摘要:

We studied the sperm changes occurring during storage in the female genital tract ofEyprepocnemis plorans(Orthoptera: Acrididae). In this species the spermatheca consists of a long duct with two terminal diverticula: a preapical one with a U-bend and a straight apical one. After copulation the spermatozoa reach the diverticula where they undergo a peculiar uncoating process which leads to the complete re moval of the glycocalyx. This prepares the spermatozoa to interact with the female gametes. A different role is performed by the two diverticula in sperm storage. In the preapical one most sperm are stored until fertilization of the egg; in the apical diverticulum a limited number of spermatozoa are stored but most are progressively dismantled. These modifications may reduce any excess of spermatozoa or operate a mechanism of selection, aiming to favour sperm from the last mating.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672325

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The meiotic divisions in the eggs of the diploid thelytokous stick insectBacillus atticus atticus(2n=34 or 33) were examined in Feulgen squashes. The reduction division is normal and results in two interphase nuclei. These nuclei fuse at the onset of prophase II and a diploid meiotic division II follows. One of the resultant nuclei degenerates and the other starts embryogenesis. This automictic type of parthenogenesis explains the clonal maintenance of cytotypes and also the transmission of different levels of heterozygosity. The degree of heterozygosity is determined by the position of the chiasmata and the orientation of the chromosomes at metaphase II. The production of diploidB. atticus/rossiushybrids and its underlying mechanism are discussed.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672326

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The free-swimming larva of the calcareous sponge turns into a sessile juvenile during metamorphosis. Electron microscopic observations of metamorphosing larvae reveal the rearrangement and differentiation of larval cells. About 12 h after the larvae were released from a mother sponge, the settled larvae without flagella consist of an inner cell mass and an enveloping layer of pinacocytes. The inner mass cells have residual flagellar rootlets which clearly show the origin of the cells. On the other hand, the pinacocytes still show the intracellular profile characteristic of the granular cells of the swimming larva. One day after release, scleroblasts and other mesohyl cells differentiate in the peripheral region of the inner cell mass. Two days after release, the central cells of the inner cell mass differentiate into choanocytes. Three days after release, a large gastral cavity is formed and lined by a layer of choanocytes. These results demonstrate the cell lineage in the metamorphosis of the calcareous sponge, that is, the pinacocytes of a young sponge are derived from the granular cells of the swimming larva and the choanocytes from the flagellated cells.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672327

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Oxygen consumption was used as a tool to investigate the actionin vitroof four agonists of sperm maturation on suspensions of sperm morulae from the lugwormArenicola marina. The agonists used were sperm maturation factor (SMF)—present as homogenates prepared from sexually mature specimens ofA. marina;8,11,14-eicosatrienoic acid; ammonium chloride; and quinacrine. Using this technique, two classes of response were identified. The action of ammonium chloride and quinacrine was very similar; it is suggested that they may function by increasing the intracellular pH of spermatozoa. The response of sperm morulae to SMF and 8,11,14-eicosatrienoic acid, although not identical, had many similar characteristics and is clearly different from that described for ammonium chloride or quinacrine. Exactly how either SMF or 8,11,14-eicosatrienoic acid function to stimulate sperm morulae breakdown is at present unknown. The presence of non-lipids was demonstrated to modulate the action of SMFin vitro. Both SMF and 8,11,14-eicosatrienoic acid were shown to have upper and lower limiting doses, below and above which they were biologically inactive. Only a lower limiting dose was observed for the action of ammonium chloride and quinacrine. The similarity in response of sperm morulae to incubation with SMF and 8,11,14-eicosatrienoic acid lends further support to the hypothesis that the active factor in homogenates of prostomia (SMF) is indeed 8,11,14-eicosatrienoic acid.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672328

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The follicular epithelium surrounding the vitellogenic oocytes ofLocusta migratoriadevelops large spaces between the cells (becomes “patent”) when the ovary is exposedin vitroto JH III or methoprene. In the presence of JH III, the optical path difference (OPD) of individual follicle cellsin vitro, as measured by quantitative interference microscopy, increases markedly (i.e., the volume of the cell decreases). This response is inhibited by ouabain, indicating the involvement of Na+/K+ ATPase in the response. Methoprene also increases the OPD. JH II is less effective, while JH I and the bis-epoxide of JH III are without effect. Extracts of the abdominal neurosecretory organs ofRhodnius prolixus, a known source of an antigonadotropin which antagonizes the action of JH I on the follicle cells ofRhodnius, also antagonize the action of JH III on the follicle cells of locusts. Antigonadotropic activity was found in crude extracts of the thoracic ganglia ofLocustabut was absent from other parts of the nervous system. These observations extend the range of species in which JH controls yolk uptake by affecting the follicle cells, and suggests that antigonadotropins may be widely spread in insects.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672329

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Sperm modifications inducedin vitroby spermathecal extracts from virgin females of the orthopteranEyprepocnemis ploranswere studied. In this species spermatozoa undergo a series of progressive changes in surface and flagellar organization during storage in the spermatheca. Similar modifications were also observedin vitro, although with different timing and quantification. The starting point of flagellar modifications is in the “triskelionlike” units of the fibrous network, a fibrillar system in the space between the axoneme and mitochondrial derivatives. The spermathecal extract induces disorganization of the “triskelions,” causing progressive dismantling of the sperm tail and suggesting that these structures are the key point of connection between the flagellar components. Only spermathecal extract from sexually mature individuals caused such modificationsin vitro. Preliminary experiments were performed to identify the components of spermathecal extract responsible for these changes.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672330

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Injecting estradiol-17β (1.2 μl of 1 × 10−7M per 10 g body weight) or estrone (1.2 μl of 2 × 10−7M) daily into the starfishSclerasterias mollisfor 16 days at early stage one of the gametogenic cycle caused an increase in the estrone and progesterone levels in the ovaries. There was a significant increase in the sizes of oocytes and protein levels in the ovaries of treated animals, but no effect on gonad index when compared with a control group. After injection higher estrone levels were found in the ovaries than in the pyloric caeca, suggesting that the ovary is the main target organ of estrogens. In the pyloric caeca ofS. mollistreated with estrogen the estrone levels increased considerably. There were also differences in the progesterone level between the estradiol-17β injected, estrone injected or control groups but not in the pyloric caeca index or in protein levels. The results of the present and earlier studies onS. mollissuggest that both estrogens and progesterone form a regulatory system to control reproduction and nutrient cycles.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672331

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

We examined the effects of phytoplanktonic food on the survival rate, growth, development, length of larval life and competence for metamorphosis for two species of echinoids from the northeastern part of the western Mediterranean Sea. For larvae ofArbacia lixulaseven diets were tested and for those ofParacentrotus lividustwo. A diet ofCricosphaera elongatayielded a high survival rate (80%) and rapid larval growth; development was shorter, rudiment diameter was larger and metamorphosis rate was higher. There was a maximum feeding level beyond which no change in growth and development rate was observed. In response to a poor diet, larvae increased the larval period and the length of the larval arms; the survival rate decreased and development was slow and more variable. However, there was no change in the post-larval diameter regardless of diet history.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672332

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The irregular echinoidClypeaster raveneliiis a conspicuous component of offshore (50–230 m depth) epibenthic communities in the northern Gulf of Mexico. Nonetheless, no information is available on its reproductive biology. Gonad condition was evaluated between November 1988 and March 1991.C. raveneliiexhibited an annual reproductive cycle with spawning in late February. Timing of gonadal production was highly consistent between years. However, the magnitude of gonadal production was much higher in 1991 than in earlier years. Annual patterns of gonadal indexes (in large part an accumulation of nutritive material) were not significantly correlated with changes in bottom sea water temperature. Annual patterns of gametogenesis and spawning were, however, highly synchronized with increasing day length during the winter. This suggests that day length may serve as an exogenous proximate cue for gametogenesis and/or spawning, at least for populations within the photic zone. Similar to most members of the genus,C. raveneliiproduces copious numbers of small eggs (mean diameter= 121 μm) which are slightly negatively buoyant in sea water. These characteristics are indicative of a broadcasting planktotrophic mode of reproduction.

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672333

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1993.9672334

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor