Schistosome female reproductive development

Schistosome parasites have evolved to produce a number of unique features in their life history; one of these is separate sexes. This has, in turn, led to a novel interplay between the male and female parasite that has been recognized for over 50 years: the growth and reproductive development of the female parasite is in some way regulated by the male schistosome. Early classical and later experimental studies established that the presence of the male schistosome is necessary not only for the initiation of female development but also for the maintenance of her mature state. The male parasite regulates the reproductive development of the female, partly by providing a stimulus that is necessary for the development of the vitelline gland. The cells of the vitelline gland provide nutrients and shell precursors for the egg. Also in this review by Philip LoVerde and Li-ly Chen, it is interesting to note that recent molecular studies have confirmed early work by showing that gene expression in the female parasite is developmentally regulated in a tissue-specific manner and that this gene expression is controlled by the presence of a male parasite.     

A male accessory gland peptide that regulates reproductive behavior of female D. melanogaster

The adult male accessory glands of D. melanogaster synthesize and secrete a peptide that represses female sexual receptivity and stimulates oviposition. Normally, this peptide is transferred to females during copulation; however, the peptide shows the same biological activity after purification and subsequent injection into the abdominal cavity of female virgins. Amino acid sequencing of the purified peptide and oligonucleotide-directed cDNA cloning established that the peptide consists of 36 amino acids. It appears to be synthesized as a precursor with a hydrophobic signal sequence of 19 residues at its N-terminal end. The precursor peptide is encoded by a short mRNA that accumulates exclusively in the male accessory gland. The gene has been localized by in situ hybridization to polytene chromosomes at 70A.     

Vomeronasal neuroepithelium and forebrain Fos responses to male pheromones in male and female mice

Male urinary pheromones modulate behavioral and neuroendocrine function in mice after being detected by sensory neurons in the vomeronasal organ (VNO) neuroepithelium. We used nuclear Fos protein immunoreactivity (Fos-IR) as a marker of changes in neuronal activity to examine the processing of male pheromones throughout the VNO projection pathway to the hypothalamus. Sexually naive male and female Balb/c mice were gonadectomized and treated daily with estradiol benzoate (EB) or oil vehicle for 3 weeks. Subjects were then exposed to soiled bedding from gonadally intact Balb/c males or to clean bedding for 90 min prior to sacrifice and processing of their VNOs and forebrains for Fos-IR. Male pheromones induced similar numbers of Fos-IR cells in the VNO neuroepithelium of oil-treated male and female subjects; however, EB-treated females had significantly more Fos-IR neurons in the VNO than any other group. There was an equivalent neuronal Fos response to male odors in the mitral and granule cells of the anterior and posterior accessory olfactory bulb of males and females, regardless of hormone treatment. In central portions of the VNO projection pathway (i.e., bed nucleus of the stria terminalis, medial preoptic area) neuronal Fos responses to male pheromones were present in female but absent in male subjects, regardless of hormone treatment. In a separate experiment, mating induced neuronal Fos-IR in these brain regions at levels in gonadally intact male subjects which were equal to or greater than those seen in ovariectomized females primed with estrogen and progesterone. This suggests that neurons in the central portions of the male's VNO pathway are capable of expressing Fos. Our results suggest that sexually dimorphic central responses to pheromones exist in mice that may begin in the VNO neuroepithelium.     

Small-molecule pheromones that control dauer development in Caenorhabditis elegans

In response to high population density or low food supply, the nematode Caenorhabditis elegans enters an alternative larval stage, known as the dauer, that can withstand adverse conditions for prolonged periods. C. elegans senses its population density through a small-molecule signal, traditionally called the dauer pheromone, that it secretes into its surroundings. Here we show that the dauer pheromone consists of several structurally related ascarosides-derivatives of the dideoxysugar ascarylose-and that two of these ascarosides (1 and 2) are roughly two orders of magnitude more potent at inducing dauer formation than a previously reported dauer pheromone component (3) and constitute a physiologically relevant signal. The identification of dauer pheromone components 1 and 2 will facilitate the identification of target receptors and downstream signaling proteins.     

Modulation by neonatal thymectomy of the reproductive axis in male and female rats during development

The effects of neonatal thymectomy, at 3 days of age, on parameters of the reproductive axis were examined in male and female Sprague-Dawley rats. Gonadal and accessory sex tissue (male: epididymis, seminal vesicle, and ventral prostate; female: uterus) weights as well as anterior pituitary, spleen, and adrenal weights were determined in the thymectomized and sham-thymectomized animals at 20, 30, 40, 50, 60, and 90 days of age. Plasma gonadotropin concentrations as well as pituitary content of the gonadotropins and prolactin were assessed at each of these time intervals. No significant difference in gonad and accessory sex tissue weights was detected in thymectomized versus sham-operated controls at each of these times. Adrenal weights were increased in thymectomized animals compared with controls at 50 days of age and older in male rats and at 90 days in females. Spleen weights were decreased in the thymectomized males at 50 and 60 days of age. Thymectomy did not affect the spleen weight of females. Plasma concentrations of gonadotropins were unaffected in thymectomized males but were altered in females during the pre- and peripubertal period (Days 20-40). Vaginal opening, however, occurred at the same time in the thymectomized and control females. Pituitary gonadotropin and prolactin content were unaffected by thymectomy of the females, except at 90 days when pituitary luteinizing hormone (LH) content was lower in thymectomized than in control animals. LH and prolactin content were significantly reduced in the males at 60 and 90 days of age. These results demonstrate that there are sexual differences in the effects of thymectomy on parameters of the reproductive axis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Differing behavioral and endocrinological effects of two female sex pheromones on male goldfish

Ovulatory female goldfish sequentially release at least two sex pheromones: 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17,20 beta P) and a mixture of F prostaglandins (PGFs). This study sought to determine whether these pheromones have different endocrinological and behavioral actions and whether the PGF pheromone, which is released by spawning females, is responsible for increasing the gonadotropin (GtH) and milt (sperm and seminal fluid) levels of spawning males. Grouped and isolated males were exposed to combinations of these pheromones, food odor, and spawning and nonspawning females. 17,20 beta P stimulated GtH increases in both grouped and isolated males but had only minor effects on behavior; because its principal function appears to be physiological it may be considered a "primer" pheromone. In contrast, exposue to the PGFs elicited large increases in sexual behavior but increased GtH only when fish were exposed as groups; this pheromone's principal action appears to be behavioral and it should be considered a "releaser" pheromone. Although males had increased GtH and milt levels after 1 hr of spawning, males allowed to interact with nonspawning females also had elevated GtH; thus, behavioral interactions appear capable of elevating GtH in the absence of either pheromone. The existence of an independent behavioral mechanism which stimulates GtH was supported by the fact that males exposed to 17,20 beta P while spawning had GtH levels much greater than males exposed to only one of these stimuli.     

A neurospora mutation that arrests perithecial development as either male or female parent

A mutant of Neurospora crassa fails to produce perithecia when crossed as either the male (fertilizing) parent or the female (protoperithecial) parent. This mutant is unique in that it appears to be due to a single mutation that blocks sexual development when crossed as either parent. As either a male or female parent, the mutant, fmf-1, produces perithecia blocked at a diameter of 120 microns and containing no meiotic figures; normal perithecia are over 400 microns in diameter. The mutant maps to linkage group IL near arg-1. Forced heterokaryons have been made between fmf-1 and fmf-1⁺ nuclei. These heterokaryons are fertile when crossed, and fmf-1 can participate as either the male or female component; the mutation is thus heterokaryon recessive and nuclear nonautonomous. Homokaryotic fmf-1 conidia were purified from a mixed conidial population derived from such a heterokaryon; these conidia failed to function as the male parent, suggesting that the fmf-1⁺ gene product is not contained in the conidium. In mixed mating-type heterokaryons, formed using tol, fmf-1 participates in ascospore formation and triggers perithecial development. Moreover, tol suppresses the action of fmf-1 if present in both components of a cross.———These data suggest that (1) fmf-1 acts in the perithecium at some time between fusion of the conidium with the trichogyne and the onset of meiosis; (2) the fmf-1 gene product is not contained in conidia; and (3) both mating types may enter the protoperithecium when a mixed mating-type heterokaryon is used as the male parent.     

Cost of male diapause indirectly affects female reproductive performance

We evaluated the cost of diapause in both females and males separately in the multivoltine bruchid Acanthoscelides pallidipennis (Motschulsky) (Coleoptera: Bruchidae). We artificially generated diapause (D) and non‐diapause (ND) individuals and compared the reproductive traits among all combinations of D and ND pairs. Diapause in both sexes had negative effects on the female pre‐oviposition period and fecundity, but not on egg volume. Females mated to D males had longer pre‐oviposition period and lower fecundity than females mated to ND males. These results showed that reproductive performance of a female could be influenced by the diapause experience not only of herself but also of the male with whom she mated.     

Coevolution of male and female reproductive structures in Drosophila

The morphology of male genitalia whilst stable within species, exhibits huge interspecific variation. This variation is likely to be as a result of sexual selection due to the direct involvement of these reproductive structures in mating and sperm transfer. In contrast, internal soft tissue components of the genitalia are generally poorly investigated as they are not directly involved in physical and mechanical adequacy during sperm transfer. However, these soft tissue structures may also drive differential male–female interactions, particularly in internally fertilising organisms where females have the ability to store sperm and bias male reproductive success. In this paper we use the drosophila model to investigate the role of male and female reproductive elements in sexual selection. Our meta-analysis supplemented with additional new data clearly shows that within species, sperm length versus testis length, and sperm length versus seminal receptacle length, are highly correlated. Thus, independent of the phylogenetic relationship among species, gamete evolution is likely to result in sexual selection interactions that drive the evolution of internal reproductive components in both sexes. Our results and discussion of the literature highlight the importance of considering internal soft structures that may influence fertilisation, when investigating selective forces acting on the evolution of reproductive traits.     

巨龙竹生殖器官形态结构及雌、雄配子体的发育

通过石蜡切片的方法对巨龙竹生殖器官结构、大小孢子的发生和雌、雄配子体的发育过程进行了观察研究。 巨龙竹为一心皮组成的单室单子房,子房内具有一个胚珠,倒生、双珠被、厚珠心。大孢子母细胞减数分裂形成线形排列的4个大孢子,合点端大孢子具功能。胚囊的发育为蓼型,具多个反足细胞。巨龙竹的花药壁由4层结构组成,包括表皮、药室内壁、中层、绒毡层;花药壁发育为单子叶型,绒毡层为腺质型。小孢子母细胞减数分裂中的胞质分裂为连续型,四分孢子为四面体型;成熟花粉粒为2细胞型,具1个萌发孔。小穗发育雌雄异熟,雌蕊的发育早于雄蕊的发育。     

Conifer reproductive development involves B-type MADS-box genes with distinct and different activities in male organ primordia

The Norway spruce MADS-box genes DAL11, DAL12 and DAL13 are phylogenetically related to the angiosperm B-function MADS-box genes: genes that act together with A-function genes in specifying petal identity and with C-function genes in specifying stamen identity to floral organs. In this report we present evidence to suggest that the B-gene function in the specification of identity of the pollen-bearing organs has been conserved between conifers and angiosperms. Expression of DAL11 or DAL12 in transgenic Arabidopsis causes phenotypic changes which partly resemble those caused by ectopic expression of the endogenous B-genes. In similar experiments, flowers of Arabidopsis plants expressing DAL13 showed a different homeotic change in that they formed ectopic anthers in whorls one, two or four. We also demonstrate the capacity of the spruce gene products to form homodimers, and that DAL11 and DAL13 may form heterodimers with each other and with the Arabidopsis B-protein AP3, but not with PI, the second B-gene product in Arabidopsis. In situ hybridization experiments show that the conifer B-like genes are expressed specifically in developing pollen cones, but differ in both temporal and spatial distribution patterns. These results suggest that the B-function in conifers is dual and is separated into a meristem identity and an organ identity function, the latter function possibly being independent of an interaction with the C-function. Thus, even though an ancestral B-function may have acted in combination with C to specify micro- and megasporangia, the B-function has evolved differently in conifers and angiosperms.     

A potential mate influences reproductive development in female,but not male,pine siskins

The role of photoperiod in avian reproductive timing has been well studied, and we are increasingly recognizing the roles of other environmental cues such as social cues. However, few studies have evaluated the extent to which males and females of the same species respond similarly to the same type of cue. Moreover, previous studies have rarely examined how variation in the quality or nature of a given social cue might modulate its effect. Here, we examine the sensitivity of male and female pine siskins (Spinus pinus) to a potential mate as a stimulatory cue for gonadal recrudescence, and we investigate whether variation in the relationship between a bird and its potential mate modulates the effect of that potential mate. Birds were initially housed without opposite sex birds on a 12L:12D photoperiod with ad libitum food. After gonadal recrudescence had begun males and females were randomly paired with an opposite sex bird or housed alone. An additional group of males was paired with estradiol-implanted females. In males, these social treatments had no effect on testis length, cloacal protuberance length, luteinizing hormone (LH) levels, or testosterone levels. In females, presence of a potential mate had a significant and positive effect on ovary score, defeathering of the brood patch, and LH levels. Among paired birds, the degree of affiliation within a pair corresponded to the extent of reproductive development in females, but not males. Thus, reproductive timing in females appears to be sensitive to both the presence of a potential mate and her relationship with him.     

Fine structure of scolopidia in Johnston's organ of female Aedes aegypti compared with that of the male.

The Johnston's organ of the female mosquito, Aedes aegypti, has only three types of scolopidia: types A, B, and C. It lacks the type D scolopidium of the male's organ. The basic structure and the location of each type in the female are similar to the counterparts in the male's organ. A single scolopidium is composed of a scolopale cell, an envelope cell, a long cap, and a third sheath, in addition to the two electron-dense scolopales produced inside the cytoplasm of two satellite cells. Each scolopidium has either two (type A) or three (type B) sensory cells. A type C scolopidium, mononematic in contrast to the amphinematic types A and B scolopidia, has two sensory cells, a microtubular cap cell, two microtubular accessory cells, and a scolopale cell with an intracellular scolopale. Even though the female Johnston's organ has all the components of the male's organ except for the single type D scolopidium, the female's organ shows relatively poorer organization and development. The female has a smaller and thinner basal plate, shorter and thicker prongs, fewer type A sensory cells, and a shorter flagellar flange, in addition to the overall smaller size of the pedicel.The probable function of each scolopidial type is discussed, especially in connexion with the probable identification of a single auditory sensillum in the male.