摘要:

Microfluorometric evaluations of DNA content carried out in both viviparous and oviparous females ofMegoura viciaehave shown that the increased nuclear volume of the nurse cell nuclei is due to repeated duplications of the whole genome. DNA over-replication begins, together with the first appearance of the ommatidia, 3 days before birth both in viviparous and oviparous female embryos, but it proceeds at different rates in the different reproductive categories. In oviparous females, 11 replication cycles take place (maximum DNA content 2048C), whereas in viviparous females only a few DNA replications occur (maximum DNA content 16C). The relationship we found between the increased DNA content in nurse cell nuclei and development of ommatidia suggests that the switch mechanism determining the beginning of DNA overreplication may be directly influenced by photoperiod effects on the developing embryos.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672457

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Optimal numbers of replicates to estimate mean oocyte sizes in female Balmain Bugs (Ibacus peronii) were determined using analyses of variance of data from a pilot study. Mean oocyte size was different in different pans of the ovary in some animals, but there were no differences within sections from the same part of each ovary. The optimal numbers of oocytes to measure was 219 or 55 per section to produce a standard error that was 5% or 10% of the mean, respectively, and for some purposes, only 20 oocytes per section needed to be measured. It is recommended that as many animals be sampled as possible, and that only a single section be taken from several parts of the ovary.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672458

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The yolk proteins inLineus lacteuswere analysed and their levels correlated with morphological and cytological features of oocyte development to define the stages of oogenesis. Three major yolk proteins (75, 41 and 40 kDa) were identified by gradient gel electrophoresis in sexually mature females and in their spawning eggs. These sex-limited glycoproteins account for a substantial proportion (62%) of the total soluble egg proteins and were found to be vitellin subunits. Their accumulation during oogenesis was monitored by electrophoresis and immunocytochemistry. Most yolk protein accumulation occurred during the third stage of oogenesis, the period of greatest oocyte growth (vitellogenic stage). Spontaneous sexual maturation was compared with experimentally induced maturation to correlate oocyte metabolism with the endocrine control of a brain hormone, the gonad-inhibiting hormone (GIH), which inhibits oogenesis. GIH was found to have a marked effect on yolk protein synthesis during accelerated sexual maturation in decerebrated worms.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672459

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Ultrastructural observations on mature sperm ofPomphorhynchus laevis(Müller, 1776), the dominant acanthocephalan parasite of fish from the River Brenta, were carried out by scanning (SEM) and transmission electron microscopy Adult males ofP. laeviswere obtained from the digestive tract ofLeucisctcs cephalus(Pisces: Cyprinidae). The spermatozoon ofP. laevisis inverted with respect to conventional sperm models; it is filiform and consists of an anterior flagellar apparatus and a posterior nucleocytoplasmic derivative. The latter includes a layer of condensed chromatin beneath the plasma membrane opposite to the flagellum, numerous large subspherical electron dense inclusions, glycogen deposits and a pentalaminar structure next to the flagellum. The nucleocytoplasmic derivative terminates caudally with a flat lamina devoid of the dense inclusions and glycogen deposits. Proceeding through the posterior lamina, the 9+2 axoneme progressively disorganizes. The ultrastructural organization resembles that reported in other acanthocephalan species, although the number of central axonemal microtubules does not vary. Hence the atypical9+naxonemal pattern with O<n<5 is still only found in the eoacanthocephalan sperm.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672460

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Morphological investigations showed that the sperm storage organ (spermatheca) of the simultaneously hermaphroditic land snailArianta arbustorumconsists of 2–8 tubules with a common entrance. Sites of sperm storage were examined in snails that mated once (eight individuals) or twice (ten individuals). After one year during which the snails laid eggs only one individual of those which copulated once had some spermatozoa in one spermathecal tubulus. In four snails of those specimens which copulated a second time after one year, a part of the tubules was filled with spermatozoa while in the remaining six animals no spermatozoa were found in the spermatheca, although they received a spermatophore 5 days before fixation. In these latter snails spermatozoa were found exclusively in the sperm-digesting bursa copulatrix. This suggests that the female reproductive system ofA. arbustorummay possibly be able to control fertilization by a selective storage of spermatozoa from different mating partners.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672461

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Incorporation of3H-leucine into TCA extracted, water soluble oocyte proteins is significantly enhanced inin vivocultures ofEulalia viridiswhich have intact supra-oesophageal ganglia and those which have undergone replacement therapy when compared to decerebrate treatments. This response is gonad specific, with no differences in the rate of uptake of3H-leucine into gut proteins between treatments. There was no significant difference in the rate of protein synthesis between oocytes culturedin vitroin the presence or absence of supra-oesophageal ganglion homogenate on culture medium containing3H-leucine. However, oocytes cultured in the presence of supra-oesophageal ganglion homogenate do show a significant increase in the rate of uptake of radiolabel when compared to oocytes cultured in the absence of prostomial homogenate when cultured on medium containing3H-labelled oocyte protein. These results indicate the presence of a gonadotrophic hormone in the supra-oesophageal ganglion ofEulalia viridiswhich promotes the uptake of external egg protein into developing oocytes. It is suggested that this is, at least in part, a heterosynthetic process with3H-leucine being incorporated into an external protein before incorporation into the developing oocytes.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672462

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This study describes and identifies the relationship between sperm development and associated structures of the male reproductive system of the Scyllarid lobsterThenus orientalis.The male gonad ofThenus orientalisconsists of paired testes, each with a vas deferens which terminates in a gonophore on the coxopodite of the fifth pereiopod. Internally the testis consists of numerous acini which are attached to coiled anterior and posterior collecting tubules. Within the acini, spermatogenesis occurs giving rise to spermatids which are liberated into the collecting tubules and subsequently grouped into spermatophores. Spermiogenesis continues as the spermatophores progress through the proximal, medial and distal vas deferens where maturity is reached. Movement through the vas deferens is assisted by apocrinal secretions of the glandular epithelium which probably functions both as a nutrient and lubricant. An external layer of smooth muscle which thickens progressively towards the distal vas deferens also assists in propelling the luminar matrix containing the spermatophores toward the gonophore.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672463

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Yolk formation has been studied in previtellogenic oocytes of the telotrophic-meroistic ovariole of the red cotton bugDysdercus intermedius(Heteroptera: Pyrrhocoridae) in the absence of the follicular epithelium (“skinned oocytes”). Early preparation for endocytosis was seen by urea gel electrophoresis and immunoblotting, which showed that cytosolic clathrin (light chain) is already present in the previtellogenic trophocyte-oocyte syncytium. The ability of these previtellogenic skinned oocytes to form yolk was studied by incubating them in physiological saline to which rhodarnine-labelled hemolymph proteins were added. These oocytes formed a peripheral band of fluorescent yolk spheres when incubated in vitellogenin-containing hemolymph proteins obtained from 6-day-old adult females but not when in hemolymph proteins from 3-day-old females, which lack vitellogenin. AVEC-DIC microscopy was used to record fluorescent protein uptake as it occurred in living, previtellogenic oocytes. Adsorption to the oolemma, endocytosis and deposition in larger vesicles in the oocyte cortex could be followed. The presence of coated pits and cortical yolk spheres in previtellogenic skinned oocytes was confirmed by electron microscopy. While juvenile hormone is known to be required for vitellogenin secretion by the fat body and for its penetration of the follicular epithelium, our results suggest that yolk formation by oocytes is more directly induced simply by exposure to vitellogenin.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672464

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672465

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672456

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor