摘要:

The separation of females and males after mating is a usual practice when the reproductive phase of astacids takes place under controlled conditions and is carried out to avoid egg losses due to male disturbance during spawning and embryonic development. In order to determine the possible effects of male presence on reproductive efficiency, two treatments were tested in the white-clawed crayfish (Austropotamobius pallipes):females alone, and females and males together throughout egg laying and embryonic development, respectively (mean female carapace length = 36.35 ± 0.57 mm). The mating period lasted 19 days. The overall rate of insemination was 98.3%. After 200 days of the experiment, a similar average number of stage-2 juveniles per female was obtained in the two treatments: 48.9± 7.1 in females alone and 46.3± 5.9 with males. In view of the difficulties in separating males and females, and the apparent lack of effect on reproductive efficiency, continued use of the practice should be reconsidered.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652430

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Oocyte development in the small penaeid shrimpMetapenaeopsis daleiwas studied histologically. Seven stages were distinguished, namely (1) oocytes 10μm in diameter are strongly basophilic and spherical, (2) weakly basophilic ooplasm appears around the germinal vesicle, (3) follicle cells appear, (4) lipid globules appear in the ooplasm, (5) yolk granules start to appear in the ooplasm, (6) the germinal vesicle shrinks and migrates marginally, (7) the follicle cells disappear. This is the first report of a fully matured penaeid oocyte without cortical crypts which release materials forming a jelly coat when the eggs are exposed to seawater. Since ovulated oocytes occur in the same section of the ovary as earlier stages,M. daleiis concluded to be a multiple spawner which has short spawning intervals.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652431

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In females of the cricketTeleogryllus commodusWalker the paired accessory sex glands are characterized by an irregular shape due to numerous ramifications of various length. Each gland consists of a basal, middle, and apical region within which the epithelium is uniformly built up by an inner cuticular intima, one layer of gland cells with basal-situated nuclei, and a basal lamina. In the direct vicinity of the gland's orifice, the epithelium is surrounded by a coat of longitudinal and circular muscle fibres which control the delivery of the secretory material into the genital chamber. In all three regions of the gland, the cuticular intima is marked by hair-like processes of unknown function which are mainly oriented in the direction of the orifice. As a special feature the intima does not show any channel-like structures or breaks facilitating the transport of secretory material into the lumen of the gland. Additionally, the cuticular layer is folded into the gland cell sporadically and thinned out considerably at those regions. In the apical and middle region of each gland the basal cell membrane shows numerous in-foldings forming a widespread lacunar system. The secretory activity of the gland cells starts 5–6 days after adult moult. The produced material is supposed to permeate the cuticular mainly at those regions where its thickness is reduced to a minimum. Regarding the development of the accessory glands, morphological changes caused by an increasing volume of the gland cells as well as ultrastructural alterations due to an augmentation of the compartments important for secretory activity are observed.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652432

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Sperm of marine organisms are usually classified as either “primitive” or “modified”. Primitive sperm, with heads comprised of a simple acrosome, spherical nuclei and mitochondria and a free flagellum, are thought to be associated with the occurrence of external fertilization. The implication is, of course, that external fertilization is a primitive condition wherever it occurs. Here the sperm of two Scyphozoa,Catostylus mosaicus(Quoy and Gaimard 1824) andPhyllorhiza punctatavon Ledenfeld 1884, are described. Both of these taxa are known to brood planulae and are likely have some sort of internal fertilization.Catostylus mosaicushas a typical “primitive” sperm with a small head (2μm long) comprised of a short cylindrical nucleus, four spherical mitochondria and a some small spherical electron dense spheres that are may be acrosomal in function. The anchoring apparatus is comprised of two centrioles, a complex of satellite fibres and a striated “spur”. The flagellum contains a typical 9+2 axoneme.Phyllorhiza punctatahas sperm with a head 6 μm long. The nucleus is a narrow cylinder, 4 μm long and curved in one plane. There are some anterior electron dense spheres, and five ellipsoidal mitochondria abut the nucleus posteriorly. Behind the mitochondria an anchoring apparatus comprised of the distal centriole and a satellite array is connected to the bases of the mitochondria. The flagellum contains a typical 9+2 axoneme. Sperm structure and the various reproductive modes occurring in Scyphozoa are reviewed and placed in a phylogenetic context based on the current classification of the group. It is concluded that external fertilization is likely to be the plesiomorphic condition in Scyphozoa, but there are various possible scenarios about the transformation to and from external fertilization within the group. Sperm structure is shown to be a poor predictor of reproductive mode. It is recommended that the terms “primitive sperm” and “modified sperm” be abandoned and replaced with terms that describe sperm in terms of function.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652433

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

One hundred sixty-eight specimens ofPotamilus alatus(Say, 1817) were collected approximately monthly from the Wheeler Reservoir (Tennessee River mile 298), Alabama, USA, between February 1995 and March 1996. Microscopic and gross examinations of gonadal tissue and marsupia were used to determine seasonal timing of gamete production, spawning, brooding and glochidia discharge. All individuals examined were dioecious. Spermatogenesis occurred between July and August. Spermatozoa numbers peaked in late August and male spawning occurred over a 2–3-week period in late August and early September. Oogenesis and female spawning had patterns similar to spermatogenesis and male spawning. Brooding of glochidia occurred between September and April. Glochidia discharge occurred in April and possibly early May, and coincided with the onset of the spawning season of the reported fish host,Aplodinotus grunniens(Rafinesque, 1819). The temporal patterns of gamete production and spawning inP. alatusof the subfamily Lampsilinae are in sharp contrast to members of the subfamily Ambleminae that have been similarly studied. This suggests that detailed studies of gamete production and spawning may be helpful in understanding unionid phylogeny and character evolution.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652434

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The present paper describes the ultrastructure of spermatozoa ofTaenia mustelaeas revealed by transmission electron microscopy. The mature spermatozoon of this tenid is filiform, tapered at both ends, and lacks mitochondrion. It is capped by an apical cone of electron-dense material and presents a single helical crest-like body 75-nm thick. The axoneme is of the 9+‘1’ pattern of trepaxonematan platyhelminthes and lacks a periaxonemal sheath. Transverse intracytoplasmic walls are observed in several regions of the spermatozoon. In cross-section, the spiralled nucleus shows a horse-shoe to annulus shape. The submembranous cortical microtubules are spiralled at an angle of about 45° to the hypothetical spermatozoon axis.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652435

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Sperm competition theory predicts that males exposed to an increased risk of sperm competition should maximize fertilization prospects by inseminating more sperm per ejaculate. We designed a laboratory experiment to examine the effect of increased sperm competition risk on male and female reproductive traits in individuals of the simultaneously hermaphroditic land snailArianta arbustorum.Courtship behaviour, spermatophore size and number of sperm delivered were not influenced by a higher sperm competition risk. However, snails constantly exposed to mucous trails of conspecifics deposited more egg batches than snails denied any cues from conspecific mucous trails. On the individual level, the number of sperm delivered was positively correlated with the number of eggs produced. This finding contradicts the basic prediction of sex allocation theory that there is a trade-off between resources allocated to male and female function in simultaneous hermaphrodites. Most probably this trade-off may only occur if resources are limited.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652436

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The effects of serotonin, dopamine, and prostaglandins E2and F2α(PGE2, PGF2α) on the release of oocytes, as well as reinitiation of meiosis in them, were evaluated for the scallopArgopecten purpuratus.Germinal vesicle breakdown, signalling reinitiation of meiosis in oocytes, occurs just prior to their release to the environment and was seen in histological sections of female gonad and kidney, made at the time when the scallop appeared ready to release the female gametes. Studies of the effects of the amines and prostaglandins were madein vitrowith fresh sections of the female gonadal sector using varied concentrations and exposure times. Serotonin (10−6to 10−4M) increased the number of oocytes released, and these numbers increased in relation to the time of incubation. Release of oocytes, relative to control, was reduced by dopamine (10−6to 10−4). The effects of the amines on oocyte release were blocked by pre-incubation with indomethacin, an inhibitor of PG synthesis. PGE2(10−6M) increased oocyte release; PGF2α(10−6M) did not affect this process. Serotonin and the two prostaglandins increased the rupture rate of germinal vesicles, a process unaffected by the presence of dopamine. The results suggest separate mechanisms for the regulation of the processes of egg release and reinitiation of meiosis in this mollusc.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652437

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The present study confirmed that imaginal aestivation diapause in the seven-spotted lady-beetle,Coccinella septempunctata brucki, was characterized by the arrested reproduction not only in females (Okuda and Chinzei, 1988) but also in males. Changes in spermatogenesis by the testicular follicles and development of the male accessory gland were observed during prediapause, diapause and the post-diapause period. DNA synthesis by testicular follicles was examined as a criterion to assess spermatogenesis. DNA synthesis in the testicular follicles from pre-diapause male adults was as active as that from post-diapause ones. DNA synthesis gradually decreased with the induction of diapause and reached minimum activity on day 30 after emergence. Later DNA synthesis gradually resumed and reached its maximum activity when the male adults completed diapause on day 120. The male accessory glands developed intermediately during the pre-diapause period based on total protein content, which showed its minimum value in the middle of diapause and regeneration occurred with the termination of diapause. Methoprene treatment to diapausing male adults induced reproductive activation, i.e., increases of DNA synthesis by the testicular follicles and protein content of the male accessory glands. In contrast to thein vivoresults, 5-h incubation of testicular follicles from diapausing males in Grace's medium containing methoprene induced no significant elevation of DNA synthesis. Histological study suggested an occurrence of a diapause-specific lipid in the testicular follicles, and this was confirmed by thin layer chromatography analysis.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652438

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652439

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor