摘要:

Spermatozoal morphology of the anomuran crabCervimunida johniwas investigated using scanning and transmission electron microscopy. The spermatozoon has an elongate shape and exhibits a total length of 22.7 μm with a maximum width of 4.4 μm. Three parts can be distinguished: (1) the elongate-ovoid acrosome located anteriorly, measuring 7.7 μm in length and 2.7 μm in width; (2) the cytoplasmic region, 3.0 μm in length and 1.5 μm in width; and (3) the nuclear region measuring 11.9 μm in length and 4.4 μm in width. The acrosome is composed of a thick electron-dense wall and a less electron-dense subacrosomal space showing actin-like filaments. The cytoplasmic region connects the acrosome with the nucleus, and three arms filled with microtubules arise from this region. The cytoplasm contains irregular mitochondria. The elongate nucleus has uncondensed DNA, its outer surface is highly folded and shows three principal longitudinal grooves. The microtubular arms are located in these three nuclear grooves when the spermatozoa are inside the spermatophore, and extend laterally when they are placed in seawater. The spermatozoon ofC. Johnifollows the general pattern described for other anomuran decapods.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672467

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Formation of the primary epidermis in freshwater triclad embryos was examined by transmission electron microscopy. After formation of the yolk-cell syncytium, the blasto-meres within it increased in number in the central region. At 57–40 h, most of them move peripherally as an elongate cluster. Oval cells occupying the frontal region of the cluster form precursor cells of the primordium of the primary epidermis. At 63–66 h, these precursor cells reach the surface of the yolk-cell syncytium and fuse to form a syncytium. The epidermal primordium then extends out over the surface of the yolk-cell syncytium. After 68–70 h, the primordium spreads to the opposite pole through the narrow space between the yolk-cell syncytium and its surrounding nonfused yolk cells. By 72–74 h, the spreading primary epidermis completely embraces the yolk-cell syncytium, suggesting that formation of the primary epidermis in the triclad embryo involves an epiboly-like movement of cells similar to that described for other neoophoran groups. We regard the primary epidermis as the organ of ectodermal nature. The formation and position of the blastopore in connection with germ-layer formation is discussed.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672468

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Egg vitellin of the terrestrial isopodOniscus asselusis a 290 kD, female-specific lipoglyco-protein (V1) comprising two subunits, A (98 kD) and B (82 kD). An additional related protein (V2, 180 kD) was found in developing oocytes but not in mature eggs. Vitellogenin (VG) is electrophoretically and immunologically indistinguishable to V1and was detected in oocytes, fat body and haemolymph of vitellogenic females.In vitroincorporation studies revealed that VG is synthesized by both fat body and ovaries, but by no other tissues of either females or males.OniscusVG, therefore, has both intra- and extra-ovarian origins. Following long-term incorporation, the VG synthesized by either fat body or ovaries comprises only subunits A and B of V1. However, following short-term incorporation, larger polypeptides are present in these tissues, which are also recognized by an antiserum raised against V1. It is speculated that VG inOniscusis synthesized as a large polypeptide which is subsequently processed to smaller fragments. Synthesis of VG by explants of fat body was studied throughout the intermoult cycle. A single large peak of VG synthesis was seen in the second half of premoult; during this time, VG comprises 40% of the total protein synthesized by fat body and oocytes increase in volume 100-fold. The chronology of VG synthesis and oocyte growth are related to known times of release of hormones inOniscus.It is suggested that vitellogenesis is regulated by both ecdysteroids and neuropeptide(s) from the sinus gland.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672469

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Although it has been widely assumed that the presence of a visible clitellum closely parallels maturation of the female reproductive system in members of the family Erpobdellidae, this has never been thoroughly tested.Nephelopsis obscurawas maintained at 15°C and 20°C and fed 3x, 2x or 1x a week withad libitumprey. The leeches were examined weekly for the presence of a visible clitellum, spermatophores, the presence of vasa deferentia, and the stages of gametogenesis present determined. Feeding regime affected the time to the first occurrence of a visible clitellum with the leeches fed 3x a week exhibiting a clitellum 18–20 weeks before the first appearance of a clitellum in the groups fed 2x or lx a week at 15°C or 20°C. Regardless of feeding regime, all the leeches exhibited a second appearance of a clitellum after 41–48 weeks. The first appearance of a visible clitellum did not coincide with either spermatogenic or oogenic maturity, but at the second appearance of a clitellum leeches fed 3x and 2x a week showed fully mature ova at both temperatures. None of the leeches fed 1x a week ever showed spermatogenic or oogenic maturity. The presence of spermatophores was also not a reliable indicator of maturity with only 4% of the mature size range animals having an attached spermatophore. It is very probable that the presence of a visible clitellum is not a good indicator of maturity in most or all species in the family Erpobdellidae.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672470

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Spermiogenesis and mature spermatozoa ofMaehrenthaliasp. (Byrsophlebidae) andBresslauilla relicta(Graffillidae) were investigated by transmission electron microscopy. Spermiogenesis inMaehrenthaliaclosely resembles the process previously observed in Temnocephalida, some dalyelliids and other typhloplanids. Dense heels form at the base of basal bodies and these later become spur-shaped in the mature sperm, and rotation of flagella around the shaft results in compression of a semi-circle of peripheral microtubules in towards the centre of the shaft. The inner microtubules join the outer row over a short length of the shaft and do not form a spiral arrangement as is found in temnocephalids. Mature sperm have two free flagella that appear to be oriented distally, away from the main shaft, at least while sperm are in the ducts. Spermiogenesis inB. relictainvolves fusion of two initially free flagella, first with each other and then with the spermatid shaft, and attachment zones are associated with each axoneme. Incorporated axonemes are superficially attached externally to the cortical microtubules. In both species investigated, longitudinal rows of small granules lie beneath the cortical microtubules in mature sperm, there are two kinds of dense bodies, one or two rows of mitochondria, and the nucleus extends a trailer to the plasma membrane. It is now apparent that there is a useful range of character states observable in spermiogenesis and mature sperm of rhabdocoel turbellarians that will eventually facilitate parsimony analysis to determine the phylogeny of this large, diverse taxon.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672471

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Ultrastructural features of euspermiogenesis and euspermatozoa inCerithium caeruleumare described. Early spermatids possess round eccentric nuclei with fine chromatin material. The cytoplasm contains sparse endoplasmic reticulum, few mitochondria, and a well developed Golgi complex with which a proacrosomal vesicle is associated. Acrosome differentiation starts with a U-shaped vesicle plugged with a dense interstitial granule. Later, the vesicle becomes flask-shaped with plate-like substructures in its core and external supporting structures at its margins. The early oval nucleus becomes hammer-head and eventually bullet-shaped with a posterior invagination accommodating the proximal portion of the axoneme. Chromatin changes from fine granular to fibrillar, lamellar, and finally a complete dense material. The mature flat acrosome consists of a cone with internal plate-like substructures, a rod, and a basal plate. The middle piece comprises two large and two extremely small non-helically arranged mitochondria, which were derived from four large mitochondrial spheres in early spermatids. Microtubules surround the nucleus and the middle piece at late stages of their development. A dense ring structure separates the middle piece from the glycogen piece. The latter consists of nine tracts of glycogen granules associated with the axoneme. Based on fine features of euspermiogenesis, we suggest that Cerithiacea may represent an evolutionary link between Archaeogastropoda on one hand, and Mesogastropoda and Neogastropoda on the other. Also, we believe that euspermatozoan ultrastructure is useful in building taxonomic affinities between major groups of gastropods at and above the family level, with no consistent species-specific characters.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672472

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Serotonin (5-HT) was detected in various body tissues of the scallop using both immunocy-tochemistry and high performance liquid chromatography with electrochemical detection (HPLC-ED). Much of the 5-HT in the body appears to originate from nerve cells in pedal and cerebral ganglia. Neuropilar regions of these ganglia are also abundant in 5-HT. Far fewer 5-HT containing cells reside within the parietovisceral ganglion, although the accessory lobe contains numerous such cells. The lateral lobes of the parietovisceral ganglion are richly innervated with 5-HT containing fibres. Immunoreactive fibres were also found in the heart, kidneys, labial palps, gills and various muscles. The digestive tract contained numerous immunoreactive cell bodies. Immunoreactive fibres were found principally around the collecting tubules of both the testes and the ovaries in the spring, but also around the germinal acini by autumn. HPLC-ED was used to quantify the amount of 5-HT present in the above-mentioned tissues in the spring. Contents ranged from about 200 pg/mg wet weight of labial palps to about 2500 pg/mg wet weight of foot. It is concluded that 5-HT has the potential to influence numerous physiological processes in the scallop including reproduction, respiration, feeding, digestion, excretion, movement and visual information processing. Both seasonal variations and artificially induced changes in systemic 5-HT levels are therefore likely to have wide ranging effects.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672473

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The reproductive characteristics of trogloxenicGoniosoma spelaeumwere studied directly in the field in caves of the Ribeira River Speleological Province, São Paulo State, south-eastern Brazil. They reproduce throughout the year, with one marked peak during the rainy season and a second minor peak in the dry season. During copulation, the male grasps the female pedipalps with his pedidalps, and the pair keep a face-to-face position. After mating, the male stays close to the female, waving his second legs over her body while she proceeds with egg-laying. Each group contains ca. 60–80 eggs of 2.1–2.3 mm diameter. Females remain over their eggs throughout embryonic development, leaving the site only after dispersion of the nymphs begins. The post-embryonic phase contains six nymphal stages, which are characterized both morphologically and morphometrically, and lasts about 1.5 years. Secondary sexual dimorphism appears during the post-embryonic development. The adult phase lasts more than 2 years, giving a total life-span of more than 3.5 years.

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672474

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672475

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.1995.9672466

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor