Sex ratios and sex-biased infection behaviour in the entomopathogenic nematode genus Steinernema

In experimentally infected insects, the sex ratio of first generation nematodes of five species of Steinernema was female-biased (male proportion 0.35-0.47). There was a similar female bias when the worms developed in vitro (0.37-0.44), indicating that the bias in these species is not due to a lower rate of infection by male infective juveniles (IJs). Experimental conditions influenced the proportion of males establishing in insects, indicating that male and female IJs differ in their behaviour. However, there was no evidence that males are the colonising sex in any species, contrary to what has previously been proposed. Time of emergence from the host in which the nematodes had developed influenced sex ratios in experimental infections. In three species (Steinernema longicaudum, Steinernema glaseri and Steinernema kraussei), early emerged nematodes had a higher proportion of males than those that emerged later, with the reverse trend for Steinernema carpocapsae and Steinernema feltiae. In a more detailed in vitro study of S. longicaudum, the proportion of males was similar whether or not the nematodes passed through the developmentally arrested IJ stage, indicating that the female bias is not due to failure of males to exit this stage. The sex ratio in vitro was independent of survival rate from juvenile to adult, and was female-biased even when all juveniles developed, indicating that the bias is not explained by failure of males to develop to adults. The female-biased sex ratio characteristic of Steinernema populations appears to be present from at least the early juvenile stage. We hypothesise that the observed female bias is the population optimal sex ratio, a response to cycles of local mate competition experienced by nematodes reproducing within insect hosts interspersed with periods of outbreeding with less closely related worms following dispersal.     

Sperm cell surface characteristics of Plumbago zeylanica L. in relation to transport in the embryo sac

Myosin associated with the male germ cells of angiosperms interacts with actin, promoting transport of the non-motile generative and later sperm cells in the pollen tube. Myosin localizing on the sperm cell plasma membrane seems negligible in Plumbago, as reflected by the absence of: (i) anti-myosin labeling using immunoelectron microscopy, (ii) sperm motility on actin matrices, and (iii) electrophoretic movement changes after addition of antibody. Sperm cells injected directly into actively streaming Nitella internodal cells, however, follow actin bundles and their movement is sensitive to ATP and Mg²⁺. This may be based on simple charge binding since negatively charged latex beads also migrate on actin, whereas neutral or positively-charged latex beads do not. Sperm cells are negatively charged according to capillary microelectrophoresis, whereas killed sperm cells, which are positively charged do not migrate. The sperm cell that normally fertilizes the egg has a higher calculated charge (8.277 × 10³ esu/cm²) compared with the sperm cell that fuses with the central cell (6.120 × 10³ esu/cm²). Received: 15 December 1998 / Accepted: 21 January 1999     

A variable selection index for the compensation of correlated genetic change

Summary A selection index for two traits has been constructed which allows partial restriction for one of the traits. The index is used in a situation where correlated response to selection in one sex is compenstated for by selection for other traits in the opposite sex. A numerical example is given.     

雄性水狼蛛生殖球顶部的扫描电镜研究

本文对我国已知的十一种水狼蛛(蜘蛛目:狼蛛科)生殖球顶部用扫描电镜进行了研究。结果表明,水狼蛛属蜘蛛插入器细长,其后端位于顶突上一突起的凹槽内,顶突作为功能引导器保护着插入器,而无其他狼蛛属具有的次生真正引导器;顶突的形状和其上的突起、顶突与插入器的相互关系对于种的分类与鉴定,特别是对于近似种的区分有较大的参考价值,但仅根据插入器从顶部升起的位置来作为分新属的主要标准,笔者认为还值得商榷和进一步探讨。     

鼎突多刺蚁群体结构和生活史的研究

本文报告了鼎突多刺蚁(Polyrhachis vicina Roger)的群体结构和生活史。通过研究表明,鼎突多刺蚁一年发生一代,以蚁后、雄蚁、工蚁、幼虫和卵越冬。卵和幼虫在冬天发育停滞(或极慢)。到了春天,随着气温的上升,卵和幼虫又恢复正常发育。据室内人工饲养观察,卵的发育历期为23.8±2.5天(平均温度26℃)幼虫为20.4±4.4天(26℃),工蚁蛹为19.8±5.5天(27℃)。成长工蚁在5—11月出现;8—11月,雄蚁从蛹中羽化;10月,雌蚁从蛹中羽化。雌蚁分飞交尾后,进入邻近蚁巢或回到原巢,脱翅成为蚁后。蚁巢内存在着多后现象。     

Developmental appearance of the Ca2+-binding proteins parvalbumin,calbindin D-28K,S-100 proteins and calmodulin during testicular development in the rat

Summary Calcium and intracellular Ca²⁺-binding proteins are possibly involved in hormone production and spermatogenesis in rat testis. Parvalbumin, calbindin D-28K, S-100 proteins and calmodulin were localized in the Leydig cells, which are sites of testosterone synthesis. Only the appearance of parvalbumin-immunoreactivity is closely correlated to testosterone production during development of the testes. Calbindin D-28K-immunoreactivity persisted in foetal-type Leydig cells and in adult-type Leydig cells at all stages of development. S-100-immunoreactivity was low during all foetal stages, absent between birth and puberty, and increased thereafter. Calmodulin staining is most prominent in the cytoplasm of developing spermatocytes and of maturing spermatids. All four proteins co-exist in the seminiferous tubules. The distinct localization and developmental appearance of these proteins suggests different regulatory roles in Leydig cell function and spermatogenesis.     

Localization and identification of nuclear radioactivity in the pituitary gland and genital tract after administering 3H-testosterone, 3H-dihydrotestosterone,or 3H-estradiol to male rhesus monkeys

Summary Target cells for testosterone, dihydrotestosterone, and estradiol in the pituitary gland and genital tract of the male primate were localized by thaw-mount autoradiography, and high performance liquid chromatography was used to identify the metabolites of these steroids in cell nuclei. Castrated rhesus monkeys were injected with ³H-testosterone, ³H-dihydrotestosterone, or ³H-estradiol and killed 60 min later. In the anterior pituitary gland, fewer cells were labeled and less radioactivity was taken up by cell nuclei following the administration of either ³H-testosterone (4% of pars distalis cells and 5 dpm/g DNA) or ³H-dihydrotestosterone (5% of cells and 13 dpm/g DNA) than following the administration of ³H-estradiol (43% of cells and 214 dpm/g DNA). Most of the radioactivity in nuclei was in the form of the unmetabolized parent compound (78–94%). In prostate, seminal vesicles, and penis, ³H-dihydrotestosterone was the predominant form of nuclear radioactivity following both ³H-testosterone (67–90%) and ³H-dihydrostestosterone (94–97%) administration, and both androgens labeled epithelial and smooth muscle cells. In contrast, ³H-estradiol was taken up in unchanged form, by cell nuclei of the genital tract and it labeled connective tissue fibroblasts, but not epithelial cells. Thus, the distributions of target cells for androgens and estrogens were clearly different in all these tissues, and the uptake of testosterone resembled that of its androgenic rather than that of its estrogenic metabolite.     

The plasma membrane and generative cell organization in pollen of the mimosoid legume,Acacia retinodes

Summary Cytological changes associated with the final maturation, and dehiscence of the 16-grain compound pollen (polyads) have been followed in anthers at female and male phase of flowering. InAcacia retinodes, the transition from female to male phase takes approximately 24 h. The spherical generative cell at female phase is connected with the vegetative cell plasma membrane by a junction zone. This is sited adjacent to a germinal aperture, comprising wall ingrowths and membrane labyrinths. By male phase, the generative cell has elongated into a spindle-shape, and its surface is characteristically scalloped. The membrane labyrinths, especially those at the apertures, now contain masses of coated vesicles, implicated in the transport and secretion of proteins. Two-dimensional projections indicate that the generative cell and vegetative nucleus are closely associated forming a male germ unit.     

The reconciliation behavior of golden monkeys (Rhinopithecus roxellanae roxellanae) in small breeding groups

Observations were made following 130 spontaneous aggressive incidents in two small breeding groups of captive golden monkeys (Rhinopithecus roxellanae roxellanae). Participants were observed both during the first 10 min following these incidents and during matched control observations. An increased contact rate was observed between opponents following the aggressive incident. Post-conflict contacts were characterized by a number of behavior patterns: open mouth, rapid grooming, embrace, and crouching. Adult males played an important role as mediator in agonistic disputes among females: males intervened in 93.6% of female fights. It is speculated that this intervention behavior is related to the species' organization into one-male units.