摘要:

Genital gland-kidney-digestive gland tissues from the scallopPecten maximuswere fixed for histological study at the onset of spawning. Examination of serial sections of these tissues allowed for the determination of the oocytic pathway and the reconstruction of the genital tract. Results indicate that there are two oocytic collector ways in the genital gland ofP. maximuswhich are independent of one another throughout most of the gonad. Depending on their localization in the gonad, the oocytes are evacuated from the acini into the surrounding seawater environment via the gonoducts of one of these two oocytic ways. In the female gonad, each way is made up to two main oocytic collectors. In the male gonad there is only one collector for each way, and these collectors join up at their proximal extremity to form a short gonoduct that discharges all the oocytes into the right kidney. A portion of these oocytes is evacuated directly into the surrounding seawater via the urogenital orifice of this kidney. The rest are transferred into the left kidney by way of an interrenal communication located in front of the digestive gland and are then emitted into the surrounding seawater.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672477

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The brood sac of the viviparous cockroachDiploptera punctataproduces a protein-rich milk to nourish its young during gestation. Competence for milk production begins 7 days postoviposition and 5 days prior to the onset of milk synthesis. Brood sacs that have become competent and have not begun to produce milk can be identified by their ability to generate milk when implanted into the hemocoel of females that are actively synthesizing milk. Factors responsible for the development of competence were examined by various experimental treatments. Topical application of the juvenile hormone analog, 7S-hydroprene, to postoviposition females in doses sufficient to support a second vitellogenesis prevented competence; lesser doses permitted competence. Thus, elevated juvenile hormone titer during vitellogenesis (days 34) is sufficient to prevent competence at this time but the low titers that follow the onset of oviposition are not. Allatectomy of mated animals demonstrated dependence on the corpora allata for the development of competence. However, unmated animals became competent despite the presence or absence of corpora allata. The brood sacs of allatectomized mated females failed to become competent following removal of the spermatophore, denervation of the reproductive organs, or mating to sterile males. Therefore the effect of mating that produces corpus allatum-dependent competence was not generated by mechanical stimulation of the spermatophore in the bursa, sperm in the spermatheca, or neural feedback from any of the reproductive organs. However, competence did occur in allatectomized mated females if their ovaries were removed. Therefore mating in allatectomized females induces a change in the ovary that inhibits competence. Additional changes must subsequently occur that enable competence to manifest itself at the appropriate time.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672478

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The fat body produces vitellogenic proteins, which are released to the haemolymph and incorporated into developing oocytes. In the cockroachBlattella germanica, endocrine and other physiological cues regulate vitellogenesis in a complex homeostatic pattern, which is not fully understood. Thein vitroapproach may be useful to study this pattern, and the present paper describes an experimental set-up based on the incubation of the periovaric portion of the fat body and the measurement of vitellogenin production with an EIA method. The results correspond fairly well with equivalent data obtainedin vivoand suggest that the periovaric fat body is an appropriate anatomical unit to study vitellogenin productionin vitro.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672479

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A quantitative method of staging reproductive development based on the use of cell measurements and computerized image analysis of histological sections is described. The method has been applied to samples of eastern king prawn,Penaeus plebejus, collected in Queensland, Australia. Luminance measurements of selected tissue structures within the ovary were used to determine three luminance ranges which characterized ovarian development in histological sections. Cell diameter, average luminance and percent area of an ovary section within a luminance range of 200–245 were the most useful variables to discriminate between the different ovarian developmental stages. Discriminant analysis successfully separated maturing, mature and resorbing groups in 94% of the samples, but discrimination of stages within the above groups was as low as 30%. The estimated discriminant functions suggest there is a continuum of development which can be characterized by a combination of measurements obtained from histological sections.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672480

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

An electron microscopic study of sperm and spermiogenesis revealed the process of formation of the monoaxonemal sperm inBaltoplana magna.Two basal bodies are present in the zone of differentiation of the young spermatid, on either side of an intercentriolar body, but only one develops into a normal flagellum. The other remains as a flagellum bud that disappears after the spermatid has become elongated and the normal flagellum has fused with the spermatid shaft in a distal to proximal direction. The mature sperm has a single incorporated axoneme of the trepaxonematan 9+“1” configuration, a full ring of longitudinal cortical microtubules, an elongate mitochondrial rod and an elongate nucleus with a number of dense longitudinal chromatin rods. There are no dense bodies present in the spermatids nor in any region of mature sperm.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672481

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The nematodeRhabdias bufonisis an anuran lung parasite with a heterogonic life cycle, characterized by alternation of gonochoristic (free-living) and hermaphroditic (parasitic at late larval and adult stages) generations. Adult parasites containing unhatched embryos were isolated from infected amphibians, but all other stages were cultured under controlled laboratory conditions with bacteria on agar plates. Development was studied with particular reference to a comparison of the two generations. No deviation from the strict heterogonic life cycle could be induced by alterations in the conditions of culture. The early embryonic lineages in the two generations are similar but not identical. Early development in both generations takes approximately twice as long as that inCaenorhabditis elegans, and the sequence of divisions is more variable. Nuclei counted in late embryos were similar in number (mean numbers: free-living generation 502; parasitic generation 570). Their number increases only moderately in the free-living generation, reaching a mean of 873 for non-gonadal tissue in adults, similar to that (816) inC. elegans.In contrast, parasitic adults contain in total approximately 4700 somatic and of these 2600 intestinal nuclei—about five times and one hundred times, respectively, the numbers present in free-living adults. We conclude that the dramatic differences in body size and cell numbers between the two generations can be attributed mainly to additional gut tissue-specific cell divisions during the late larval or adult stages of development of the parasitic generation.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672482

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Antennal tendinal cells of the brine shrimpArtemia aremodified epidermal cells containing acentric bundles of microtubules and microfilaments that traverse the cell from the muscle insertion site on the basal surface to the cuticle on the apical surface. Morphometric determinations of growth of the antennal endite retractor muscle revealed that the muscle increased in length and width, and the nuclei replicated during the fourth instar. The attached tendinal cell, however, demonstrated no increase in the area of the microtubule- and microfilament-rich region or the apical surface, and the nucleus remained in G1, showing that muscle growth can occur without an equivalent increase in microtubules and microfilaments in the tendinal cell. The basal membrane associated with the muscle insertion site was the only region of the tendinal cell to increase in dimension. Expansion of this region preceded growth of the muscle, suggesting that interactions at the muscle insertion-tendinal cell junction may be involved in coordinated growth of the muscle and epidermis.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672483

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Eggs that had been released into the ovarian cavity were examined inAchaearanea tepidariorumby light and electron microscopy. The nuclear division of the primary oocyte was observed in the periplasm. The nucleus was in telophase and the spindle was oriented parallel to the egg's surface. The presence of a sperm nucleus that had already been incorporated into each egg indicated that internal fertilization occurs in this spider. The sperm that have been stored in the seminal receptacles in the female may be activated prior to oviposition and then migrate into the ovarian cavity.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672484

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672485

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672486

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor