摘要:

The structure of the spermatozoa of four species ofMelanopsis(Melanopsidae) is described by light and transmission electron microscopy. All species produce two types of spermatozoa, euspermatozoa (fertilizing) and paraspermatozoa (non-fertilizing). The eusperm of all species are about 42–44 μm long and have a morphology similar to that of other cerithioideans. The head is composed of a laterally flattened nucleus and conical acrosome of approximately equal size. The nucleus has a shallow posterior fossa which houses a centriolar derivative from which the axoneme emerges. The four equal-sized mitochondria of the midpiece are non-helically arranged around the axoneme. Each mitochondrion has an anterior flange and the cristae are plate-like. This midpiece arrangement suggests that the Melanopsidae are more closely related to the Modulidae, Potamididae and possibly Pachychilidae than to other cerithiacean taxa. Posterior to the midpiece is a 10–12 μm-long glycogen piece in which the glycogen granules encircle the axoneme as inner and outer rings. Although the structure of the euspermatozoa is very similar in all four species, there are significant differences in the lengths of the nucleus, acrosome and midpiece between species. These dimensional differences suggest that sperm morphology could be of value in the separation and identification of species within the genusMelanopsis.The oligopyrenic parasperm are about 65 μm long and consist of a head and tail region of multiple flagella. The axonemes of the flagella are positioned centrally within the head and run for its length. Spermiogenesis (both eu- and paraspermiogenesis) is as described for other caenogastropods. During sperm development, spermatids are closely associated with Sertoli cells. Unlike previous reports for some caenogastropods, the Sertoli cells do not completely surround the early spermatids. Instead, long tubular cytoplasmic processes from the Sertoli cells encircle the developing spermatozoa. These processes contain microfilaments which are thought to be composed of actin.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652419

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This study provides a qualitative and quantitative description of larval development ofTetrapygus nigerto metamorphosis. After fertilization, the length of the planktonic interval (developmental time) forT. nigerat room temperature (14–18°C) ranged from 94 to 120 days. Competent larvae were induced to metamorphose by transferring them into culture vessels containing bacterial films and diatoms. About 40% of the larvae reached the juvenile stage, with complete metamorphosis from the feeding larval stage to the feeding adult stage taking 4–6 days. Although the morphology ofT. nigerlarvae is atypical compared with most regular extant echinoid species, it is similar to another arbacioid species,Arbacia punctulata.This suggests that larval morphology needs to be included in studies aimed at establishing phylogenetic relationships. The large larval size (>3.0 mm close to metamorphosis) and uniform pattern of ciliation observed inT. nigerlarvae have also been observed in non-feeding larvae. However, asT. nigerlarvae feed, we believe these characteristics reflect a functional solution to the swimming and feeding requirements of a long planktonic life. The maximum size (>4.5 mm) achieved byT. nigerlarvae in thisin vitrostudy represents the largest recorded for echinoid larvae.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652420

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Monoclonal antibodies specific toPenaeus monodonvitellin subunits were produced from mouse immunized with sodium dodecyl sulfate (SDS) treated ovarian extract prepared from gravid ovaries. After fusion of mouse spleen cells with P3X myeloma, hybridomas were selected by indirect immunoperoxidase ELISA againstP. monodonovarian extract. This was followed by dot-blotting against native and denatured proteins from ovarian extract, female haemolymph, and male haemolymph, then by dot-blotting against each vitellin subunit. Hybridoma clones producing antibodies specific to each of vitellin subunits with a molecular mass of 83, 74, 104 and 58, 104 and 45 kD, antibodies specific to the 215 kD protein, an oocyte-specific protein, and one monoclonal antibody specific to haemocyanin were isolated. All monoclonal antibodies could bind to both native and denatured proteins. Western blot analysis of ovarian extract and female haemolymph from gravid ovary prawns separated by PAGE and SDS-PAGE revealed five vitellin subunits, molecular mass of 104, 83, 74, 58 and 45 kD in ovarian extract, and four vitellogenin related polypeptides, molecular mass of 200, 104, 83 and 74 kD in the female haemolymph. From the immunoreactive relationships among these proteins, it could be assumed that vitellogenin may be released into the haemolymph in two forms, 200 and 74 kD, then the 200 kD polypeptide was either processed into the 104 and 83 kD polypeptides, or directly taken up into the oocyte. In the oocyte, the 104 kD protein would be further cleaved into 58 and 45 kD polypeptides while the 74 kD protein would undergo slight modification or remained unchanged. Western blot analysis of vitellin subunits at various stages of ovarian development revealed that the 200 kD protein appeared in the oocyte during early ovarian development and the 45 and 58 kD proteins appeared during the late development.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652421

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Ultrastructural changes during spermiogenesis in the stag beetle,Aegus lavicollis, were studied with special attention to the organizing process of the centriole adjunct. In early spermatids the formation of acrosome and flagellum occurs simultaneously in the cytoplasm before nuclear condensation. The centriole adjunct first appears as a sheath surrounding a centriole in a concavity of the nucleus from which the flagellar axoneme is organized. A mass of electron-dense material accumulates progressively in the vicinity of the centriole. As nuclear transformation proceeds, electron-dense material is found at the posterior end of the nucleus and extends beyond the centriolar region to form a partial sheath around mitochondrial derivatives. Electron-dense material seems to contribute to the formation of the centriole adjunct because the former is closely attached to the latter until the latter is completely formed. In mature spermatozoa the centriole adjunct is characterized by its peculiar disposition, extending across about half the length of the flagellum and partly covering the outside of two mitochondrial derivatives.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652422

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In the dung flyCoproica vagansHaliday 1833 (Diptera, Sphaeroceridae), a firm but elastic mating plug blocks the female genital opening after copulation. The plug does not contain sperm. Sperm are present in the form of a mass that fills the vagina anterior to the mating plug. Experiments using males marked with acridine orange demonstrated that the mating plug is produced by males. Copulations always resulted in plug formation. Male remating intervals seem to be adjusted to the time needed to replenish the material needed for mating plug production. Two non-exclusive functions of the mating plug are proposed: retention of sperm in the vagina after copulation and paternity assurance by preventing females mechanically from remating until oviposition. Shape and position of theC. vagansmating plug provide evidence for a capability of retaining sperm inside the vagina until sperm reaches the female storage organs. The mating plug prevents remating while it is in the vagina. Following copulationC. vagansfemales are not sexually available to other males. Mechanical manipulation of females seems to be the main cause for this post-mating loss of ability to copulate. Mating plugs persist unaltered until oviposition begins. Males were not able to induce plug expulsion or remove plugs with their genitalia. The mating plug is pushed out when the first egg is laid. Eggs are deposited in batches. Remating occurred on days when an egg batch laid by that female was observed, never on following days. In the field 96% ofC. vagansfemales carry a mating plug. Copulation duration is fairly constant and is not correlated with female mating status.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652423

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In echinoid larvae the adult rudiment develops on the left side of the larval body at the eight-armed pluteus stage. Previously we found that a removal of a portion of ecto-mesodermal tissues on the right side of echinoid gastrulae evoked reversal of the left-right location of the adult rudiment in some treated larvae (Aihara and Amemiya, 2000). In the present study we extirpated a portion of tissues on the right side of the larvae at the two-armed pluteus stage and examined effects of the operation on the development of the adult rudiment. Many of the operated larvae formed an extra right adult rudiment, resulting in double adult rudiments. The rest of the operated larvae formed the adult rudiment normally on the left side. No larvae with only one right adult rudiment were found in the experiment, indicating that the formation of the extra adult rudiment on the right side did not affect adult rudiment formation on the left side. In larvae with double adult rudiments, no notable morphological defects in the extra adult rudiment formed on the right side were found, although initiation of the adult rudiment formation was slightly retarded compared to that on the left side. The larvae with double adult rudiments were competent to metamorphose into conjoined juveniles, both the bodies being joined at their aboral sides. The results indicate that the potential to form the adult rudiment is still retained in the right side of the echinoid larvae at the two-armed pluteus stage, suggesting that the fate of the right side with respect to initiation of the formation of the adult rudiment is not committed at this stage.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652424

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Ten parastacid species inhabit South American continental waters, grouped in the generaSamastacus, VirilastacusandParastacus.The sexuality of these species is one of the most unknown and controversial features of their biology. This article gives updated information about these species sexuality. Information is also provided on the geographic distribution, habitat and lifestyle of each of these parastacids. Three patterns of sexuality are distinguished: (1) gonochorism, in the lake populations ofS. spinifronsandV. araucanius;(2) permanent intersexuality inP. pugnax, P. varicosus, P. pilimanus, P. defossusandP. saffordi;and (3) partial protandric hermaphroditism in the fluvial populations ofS. spinifronsandP. nicoleti.None of these patterns can be assigned toP. laevigatusandP. brasiliensissince no studies of this kind are available forP. laevigatus, and those conducted onP. brasiliensisyield contradictory results.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652425

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In order to extend the period of time during which Colorado potato beetle (CPB) eggs are suitable hosts for the parasitic waspEdovum puttleri, CPB eggs were subjected to various doses of gamma radiation between 2.5 x 104and 5.0 x 106rads prior to storage. For given storage times there were specific doses of radiation that resulted in notably, but not significantly, higher percent absolute emergence (number of adult wasps that emerged/total number of CPB eggs exposed toE. puttleri).After 7 days of storage, absolute emergence was highest after exposure to 2.5 x 104, 4.4 x 105and 1.2 x 106rads; and after 14 days of storage it was highest after exposure to 4.4 x 105and 1.2 x 106rads. For these doses of radiation and storage times, percent absolute emergence was equal to 40 ± 8%, a value that overlaps the range reported for CPB eggs that have not been irradiated. With increased storage time, absolute emergence dropped below 25%. While storage of irradiated eggs had a negative effect on percent parasitization, it did not affect the percentage of wasps that emerged (percent emergence = number of adult wasps that emerged/number of CPB eggs that were parasitized) from parasitized eggs. Percent emergence from non-irradiated eggs has been reported to average 78%, while in these studies, percent emergence from irradiated eggs typically was greater than 90%. Irradiation and storage of CPB eggs had little effect on the weights of adult wasps, and these wasps appeared to be active and in good condition. However, for unfed adult wasps, longevity decreased with increasing doses and storage times. Gamma irradiation of CPB eggs can be used to kill developing CPB embryos and to prevent deterioration of the host eggs. Our results show that irradiation can increase the period of time (from 72h to 14 days) in which CPB eggs are suitable hosts for rearingE. puttleri.

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652426

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652427

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0792-4259    

DOI:10.1080/07924259.2000.9652428

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor