摘要:

As in many prosobranchs, two cell lines develop in the testis ofStrombus gigas. The typical spermatogenesis is similar to that described in many species. The spermatic cell development is characterized by cell divisions. Typical spermatogenesis leads to a mature spermatozoa with a column-shaped nucleus. The acrosome consists of an acrosomal rod covered by an acrosomal cone and topped by a hemispherical vesicle. The middle piece is made up of nine mitochondria helically arranged around the axoneme. A ring centriole is present between the middle piece and the flagellum. The tail contains the axoneme and glycogen granules. During atypical spermatogenesis no division of the cells is observed. The cytoplasm of atypical spermatogonia increases in size while the nucleus degenerates. In the cytoplasm dark granules and vesicles with double membranes develop. The mature atypical spermatozoa are spindle-shaped. The cytoplasm contains large dark granules, but no remnants of the vesicles with double membranes are observed. Each side of the atypical spermatozoa is formed by an undulating membrane containing numerous axonemes. The possible functions of the atypical spermatozoa are discussed in this paper.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672404

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The effect of retinoic acid [RA] on the morphogenesis of freshwater sponges (Spongilla lacustris, Ephydatia fluviatilis, Ephydatia muelleri) was studied. At a concentration of 2 μM, RA had no overt effect on pinacocytes and choanocytes but had already altered mesohyl cell movement and adhesion after 1 h treatment. It interfered with morphogenesis of sponges developing both from larvae and gemmules, inhibiting the formation of the aquiferous system, and promoting formation of reduction bodies. The same was observed in treatment of functional sponges with RA. We conclude that RA induces modifications in mesohyl cell adhesion and interaction, analogous to that observed in induction of reduction bodies formation or gemmulogenesis.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672405

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The organization of the eggs ofTethya tenuiscleraandTethya seychellensis(Porifera, Demospongiae), collected inside the lagoons of two Maldive Islands, was studied by SEM and TEM. The cytoplasmic matrix is vacuolated and filled with stored material. Phagosome-like and rod-like inclusions represent the major components. Phagosome-like inclusions correspond to the egg yolk; rod-like inclusions undergo modifications resulting in filament bundles that accumulate underneath the cell membrane. The occurrence of undigested bacteria in membrane-bound vacuoles within the cytoplasmic matrix suggests a maternal transmission of symbionts. InT. seychellensisthe layered appearance of the cell surface results from the accumulation of membranes associated with cytoplasmic vacuoles. This structure constitutes an envelope along the egg peripheral border and is interpreted as a protecting sheath improving egg survival after spawning.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672406

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We studied the life history of tardigrades with a particular focus on the maturative patterns of the ovary and testis. Specimens collected in nature belonging to four species of one freshwater and two semiterrestrial genera of eutardigrades were examined. The females of all examined species are always iteroparous; they have several maturative cycles with synchronously developing oocytes. Four maturative stages can be distinguished in each ovarian cycle, which is clearly correlated with moulting. In contrast, gametocyte maturation does not seem to be correlated with moulting in males and varies markedly in the considered genera. The testes of adult specimens ofMacrobiotusalways contain both mature spermatozoa and cells at earlier stages in spermatogenesis (continuous maturation). The testis ofPseudobiotus megalonyx, the only freshwater species examined, shows a gradual increase in spermatozoa that in the end completely fill the gonad (progressive maturation, tied to a semelparous life cycle). The testis in adult males ofAmphibolusis either filled exclusively with spermatozoa or alternatively with immature germinal cells, revealing an iteroparous condition similar to that of the females (cyclical maturation). The different types of gonad maturation in males seem to be correlated with habitat and the capacity to enter cryptobiosis.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672407

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

InHelcion pellucidusthe cytoplasm of spermatogonia contains granulo-fibrillar dense bodies, a Golgi apparatus and a pair of centrioles. In primary spermatocytes a flagellum arises and putative small dense proacrosomal vesicles are formed from golgian activity. The mature spermatozoon is of the primitive type and does not contain a perforatorium. Silver stained the centriolar fossa, the periphery of centrioles and the pericentriolar complex, while phosphotungstic acid-chromic acid did not stain the acrosome. Similar cytochemical results were obtained inPatella rustics. The different morphological aspects of spermatogenesis in Patellogastropoda and Archaeogastropoda and the use of silver and PTA stainings in the Mollusca are reviewed and discussed.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672408

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The possibility that 5-hydroxytryptamine (5-HT) stimulates testicular maturation in the red swamp crayfish, Procambarus clarkii, was investigated. A series of 5-HT agonists and antagonists was used in addition to 5-HT itself. 5-HT and its agonists not only induced testicular maturation but also development of the androgenic glands. In contrast, the 5-HT antagonists had no stimulatory effects on the testes or androgenic gland. This stimulatory action of 5-HT is hypothesized to be indirect, 5-HT stimulating release of the gonad-stimulating hormone, which in turn activates the androgenic gland to synthesize and release androgenic gland hormone, and the androgenic gland hormone then triggers testicular maturation.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672409

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Embryonic and early postembryonic development was studied inIschnothele guyanensis, a neotropical mygalomorph spider of the family Dipluridae. Special attention was paid to the visual system, that is the eyes, nerves and optic centers. The morphology of developing individuals is described from egg laying up to the third postembryonic instar. Scanning electron microscopy was used for the first time on early stages of spider embryos, especially during inversion. The internal developmental processes of the visual system were studied by light microscopy using a series of histological sections. Morphological events inIschnothele guyanensisdo not differ much from those in other spiders showing inversion. Scanning electron microscopy reveals multiple depressions on the cephalic lobe whose openings will fuse together to form the semilunar grooves which constitutes the first step of brain ontogeny. The two types of eyes are formed differently. The direct eyes proceed from secondary invaginations of the semilunar grooves, while the indirect eyes arise from independant ectodermic cellular proliferations. The visual system appears morphologically complete only after the second exuviation, that is at the third postembryonic instar.Ischnothele guyanensis, as well as other diplurid spiders, shows an almost complete inversion and would represent an intermediate state between Liphistiomorphae and some primitive Mygalomorphae (no inversion) and most of the Araneomorphae (complete inversion). Thus, the family Dipluridae may be of interest for the study of the evolutionary modes of inversion in the Order Araneae.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672410

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Morphometry of the colleterial gland and its removal (colleterectomy) were made to observe its effect on egg laying and hatching behaviour in the female Tasar silk moth,Antheraea mylittaD. during three study season. The paired colleterial gland, which is divided into two distinct regions, was found to be attached at the terminal part of a common oviduct and secretes an adhesive substance which pastes the eggs to the substratum during oviposition. Colleterectomy of the female Tasar moth just after mating and thereby removal of the gluing material induced the deposition of loose white eggs and enhanced egg laying capacity and hatching efficiency followed by a shorter incubation period without any adverse effect on the progeny. No marked changes were observed in hatching initiation and duration. Further the overall pattern of egg laying was observed continuously for 3 consecutive days in each brood of control females, while the total egg hatchability was recorded for 3 consecutive days in the first and third brood, but it was continued for 4 days in the second brood. Again the egg incubation period in the third brood was observed to be longer than in the first and second broods of control insects. Although colleterectomy did not significantly alter the normal pattern of variation, it was able to influence these events.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672411

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The spermatozoa of two genera and species of Cyclodorippidea,Xeinostoma richeri(Xeinostominae) andTymolussp. (Cyclodorippinae), and one species ofCymonomussp. (Cymonomidae) are found to constitute a distinctive cyclodorippoid sperm-type characterized by (1) sperm anteroposteriorly depressed, mean ratio of length to width 0.54–0.63; (2) operculum extending to the lateral limits of the acrosome (autapomorphy of cyclodorippoids) and centrally perforate or (Cymonomussp.) thinner; (3) contents of acrosome vesicle with two major horizontal zones, as in homolids and dynomenids, including a dense lower (posterior) zone; (4) perforatorium very wide (0.3 width of acrosome), anteriorly rounded, not capitate, lacking radiate projections; (5) acrosomal capsule with external projections over its posterior half; (6) slender dense filaments extending into the perforatorium from its walls, their bases associated with corrugations of its basal wall; (7) nucleus, cupping the acrosome and cytoplasm, with well-developed posterior median process; (8) nuclear arms lacking microtubules; (9) cytoplasm, a narrow postacrosomal band extending anteriorly as far as the operculum, associated with a few degenerate mitochondria. The noncapitate form of the perforatorium differs from the capitate condition in dromiids, the related dynomenids, homolids and the raninoidLyreidus. The cyclodorippoid sperm resembles homolid and raninoid sperm in possessing a posterior nuclear process (questionably apomorphic) and resembles homolid sperm in the horizontal zonation of the acrosome with a dense lower zone. Features which resemble the sperm of raninoids are: the periacrosomal flange (Xeinostoma richeri) and smaller evaginations of the acrosome membrane (or capsule?) (X. richeri, less distinctlyCymonomussp. andTymolussp.) reminiscent of the single acrosomal flange ofRaninaandRaninoidessperm and the multiple keels of theLyreidussperm; and corrugations of the wall of the perforatorial chamber, as in raninoids though with significant differences. A dynomenid similarity (homoplasy?) is the discontinuous flange-like peripheral continuation of the lower zone of the acrosome contents inCymonomussp.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672412

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672413

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor