摘要:

In a series of bioassays, four planarian species—Dugesia dorotocephala(Woodworth),Dugesia tigrina(Girard),Cura foremanii(Girard),Dendrocelopsis vaginatus(Hyman)—were evaluated against six water quality parameters (hardness, temperature, salinity, pH, dissolved organics, and dissolved oxygen) for effects on species survival and asexual reproduction. No significant (P<0.05) effects were determined on survival and asexual reproduction of three species exposed to various levels of hardness.Dugesia tigrinawas determined to have a significant increase in asexual reproduction with an increase in hardness. Dissolved oxygen was determined to be a critical parameter affecting both survival and reproduction of the species evaluated.Dugesia dorotocephalaandD. tigrinawere determined to be the most adaptable and tolerant of the species evaluated.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672362

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The matureS. sandonispermatozoon exhibits an apical cone of electron-dense material about 1 μm long and a helicoidal crest-like body 50–100 nm thick. The cortical microtubules, varying in number from 0 to 18 depending on where the section is cut, are of different lengths, spiralized, and in close contact with the plasma membrane in regions III and IV of the spermatozoon where they form one or two fields of 1 to 9 units, which are associated with electron-dense subjacent material and are either laterally delimited or not by submembranous thickenings. The cytoplasm contains amorphous electron-dense material in regions II, III and IV of the gamete. The nucleus is a fine cord coiled in a spiral around the axoneme. This is of the 9+“1” pattern. Its posterior extremity is made up of only the axial element surrounded by nine singlets formed by the A microtubules attached to the plasma membrane. This type of posterior extremity of the flagellum has never been described in a platyhelminth. Similarly, submembranous thickenings and microtubular fields associated with electron-dense subjacent material have never been observed in a cestode spermatozoon. Moreover we report for the first time the existence of a spermatozoon with a single axoneme and crest-like bodies in the Proteocephalidea.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672363

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Diflubenzuron was found to affect both the DNA content and the incorporation of tritiated thymidine in the ovaries ofTenebrio molitor.The decrease in fecundity observed in several insect species may be due to the inhibition of ovarian DNA synthesis.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672364

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The structure of the spermatozoon and spermatogenesis ofDiscinisca tenuis(Inarticulata) andKraussina rubra(Articulata) are described by transmission electron microscopy. The spermatozoon ofD. tenuishas a similar morphology to that of other inarticulate brachiopods. The head (about 1.9 μm long) is composed of a nucleus which is invaginated anteriorly and posteriorly, the anterior invagination partially housing the pyriform acrosome. The acrosome is differentiated internally and is separated from the nucleus by subacrosomal material. The mid-piece is composed of a ring of four or five spherical mitochondria which surround the proximal and distal centrioles which are arranged orthogonally. By contrast the spermatozoon ofK. rubrahas a head which is 2 μm long × 1.1 μm in diameter. The nucleus which is rounded anteriorly is capped by a small (0.5 μm diameter) disc-shaped acrosome. The mid-piece has a single ring-shaped mitochondrion which surrounds the centrioles which are almost in line with each other. In both species, during spermatogenesis, each spermatogonium and spermatocyte develops a flagellum which appears to be absorbed prior to cell division. InD. tenuis, proacrosomal vesicles form within spermatogonia whereas acrosome formation inK. rubradoes not commence until spermiogenesis. In the early spermatid of both species a single acrosomal vesicle forms in the presumptive posterior of the cell and during spermiogenesis the developing acrosome migrates anteriorly where it assumes its mature form.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672365

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The number of nuclei in the nurse chamber and the frequency distribution of nurse chambers with different numbers of nuclei in seven different species of non-paedogenetic gall midges of the subfamily Cecidomyiinae were analyzed. No evidence was found to indicate that the egg follicles with a low number of nurse nuclei undergo a selective degeneration in the ovarian development of non-paedogenetic gall midges. It is known that the multinucleate nurse chamber in Cecidomyiidae develops by the fusion of a variable number of somatic cells with the germ-line-derived nurse cell. This situation is interpreted by us as an unusual oogenetic strategy for increasing the number of rDNA templates available for transcription, which evolved in the insect group extremely poor in ribosomal RNA genes.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672366

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Three consecutive-day injections with different doses (0.1, 0.25, 0.5, 1.0, 2.0 and 4.0 μg/g) of estradiol-17β (E2) produced statistically significant increases in the cytosolic NADP-linked malate dehydrogenase and glucose-6-phosphate dehydrogenase activities in the ovary of the freshwater prawn (Macrobrachium rosenbergii) on the 4th day of treatment over the control values, depending upon the doses administered. Dose-dependent increases in the malate dehydrogenase and glucose-6-phosphate dehydrogenase activities were observed between 0.1–0.25, 0.25–0.5, and 0.5–1.0 μg/g doses. A similar magnitude of response was found at 1.0, 2.0 and 4.0 μg/g dose in both the cases of malate dehydrogenase and glucose-6-phosphate dehydrogenase activities. A lower dose of 0.5 μg/g was ineffective in eliciting any response to either enzyme. Ergosterol (2.0 μg/g) did not evoke any change in the malate dehydrogenase and glucose-6-phosphate dehydrogenase activities in comparison to the control values.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672367

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The comparative morphology of the foregut during development from embryonic larva to adult inCherux quadricarinatuswas examined by light and scanning electron microscopy. Major ontogenetic changes occurred in the gastric mill dentition in terms of denticle shape, appearance of vertical ridges in the lateral teeth, roughness of masticating surfaces, degree of sclerotization and proportional sizes of the median tooth components. Natural food types appropriate for the various life history stages during artificial rearing ofC. quadricarinatusmay be inferred from the morphology of the gastric mill dentition of those stages. Cardiopyloric valves and the gland filter appeared prior to development of functional gastric mill teeth. Compared with the foregut of adult astacid crayfish, that of adultC. quadricarinatusshows differences in the ventral cardiopyloric valve, pyloric funnel and lateral valves.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672368

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The initiation of the first embryo-derived cell cultures and the establishment ofin vitrometamorphosis from aseptic tadpole larvae are described in the cosmopolitan, shallow water colonial tunicate,Botryllus schlosseri.A total of more than 1,600 embryos, collected from different colonies at various stages of blastogenic cycles, were used in ten experiments (up to 350 embryos/experiment). Embryos were fully dissociated by mechanical or chemical treatments. In three experiments we succeeded in initiating continuous cell lines from embryonic tissue (designated NIO-BSE-1 to −3). Using different substrates and supplements, we found that embryonic cells cultured in botryllid cell culture medium (Rinkevich and Rabinowitz, 1993) supplemented with either chick embryo extract or heat inactivatedBotrylloideshemolymph and on plastic or gelatin coated substrates may acquire cell-line characteristics. Tunic cells of maternal origin were found in all wells of primary cultures but subsequently disappeared. These cultures grew slowly for the first several weeks, but after transfer to 25 ml culture flasks, proliferation accelerated. When co-cultured with freshly collected blood cells from allogeneic colonies, the embryo-derived cells exhibited antibacterial properties. Two of the cell lines were frozen for future experiments. By using 24-well culture plates and 1–8 embryos/well under aseptic conditions (produced by a cocktail of antibiotics), almost 100% of 399 embryos at all developmental stages successfully metamorphosed and produced oozooids under thosein vitroconditions. The oozooids could be obtainedin vitrowithout feeding up to 40 days. Retinoic acid and different illumination regimens shorten the time for metamorphosis and improve the state of oozooids' health. The potential use of the embryo-derived cell cultures and thein vitroculture of metamorphosed larvae for studying developmental biology and organogenesis of colonial protochordates is discussed.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672369

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We examined adult representatives of marine echinoderms, molluscs, and crustaceans for the presence of fatty acid binding protein and enzymes of fatty acid catabolism. In all cases there was no evidence for an intracellular fatty acid binding protein or for enzymes involved in the mitochondrial import of long-chain fatty acids (carnitine palmitoyltransferase). In all cases, regardless of phyletic relationship, 3-L-hydroxyacyl CoA dehydrogenase activity was present indicating the ability to catabolize fatty acids in some manner. Two possibilities are offered in explanation. One scenario suggests that the absence of carnitine palmitoyltransferase and fatty acid binding protein and the presence of 3-hydroxyacyl CoA dehydrogenase result from a developmental change to adult stages from pre-adult stages where fatty acids, predominantly as triacylglycerides, are important for growth and buoyancy. Another possibility is an extra-mitochondrial β-oxidation to shorten long-chain fatty acids such as a peroxisomal system. In this light we report the detection of a peroxisomal oxidation of palmitoyl CoA, oleoyl CoA and octanoyl CoA in the ventricle and hepatopancreas of lobster (Homarus americanus) and hepatopancreas, but not the ventricle, of scallop (Placopecten magellanicus) as reflected in readily measured activities of acyl CoA oxidase. In addition, the tissues of the scallop and lobster contained significant activities of carnitine octanoyltransferase and carnitine acetyltransferase thought to be involved in the transmembrane transport of medium- and short-chain fatty acids. Chain-shortened fatty acids, because of greater solubility, may preclude the requirement of fatty acid binding protein.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672370

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In the holothurian,Cucumaria japonica, deep invaginations of the germinal epithelium of the testis are formed during the period of active spermatogenesis (January-February) but are reduced in prespawning animals (August). The invaginations contain basal lamina which envelope the testis and separate the haemal sinus from the gonad lumen. They are lined with germinal epithelium. Nurse cells are not present within regions of the germinal epithelium associated with invaginations of the lamina. These regions are invested by spermatogenic cells only.

ISSN:0792-4259    

DOI:10.1080/07924259.1994.9672371

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor