Induction of gynogenesis and gonad development in the muskellunge

Muskellunge Esox masquinongy eggs activated with UV-irradiated yellow perch Perca flavescens sperm were subjected to heat shock at 31 ± 1° C for 6 min, 20 min after fertilization in three experiments. Survival at eyed stage was 1·7 ±1·6, 6·8 ± 4·8 and 2·3 ±0·5% in experiments I, II and III, respectively. After rearing the gynogenetic muskellunge in troughs and then in ponds, the sex ratio of gynogens in experiment I did not significantly (P>0·05) differ from the expected ratio 0:1 (male: female), however, one male and one intersex were observed. In experiments II and III, the sex ratio of gynogens differed significantly from expected (0 : 1). Three months after hatching, the growth of females did not significantly (P>0·05) differ among control and gynogenetic groups, whereas male growth was significantly (P<0·01) higher in the control v. gynogenetic group. The histological structures of the gynogenetic fish gonads in both sexes were similar to those described in the gonads of control muskellunge. After the overwintering period, signs of active spermatogenesis were observed in the testis of 1 + year old gynogenetic fish, whereas ovaries contained only oocytes at the perinucleolar stage. At this stage, plasma sex steroids testosterone (T) and oestradiol-17β (E2) cannot be used to discriminate the sex of gynogenetic muskellunge, as intersex, male and female fish had similar levels of T and E2.     

Induction of meiotic gynogenesis in ship sturgeon Acipenser nudiventris using UV-irradiated heterologous sperm

Diploid gynogenesis was induced in ship sturgeon Acipenser nudiventris using UV-irradiated sperm from Siberian sturgeon Acipenser baerii. The optimal condition for the retention of the second polar body in ship sturgeon was determined to be 10 min after activation/fertilization in experiments. The temperature of cold shock and its duration were 2.5 °C and 30 min, respectively. A total of 30 gynogens of known parentage from experimental treatments were screened using microsatellite DNA analysis, and uniparental transmission in meiogens was confirmed. The results show that heterologous Siberian sturgeon sperm is applicable as UV-irradiated sperm for the induction of gynogenesis in ship sturgeon. This technique may recover the critically endangered sturgeon species that are becoming extinct.     

Induction of diploid gynogenesis in an evolutionary model organism, the three-spined stickleback (Gasterosteus aculeatus)

Background

X-linked alpha thalassemia, mental retardation syndrome in humans is a rare recessive disorder caused by mutations in the ATRX gene. The disease is characterised by severe mental retardation, mild alpha-thalassemia, microcephaly, short stature, facial, skeletal, genital and gonadal abnormalities.

Results

We examined the expression of ATRX and ATRY during early development and gonadogenesis in two distantly related mammals: the tammar wallaby (a marsupial) and the mouse (a eutherian). This is the first examination of ATRX and ATRY in the developing mammalian gonad and fetus. ATRX and ATRY were strongly expressed in the developing male and female gonad respectively, of both species. In testes, ATRY expression was detected in the Sertoli cells, germ cells and some interstitial cells. In the developing ovaries, ATRX was initially restricted to the germ cells, but was present in the granulosa cells of mature ovaries from the primary follicle stage onwards and in the corpus luteum. ATRX mRNA expression was also examined outside the gonad in both mouse and tammar wallaby whole embryos. ATRX was detected in the developing limbs, craniofacial elements, neural tissues, tail and phallus. These sites correspond with developmental deficiencies displayed by ATR-X patients.

Conclusions

There is a complex expression pattern throughout development in both mammals, consistent with many of the observed ATR-X syndrome phenotypes in humans. The distribution of ATRX mRNA and protein in the gonads was highly conserved between the tammar and the mouse. The expression profile within the germ cells and somatic cells strikingly overlaps with that of DMRT1, suggesting a possible link between these two genes in gonadal development. Taken together, these data suggest that ATRX has a critical and conserved role in normal development of the testis and ovary in both the somatic and germ cells, and that its broad roles in early mammalian development and gonadal function have remained unchanged for over 148 million years of mammalian evolution.     

Induction of external abnormalities in offspring of male mice irradiated with 252Cf neutron.

To assess the genetic effects of fission neutron, the induction of external malformations was studied in F1 fetuses after F0 male mice were irradiated. Male mice of the ICR:MCH strain were irradiated with 252Cf neutron at doses of 0.238, 0.475, 0.95 and 1.9 Gy. They were mated with non-irradiated female mice at 71-120 days after the irradiation. Pregnant females were autopsied on day 18 of gestation and their fetuses were examined for deaths and external abnormalities. No increases of pre- and post-implantation losses were noted at any dose. External abnormalities were observed at rates of 1.40% in the 0.238 Gy, 2.23% in the 0.475 Gy, 3.36% in the 0.95 Gy and 3.26% in the 1.9 Gy groups; the rate in the control group was 1.65%. The dose-response curve was linear up to 0.95 Gy, and then flattened out; the induction rate of external abnormalities was 2.7 x 10(-4)/gamete/cGy based on the linear regression. These results indicated that fission neutron effectively induces external abnormalities in F1 fetuses after spermatogonial irradiation.     

Cytological mechanisms of gynogenesis and sperm incorporation in unreduced diploid eggs of the clonal loach, Misgurnus anguillicaudatus (Teleostei: Cobitidae)

The loach Misgurnus anguillicaudatus comprises diploid clonal, triploid and diploid-triploid mosaic individuals in a wild population on Hokkaido island, Japan. When diploid eggs of clonal loaches are fertilized by haploid sperm of normal bisexual loaches, both diploid clonal and non-diploid aclonal individuals occur in the progeny. Flow cytometry and microsatellite analyses revealed that the occurrence of triploid, diploid-triploid and other progeny was essentially due to the genetic incorporation of sperm to diploid clonal genomes of unreduced eggs. In this study, we examined the influence of water temperature from fertilization to early embryogenesis on frequencies of diploid clonal and other progeny and observed that progeny of three out of four clonal females examined exhibited approximately constant rates of diploid clonal individuals (54.2-68.9%) at hatching stage. Thus, no drastic increase of non-diploid progeny was detected. However, the 28 degrees C group of the fourth clonal female gave significantly lower rate (28.1%) of diploid clonal progeny, suggesting that this temperature might be a critical or a borderline temperature inducing sperm incorporation. We also examined the cytological process by which diploid clonal and other aclonal progeny develop after fertilization. In some fertilized eggs, the sperm nucleus remained condensed throughout fertilization and early embryogenesis and never fused with the female pronucleus. This cytological observation concludes that clonal eggs develop by the mechanism of gynogenesis. However, some other eggs showed the cytological process of syngamy between the female pronucleus and an accidentally formed male nucleus, suggesting the formation of triploid progeny. The syngamy between an accidentally activated sperm nucleus with a male pronucleus-like structure and nucleus of a blastomere of gynogenetically developing clonal diploid embryo might produce a diploid-triploid mosaic individual.     

Production of WW super females by diploid gynogenesis in Xenopus laevis

Summary In Xenopus laevis, which does not show sex chromosomal dimorphism, the female is heterogametic (WZ) and the male is homogametic (ZZ). By activating eggs with UV-irradiated spermatozoa, and by inhibiting the formation of the second polar body gynogenetic diploids were obtained, including some WW females. These super-females are fertile and not sublethal; by gynogenetic reproduction they in turn generate only WW females, while after mating with a male they give rise to WZ females exclusively.From the sex ratio of the gynogenetic progeny of normal WZ females, the map distance between the centromere and the sex determining gene(s) has been calculated. By examining the sex ratio and the distribution of individuals exhibiting the phenotype of periodic albinism in the gynogenetic offspring of a^p/+females, it has been demonstrated that the a^p gene and the sex determining gene(s) are not linked.     

Induction of triploidy and gynogenesis in teleost fish with emphasis on marine species

The induction of triploidy and gynogenesis by chromosome set manipulation has traditionally been studied more intensively in freshwater than in marine fish. In the last years, however, several studies have applied these manipulations in about a dozen marine species, including mainly sparids, moronids and flatfishes. This paper focuses on the methodologies used to induce, verify, and assess performance of both triploids and gynogenetics of these marine species. Since many of them are batch spawners and have small and fragile eggs and larvae, peculiarities relating to broodstock management, gamete quality and mortality assessment during early larval stages are also taken into account. However, data show that if handling is correct and the treatments are optimized, triploid and gynogenetic rates of 100% can be easily achieved. Survival of triploids with respect to the controls is about 70–80%, whereas in gynogenetics it is generally low and more variable, depending on the species considered. In the marine fish investigated so far, triploidy has not resulted in significantly higher growth rates. On the other hand, the induction of gynogenesis has resulted in the production of both all-female and mix-sex stocks. Throughout the paper, special reference is made to the European sea bass (Dicentrarchus labrax L.), a species of both basic and applied interest, for which a comprehensive study has been carried out on the induction, verification and performance of triploids and gynogenetics.Author for correspondence     

用团头鲂精子诱导金鱼雌核发育研究

本文用紫外灭活的团头鲂(Megalobrama amblycephala)精子激活金鱼 (Carassius auratus Goldfish)卵子,用0－4℃冷水冷休克处理卵子使其染色体加倍,得到成活的雌核发育金鱼。使用与金鱼不同亚科的团头鲂精子做为激活源能极大提高雌核发育后代的鉴定效率,只需依据外形特征、染色体数目和性腺发育程度,就能容易地将雌核发育金鱼和与团头鲂杂交后代区分开。雌核发育金鱼有两种体色不同的后代,但都为双尾,体形似金鱼,染色体数目为2n=100,全雌,性腺发育正常;而杂交后代为单尾,体形似鲫鱼,染色体数目为3n=124,性腺发育滞后。本实验为证明金鱼的性别决定方式为XX/XY型提供了细胞遗传学证据。得到两种体色皆不同于母本体色的后代,体色不同可能是基因座位纯化导致后代性状分化,也可能是异精效应导致。     

School fidelity in fishes: The yellow perch pattern

School fidelity concerns the cohesiveness of social aggregations over time, as measured by the regularity or repeatability with which known individuals re-occur as members of a school. School fidelity was measured by divers who observed yellow perch (Perca flavescens) marked with individually recognizable tags in Cazenovia Lake, New York. Yellow perch were facultative schoolers, with individual differences in schooling tendency (measured as percentage of time in schools) accounting for different numbers of observations of schooled versus solitary fish. The greatest co-occurrence was found between fish with strong schooling tendencies, but within this group co-occurrence was random. Home ranges overlapped greatly between individuals, yet co-occurrence was more a function of schooling tendency than of overlapping home ranges. Individuals with overlapping home ranges but with weak schooling tendencies seldom co-occurred. Home range size increased directly with schooling tendency: the distances that individuals moved apparently depended on the movements of the schools they joined, with strongly schooling fish remaining in schools longer. Individuals joined and left schools frequently; this also reflects a lack of fidelity between fish. Fish schools that form primarily for predator avoidance may show higher levels of fidelity than do schools that form for foraging or hydrodynamic efficiency.     

Failure to induce over-compensation of growth in maturing yellow perch

Unlike juvenile F1 male bluegill Lepomis macrochrus × female green sunfish L. cyanellus , maximized episodes of compensatory growth (CG) in 2 year yellow perch Perca flavescens did not surpass control masses because internal regulation caused abrupt appetite reduction upon catch-up. Together, the hybrid sunfish study and present work indicate that CG-maximizing feeding schedules and absence of an internal growth limiting mechanism are both required to produce substantial growth overcompensation (GOC). The less vigorous and less resilient CG responses of the yellow perch relative to those of the similarly fed hybrid sunfish appear indicative of the lack of GOC capacity in the former. This contrast, and results of previous studies are interpreted to suggest that GOC capacity may be limited to early life stages of fishes which have a substantial reproductive potential but are at high risk of mortality due to their small size. The possibility that GOC capacity is time-of-year-dependent and species-specific is considered also. Food deprivation periods that produced the strongest CG responses differed for male (2 days) and female (12 days) yellow perch. Among controls fed without restriction, growth rate and growth efficiency of female yellow perch exceeded those of males two-fold, however, males showed a greater capacity to catch-up to same-sex controls when undergoing CG. A feeding schedule using maintenance feeding v. food deprivation to elicit CG yielded the most rapid catch-up to control masses in the yellow perch. Such feeding schedules may produce even greater GOC than was achieved previously in hybrid sunfish, where feeding schedules involving food deprivation were employed.     

Cortisol responses of pallid sturgeon and yellow perch following challenge with lipopolysaccharide

Plasma cortisol responses of pallid sturgeon Scaphirhynchus albus and yellow perch Perca flavescens following injection with equal doses of lipopolysaccharide were compared. Concentrations of cortisol in plasma from pallid sturgeon did not change following injection (6·0–11·0 v. 6·4 ng l⁻¹ pre-stress) while in yellow perch plasma they were shown to increase up to 6 h (117·0 v. 9·8 ng l⁻¹ pre-stress) after the injection. These results are consistent with other reports for pallid sturgeon that illustrate a reduced cortisol response following other applied stressors relative to teleosts and suggest differences in the expression and regulation of their inflammatory responses.     

Variation in field estimates of daily ration in young yellow perch

The quantity of food in the complete digestive tract of young-of-the-year yellow perch Perca flavescens varied between samples taken at the same time of the day over 2–3 consecutive days, resulting in a 1·7- to 2·5-fold variation of in situ estimates of daily ration. Increased food intake rates were related to increased consumption of large prey items suggesting a day-to-day pattern in the quantity and size of food consumed.     

Change in diel catchability of young-of-year yellow perch associated with establishment of dreissenid mussels

1. Non‐native mussels have increased water clarity in many lakes and streams in North America and Europe. Diel variation in catchability of some fish species has been linked to visibility during survey trawls (used to measure escapement). 2. Water clarity increased in nearshore areas of western Lake Erie by the early 1990s, following passage of legislation in 1972 to improve water quality (e.g. reduce phosphorus loading) and the invasion of dreissenid mussels (Dreissena spp.) beginning in 1987. 3. We hypothesised that increased water clarity in Lake Erie resulted in decreased catchability of young‐of‐year (age‐0) yellow perch (Perca flavescens Mitchill) during daylight compared to during night. We used a two‐tiered modelling approach to test this hypothesis on the ratio (R) of catch per hour (CPH) during night to CPH during daylight in bottom trawl surveys conducted during 1961–2005. 4. First, we examined seven a priori models. The first model, the ‘null’ model, represented no change in R over time. Three more models tested whether the timing of the change in R was associated with passage of water quality legislation only, dreissenids only (two‐period models) and both legislation and dreissenids (three‐period models). Three additional models included a 3‐year lag before the effects of legislation, dreissenids or both occurred. Secondly, all possible two‐ and three‐period models with a minimum of 2 years per time period were explored a posteriori. The a posteriori procedure determined the temporal transitions to higher R that were best supported by the data, without regard to a priori hypotheses. 5. Night CPH was greater than daylight CPH in 3 of 11 years during 1961–72, in 10 of 15 years during 1973–87, and in 14 of 18 years during 1988–2005. During 1991–2005 night CPH exceeded daylight CPH in all years except one, and night CPH was more than twice daylight CPH in 10 years during this period. 6. The best a priori model had two periods, with a break between 1990 and 1991, corresponding to 3 years after the dreissenid invasion. Similarly, the best two‐ and three‐period a posteriori models both had breaks between 1990 and 1991. The results supported our hypothesis that age‐0 yellow perch exhibited a transition to lower catchability during daylight compared to night, and the timing of the transition coincided with the establishment of dreissenid mussels. 7. The most plausible mechanism for our results was increased visibility of the trawl during daylight, resulting in increased avoidance of the trawl. These results have potential applications wherever non‐native mussels have increased water clarity.     

Plasma concentrations of steroid hormones in male yellow perch, Perca flavescens: the effect of age and photothermal manipulation

Plasma steroid concentrations in two and three year-old male yellow perch maintained under two different photothermal regimes were investigated. Initially, all fish kept indoors were exposed to the same water temperature (22 °C) and photoperiod (15L:9D). By the end of August, following the first sampling, fish were exposed to different photothermal regimes. Groups A₂ (2 year old) and A₃ (3 year old) were maintained under photothermal conditions similar to those of southern Ohio. Groups B₂ (2 year old) and B₃ (3 year old) were exposed to a condensed light/temperature regime designed to accelerate maturation. Testosterone (T) was the major circulating androgen in all groups. In regime A fish, plasma concentrations of 11-ketotestosterone (11KT) and T were very low in August, increased in October and remained elevated until March. In regime B plasma androgens were high until February and then dropped abruptly in March. The elevated circulating levels of 11KT and T were associated with production of sperm. The highest sperm concentration in the groups A₃ and B₃ was observed in February and December, respectively. There were no major differences in profiles and levels of plasma steroids between two age categories within each photothermal regime. These data indicate that the compression of the photothermal cycle accelerated both the occurrence of the low postspawning levels of circulating steroids and the completion of milt production. Higher sperm concentration observed in B₃ group earlier in the season compared to A₃ group also support the notion that the condensed photothermal cycle accelerated gonadal maturation. It appears that modification of the environmental cues may be a useful tool for manipulation of reproductive processes in male yellow perch. This revised version was published online in July 2006 with corrections to the Cover Date.     

Diploid radiation gynogenesis in carp. I. Massive production of diploid gynogenetic progeny]

Mass lost of diploid gynogenetic carp offspring were obtained with the use of fish-farm method of reproduction. The average yield of gynogenetic diploids in usual experiments was 0.1% (from fertilized eggs). The cooling of unfertilized spawn (at the stage of metaphase II) to 8--10 degrees C during 3.5--4.5 hours in 50% of cases permitted to increase by tens of times (in the most successful experiments up to 8%) the yield of gynogenetic diploids. The rate of survival of carps remained relatively low during the first two years of life, particularly during the first hibernation that is a critical period. No specific depression of growth in gynogenetic diploid carps was observed. A high yield of gynogenetic diploids (3.9% of fertilized eggs) and their relatively high rate of survival were observed in the second generation of artificially induced gynogenesis.     

Multiple mating in the ant Cataglyphis cursor: testing the sperm limitation and the diploid male load hypotheses

Multiple mating (i.e., polyandry) by queens in social Hymenoptera is expected to weaken social cohesion since it lowers within-colony relatedness, and hence, indirect fitness benefits from kin selection. Yet, there are many species where queens mate multiply. Several hypotheses have been put forward to explain the evolution and maintenance of polyandry. Here,we investigated the ‘sperm limitation’ and the ‘diploid male load’ hypotheses in the ant Cataglyphis cursor. Genetic analyses of mother-offspring combinations showed that queens mate with up to 8 males, with an effective mating frequency of 3.79. Significant paternity skew (unequal contribution of the fathers) was detected in 1 out of 5 colonies. The amount of sperm stored in the spermatheca was not correlated with the queen mating frequency, and males carry on average enough sperm in their seminal vesicles to fill one queen’s spermatheca. Analyses of the nuclear DNA-content of males also revealed that all were haploid. These results suggest that the ‘sperm limitation’ and the ‘diploid male load’ hypotheses are unlikely to account for the queen mating frequency reported in this ant. In light of our results and the life-history traits of C. cursor, we discuss alternative hypotheses to account for the adaptive significance of multiple mating by queens in this species. Received 13 August 2008; revised 19 November 2008; accepted 21 November 2008.