The effects of precocene II on early adult development in male Locusta

Haemolymph protein synthesis and the accumulation of protein in haemolymph and accessory reproductive gland of normal adult male locusts were compared to that of males treated with precocene II. The precocene-treated insects showed a lower level of protein synthesis in both the fat body (source of haemolymph protein) and accessory reproductive gland. Topical application of juvenile hormone reversed the effects of precocene treatment. It would appear that the observed effects are the result of a reduction in juvenile hormone titre in the treated animals.     

Long hyaline gland discharge and multiple spermatophore formation by the male grasshopper, Melanoplus sanguinipes

ABSTRACT. Discharge from the male accessory reproductive gland (ARG) by the male grasshopper, Melanoplus sanguinipes (Fabr.), has been studied by assay of a characterized product, a glycoprotein LHPI, and the rate of formation of spermatophores. LHPI is an exclusive long hyaline gland (a prominent ARG tubule type) product whose discharge is symmetrical from the bilaterally paired glands. LHPI forms 65% of a viscous secretion that is discharged concomitantly with the spermatophores. Though low ARG reserves in 5-day-old males limit both the number of spermatophores formed and LHPI discharged in copulations ≤6 h, this appears to be the result of shorter copulations. The number of spermarophores formed in 1 h was not impaired by general depletion of ARG protein (by repeated copulations) or by selective depletion of long hyaline gland protein (by unilateral and bilateral long hyaline gland removal), though these manipulations reduced LHPI discharge by 22%, 44% and 100%, respectively. However, 56% of spermatophores formed by males with the long hyaline gland bilaterally ablated failed to uncoil properly. These results indicate LHPI and/or other long hyaline gland proteins may act as lubricants. Unlike spermatophore formation and LHPI discharge, which increased steadily up to 90–120 min then levelled off, transfer of radiolabelled male ejaculate to the spermatheca was very variable. In 90 min copulations, only 1% of the total radioactivity (representing c. 5 μg protein) lost from the ARG complex was transferred to the spermatheca. The importance of male-derived protein in vitellogenesis is discussed.     

Sperm survival in the female reproductive tract in the fly Scathophaga stercoraria (L.)

While sperm competition risk favours males transferring many sperm to secure fertilizations, females of a variety of species actively reduce sperm numbers reaching their reproductive tract, e.g. by extrusion or killing. Potential benefits of spermicide to females include nutritional gains, influence over sperm storage and paternity, and the elimination of sperm bearing somatic mutations that would lower zygote fitness.We investigated changes in sperm viability after in vivo and in vitro exposure to the female tract in the polyandrous fly, Scathophaga stercoraria. Sperm viability was significantly lower in the females' spermathecae immediately after mating than in the experimental males' testes. Males also varied significantly in the proportion of live sperm found in storage in vivo. However, the exact mechanism of sperm degradation remains to be clarified. In vitro exposure to extracts of the female reproductive tract, including female accessory glands, failed to significantly lower sperm viability compared to controls. These results are consistent either with postcopulatory sperm mortality in vivo depending entirely on the male (with individual differences in sperm viability, motility or longevity) or with postcopulatory sperm mortality being subtly affected by female effects which were not detected by the in vitro experimental conditions. Importantly, we found no evidence in support of the hypothesis that female accessory glands contribute to sexual conflict via spermicide. Therefore, female muscular control remains to date the only ascertained mechanism of female influence on sperm storage in this species.     

Age-specific energetics of reproduction in Nucula turgida (Leckenby and Marshall) a bivalve with lecithotrophic larval development

Summary

Nucula turgida is a protobranch bivalve of the shallow sublittoral which produces, for a bivalve, unusually large eggs with a high lipid content to sustain the lecithotrophic development of the larvae. Males and females have similar reproductive investments, and the most noticeable feature of their output is the proportional increase in reproductive output as the animals age. Reproduction, as a proportion of the assimilation (Rep/C), was around 0.17 at population level but ranged from 0.055 in the 3 + year class to 0.54 in the 7 + year class. Similarly, C(=1 ? [(A ? G/R]) where A is assimilation, G gonad production and R is respiration, which appeared to be almost perfectly balanced at population level (C= ?0.05) in fact varied from very conservative (C= ?1.63) at 3 + to very “reckless” at 7+ (C=0.57). Using age-specific data, more accurate estimates can be made of future recruitment, and by back-calculation the survival rate from spawning to appearance in the benthos can be calculated.     

Nuclear binding sites for juvenile hormone III in the male accessory reproductive glands of Melanoplus sanguinipes

Summary

We have identified a potential nuclear juvenile hormone (JH) receptor in the long hyaline tubules (LHT), part of the male accessory reproductive gland (MARG) of M. sanguinipes. The MARG was incubated in vitro with [³H]JH III, and the distribution of the [³H]JH III among the cellular fractions of the LHT was determined. Some 37±4% of the radioactivity was associated with the crude nuclear pellet, while the cytosolic, microsomal and mitochondrial fractions contained 30±3%, 23±2% and 10±1%, respectively. The bound JH III was measured in nuclear extracts of LHT from males up to 15 days post-eclosion. These results revealed that JH binding increased in an age-dependent manner up to day 7, then levelled off to day 12, to increase again on day 14. The nuclear-binding component in the LHT had a very strong affinity for JH III, with a K_D value of 0.8 nM. Our observations are considered in relation to the potential site and mode of action of JH.     

Evidences of the extraglandular origin of two secretory proteins in the male accessory reproductive glands of Chilo partellus (Pyralidae,Lepidoptera, Insecta)

Summary

The male accessory reproductive glands (MARG) play an important role in contributing proteins for the formation of the spermatophore, a structure that transports sperm from the male to the female. Several studies have shown that these proteins could be either of intraglandular or extraglandular origin. SDS-PAGE analysis revealed proteins in the adult MARG of Chilo partellus, which comigrate with the larval hemolymph proteins (LHP). Ouchterlony's immunodiffusion showed that the antiserum raised against MARG extract cross-reacts with the proteins present in the adult hemolymph and fat body. Immunoprecipitates of labelled hemolymph proteins with anti-LHP or anti-MARG proteins reveal two polypeptides that comigrate with LHPs. Thus, there appear to be some proteins of extraglandular origin in the MARG of C. partellus, and the LHP could belong to this category.