摘要:

Spermatid differentiation and the morphology of mature spermatozoa in Nucella crassilabrum, a muricid snail, was investigated. Five phases of spermiogenesis considering the polarization of organelles, nuclear elongation and chromatin condensation are described. Characteristics observed are compared to those of other muricaceans gastropods. The comparison of the proportional size of the different sperm segments (head, middle- and principal piece) between these species, is emphasized.

ISSN:0792-4259    

DOI:10.1080/07924259.1989.9672039

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Factors that contribute to the onset of milk production by the brood sac of the viviparous cockroachDiploptera punctatawere studied. Milk, which normally begins to be secreted on day 20 of adult age, was detected in brood sac tissue by rocket-immunoelectrophoresis. Humoral factors were shown to initiate milk synthesis in that: (1) brood sacs denervated on day 10 initiated milk synthesis normally, and (2) milk synthesis was initiated in brood sacs from 12-to 18–day donors after implantation into 50 day hosts (i.e., actively synthesizing milk). Implanted brood sacs from donors younger than day 10 did not produce milk suggesting that they were not competent to respond to the humoral factors within the host. Brood sacs from 15–day donors implanted into hosts with increasing levels of milk production contained milk in amounts that increased with that of the host. The humoral factors are not derived from the head because decapitation did not prevent the onset of milk synthesis. Milk production began, with a slight delay, in the presence of unfertilized eggs in the brood sac but did not continue to increase. This indicates that developing embryos are not needed to initiate milk production but are needed for its proper timing and subsequent potentiation. Thus, the onset of milk synthesis requires stimulation by humoral factors and development of the competence of the brood sac to respond to them.

ISSN:0792-4259    

DOI:10.1080/07924259.1989.9672040

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Testes from young fifth instarOstrinia nubilalisproduced very small amounts of ecdysteroids while those from larvae that had purged their gut produced considerably more immunodetectable ecdysteroidin vitro. Larval testes that had fused produced 2.2 times more ecdysteroid than those that remained separate. It was the sheath of the testes rather than the contents that was physiologically active. Synthesis was questionable in testes from day-1 pupae and was not observed in testes from pharate pupae, from day-2 pupae or from pharate adults. Thus, synthesis only occurred at specific times in the life cycle. Ecdysteroid profiles for testes from wandering larvae whose testes had fused showed a net increase in all normally observed ecdysteroids, with the greatest increase being in 20-hydroxyecdysone. For testes from day-1 pupae, the nature of the ecdysteroid profile changed after 24 h of incubation, with some ecdysteroids showing increases and other decreases. There appear to be considerable differences among species regarding the times of testis synthesis and the amounts and nature of the ecdysteroids synthesized.

ISSN:0792-4259    

DOI:10.1080/07924259.1989.9672041

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The A and C blastomeres at the 4 cell stage ofIlyanassa obsoletawere deleted and the resulting BD half embryos were cultured until the age of seven or eight days. The embryos were observed daily for developmental progress. The week-old larvae were fixed and closely examined for the presence of velar lobes, velar pigment, everted stomodeum, eyes, foot, operculum, statocysts, external shell, internal birefringent masses, and gut pigment. These traits were then assessed for their ability to develop in a mosaic and/or regulative manner. Both mosaic and regulative developmental controls function in the organogenesis of allIlyanassalarval organs, with one exception. Since a fully normal intestine was observed in larvae, the fate of the endodermal derivatives from the 4d cell are strictly mosaic. It is clear that the D quadrant is necessary for the normal development of bilateral organs, even though it does not directly contribute to them, and it can regulate the production of these organs when the A, B, or, C quadrant is missing. In addition, more right than left eyes and statocysts were present in BD halves. This may be explained by the presence of cytoplasm in the D quadrant which determines the right side of the larvae. This cytoplasm, present in the CD cell at the 2 cell stage, is partitioned into both the C and D cells at the next division, but normally only effects development of the C quadrant.

ISSN:0792-4259    

DOI:10.1080/07924259.1989.9672042

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

There is a large influx of water into the pupal testis ofM. configurataduring eupyrene spermiogenesis, and subsequently, an almost equally large efflux of water from the testis after all the spermatozoa within spermatocysts have become fully elongated. The temporal pattern, direction and magnitude of change in the taurine content of the testis are similar to the movement of testis water, indicating that testis hydration-dehydration and taurine influx-efflux are linked osmotically. An osmotic model for membrane translocation in me testis during spermatogenesis is suggested in which low molecular weight precursors such as amino acids in the haemolymph that are required for spermiogenesis cross the testis wall in response to the osmotic gradient generated by testis hydration. After the precursors have been fixed in macromolecular structures of the elongated spermatozoa, waste products and other substances leave the testis with water during testis dehydration.

ISSN:0792-4259    

DOI:10.1080/07924259.1989.9672043

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The possible involvement of ecdysteroids in the endocrine interaction between digenetic trematode parasites and their intermediate hosts, freshwater snails, was studied in the combination Lymnaea stagnalis-Trichobilharzia ocellata.

ISSN:0792-4259    

DOI:10.1080/07924259.1989.9672044

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The lugworm,Arenicola marinaL. has an annual cycle of reproduction with epidemic spawning and external fertilisation. The spermatozoa ofArenicolaare unusual in that they are held immotile (as plates of several hundred cells known as morulae) in the coelomic fluid until activated just prior to spawning. Activation ofArenicolasperm is brought about by a sperm maturation factor (SMF) from the prostomium and can be carried outin vitrousing an assay technique developed by Bentley (1985). Scanning electron microscopy is used here to examine the changes which occur duringin vitroactivation. This revealed that the bundles of flagella of inactive sperm become disorganised as flagella beating commences but the flagella at this stage are still bound together at their tips. The sperm heads then become separated from the cytophore and finally the distal binding of the flagella is broken to give free-swimming spermatozoa. Coelomocytes present in the coelomic fluid resorb unspawned gametes prior to the initiation of the next gametogenic phase.

ISSN:0792-4259    

DOI:10.1080/07924259.1989.9672045

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Development of the upper vas deferens and seminal vesicle, and the ecdysteroid titers of the cabbage armyworm (Mamestra brassicae) during pharate adult stage were investigated to provide evidence of endogenous control of the sperm movement through the reproductive tract. Apparently, development of the upper vas deferens is initiated when ecdysteroid titers increase after pupation and continues until eclosion. Sperm movement correlates with the decrease of ecdysteroid titers. When ecdysteroid titers remained at low levels, sperm release from the testis was observed one day before eclosion.

ISSN:0792-4259    

DOI:10.1080/07924259.1989.9672046

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Several 5-hydroxytryptamine (5-HT) agonists were used to induce maturation inSpisulaoocytes and antagonists to block 5-HT-induced germinal vesicle breakdown. Among the analogs tested, only 8-hydroxy-2-(di-n-propylamino)-tetralin induced maturation ofSpisulaoocytesin vitroand mianserin blocked 5-HT-induced maturation. The present findings suggest thatSpisulaoocytes may possess 5-HT1Areceptor sites.

ISSN:0792-4259    

DOI:10.1080/07924259.1989.9672047

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

We compared prefeeding development times, from fertilized egg to prism larva, forStrongylocentrotusembryos from four clutches of eggs (each from a different species) differing in size. Development times did not vary consistently with egg diameter, and trends among eggs of different sizes varied with stage of development. In some cases, development times for eggs of intermediate diameter (S. franciscanus) were longer than those for larger or smaller eggs. Although mean egg diameters in clutches ranged from 84 μm (S. purpuratus) to 162 μm (S. pallidus), differences in development time to the last embryonic stage (prism) were very small. We conclude that the inverse relationship between parental investment in offspring and premetamorphic development time in echinoids depends only on the functional consequences of reduced size of feeding larval stages: effects of egg size on prefeeding development time are not evident.

ISSN:0792-4259    

DOI:10.1080/07924259.1989.9672048

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor