摘要:

The order Verongida, considered to be exclusively oviparous and dioecious, exhibits great range in body form, including thin-bodied, rope- and stick-form members which have been postulated to be morphologically adapted to exploit fragmentation as an important asexual reproductive process. Here we report results of a one-year survey of sexual reproductive stages in a rope-form verongid,Aplysina cauliformis, which test the hypotheses of verongiid sexual pattern and reduced resource allocation to sexual reproduction in rope-form sponges. Results confurn the verongiid pattern of oviparity, dioeciousness and production of small oocytes. Data also support the hypothesis that rope-form sponges are characterized by reduced investment in gamete production relative to sponges of other body forms. The sexual reproductive pattern of the main macrosymbiont (parasite) polychaete,Haplosyllis spongicola, shows no correlation to that of its sponge host.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672598

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The protein and lipid content of the eggs, fed and starved larvae ofEncope micheliniwere examined in the laboratory and results compared with those of other obligate planktotrophs. The protein and lipid content of the eggs ofE. micheliniwere higher, and the lipid:protein ratios were five to nine times higher than in most other obligate planktotrophs. Increase in larval size and development to the 8-arm stage was accompanied by a decrease in protein and lipid content for starved larvae but an increase for fed larvae. The main advantage of producing planktotrophic eggs with a high protein and lipid content is that it reduces the amount of endogenous food that must be obtained by feeding to construct the complete set of larval arms. This reduces the total time spent in the plankton and thus the risk fiom being eaten. In addition, after a period of food scarcity, a filly developed 8-armE. michelinilarvae would be more efficient at capturing particles than a 4-arm larva fiom smaller eggs with a low protein and lipid content.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672599

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Fatty acids and their derivatives are involved in events associated with reproduction in invertebrates. The purpose of this study was to investigate the presence and variation in amount of selected fatty acids during vitellogenesis in the crayfishProcambarus paeninsulanus.Particular attention was given to possible precursors of eicosanoid production. Ovarian homogenates were prepared and analyzed by gas chromatography. Results demonstrated a dramatic increase in several fatty acids fiom the onset of secondary vitellogenesis to just prior to ovulation. It is possible that unsaturated fatty acids or their derivatives may be involved in the importation of exogenous proteins to support yolk formation. In addition, results demonstrate ample substrate exists in crustacean ovaries to support production of reported eicosanoids by lipoxygenase andfor cyclooxygenase pathways.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672600

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Onychophorans possess a combination of annelidan and arthropodan characters and are always prominent in discussions of arthropod evolution. The chitinous cuticle is moulted periodically in juveniles as well as in adults. Using radioimrnunoassay (RIA) and high performance liquid chromatography (HPLC), the presence of fiee and conjugated ecdysteroids is reported in the body wall, digestive tract, slime gland and ovary/uterus of adult females ofEuperipatoides leuckartii.Within fiee ecdysteroids, ecdysone is dominant. The hctional significance of ecdysteroids is discussed in the light of the evolutionary history of moulting hormones.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672601

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The male reproductive system ofGordius aquaticusL., 1758 is made up of two dorsolateral testis tubes that fuse at their posterior end by a vertical duct and lead via a single duct into the intestine. The testes have an epithelium that becomes disintegrated and is finally completely absent. After copulation, the mature spermatozoa modifj their morphology. Three different stages of spermatogenesis can be found in the male reproductive system, on the outside of the posterior end of the female and in the female seminal receptacle, respectively. The number of compartments in the spermatozoa diminishes. The shape of the cells varies from rod-shaped to filiform, but the length does not vary significantly.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672602

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

There is little information available about the internal anatomy of the polychaete family Cossuridae Day, 1963. In the interests of clarifying the systematic position of this group, we describe the structure of the abdominal body wall, coelomic organization, spermatogenesis and oogenesis ofCossuracf.longocirrataWebster and Benedict, 1887. There is a spacious coelomic cavity in the abdominal region unlike the thoracic region of the body, though as in the thorax there is no outer peritoneal lining. Muscle layers are virtually absent in certain areas of the abdomen, explaining the tendency for cossurids to disintegrate very easily. Oogenesis in this species is extraovarian but each oocyte is ensheathed by a few follicle cells. The follicle cells appear to be of the “inactive” type since they show no microvilli of the outer surfaces, and no rER or Golgi bodies. Spermiogenesis occurs with synchronously developing clusters of cells attached to a central cytophore. Mature sperm have a spherical head, a conical acrosome and a simple midpiece. This morphology is typically seen in species using external fertilization and thus the sperm are probably classifiable as ect-aquasperm, though this should be confirmed. The present results do little to help with the systematic placement of the Cossuridae. Further detailed study of gametogenesis and other organ systems across the Polychaeta are required in this regard.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672603

