摘要:

The large LucinidaeLucina pectinata(Gmelin) is a dominant species in the most confined areas of mangrove swamps where it lives deeply burrowed in reducing mud. In most female individuals, the gonads of this protandric species are in an apparently permanent state of maturity, having a various proportion of small previtellogenic oocytes together with larger oocytes undergoing vitellogenesis and full-grown oocytes which are characterized by their thick jelly coat. Oocyte resorption is also frequent in these gonads. Such a maturation schedule results in a continuous reproductive competence. Resorption of spermatozoa and simultaneous oogonia multiplication take place in spent male gonads allowing for a progressive sex change. In spent and developing stages, gonad-wall cells constitute a thick pseudo-stratified epithelium which gets progressively thinner with gonad maturation and thickens again soon after spawning. The complex cycle of these follicular cells is the result of two complementary functions: storage of lipid, protein and carbohydrate compounds ready for transfer to maturing oocytes, and resorption of degenerating oocytes through a peculiar lysosomal activity, demonstrated by cytoenzymological identification. Having permanently mature gonads ready for spawning is a reproductive strategy ofL. pectinatawhich, in addition to gill sulfur-oxidizing bacterial endosymbionts and high bacteriocyte hemoglobin concentration, is adapted to the high-stress environment of mangrove swamps. Resorption of oocytes and recovery of metabolites through the follicular cell lysosomal function appears to be the most efficient means to minimize the metabolic cost of maintaining a permanent state of maturity.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672577

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Methyl farnesoate (MF), an unepoxidated form of insect JH III, is present in Crustacea. MF is synthesized by the mandibular organs and is degraded to fomesoic acid (FA) by peripheral tissues. In this study we investigated MF degradation by esterases in hepatopancreas, ovary, testes and hemolymph of the spider crabLibinia emarginatacollected at different times of the year to determine seasonal differences. The conversion of MF to FA varied among the tissues. In the summer, the hepatopancreas showed the greatest esterase activity (52.8% conversion in females and 59.16% in males), and it was twice as high (28.86%) in ovaries than in the testes (12.16%), but was low in the hemolymph of both sexes (10.84% in males, and 6.97% in females). In the fall, the conversion of MF to FA was significantly reduced in all tissues (ovary 8.55%, testes 6.21%, hepatopancreas 10.22%, hemolymph 3.96%). Eyestalk ablation of animals in the fall restored MF esterase activity to summer levels. When tissues from these animals were incubated with OTFP, a specific inhibitor of JH esterase, MF metabolism was significantly reduced. These results suggest that MF esterase activity depends on direct induction by MF, and its degradation is by a specific esterase(s).

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672578

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Vitellin from the ovaries of the shrimpMetapenaeus ensiswas isolated using gel filtration and anion exchange chromatography. Gel filtration revealed the presence of three peaks in an extract of mature ovaries. Two of these peaks were hardly noticeable in ovaries from immature shrimp. One of these was identified to be vitellin based on the results of Sudan black B and PAS staining for lipoprotein and glycoprotein, respectively. Purified vitellin with a molecular weight of 350 kD was composed of four subunits as revealed by SDS-PAGE. The two major subunits exhibited a molecular weight of 76 and 102 kD, respectively. Amino acid analysis of native vitellin revealed that glutamate/glutamine, alanine, valine and aspartate/asparagine were the major residues. A comparison with the amino acid compositions of vitellins reported for other penaeids shows that there are no great differences among penaeids. Vitellin fromM. ensisdemonstrated an isoelectric point of 5.0 because of a high level of acidic amino acid residues. It possessed a lower level of arginine (0.96%) and threonine (0.14%) residues when compared to vitellins of other penaeids.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672579

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A radiochemical method was adopted to analyze the in vitro products of the corpus allatum (CA) ofPlautia stali.The radiolabel derived from3H-methionine added to the incubation medium was incorporated and released by CA as two main radiolabelled products. They showedRfvalues of about 0.3 and 0.5, respectively, in the thin layer chromatography (TLC) system used. The release of these products was shown to be CA-specific since in control incubations using the brain, midgut, aorta and flight muscle, virtually no release of these products was observed. The locations where these main products migrated on the TLC did not coincide with spots of synthetic standards of JH I-III or JHB3, a JH found in higher Diptera. An addition of precursors of JH III, farnesoic acid or farnesol stimulated the CA to biosynthesize the products with anRfvalue of 0.5 up to about 10-fold, suggesting that the product in question may have a sesquiterpenoid skeleton similar to JH III. Topical applications of the hexane extracts of the medium in which the CA had been incubated exerted a juvenilizing, metamorphosis-inhibiting effect on final instar nymphs in a dose-dependent fashion. The nymphs treated with the hexane extracts at a high dose moulted to intermediates with reduced forewings and scutellum, as well as nymphs implanted with the CA from reproductively active females. Based on this juvenilizing effect found in the hexane extracts, the JH-active fraction was determined after TLC separation. This assay indicated that the products found at anRfvalue of about 0.5 was JH-active. These results suggest the presence of a new JH different from any known JHs inP. stali.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672580

