）两种颜色的卵子及其早期胚胎中磷脂含量和核酸含量，并进行比较。结果表明，橘红色卵子的RNA含量较浅黄色的略高，而两种颜色卵子的DNA含量却非常相似；在2细胞期，高受精率的受精卵其RNA量迅速增加，DNA和磷脂含量变化不大，但低受精率的受精卵相对未受精卵而言，其DNA、RNA和磷脂含量略有降低；在32～64细胞期，受精率高的胚胎中DNA和磷脂含量增加幅度大，RNA基本保持恒定。磷脂含量与卵子或胚胎的颜色可能有关，核酸、磷脂含量的变化与受精率高低有关。本实验旨为鉴定扇贝卵子的质量提供了科学依据。  相似文献   

15.
Interspecific allo-tetraploidy was induced by a combination of hybridization of Megalobrama amblycephala ♀× Megalobrama terminalis ♂ and thermal shock. A thermal shock at 40 °C for 2 min applied to eggs 33 or 26 min (τ0: 1.40) after fertilization resulted in a significantly ( P <0.01) higher yield of allo-tetraploids than hybrid crosses without heat shock. The yield of allo-tetraploids in embryos from mid-gastrula to hatching stages was 15.7–24.4% in different thermal shock treatment groups. The allo-tetraploidy rate in 330-day-old juveniles was 9.3% and 6.7% in different year treatment groups. After 2 years of rearing, allo-tetraploidy males attained sexual maturity with milk-like milt at the age of 2+, while allo-tetraploidy females at the age of 2+, and even at 3+, did not show any signs of sexual maturation exhibiting obviously delayed maturity. Only a few allo-tetraploidy females (three individuals) showed maturation characters at the age of 4+ and these females were induced to spawn.  相似文献   

16.
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17.
Abstract. Pressure treatment has up to now been the best method to inhibit the disjunction of chromosomes during the first mitosis of salmonid embryos. We have determined the optimum conditions to maximize the yield of tetraploid embryos (fertilization with normal sperm), and the yield of diploid mitotic gynogens (insemination with irradiated sperm). This study has provided two major results: the replacement of gamma-rays by ultraviolet rays, in order to inactivate the sperm for gynogenesis, markedly increases the yield of viable mitotic gynogens, probably because they reduce the risk of any'toxic'partial paternal transmission. The optimal pressure levels for mitotic inhibition are higher than those we had indicated in an earlier study. We interpret this discrepancy as an error of calibration of the pressure apparatus which had been used.  相似文献   

18.
The purpose of this study was to investigate the possibility of producing tetraploid fishes. Eggs of salmon (Salmo Salar) and rainbow trout (Salmo gairdneri) were treated with concentrations of cytochalasin B ranging from 1 μg/ml to 100 μg/ml for varying periods of time. All treated groups had higher death rates than untreated controls. If the treatment was started immediately after fertilization and before the eggs had swollen all eggs died. The highest frequency of mosaic embryos and polyploid cells was obtained when the treatment started 35–70 h° (hour-degrees) after fertilization and lasted until about the 4-cell stage of development. A dose of 10 μg/ml of cytochalasin B gave the most satisfactory results. This concentration was used for further work. Two batches of 6000 salmon eggs and several groups of rainbow trout eggs were treated and hatched. The hatchability was generally low while the control group had a normal hatchability. If some of the treated fish are eventually found to be tetraploids and fertile, they will be used to produce triploid offspring by crossing with normal diploid fish.  相似文献   

19.
ABSTRACT:   To evaluate the aquaculture performance of triploid barfin flounder Verasper moseri , the sex ratio, maturation, growth and the relative proportion of body parts were examined. The sex ratio of triploids was similar to diploids under communal rearing conditions, but the proportion of female diploids was higher than that of triploids under separate rearing conditions. The gonadosomatic index of triploid females was very low even during the spawning season, and the ovaries were rudimentary. These results suggest that triploid barfin flounder females were sterile. In addition, triploid males produced a small quantity of milt containing very few spermatozoa with abnormal shapes. Spermatozoa obtained from triploids were aneuploidies. When normal eggs were fertilized with sperm from triploid males, no fry developed. These results suggest that triploid barfin flounder males were functionally sterile. Triploid males grew more slowly than diploid males, and triploid females showed similar or slower growth than diploid females, whether reared separately (23 months) or communally (35 months). The ratios of visceral weight to the edible parts for triploid males were similar to those for diploid males, but ratios for triploid females were higher than for diploid females during the spawning period. In conclusion, a significant improvement of growth was not found in triploid barfin flounders.  相似文献   

20.
The silver catfish, Rhamdia quelen , is endemic to North, Central and South America with high aquaculture potential and wide acceptance in the market. Breeder fish were subjected to induced reproduction through hypophysation using a crude common carp pituitary extract. Egg characteristics, oocyte surface ultrastructure and histology of larval ontogenesis until whole yolk resorption were described for the first time for this species. Oocytes and semen were obtained by manual extrusion, and fertilization was conducted using the dry method. After fertilization, eggs were kept in incubators at 24 °C. The embryonic development was monitored using a stereomicroscope every 10 min until hatching. To analyse the larval development, larvae samples were collected from incubators daily until the fifth day, fixed in Bouin's fluid and subjected to routine histological techniques. The oocyte extrusion occurred 8 h after the second hormone dose at 26 °C. The oocytes were spherical, non-adhesive and yellow, with a diameter of 1471.75±47.63 μm. Scanning electron microscopy revealed a thin jelly coat covering the zona radiata in the animal pole around the micropyle. The blastopore closure occurred within 8 h after fertilization, and the fertilization rate was 79.9±5.2% at 24 °C. Embryonic development was completed within 25 h 30 min after fertilization. The complete resorption of the yolk and the formation of the digestive system organs and the mouth opening occurred on the fifth day, indicating a need for exogenous feeding. The results of this study provide information important for improvement in R. quelen culture and management.  相似文献   

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