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Variation in size and nutrient content of eggs deposited in successive batches is a life-history aspect that has received little attention. We examined the size and nutrient content of eggs laid in successive batches by the land snailArianta arbustorum.Snails from three populations (a lowland, a subalpine and an alpine locality in Switzerland) differed in number of batches produced, clutch size, egg size and nutrient concentration and energy content of eggs. This was partly due to differences in shell size, since reproductive characters ofA. arbustorumscale with shell size. In the first batch snails from the lowland and subalpine population laid eggs that had a higher protein concentration (28.1%) than snails from the alpine population (25.6%). Similarly, eggs from the first batch did not differ in carbon concentration in the lowland and subalpine population, whereas eggs from the alpine population had a lower concentration. Clutch size tended to decrease in successive egg batches in all populations. Egg size increased over the reproductive season in snails from the lowland population, whereas no seasonal change was observed in the subalpine and alpine population. Protein concentration decreased in successive batches in the lowland and alpine population but tended to increase in the subalpine population. Carbon concentration decreased over the season in the lowland population but not in the other two populations. This indicates (1) egg characteristics show different changes in successive batches in different snail populations, and (2) the trade-off clutch size vs. egg size can be influenced by alterations of the nutrient concentration and energy content of eggs.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672604

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Development ofLeptodora kindti(Crustacea, Cladocera) was observed from the first cleavages to early segmentation and neurogenesis. The mode of cleavage is superficial. The first to seventh divisions are synchronous. After reaching the blastoderm stage at 128 cells, cells start to differ in timing and orientation of divisions. The prospective ectoderm cells divide superficially as before, prospective yolk cells stop dividing and prospective mesendoderm cells divide mostly perpendicular to the surface. After gastrulation, the germ band is elongated by equally distributed divisions and not by a budding zone like other entomostracan crustaceans nor by specialized cells like ectoteloblasts in the Malacostraca. After germ band elongation, a streak of median ectoderm cells differentiates into neuroectoderm. During thoracic segmentation, intersegmental furrows simultaneously divide ectoderm and neuroectoderm into segments. The neuroectoderm consists of neuroblasts and median cells. Divisions of the median cells are equal and tangential. The neuroblasts produce ganglion mother cells by highly unequal divisions perpendicular to the surface. The findings are discussed with regards to hypotheses on evolution of crustacean and mandibulate cleavage, segmentation and neural development.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672605

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Spermatocytes (nuclei with synaptonemal complexes) have already well developed Golgi complexes that produce large numbers of dense granules. In spermatids (or late spermatocytes?) the granules are densely packed and the chromatin condenses showing a small dense protrusion (or protrusions?). Two centrioles, arranged at an angle to each other, are formed close to the nucleus, and peripheral microtubules are close to them. The microtubules extend into an outgrowing cytoplasmic process, with the centrioles located in it. The nucleus elongates, its chromatin showing a characteristic fibrillar-reticular configuration, and several long mitochondria surround it in parts of the cell arranged in several rows separated by intracellular “septa”. Parts of the nucleus are strongly coiled. The peripheral microtubules are arranged in two rows of (usually) four on opposite sides of the sperm. They extend along the distal part of the sperm which is filled with many dense granules, but not into the proximal part containing only nucleus and mitochondria. A long dense rod arranged in a screw-like fashion extends in the distal part of the sperm and microtubules decrease in number at the distal tip. At the proximal tip, only the nucleus is present. Mature sperm from the sperm duct differ from those in the testis mainly in the more condensed nucleus. This is the first time that flagellar elements (centrioles) have been clearly identified in macrostomid spermatid by electronmicroscopy.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672606

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Time to pupation, percent survival to pupation, and percent adult emergence ofAnopheles albimanusWiedemann decreased at higher larval rearing temperature. Mosquitoes reared at 30°C experienced higher mortality during the pupal stage than did mosquitoes reared at 22°C. Analysis of variance revealed that wing length and costal wing spot patterns of adult femaleA. albimanuswere affected by larval rearing temperature. FemaleA. albimanusreared at 22°C had longer wings, and larger basal pale + prehumeral pale, prehumeral dark, and humeral pale costal wing spots than did female siblings reared at 30°C. FemaleA. albimanusreared at 30°C had larger subcostal pale spots than did female siblings reared at 22°C. Analyses of 2x2 contingency tables indicated that sex ratio was independent of larval rearing temperature, whereas survival to the adult stage and coalescence of wing spots were not independent of rearing temperature. The need to examine stability of morphological characters under differing environmental conditions is discussed.

ISSN:0792-4259    

DOI:10.1080/07924259.1997.9672607

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor