摘要:

We have carried outin vivoandin vitroexperiments to determine the effect of 20-hydroxyecdysone (20HE) on the development of the male accessory reproductive glands (MARG) of fifth instarLocusta migratoria.20HE stimulates protein synthesis in the MARG, but only after day 2 of the final stadium. Thein vitroeffects of20HE and juvenile hormone III on the polypeptide profile of MARG from adults 1–10 days post-mergence were investigated using fluorographic and radiometric analyses. Synthesis of several polypeptides was influenced by both hormones in the short hyaline tubules and white tubules while in the long hyaline tubules the hormones were without effect.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672587

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The female gonad of two fresh-water prorhynchids,Geocentrophora balticaandProrhynchus stagnalis, has been investigated by means of conventional electron microscopy and cytochemical techniques. Both species have an unpaired germovitellarium located under the gut; accessory cells surround the germovitellarium ofG. baltica.The germovitellarium consists of a restricted germinative area where early differentiating oocytes and vitellocytes are randomly associated, and an extensive growth area with follicular organization. Each follicle consists of a single alecithal oocyte surrounded by numerous vitellocytes. The main features of oocyte differentiation are the accumulation of lipid droplets and the appearance of Golgi complexes and small bodies possibly representing secondary lysosomes. Vitellocytes show features typical of secretory cells, including well-developed rough endoplasmic reticulum (RER) and Golgi complexes which are involved in the production of type A and type B inclusions, hi both species, type A inclusions appear first, have a glycoprotein content, do not contain polyphenols, and become localized in the peripheral cytoplasm of mature vitellocytes; they have been interpreted as eggshell forming granules. Type B inclusions are larger, have a proteinaceous content with a different structure in the two species examined, and remain scattered in the cytoplasm of mature vitellocytes; they are considered to be yolk. The finding of eggshell forming granules without polyphenols in prorhynchids contrasts with the condition in most platyhelminths that have a sclerotized eggshell formed through a tanning process of polyphenolic substances. The small bodies in the oocytes and the eggshell granules in the vitellocytes of Lecithoepitheliata differ from those observed in prolecithophorans, which have oocyte and vitellocyte inclusions similar to those of the Rhabdocoela.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672588

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Previous studies onArenicola marinasuggested that oocyte maturation was induced by a single maturation hormone from the prostomium. This maturation hormone was thought to act directly on the oocyte (Meijer and Durchon, 1977), A recently described species,Arenicola defodiens(Cadman and Nelson-Smith, 1993), morphologically very similar toA. marina, has been found at the sampling sites described by Meijer and Durchon (1977). Results presented here from studies on British populations ofArenicola marinashow that in this species, oocyte maturation is controlled by two hormonal steps. The first step involves the prostomial maturation hormone. The second step depends on a maturation inducing substance in the coelomic fluid. We will refer to this as the coelomic maturation factor (CMF). A reliablein vitroassay for oocyte maturation in the lugwormArenicola marinahas been adopted. It utilizes fluorescence staining of the chromosome material with DNA labelling dyes (Hoechst 33342 and 33258). Maturation of oocytes inA. marinainvolves germinal vesicle breakdown (GVBD). This is accompanied by the movement of chromosomes from late prophase to metaphase of meiosis I and chromosome condensation. The chromosomes are stained brightly by the dyes and their relative positions can be easily identified so that mature and immature eggs can be distinguished by the differences in chromosome position and form. The development of thein vitrofluorescence assay has enabled us to demonstrate that there are two endocrine steps involved in the induction of oocyte maturation. We have begun the characterization of CMF, and data show this to be a thermolabile molecule with a molecular mass greater than 10 kd.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672589

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Sulfide-rich cold seeps in Monterey Canyon support dense communities of vesicomyid clams, which harbor chemosynthetic bacterial endosymbionts. Because these animals rely upon non-photosynthetic food sources, their life histories may be decoupled from seasonal phytoplankton productivity. We examined this hypothesis by investigating temporal changes in gametogenesis in two vesicomyid clam species. Clams were collected from two cold seeps (600 m and 900 m depths), and their gonads were removed and processed for histological analyses. Oocyte diameters and relative abundances of tissue types were measured in thin sections taken across the gonad. Mean oocyte diameters ofCalyptogena kilmeriincreased from August to November, 1994, but did not change by March, 1995. Relative proportions of ovarian tissue types (reproductive vs. somatic) also changed during this period, indicating reproductive seasonality. Analyses ofCalyptogena pacificatissues showed no significant change within a 3-month period. Existence of seasonal cycles for vesicomyid clams suggests that either (1) chemosynthetic production is seasonal or (2) reproductive output is tied to factors other than food production, such as synchrony of spawning to maximize fertilization success, or larval survival.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672590

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Four species of sea urchins of the genusEchinometra, designated species A, B, C, and D, occur along the coast of Okinawa; they are distinguished by color pattern and other characteristics. The two most distinct species,Echinometrasp. A (Ea) with white-tipped spines andEchinometrasp. D (Ed) with nearly black spines (possiblyE. oblonga), were examined for potential hybridization through a series of fertilization experiments and rearing of the resulting hybrids. Fertilization was reciprocally asymmetrical; Ed ova were readily fertilized by sperm of Ea, but less than 20% of the ova of Ea were fertilized by sperm of Ed. Nevertheless, hybrids resulting from crosses in both directions developed normally through larval and juvenile stages to produce sexually mature adults. Larvae of Ed♀×Ea♂ and Ed♂×Ed♀ were larger than those of Ea♂ × Ed♀ and Ea♂ × Ea♀, reflecting the larger eggs of Ed. However, Ea♂×Ea♀ juveniles and later stages, up to maturity, were consistently larger than those of equivalent ages of the other crosses; largest to smallest were Ea♂×Ea♀, Ed♂×Ea♀, Ea♂ × Ed♀, and Ed♂×Ed♀, respectively. Ova and sperm of the hybrids were viable and fertilizable in all combination of crosses, although fertilization of those of Ed♂×Ea♀ hybrids was consistently higher than those of Ea♂ × Ed♀ hybrids. These experiments represent the first reported successful production of hybrid sea urchins with viable gametes. They indicate that reproductive isolation is achieved by prezygotic isolating mechanisms in these two species. Of these mechanisms, gametic incompatibility is probably only partly involved, if at all, and differences in spawning times, habitat segregation, or other factors appear to be important for maintaining reproductive isolation in these closely related species.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672591

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The structure of the female gonad has undergone important evolutionary modifications in Platyhelminthes-Turbellaria. The primitive condition consists of single oocytes freely distributed in the parenchyma autosynthetically producing both yolk and eggshell forming granules (e.f.g.) (archoophoran level of organization). A derived condition is the presence of a compact, hetero-cellular gonad enveloped by a cellular tunica and/or an extracellular lamina-like layer and composed of germaria with alecithal oocytes and vitellaria with vitelline or yolk cells producing and accumulating both yolk and e.f.g. (neoophoran level of organization). In the last three decades the female gonad of a number of turbellarian taxa has been investigated by means of electron microscopy and cytochemistry, and several characters of oocytes and vitellocytes have been hypothesized to have a potential phylogenetic value. Some of these characters and their possible phylogenetic implications are briefly reviewed.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672592

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The breeding cycles of lugworm taken from three locations on the east coast of Ireland have been investigated through examination of coelomic fluid samples which contain the gametes, taken at monthly intervals. These reveal major differences in the timing and duration of breeding between the populations despite their geographic propinquity. The differences in breeding cycle cannot be ascribed to varietal or species differences and may arise from the different habitats occupied by the lugworm populations studied.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672593

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The hyaline layer (HL) around the embryos and larvae ofPatiriella calcaris examined by transmission electron microscopy.P. calcarhatches at the gastrula stage and develops through a lecithotrophic planktonic brachiolaria. The hyaline layer of unhatchedP. calcaris poorly developed and is comprised of wispy fibrils scattered among the epithelial microvilli. Fibrils are also occasionally seen associated with the inner surface of the fertilization envelope. By the hatched gastrula stage, the hyaline layer is organized into three strata: the intervillous layer, the supporting layer and the coarse outer meshwork layer. Seven-day-old brachiolaria also have a hyaline layer comprised of three strata. In these larvae the supporting layer elevates away from the epithelial surface due to the tuft-like organization of the underlying microvilli. This results in the formation of local outpockets giving the surface of the HL a lobed appearance. Bacteria are occassionally seen in the intervillous layer, particularly in association with the outpockets. These bacteria are phagocytosed by the epithelial cells and, in larvae that have bacteria, may play an augmentive role in larval nutrition. The structure of the hyaline layer ofP. calcaris compared with that of the hyaline layer of otherPatiriellaspecies to determine if it is more similar to the external coats around its planktonic (P. regularis) or benthic (P. exigua) developing congeners. The comparison shows that the hyaline layer ofP. calcaris virtually identical to that ofP. regularis, a similarity that may reflect the pelagic life histories of these species.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672594

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672595

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672596

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor