Alternative reproductive styles in seabreams (Pisces: Sparidae)

Synopsis A review of sexuality in the Sparidae shows that protandrous, protogynous, simultaneous and rudimentary hermaphroditism have all been reported in the family. Careful histological study shows that even in those species reputed to have separate sexes, intersexuality is found in the juvenile condition. We suggest that two reproductive styles, sex change and late gonochorism are found in the family. The bi-potentiality of the sparid gonad is considered to be a pre-adaptation for the development of sequential hermaphroditism in species in which reproductive success is size related. In these species sex change is an alternative reproductive style that enables individuals to maximise their lifetime reproductive success by functioning as one sex when small and the other sex when large.     

Temperature effects on sex differentiation of two South American atherinids, Odontesthes argentinensis and Patagonina hatcheri

Synopsis The present study investigated the effects of water temperature (18, 21, and 25 °C) on the histological process of gonadal sex differentiation of two commercially important atherinid fishes from South America, Odontesthes argentinensis (sea pejerrey) and Patagonina hatcheri (Patagonian freshwater pejerrey). In both species, female gonadal sex differentiation began with the formation of lateral stromal cell outgrowths and the appearance of meiotic oocytes. The male gonads remained quiescent for about twice as long as the female gonads, with differentiation becoming evident by the formation of the main sperm duct and of cysts of germ cells at the periphery of the gonads. Meiosis in males occurred relatively long after somatic differentiation of the testis. The ovaries of O. argentinensis differentiated at 28 days (20.3 mm) at 25 °C, 42 days (24.0 mm) at 21 °C, and 56 days (23.8 mm) at 18 °C. In the males, differentiation was observed at 98 days at 25 and 21 °C (39.4 mm and 40.4 mm, respectively), but at 112 days under 18 °C (40.7 mm). In P. hatcheri, differentiation of females occurred at 21 days (17.8 mm) at 25 °C, 28 days (20.8 mm) at 21 °C, and 35 days (23.2 mm) at 18 °C. Male differentiation became evident at 56 days under 25 and 21 °C (30.8 and 32.7 mm, respectively), and at 70 days (37.7 mm) at 18 °C. The sex-ratios of O. argentinensis reared at 18 or 21 °C were female-biased whereas those at 25 °C were not; groups reared at 18 °C had significantly more females than groups from the same progeny reared at 25 °C. In contrast, the sex-ratios in all groups of P. hatcheri did not differ significantly from 1:1 and no significant differences were found between groups of the same progeny reared at different temperatures. These results suggest the occurrence of thermolabile sex determination (TSD) in O. argentinensis whereas in P. hatcheri gonadal sex appears to be strongly genetically determined.     

间接免疫荧光法鉴别小鼠早期胚胎性别的研究

以间接免疫荧光法检测昆明系小鼠早期胚胎雄性特异性H—Y抗原的表达。结果表明:54%的胚胎为H—Y阳性(雄性);46%为H—Y阴性(雌性)。经与昆明系小鼠的自然性比率(♂:52%;♀:48%)比较,两者无显著性差异。 经细胞遗传学方法确证,以免疫荧光法鉴别的胚胎性别,雄性的鉴别准确率为75.50%;雌性为82.97%。 本文还就影响鉴别准确率的若干因素以及本方法在生产中的应用前景等问题进行了分析讨论。     

The evolution of sex-change mechanisms in fishes

Synopsis Five distinct sex-change mechanisms are identified among sequentially hermaphroditic fishes based on socio-ecological characteristics. The primary determinants of the sex-change mechanisms appear to be social organization and mating system, which in turn depend on resource distribution in space and time. The ability of a single individual to control all mating in the social unit, which is related to the size of the social unit, differentiates three suppression mechanisms from two induction mechanisms. Sex-change suppression, which is characteristic of species with small group size and rigid dominance hierarchies, refers to inevitable sex change in the absence of group dominance. Ability to migrate between resource patches differentiates protogynous suppression (e.g. inLabroides dimidiatus) from protandrous suppression (e.g. inAmphiprion spp.). Early sex change appears to have evolved from protogynous suppression under special conditions involving the loss of mating control by a single dominant individual in certain species (e.g.Centropyge spp. ). Sex-change induction, which is characteristic of species with large social groups lacking rigid dominance hierarchies, refers to the requirement that sex change must be induced by specific characteristics of (or changes in) the social group, regardless of dominance status. Ability to distinguish sex, or its importance, differentiates sex-ratio induction (e.g.Anthias squamipinnis) from size-ratio induction (e.g.Thalassoma spp.). Alternative models account for the possibility that all cases of sex change require stimulation from smaller conspecifics (universal induction-inhibition model) or that all fish have the genetic capacity to switch mechanisms, depending on changing ecological conditions and resulting changes in mating system (behavioral-scaling model). Neurophysiological models suggest that induction mechanisms, which require at least two categories of environmental stimuli, may have evolved from the simpler suppression mechanisms, which require only one kind of input from the environment.     

Social system of an inshore stock of the red hind grouper,Epinephelus guttatus (Pisces: Serranidae)

Synopsis According to sex allocation theory, the decision by a female in protogynous fish species to change sex or not should be influenced by, among other things, the mating sex ratio during spawning periods and/or by factors that vary directly with the spawning sex ratio, such as relative rates of behavioral interaction with males and females outside of spawning periods. In groupers that only spawn during a few weeks of the year in large aggregations, individuals must assess the relative value of changing sex or not entirely within the aggregation unless the social system during the remainder of the year provides a behavioral equivalent of the mating sex ratio. Fifty-five individuals of the red hind,Epinephelus guttatus, were tagged and repeatedly located during a 152-day period within a 100 × 100 m grid on a shallow forereef off southwestern Puerto Rico. The home ranges of 22 tagged individuals sighted 10 or more times were 112–5636 m² in area. Individual home ranges overlapped with the home ranges of 1–18 other individuals. Home ranges of small fish were not clustered within the borders of the home range of larger fish, i.e. fish did not form spatially defined social units. At the end of the study, 31 tagged individuals remained on the grid together with five newly sighted fish. All 36 individuals proved on histological examination to be females similar in size to females in the spawning aggregation of the following year. The sex ratio of this all-female inshore stock differed significantly from the sex ratio of that spawning aggregation. Hence, information predicting the reproductive value of a sex change is not available to females in the inshore stock during nonspawning months.     

Influence of the major histocompatibility comp(MHC) on the response to and expression of H-Y in rats

The influence of the major histocompatibility complex (MHC) on the survival of H-Y-incompatible skin grafts in rats has been determined by challenging normal and previously sensitized females of various isogenic and congenic strains with male trunk or ear skin isografts. The MHC's influence on the potency of H-Y has also been evaluated by determining the survival of male parental strain ear skin grafts on sensitized (with F₁ hybrid male cells) F₁ hybrid females of two different MHC congenic strains. The results indicate that, as in mice, the MHC has a dual affect on H-Y; it is involved in determining the ability of females to respond to the antigen as well as influencing its potency.     

Estimating the costs of allocation to male and female functions in a monoecious cucurbit,Lagenaria siceraria

Costs of allocation to male versus female functions were determined for the monecious, annual vine Lagenaria siceraria by removing all flower buds of a given gender and using the additional vegetative growth as a measure of the cost of allocation to that gender (following methods of Silvertown 1987). In this cucurbit, we found significant costs associated with male flower production and fruit production, but not with female flower production. These results are not surprising given the strongly male-biased floral ratio (20 male:1 female) and the large gourds of this species. However, our results are in contrast to Silvertown's study of Cucumis sativus which found no cost to male funtion. In addition, our treatments significantly affected floral sex expression, resulting in increased femaleness for treatment plants. This increase is a consequence of increased lateral branch initiation in these plants and the almost exclusive production of female flowers on lateral branches. Fruit production was associated with a shut-down of subsequent flower production. Given that plant architecture leads to pronounced protandry (on average, 17 male flowers bloom before the first female flower) and that male costs are associated with flower production and the bulk of female costs with fruit production, this shutdown effectively separates male and female functions temporally. We agree with Silvertown's conclusion that this form of protandry is an important factor in the maintenance of cosexuality.     

Reproductive styles of shallow-water groupers (Pisces: Serranidae) in the eastern Gulf of Mexico and the consequences of fishing spawning aggregations

Synopsis Seasonal and spatial aspects of spawning for three commercially important grouper species in the northeastern Gulf of Mexico are detailed. These species — all of which are protogynous hermaphrodites - spawn in deep water (> 25 m for red grouper,> 40 m for gag and scamp), making it difficult to observe spawning behaviors without ROV or submersible support. They respond to intense fishing pressure in ways that are directly related to their respective reproductive styles. Species that aggregate appear to be more susceptible to such pressures than those that do not, as evidenced by marked skewing of sex ratios in favor of females. Gag, Mycteroperca microlepis, have suffered a drop in the proportion of males from 17% to 1% in the last 20 years; scamp, Mycteroperca phenax, have dropped from 36% to 18%; and red grouper, Epinephelus morio, which do not aggregate, have shown little change in the sex ratio over the past 25–30 years.     

Production of H-Y antibody in the ascites fluid of mouse and localization of the antigen on cells and tissues

A procedure is described for the production of large amounts of ascites fluid containing specific H-Y antibody. The distribution of H-Y antigen on mouse epididymal spermatozoa, thymocytes, and splenocytes was carried out using this specific antibody in the microcytotoxicity test and ELISA. Employing the indirect immunofluorescent technique, the H-Y antigen was localized on the acrosomal membrane of mouse epididymal and washed ejaculated human spermatozoa and on the entire membrane of mouse splenocytes and thymocytes. Immunohistochemical localization of the antigen in the testicular section indicated its presence in the cytoplasm of Leydig cells and on the membrane of Sertoli cells and sperm heads.     

Histological evaluation of gonadal differentiation in fathead minnows (Pimephales promelas)

The timing of sex determination and the pattern of sex differentiation have not been studied in fathead minnow even though this species of fish are commonly used as a research model for toxicological studies. In this study, the developmental histology of gonadal development was investigated. Fish were cultured in the laboratory conditions and spawning obtained at a photoperiod of 16 h-light and 8 h-dark. Samples were collected from day 7 fish post-spawning (day 7 fps) to day 150 fps and their gonads were processed for histological examination. Developmental histology was assessed by using a light microscopy. The results showed that ovarian differentiation normally occurs at around day 13 fps, while testicular differentiation normally occurs at around day 22 fps.     

Generation time and the stability of sex-determining alleles in oyster populations as deduced using a gene-based population dynamics model

Crassostrea oysters are protandrous hermaphrodites. Sex is thought to be determined by a single gene with a dominant male allele M and a recessive protandrous allele F, such that FF animals are protandrous and MF animals are permanent males. We investigate the possibility that a reduction in generation time, brought about for example by disease, might jeopardize retention of the M allele. Simulations show that MF males have a significantly lessened lifetime fecundity when generation time declines. The allele frequency of the M allele declines and eventually the M allele is lost. The probability of loss is modulated by population abundance. As abundance increases, the probability of M allele loss declines. Simulations suggest that stabilization of the female-to-male ratio when generation time is long is the dominant function of the M allele. As generation time shortens, the raison d’être for the M allele also fades as mortality usurps the stabilizing role. Disease and exploitation have shortened oyster generation time: one consequence may be to jeopardize retention of the M allele. Two alternative genetic bases for protandry also provide stable sex ratios when generation time is long; an F-dominant protandric allele and protandry restricted to the MF heterozygote. In both cases, simulations show that FF individuals become rare in the population at high abundance and/or long generation time. Protandry restricted to the MF heterozygote maintains sex ratio stability over a wider range of generation times and abundances than the alternatives, suggesting that sex determination based on a male-dominant allele (MM/MF) may not be the optimal solution to the genetic basis for protandry in Crassostrea.     

血清学检测H-Y噬菌体Fab抗体阳性克隆的分析

目的 为分析H-Y噬菌体Fab抗体特异性,筛选用于抗体亲和力提高的H-Y噬菌体Fab抗体阳性克隆.方法 以从噬菌体Fab抗体库中筛选到具有雄性特异性结合活性的阳性克隆A6、A8、E6为基础,通过C57BL/6鼠脾细胞为抗原的ELISA分析3株阳性克隆的特异性,镜下观察亲和力较好的A8阳性克隆ELISA结果,利用生物信息学方法预测分析该克隆的抗体基因可变区序列和结构.结果 ELISA分析显示3株阳性克隆具有雄性特异性,其中A8阳性克隆具备较好的雄性特异性.A8克隆具有免疫球蛋白轻链和重链可变区结构,其重链、轻链可变区分别属于VHI和VκIV基因家族.结论 A8阳性克隆可用于后续的导向筛选和抗体基因改造等研究工作.     

Identification of a male-specific histocompatibility protein on preimplantation porcine embryos

An indirect immunofluorescence assay was used to detect the presence of male-specific protein(s) on various stages of preimplantation porcine embryos. Embryos were collected at slaughter from the reproductive tracts of day?2.5, ?4, ?5, ?6, and ?8 (day 0 = first day of estrus) sows and gilts. Embryos were placed in medium containing an anti-male primary antibody, washed, and transferred to culture drops containing a fluorescein isothiocyanate (FITC)-labeled secondary antibody. Embryos were classified as either fluorescent (H-Y positive) or nonfluorescent (H-Y negative), transferred to coded drops, and karyotyped to examine sex chromosomes. A total of 91 eight-cell to blastocyst stage embryos were evaluated; of these, 46% were classified as fluorescent and 54% as nonfluorescent. Of readable metaphase spreads (65%) from these embryos, 81% (48 of 59, P < 0.005) were correctly sexed by immunological detection of the male-specific antigen. Although 13 % (2/15)of four-cell embryos evaluated were classified as fluorescent, the accuracy with which embryos at this stage were sexed by detection of H-Y antigen was not different from 50%. Fifty percent of eight-cell embryos were classified as H-Y positive with 78% of embryos correctly sexed. It was concluded that the eight-cell embryo is the earliest stage of development for which there is evidence for expression of H-Y antigen. Detection of the male-specific protein was difficult at the expanded blastocyst stage.     

Binding of anti-H-Y monoclonal antibodies to separated X and Y chromosome bearing porcine and bovine sperm

Studies designed to answer the question whether or not H-Y antigen is preferentially expressed on Y chromosome bearing sperm have resulted in conflicting results. This is probably due to the absence of reliable methods for estimating the percentage of X and Y chromosome bearing sperm in fractions, enriched or depleted for H-Y antigen positive sperm. In recent years a reliable method for separating X and Y chromosome bearing sperm has been published. With this method, separation is achieved by using a flow cytometer/cell sorter, which detects differences in DNA content. This technique provided the first opportunity for testing anti-H-Y antibody binding to fractions enriched for X and Y chromosme bearing sperm, directly. A total of 7 anti-H-Y monoclonal antibodies were tested using sorted porcine sperm and in one experiment also sorted bovine sperm. All monoclonal antibodies bound only a fraction of the sperm (20 to 50%). However, no difference in binding to the X and Y sperm enriched fractions was found. Therefore, the present experiments do not yield evidence that H-Y antigen is preferentially expressed in Y chromosome bearing sperm. © 1993 Wiley-Liss, Inc.     

鼠源性抗雄性特异性抗原噬菌体Fab抗体的制备及分析

利用噬菌体抗体库筛选技术获得抗雄性特异性抗原的噬菌体Fab抗体,首次采用雄鼠脾细胞对鼠源性抗雄性特异性抗原噬菌体Fab抗体库进行3轮亲和富集和2轮雌鼠脾细胞吸附,对筛选后特异性噬菌体Fab抗体进行ELISA分析,重组率鉴定及基因测序分析。结果显示,5次筛选后的15个菌落中有9个能产生抗雄性特异性抗原特异性噬菌体抗体,噬菌体Fab抗体的基因重组率为60%,E5克隆的重链、轻链可变区序列分别属于VH1和VκⅣ基因家族,这为挑选出高亲和力的抗雄性特异性抗原噬菌体Fab抗体奠定了实验基础,将推进雄性特异性抗原及其抗体的研究进程,并为性别控制研究开创新途径。     

The Effects of Inflorescence Size and Flower Position on Biomass and Temporal Sex Allocation in <Emphasis Type="Italic">Lobelia sessiliflora</Emphasis>

To test the prediction of sex allocation theory that plants or flowers high in resource status emphasize the female function, we explored the variation in both biomass (the number of pollen grains and ovules) and temporal (male and female durations) sex allocation among and within plants of protandrous Lobelia sessilifolia in relation to plant size and flower position within plants. Among plants, the mean number of pollen grains and ovules per flower of a plant increased with plant size, whereas the mean P/O ratio (number of pollen grains/number of ovules ratio) decreased with plant size. The mean male duration, the mean female duration, and the mean ratio of male duration/flower longevity per flower of a plant were not correlated with plant size. Thus, large plants emphasized female function in terms of biomass sex allocation, which is consistent with the prediction of size-dependent sex allocation theory. The results for temporal sex allocation, however were inconsistent with the theory. Within plants, the mean number of pollen grains and ovules per flower at each position decreased from lower to upper flowers (early to late blooming flowers) and that of the P/O ratio increased from lower to upper flowers. The mean male duration and the mean female duration per flower decreased from lower to upper flowers, whereas the mean ratio of male duration/flower longevity increased from lower to upper flowers. The population sex ratio changed from male-biased to female-biased. Thus, later blooming flowers emphasized the male function in terms of both biomass and temporal sex allocation, consistent with the sex allocation theory, regarding the change in the population sex ratio.     

Evaluation of the presence of a specific histocompatibility protein on equine embryonic cells

An indirect immunofluorescence assay was used to detect the presence of H-Y antigen on equine blastocysts. A total of 33 blastocyst stage horse embryos were collected 6 to 7 days post-ovulation by trans-cervical flush and were immediately evaluated for the presence of H-Y antigen. Additionally, 17 embryos, were collected and cultured for 72 h to the expanded blastocyst stage and similarly evaluated. Embryos were placed in medium containing monoclonal antibodies to H-Y antigen followed by incubation in medium containing 1/10 (v/v) fluorescein isothiocyanate conjugated goat anti-mouse IgM Fc specific antiserum. Embryos were individually evaluated at 400X to identify cell specific fluorescence. Following evaluation, embryonic sex was independently verified with karyotypes to identify sex chromosomes. Of the 50 embryos evaluated, 29 were evaluated as non-fluorescent and 21 fluorescent. Expression of H-Y antigen was determined to be uniform in those embryos classified as fluorescent. Twenty-three of 28 (82%) readable karyotypes corresponded to the predicted sex. These results indicate a specific histocompatibility antigen is expressed and maintained at the blastocyst stage of development. In addition, no segregation of this protein on specific cell types occurs in this species.     

The reproductive system of Hippolyte niezabitowskii (Decapoda, Caridea)

Data on the reproductive biology of the genus Hippolyte are available from studies of Hippolyte inermis. These findings support the idea that these species are protandric hermaphrodites, exhibiting sex reversal. However, recent studies of this and other species, such as Hippolyte obliquimanus and Hippolyte williamsi, have not reported sex reversal and suggest a gonochoric condition. In the present study, histological analyses were conducted of the ovaries, testes, oviducts, vasa deferentia and the development of the male appendage. The results of this study show that the Hippolyte niezabitowskii population from southern Spain should also be viewed as a gonochoric species. The study found no evidence of sex reversals. These conclusions are also supported by information on the structure of the population and by the results of studies of the male appendage. The population structure involves different size distributions of males and of females. Size classes 2-14 exhibit substantial overlap. No evidence of sex reversal was obtained from the study of the male appendage.