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Activity directed isolation studies of the ethanol extract ofBontia daphnoidesL (Myoporaceae) leaves and stems led to the isolation of epingaione, a sesquiterpene furan. This compound was previously described by Chinnock et al. (1987) from the same plant. The compound showed growth regulatory activities on gravid adult femaleBoophilus microplusCanestrini (the southern cattle tick). The dose required for inhibiting the hatching ofB. micropluseggs by 50% (Fid50)was 0.4±0.06 mg/g of the tick body weight. The Fid50dose inhibited the sequestration of protein into eggs oviposited by 80%. These eggs were non-agglutinated and wrinkled. Histological examination of ovarian sections from the treated ticks revealed significant degeneration of funicle cells and reduction in yolk content.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672581

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Caste-specific differentiation of the female honey bee gonad takes place in the fifth larval instar. In queen larvae most ovarioles exhibit almost simultaneous formation of numerous germ cell clusters within the first 20 h after the last larval molt. Ultrastructurally distinctive fusomal cytoplasm connects these cystocytes. Germ cell differentiation is accompanied by morphological changes in somatic components of the ovarioles, the follicle and the terminal filament cells. Subsequently, queen ovarioles elongate and differentiate basal stalks that coalesce in a basal calyx. A second round of mitotic activity was found to occur in the late prepupal and early pupal queen ovary. This round may elevate germ cell numbers composing each cluster to levels observed in follicles of adult honey bee queens. In contrast, germ cell cluster formation does not occur in most of the 120–160 ovarioles of the larval worker ovary, but instead many cells in such ovarioles show signs of impending degeneration, such as large autophagic bodies. DNA extracted from worker ovaries did not reveal nucleosomal laddering, and ultrastructurally, chromatin in germ cell nuclei appeared intact. In the 4–7 surviving ovarioles of the small worker ovary, germ cell clusters were found with ultrastructural characteristics identical to those in queen ovarioles. The temporal window during which divergence in developmental pathways of the larval ovaries initiates shortly after the last larval molt coincides with caste-specific differences in juvenile hormone titer which have long been considered critical to caste-specific morphogenesis.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672582

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Chemical communication is an ancient yet still immensely important part of reproduction. Amongst all invertebrates, the most sophisticated “chemical languages” are used by social insects. Here the sex- and caste-specific pheromonal messages consist of multicomponent mixtures. In the neotropical stingless beeScaptotrigona postica, an inhabitant of dense tropical rain forests, the cephalic volatiles of a queen transmit information on her reproductive status to males. A distinct ontogenetic pattern of the queen pheromone composition allows drones to discriminate receptive virgins which are then chased during the short nuptial flight through the forest understorey. By means of gas chromatographic/mass spectroscopic analyses, the numerous volatile compounds found in pentane extracts of individual bee heads could be identified. Qualitative as well as quantitative changes of these volatiles in the course of imaginal development could be determined, and bioassays with synthetic compounds were undertaken in order to decode the chemical signals used during the short encounter of a young queen and her mate.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672583

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We have identified a potential nuclear juvenile hormone (JH) receptor in the long hyaline tubules (LHT), part of the male accessory reproductive gland (MARG) ofM. sanguinipes.The MARG was incubatedin vitrowith [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 KDvalue of 0.8 nM. Our observations are considered in relation to the potential site and mode of action of JH.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672584

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

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 ofChilo 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 ofC. partellus, and the LHP could belong to this category.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672585

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Our analysis of spermiogenesis ofDrosophila subobscuraindicates that the axoneme takes part in the elongation of the spermatid nucleus, as follows. In sperm ofD. subobscurathe axoneme accompanies the nucleus in its full length up to the acrosome. Before the elongation of the nucleus begins, the centriole contacts the nuclear membrane, and is orientated with its axis to the centre of the spherical nucleus. Later in development, at the beginning of nucleus elongation, the axis of the centriole does no longer point to the centre of the nucleus but is dislocated more to one side of the nucleus. Subsequently, the axoneme which is growing from the centriole, pushes the nucleus which develops a cap-like structure over the anterior end of the centriole. By the continuosly growing axoneme stretching forces are applied to the anterior part of the nucleus. Consequently the elongating nucleus gets a smaller diameter anteriorly than posteriorly. And the longer the total length of the sperm is the longer is the nucleus. During elongation the chromatin shows a network-like structure. Nucleus elongation stops when the chromatin is fully condensed but the axoneme continues to grow. Thereupon the cap is no longer seen, and the anterior part of the nucleus which previously was the cap, forms now a bulge beside the centriole and the axoneme.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672586

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor