摘要:

Sexual reproductive cycles of a Florida, U.S.A., population of four Caribbean commercial sponge species,Hippospongia lachne, Spongia barbara, S. cheirisandS. graminea, were determined by analysis of tissue samples collected over a three-year period. Spermatogenesis in these species was studied using light and transmission electron microscopy. The production of male gametes occurs in cysts within the endosomal tissue of mature specimens. Reproductive elements within an individual cyst develop synchronously while development between cysts is asynchronous. All available evidence suggests that these species are dioecious. Spermatogonia differentiate directly from choanocytesin situ.All cells of the chamber lose their collars and flagella and undergo mitosis to produce primary spermatocytes, each possessing a single flagellum. The ratio of nucleus to cell diameter in these cells is almost double that of choanocytes. Circumstantial evidence suggests that primary spermatocytes undergo meiosis to produce four spermatids, but confirmational chromatid linkage figures are still lacking. The mature spermatozoa lack both intermediate segments and acrosomes. Male gametes displayed a bright yellow-white autofluorescence when excited with blue light (460–485 nm).

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672151

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Oogenesis in four commercial Caribbean sponge species,Hippospongia lachne, Spongia barbara, S. cheirisandS. graminea, was studied using light and transmission electron microscopy. Eggs and embryos develop asynchronously in localized endosomal nurseries of these viviparous and gonochoristic species. Statistical analyses of specific morphological characteristics of reproductive elements have unequivocally identified four specific stages in the process of oogenesis. Oogonia undergo mitotic division to produce primary oocytes. Meiotic division occurs producing secondary oocytes which are fertilized before zygotes undergo major growth by phagocytosis and the transfer of nutrients through cytoplasmic bridges. During cleavage of the zygote, umbilici form between embryos and nurse cell layers and these function in the transfer of symbiotic bacteria and other mesohyl substances from the maternal parent to the embryo. These symbionts were observed dispersed between blastomeres of all young and maturing embryos and between internal cells of cytodifferentiated parenchymella larvae. Extracellular transfer of symbiotic bacteria from maternal tissues to developing embryos has not been reported in any other viviparous invertebrate.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672152

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Larval behaviour, settlement, and metamorphosis were investigated in four Caribbean commercial sponges,Hippospongia lachne, Spongia barbara, S. cheirisandS. graminea, using light and transmission electron microscopy. The parenchymella larvae of these viviparous and gonochoristic species have an average size of 350 μm by 420 μm when released. Symbiotic bacteria occur intercellularly in both larvae and post-larvae. Laboratory behavioural studies demonstrate that free-swimming larvae display directional swimming with constant lateral rotation and negative phototaxis. Larval settlement occurs 26–56 hours after release from the parent and involves the formation of a basal lamella between the post-larva and substrate. There is no evidence of larval substrate selection by type or orientation. The canal system begins to form six days after settlement and oscules are apparent eleven days post-settlement. Available evidence suggests that larval ciliated epithelial cells are terminally differentiated and do not appear to contribute to formation of post larva or adult in this group of Porifera.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672153

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Ovaries from 24h liver-fed female flies ofPhormia reginawere exposed to various extracellular tracers eitherin vivoorin vitroto gain insight on how hemolymph proteins may enter terminal follicles. Ruthenium red and lanthanum nitrate administered to aldehyde-fixed ovaries permeated the intercellular spaces of the follicular epithelium to some extent, but thorium dioxide did not even enter the basal lamina.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672154

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Chronological changes of the chromosomes upon feritilization of the giant freshwater prawn,Macrobrachium rosenbergii(de Man), were followed. Egg chromosomes, within 2 min after spawning, were at the second meiotic metaphase whereas sperm nucleus retained a cupped shape of the base region. The egg chromosomes progressed to the second meiotic anaphase by 10–15 min and completed maturation by 20 min after spawning. Both female and male pronuclei were clearly differentiable at 1 hr after spawning. Female pronucleus was larger than the male pronucleus. But both pronuclei enlarged to an equal size when they were in proximity by 3 hr after spawning. Pronuclear fusion took place by 4 hr after spawning. The fused nucleus advanced into the first mitotic division rapidly so that the first mitotic metaphase or anaphase was observed by 5 hr after spawning. The first and the second nuclear divisions were completed by 6 and 8 hr after spawning, respectively. While the first and the second cytokineses occurred simultaneously at 9 hr after spawning resulting in a 4-cell embryo. Observations of chronology of the chromosomal events upon fertilization provide informations concerning the crucial times for further chromosome number manipulation.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672155

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Hemispheric-apex cells (HC), which are situated at the intersection of the three branches of Hoyle's organ inLoligo vulgarisandLoligo forbesiembryos, were investigated using light- and transmission-electron microscopy. The surface membrane of the HC exhibits many microvilli. Desmosomes between HC were distributed in patches along the plasma membrane. These desmosomes were also found between HC and the hatching enzyme producing cells of Hoyle's organ (CHO) and between neighbouring CHO. The area below the most apical desmosomes shows many cellular interdigitations. One (or several) small Golgi apparatus and many mitochondria were found in the cell centre. Mitochondria were also abundant in the most apical part of the cell. In the HC the nucleus is situated near the cell centre. The cell shape of the central part of the cell usually corresponds grossly to the nuclear form. Endoplasmic reticulum was found near the nucleus and in the lowermost part of the cell, but is never as abundant as in the CHO. In the most apical part of the HC many oval vesicles were found containing electron lucent material. Sagittal ultrathin sections showed that the tapering proximal part of the HC, directed toward the underlying tissue may end in a T-shaped form. As the HC and CHO degenerate after hatching, it is concluded that both structures are transient embryonic cells.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672156

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The reproduction of a population of the scallopPecten maximusin Brittany (France) has been studied for two years using two different methods: (i) determination of the gonad index; (ii) measurement of oocyte diameters by image analysis of histological sections.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672157

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The data presented here document the variations of ecdysteroids in different tissues during the life-span of the tsetse fly. HPLC analyses were performed to determine the nature of immunoreactive compounds detected by RIA.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672158

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Volatile compounds in the coelomic fluid of ripeNereis succinea(Frey & Leuckart 1847) were isolated by using a closed loop stripping technique and identified by GC-MS. One major compound is the sex pheromone of the closely related speciesPlatynereis dumerillii, 5-methyl-3-heptanone. This substance increases the swarming activity during the nuptial dance reproductive behaviour and induces the males to release a very small cloud of sperm.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672159

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672160

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor