摘要:

The process of autotomy-induced cheliped regeneration in the megalopa of the mud crab,Rhithropanopeus harrisiihas been studied by light microscopy and transmission electron microscopy. Following blastema eruption, four time intervals were selected arbitrarily to cover the entire period of limb regeneration. Epidermal proliferation preceded muscle and nerve regeneration. On the basis of morphologic observations, nerve tissue regenerated from existing pedal nerve. It is proposed that blood vessels arose from epidermal differentiation, while muscle differentiated from immigrant cells. Three types of haemocyte, resembling those described in adult crustaceans, were identified in the haemolymph of the larval limb bud: granular haemocytes, hyaline cells and lipoprotein cells. Two other immigrant cell types, which appear to be primitive in nature and may be variants of a single cell type, are also described. Morphological evidence is provided to suggest that the more electron dense variant differentiated into muscle; this cell type is thought to be of mesenchymal origin. This contribution provides baseline information against which the effects of xenobiotics on cheliped regeneration can be assessed.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672184

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

This paper describes the results of a histochemical study in which fluorescein isothiocyanate (FITC) labeled lectins served as reagents to detect and characterize carbohydrate containing macromolecules in mantle epithelial cells ofSepia officinalis, Loligo vulgarisandLoligo forbesiembryos and juveniles. According to these results the application of FITC labeled lectins is an effective method for characterizing cells and organs in decapod cephalopod embryos. In the mantle epithelium of all species examined, the cells of Hoyle's organ (CHO) could very easily be distinguished following application of UEI lectin. Because the UEI binding sites are probably exclusively restricted to CHO granules our investigations provide some circumstantial evidence that the hatching enzyme ofL. vulgaris, L. forbesiandS. officinalisis a α-L-fucose containing glycoprotein. The most suitable lectin to label the hemispheric-apex cells (HC) appeared to be Con A because no other cells in the mantle epithelium were stained with this agent. The Con A binding sites were found in the cell coat and in the supranuclear region of the cell, probably inside the granules. Most likely the positive reaction can be ascribed to glucose or mannose residues. From our present results it can be concluded that HC and CHO are not only readily distinguishable morphologically but they can also be identified by their specific carbohydrate characteristics.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672185

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Life-cycle theory predicts that a trade-off exists between somatic maintenance and reproduction. Short-lived semelparous organisms, with a high investment in reproduction, should have lower levels of somatic cell turnover leading to accelerated senescence and reduced post-reproductive survival, than long-lived iteroparous organisms. This model has been tested by intraspecific comparison of mitotic rates and rates of regeneration, taken as indexes of somatic cell population dynamics, between two different populations of a reportedly semelparous species of freshwater triclad,Dendrocoelum lacteum, and a population of the iteroparous speciesDugesia(S)mediterranea.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672186

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Scanning electron microscopical studies were conducted on the spongy and interstitial tissues of the testis ofD. koenigiiF. following cryosectioning. The cells of spongy tissue are situated between wall and septa and have short irregular processes that make mutual contact. Spaces between the processes form an intricate system of confluent channels permeating the whole of the tissue. The loose network also leaves some spaces adjacent to the inner surface of the outer testicular wall. Prominent vacuoles and tracheae were observed in spongy cells. Openings are also present on the inner wall of the testis that faces the lumen containing developing spermatocysts. The cells of the interstitial tissue bordering spermatocysts and inner lining of septa give rise to numerous villi extending into the lumen of the cysts and also form cytoplasmic bridges between the outer surfaces of adjacent cysts. A feature of the villi was their apparent transformation into bulbous bodies that either burst and release their contents near the metamorphosing spermatids or bud off and accompany the nearly mature spermatozoa within the lumen of the cyst. These intact bulbous bodies each possess an opening on their surface.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672187

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Three different patterns of population sex structure that implied distinctive patterns of sex expression were observed in isolated populations ofPinctada margaritifera (Bivalvia, Pteridae). A natural population appeared to be typically protandric; a colonizing population on an off-shore platform appeared to be gonochoristic; but an established population on a second platform appeared to have pseudo-protogynic sex change. It is proposed that this latter phenomenon was a tactical response to the stress of oil pollution.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672188

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The desert snailsSphincterochila zonataandS. prophetarumare hermaphrodites which have a distinct spermatogenic cycle. Snails aestivate (240–280 days/year) throughout the dry season. In mid-summer (May) the gonad is small and completely inactive. In August and September whilst the snails are still dormant, the ovotestis increases in size and spermatogenesis commences, continuing until winter. Oogenesis occurs in winter (December/January) just prior to egg laying. Spermatozoa produced in August and September are stored in the seminal vesicle region of the hermaphrodite duct, thus enabling the snails to copulate and exchange spermatozoa immediately after the first winter rains. During aestivation the seminal vesicle region of the hermaphrodite duct and its constituent cells decrease in size and the duct becomes a region of sperm degradation. Electron microscopy has shown that the wall of the seminal vesicle is composed of two types of cell which undergo considerable morphological change during the different phases of the reproductive cycle.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672189

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Phylogenetic parsimony analysis of sperm ultrastructure allows recognition in South African patellid limpets of four monophyletic groups: theargenvilleigroup (3 species); theaphanesgroup (2 species);theconcolorgroup (6species)and a more heterogeneouscochlear group (3 Patellaspecies and dubiously associated with these, species of the generaHelcion, NocellaandCeliano). Of 5 pairs of spermatological sister-species, each species is extensively sympatric with its sister-species. Sperm of such sympatric species may be morphologically almost identical or may show structural differences which would be expected to block hybridization. Where, as in theargenvilleiandaphanesgroups, the sperm within each group are structurally similar, it is likely that immunological and biochemical rather than structural features of the gametes act as species barriers preventing hybridization. Where contrasting morphological specializations of the sperm of sister-species are demonstrated, these are considered adaptations for fertilization in concert with but probably secondary to immunological/biochemical factors. They are presumed to augment rather than initiate reproductive isolation. Examples of such structural differences are the development of an elongate anterior acrosomal process inH. pruinosusrelative to its sister-speciesH. pectunculusand, independently, inP. granularisrelative to its plesiomorphic precursorP. longicosta.Trends in sperm evolution, from a morphology in theargenvilleiandaphanesgroups which is close to that of ‘primitive’ sperm, include elongation of the nucleus and development of a pointed conical acrosome in thecochleargroup; development of a rounded posterior acrosome lobe in theconcolorgroup; and numerous other described changes. Patellid species which are at least partly sympatric do not maintain reproductive isolation by staggering of the spawning time in terms of the time of the year, though the degree of interspecific, and intraspecific, synchrony during the day requires further investigation.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672190

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The levels of estrogens and progesterone in the gonads and pyloric caeca of maleSclerasterias molliswere determined during the annual gametogenic cycle from June 1986 to June, 1987. In the testes, the levels of progesterone and estrone were inversely related at the beginning of a new reproductive cycle whereas at the beginning of formation of spermatogenic columns they were directly related. In the pyloric caeca ofS. mollis, the annual pattern of changes in steroid levels did not differ between males and females, suggesting that changes in the steroid levels are related not only to reproductive processes, but also to other factors. Differences in reproductive strategy betweenS. mollisand the other asteroid may result from differences in the annual patterns of changes in steroid levels.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672191

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Aspects of the reproductive biology of the giant isopod,Bathynomus giganteus(Edwards) resemble those of other isopods. In females, the gonopores are located on the sternal midline of the eighth thoracic somite and the eggs are brooded in a marsupium. The reproductive tract of the males also resembles those of other isopods. The paired vasa deferentia open into two penes located on the sternal midline of the eighth thoracic somite. The vasa deferentia are formed of columnar epithelial cells with basal nuclei. The lumen is filled with seminal products consisting of aggregrates of spermatozoa surrounded by extracellular tubules. The sperm head consists of an acrosome and subacrosomal rod from which a pendant nucleus extends. The tails are composed of an amorphous core consisting of a dark band, two medium bands, two light bands followed by a dark band again. The tails are attached to the heads by a knob which is an extension of the core

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672192

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In vitroexperiments on late-larval stage fat body ofCorcyra cephalonicaindicate that treatment with 20-hydroxyecdysone (20-HE)alone does not alter the fat body acid phosphatase activity. However, a significant stimulation of fat body enzyme activity by 20-HE is noticeable when the hormone was added to the medium among with haemolymph obtained from the posterior half of the 24 h ligated late-last instar larvae. Haemolymph from the anterior half failed to show any stimulatory effect. The posterior haemolymph loses its stimulatory effect by heat, acid, alkali and enzyme treatments. These results suggest the presence of some factor(s) in larval haemolymph which potentiate the stimulatory effect of 20-HE on the fat body enzyme activity during late-larval development ofCorcyra.Furthermore, our co-culture studies reveal that these factor(s) are synthesis by the hind gut-associated lobular visceral fat body.

ISSN:0792-4259    

DOI:10.1080/07924259.1991.9672193

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor