摘要:

Formation of the germ disk in the theridiid spiderEnoplognatha transversifoveatawas examined by light and electron microscopy. Cytoplasmic regions of blastoderm cells were flat and regions with many large yolk granules protruded into the blastocoel. Most of the blastoderm cells converged in one hemisphere of the egg to form the germ disk while only a few cells remained in the other hemisphere. The embryo at the germ-disk stage contained many spherical germ-disk cells. Almost no large yolk granules were found in these cells while the flat remaining cells each contained several large yolk granules. Cytoskeletal microtubules along the cell membrane were observed in the peripheral regions of germ-disk cells and at the periphery, apart from the thin frontier region, of the remaining cells. After microinjection of colchicine (10−4M, 2 nl) into the blastoderm at the early blastula stage, large cells with a flattened cytoplasmic region formed the germ disk. By contrast, the microinjection of cytochalasin B (50 μg/ml, 2 nl) resulted in large, spherical, syncytial germ-disk cells. Cytoskeletal microtubules, which begin to appear at the periphery of the cytoplasmic region during the convergence stage, may induce the germ-disk cells to adopt a spherical shape. The remaining cells may be unable to form spheres to cover the egg surface that does not include the germ disk.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672415

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Effects of food quantity on growth, fecundity (defined as number of eggs deposited in the first spawning), egg size, egg energy content, and total reproductive output (total egg volume or total energy invested in spawned eggs) ofCapitellasp. were examined in the laboratory. Results indicate that fecundity increased with increasing food quantity, whereas egg size and egg energy content decreased with increasing food quantity. These results suggest that there is a trade-off between fecundity and egg quality (in terms of egg size and egg energy content), thus supporting the hypothesis that, when food-limited,Capitellasp. produces fewer but higher quality offspring. Results further show that minor changes in food quantity (0.1 mg dryUlva· worm−1· day−1) can produce measurable changes in fecundity and egg size, suggesting that life history characteristics of this worm are flexible which enable it to adapt to a fluctuating environment.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672416

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A monoclonal antibody against a synthetic pentadecapeptide corresponding to the N-terminal end of Bombyx-prothoracicotropic hormone (PTTH: 1–15) and a monoclonal antibody against a synthetic decapeptide corresponding to the N-terminal portion of the A-chain of bombyxin-1, bombyxin (1–10), were used as parallel probes to localize both molecules at the cellular and subcellular levels in the brain-retrocerebral complex ofManduca sexta. Immunohistochemical analysis revealed that molecules immunochemically similar toBombyx-PTTH were localized in the cytoplasm of two pairs of dorso-lateral neurosecretory cells (L-NSC III) and could be traced along their axons to the corpora cardiaca (CC) and corpora allata (CA), whereas bombyxin-like material was absent from these cells and was detected only in the cytoplasm of four pairs of median neurosecretory cells (M-NSCs). Immunocytochemical labelling at the ultrastructural level using the PTTH antibody showed high specificity with the 5 nm immunogold particles restricted to the neurosecretory granules of the L-NSCs III, their axons and their axon endings in the CC and CA. An entirely different labelling pattern was observed when the bombyxin monoclonal antibody was used with the immunogold paradigm, i.e., the particles seemed to be present in the mitochondria and rough endoplasmic reticulum in addition to the neurosecretory granules of the M-NSCs. The significant of these data is discussed in light of the absence of any known physiological role forBombyxPTTH inManduca.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672417

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We have developed an insect midgut primary cell culture from pharate fourth instar larvae ofManduca sexta. An enriched Grace's medium supplemented with pupal fat body fromLymantria disparand 20-hydroxyecdysone (20HE) supported stem cell proliferation and differentiation and maintained larval columnar and goblet cell morphology. Cell kinetics indicate that stem cells differentiate to columnar and goblet cells in culture.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672418

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The male reproductive tract ofM. australienseconsists of a pair of lobulate testes which individually give rise to a single vas deferens. The vas deferens contains four distinct regions: a short proximal section, a convoluted section, an elongate distal section and an enlarged terminal section. Spermatozoa produced in the testes acquire additional eosinophilic and basophilic matrices as they are transported along the length of the vas deferens. The resultant sperm cords are stored in the enlarged distal vas deferens until ejaculation when the products of both vasa deferentia fuse together to form the spermatophore. The sperm are typically palaemonid, being “thumb-tack” shaped, with a cup shaped central nucleus which is supported by radiating fibrils. These fibrils anastomose centrally at the base of the nucleus to form a posterior membrane bound spike.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672419

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Potassium chloride (KCI) added to filtered seawater induced larval metamorphosis of the regular urchinStrongylocentrotus droebachiensisand the irregular urchinEchinarachnius parmain the absence of any other stimulatory substance, although the sensitivities of these two species differed. Larvae ofS. droebachiensiswere not affected by concentrations below 80 mM (above normal seawater levels), whereas 10 mM was enough to induce significantly more larvae ofE. parmato metamorphose than a filtered seawater control (used to assess spontaneous metamorphosis in the absence of any inductive cue). Relatively high concentrations of KCl (i.e., above 60 mM), which did not appear to adversely affect larvae ofS. droebachiensis, were toxic to larvae ofE. parma. Presently, some 15 species of marine invertebrates (representing five different phyla) have larvae which are known to react (i.e., settle, attach, or metamorphose) in response to elevated K+(KCl) levels. K+(KCl), which is thought to induce larval metamorphosis via depolarization of externally accessible cells (Baloun and Morse, 1984), appears to be fairly non species-specific as a metamorphic inducer.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672420

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Cross-fertilization experiments were conducted using two species of asteroids, one echinoid, one holothuroid and two species of mollusks to dertermine whether gametes from members of different classes, and even different phyla, are naturally able to fertilize one another. All but one of the crosses were successful, showing variable success, 58–99% lower than for intraspecific fertilization. Although most were not viable and showed anarchic cleavage, some resulting embryos could be reared to the blastula stage. Furthermore, these experiments led to the first case of intergeneric hybridization among asteroids, resulting in viable post-metamorphic sea stars. The hybrids ofLeptasterias polaris(spermatozoa) andAsterias vulgaris(oocytes) showed a developmental kinetic, a survival rate and an external phenotype similar to those observed after normal intraspecific fertilization in A.vulgaris. In natural conditions a temporal barrier appears to be the key in preventing such hybridization, as these two sympatric species of sea stars, commonly found in the coastal water of eastern Canada, have distinct breeding seasons. However, other members of the echinoderms and mollusks among which cross-fertilization occurred are known to spawn during the same period, increasing possible wastage of gametes due to non-specific interactions. A potential chemical control of hybridization was present in a diffusible compound originating from the mature oocytes of A.vulgaris. This reduced the motility of heterospecific spermatozoa, especially those ofStrongylocentrotus droebachiensiswhich were immobilized within 12 s in the vicinity of an oocyte.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672421

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Euspermatozoa (fertilizing sperm) ofEpitoniumsp. consist of a conical acrosomal vesicle (featuring an apical bleb, and accompanied by an axial rod, basal plate and accessory membrane); a solid, rod-shaped nucleus with a shallow centriolar invagination at its base; a midpiece composed of a 9 + 2 axoneme surrounded by 7–8 helical mitochondria; an annulus; a glycogen piece (axoneme surrounded by nine tracts of granules; and a short end piece. Morphologically these cells resemble not only those of other Janthinoidea (other Epitoniidae and the Janthinidae) but also euspermatozoa of several other groups of Caenogastropoda. Eusperm and parasperm ultrastructure supports a close relationship between the Janthinoidea and the Triphoroidea (Triphoridae, Cerithiopsidae). Sperm data also clearly demonstrate that the Janthinoidea have no connection with the heterobranch superfamilies Architectonicoidea or Pyramidelloidea.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672422

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Y-organs of the crayfish Orconectes limosus revealed a phosphorylation pattern which varied in different moulting stages. A 95-kDa-phosphoprotein increased in abundance as moulting proceeded, becoming the predominant phosphoprotein in stage D1. Phosphorylation of proteins with apparent molecular masses of 68 (pp68) and 17 kDa decreased during the moulting cycle. Phosphorylation of pp68 was evoked by incubating Y-organs of premoult animals with sinus gland extract. The presence of Ca2+induced a decrease in overall kinase activity in Y-organ homogenates and also caused reduced phosphorylation of endogenous Y-organ proteins, most of them (200, 40, 31, and 17 kDa) exhibiting cAMP-dependent phosphorylation. cAMP-dependent phosphorylation of a 34- and 31-kDa-phosphoprotein (pp34, pp31) was detectable only in Y-organs of premoult animals. A 40-kDa-protein may be a substrate for an endogenous cGMP-dependent protein kinase since its phosphorylation can be stimulated by cGMP as well as cAMP.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672423

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Reproductive events ofNausitora fusticula(Jeffreys, 1860) were observed and studied in the laboratory. They always occured at the same time of the day, from noon to 5 pm, reaching a peak of activity at 3 pm, between February and April. The female has a passive behaviour whereas the male moves its excurrent siphon around very actively. One to six males were observed introducing their excurrent siphons into the incurrent siphon of one female simultaneously. Such behaviour lasted from a few minutes up to over 30 min. Males were also observed to spawn by discharge of spermatozoa into the water of the aquaria.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672424

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor