摘要:

Haemolymph ecdysteroid titres were determined throughout the intermoult cycle ofOniscus asellusand related to ecdysteroid-related physiological events. In non-breeding females, ecdysteroid titres rise during premoult to a peak two days prior to ecdysis in synchrony with formation of a new cuticle in the posterior half of the animal. However, the anterior half does not form cuticle during this time, but instead accumulates calcium. Thus, anterior and posterior halves of the epidermis respond differently to the same levels of ecdysteroids. The anterior half secretes a new cuticle at a later time and at a very low ecdysteroid titre. During the first breeding moult of a season, differentiation of a brood pouch commences in early premoult and the rise in ecdysteroid titre is delayed by two weeks. Both vitellogenin synthesis by the fat body and oocyte growth closely parallel the ecdysteroid titre. Although both of these processes are thought to be influenced by ecdysteroids, the titres of breeding and non-breeding females did not differ, indicating that other factors determine whether or not vitellogenesis will occur in the presence of ecdysteroids. Together, these findings show thatOniscusdisplays ecdysteroid-related events in strikingly unusual ways which raise questions concerning the regulation of cellular responses to ecdysteroids. The hepatopancreas accumulates ecdysteroids to levels well above those in the haemolymph during late premoult and appears to be the main route for their elimination from the haemolymph. Ecdysteroids in the hepatopancreas are translocated rapidly into the hindgut and discarded with the hindgut cuticle at the posterior ecdysis.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652652

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The vanadocytes of living juvenilePhallusia mammillataascidians were examined by utilising cytochemical localisation of vanadium(III)in situ, to help determine the commencement of vanadium assimilation. The first visual indication of accumulation of vanadium(III) within the vanadocytes occurs at five days after fertilisation, shortly after the siphons of the developing larvae have opened. At nine days a number of different cell types, including vacuolated amoebocytes, a cell type which possess numerous compartments, together with bivacuolated cells and signet ring cells, all stain positively for vanadium(III) with the ligand 2.2′-bipyridine.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652653

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Spermatozoa of a commercial Australian abalone,Haliotis laevigataDonovan, 1808 (the ‘greenlip’ abalone) are examined for the first time using transmission electron microscopy. As is characteristic of other externally fertilizing molluscs, the spermatozoa ofH. laevigataare of the structurally simple type (classic ect-aquasperm). In anterior- posterior sequence, each spermatozoon consists of a conical acrosomal vesicle (length 1.35–1.38 μm, deeply invaginated posteriorly and associated with a subacrosomal axial rod and flocculent deposits), a barrel-shaped nucleus (length 2.1–2.2 μm, with prominent lacunae), a short midpiece (consisting of a pair of orthogonally arranged, triplet substructure centrioles surrounded by a five spherical mitochondria), nine satellite fibres (connecting the distal centriole to the plasma membrane) and a 40–44 μm long flagellum (featuring a 9 + 2 microtubular pattern axoneme). Total length of spermatozoa ranges from 44–48 μm. The contents of the acrosomal vesicle can be divided into anterior and posterior portions based on differing electron densities and the occurrence anteriorly of a thin, ‘truncated cone’ structure at the periphery of the vesicle. Preliminary examination of spermiogenic stages indicates that like other vetigastropods the acrosomal vesicle ofH. laevigatadevelops through coalescence of several moderately large, electron-dense, pro-acrosomal vesicles. Comparison with other species ofHaliotiswhich have been studied reveals that spermalozoa ofH. laevigata(type of subgenusSchismotis) most closely resemble those of the Asian speciesH. japonica aquatilisandH. diversicolor supertexta(members of subgenusSulculus). Such spermatozoa differ from those of other investigated haliotids (H. discus, H. mfescensof subgenusNordotisandH. midaeof subgenusEuhaliotis) all of which have appreciably longer acrosomal and nuclear regions. The use of sperm ultrastructure for probing species relationships within the Haliotidae appears to be a most promising area for future research, particularly when directed at type species of nominal subgeneric units.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652654

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Analysis of developmental patterns ofBotryllus schlossericolonies from the eastern Mediterranean coast has been performed on 143 genets under different temperature regimens (15,20,27 °C) for up to 22 weeks. While the average maximal size as the length of the blastogenic cycle (BC) varied in respect to water temperature, ontogeny at all temperatures was characterized by 4 developmental stages: 1. the lag phase (the first 1–3 BCs, 1 bud/BC), 2. the exponential growth phase (5.5–7.8 BCs, up to 3 buds/BC), 3. the plateau phase, (7.4–8.2 BCs, 1 bud/BC), 4. the degenerative or the variable phase. Many (40.6%) colonies were not sexually reproductive, the others were male only (30.1%) or hermaphrodites. Colonies at the peak of reproduction develop 1.2 oocytes/zooid, and up to 57.7% produced >4 clutches. Analysing onset of reproduction with maximal colony size revealed 4 patterns, two for “male only” colonies and two for hermaphrodites that varied at different sea water temperatures. In two patterns, the onset of reproduction precedes colony maximal size, and in the others it starts at the peak size or thereafter. Zooids at the colony's periphery developed almost twice as many buds as did zooids at the center, but produced significantly lower numbers of eggs. Fragmentation was recorded in large colonies and was temperature dependent. Results are compared with the data available on populations from other localities indicating for dramatically different developmental modes characteristic to this cosmopolitan species.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652655

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Codakia orbicularisis a tropical lucinid harboring gill endosymbionts which are environmentally transmitted from a free living-symbiont form to the new host generation after metamorphosis. Structural changes occurring in the cellular organization from incomplete gill filaments in young aposymbiotic juveniles to full differentiated gill filaments containing bacterial endosymbionts in reared symbiotic juveniles, were analyzed for juveniles from 250 μm to 2 μm shell-length. Aposymbiotic juveniles possess differentiated gill filaments with ciliated, intermediary, and lateral zones similar to those described in wild juveniles, except for the bacteriocytes which are lacking. Granule cells, which progressively differentiate during the morphogenesis of the gill filament, do not appear as a consequence of symbiosis. Experimental colonization of aposymbiotic juveniles by the free-living symbiont form has been obtained through the addition of unsterilized sand collected from the natural habitat ofC. orbicularis.Two days after exposure to crude sand, symbiosis-competent bacteria enter by endocytosis at the apical pole of undifferentiated cells which progressively differentiate into classical bacteriocytes similar to those found in the adult gill filaments. Undifferentiated cells of aposymbiotic gill filaments remain receptive to bacteria several months after metamorphosis, and become bacteriocytes when aposymbiotic juveniles get contact with the symbiont free-living form. Therefore, the environmental transmission of symbionts does not appear to be restrained to a defined period of time during post-larval development inC. orbicularis.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652656

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Spermatogenesis and sperm ultrastructure of the trombiculid mite Hirsutiella zachvatkini (Schluger 1948) have been investigated using transmission electron microscopy and compared with other arachnids studied. Sperm differentiation takes place in groups of synchronously developed germ cells of the two large sac-like paired testes. Each testis is composed of a secretory epithelium, which occupies their medio-ventral regions, and of a germinative epithelium situated in the latero-dorsal parts of testes together with large somatic cells. The germ cells are represented on sections by spermatogonia, spermatocytes, early, middle and late spermatids, and mature spermatozoa. Spermatocytes and spermatids contain two centrioles, which disappear afterwards, and a small Golgi-like structure forming an acrosomal cistema. Mature spermatozoa, which lie both within the meshes of somatic cells and also free in the lumen of testes, are compact oval aflagellate cells provided with peripheral channels. They also contain an acrosome, flattened between the cell membrane and the round electron-dense chromatin body, an oval body of lesser density lying in close proximity to the chromatin body, and a group of 5–7 mitochondria with spherically arranged cristae situated immediately behind the nuclear bodies. An acrosomal filament may be sometimes seen beneath the acrosome in the middle spermatids and disappears in the mature spermatozoa. These findings show that the mode of differentiation and pattern of organization of the male sex cells in trombiculid mites are of rather primitive type compared with other acarine spermatozoa.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652657

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A polyclonal antibody raised against the hatching enzyme ofCiona intestinalis(D'Aniello et al., 1997) was used on larvae of different ages in whole mount immunofluorescence experiments in order to localize the cells secreting the enzyme. After staining with FITC-conjugated second antibody, the larvae were observed by confocal microscopy. Larvae just before hatching (9–10 hours after fertilization) showed the presence of the enzyme in the peripheral cells of the adhesive papillae. The newly hatched larvae showed fluorescence also in the epidermal cells of the tip of the tail. Higher magnification confocal images of the papillae revealed bright fluorescence both in peripheral cells of the papillae and in the cavity between the tunic and the apex of the papillae (hyaline cap).

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652658

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The development and improvement of artificial incubation techniques for freshwater crayfish eggs and their incorporation into the working schedule of breeding centres is of great interest for commercial production. Factors such as the water circulation system, flow rate, thermal treatment, etc., could strongly influence the success of the process. The present study attempts to test the possible influence of one of these variables, the thermal regime, on both the duration of embryonic development and the efficiency rates obtained in the artificial incubation of white-clawed crayfish (Austropotamobius pallipes) eggs. Four different thermal treatments were tested (three of them included a period at low temperature: 4°-5°C). Survival rates to juvenile stage 2 were similar in the four cases, ranging between 66.7 and 72.7%. We conclude that water cooling (an expensive management procedure) is not necessary in astacid breeding centres provided that egg development takes place at moderately low temperatures (8°-10°C) with a subsequent increase of up to 15°C from the eyed stage. However, the inclusion of periods at low temperature (4°-5°C) allows the staggered production of juvenile batches throughout a 3-week period without adverse effects on efficiency rates. This could be useful to breeding centres in meeting seasonal market requirements. In our study, egg and juvenile losses (mortality rate: 15–20%) were concentrated during the last phases of embryogenesis, particularly from the eyed stage to juvenile stage 2, during which they amounted to more than 90% of the overall mortality which took place during the artificial incubation process.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652659

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Eupyrene and apyrene spermatozoa are contained in separate cysts in the testis of the butterflyAtrophaneura alcinous.Spermatozoa of both types from various parts of the male reproductive tract were examined with particular reference to their morphological characteristics. All spermatozoa collected from the vas deferens and the vesicula seminalis were found to be immotile under a dissecting microscope. No spermatozoa of either type were recognized in any part of the ejaculatory duct. Within the testis, eupyrene spermatozoa are present in bundles and each spermatozoon has a slender nucleus with an acrosome and a long flagellum containing mitochondrial derivatives. Two kinds of appendages, lacinate and reticular, are present on the surface of the sperm membrane. They are replaced with an extracellular sheath during passage through the vas deferens. In contrast, apyrene spermatozoa have neither nucleus nor acrosome, whereas a cup-shaped structure was found at the sperm tip instead of the acrosome. Unlike eupyrene spermatozoa, they are surrounded by a concentric sheath outside the sperm membrane in the vas deferens. Individual apyrene spermatozoa and coiled bundles of eupyrene spermatozoa were both found to accumulate in the vesicula seminalis before mating. These morphological changes during passage through the male reproductive tract suggests the occurrence of a kind of maturation and capacitation process reminiscent of mammalian spermatozoa.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652660

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A polyclonal antibody raised against allatostatin-3 ofBlattella germanica(BLAST-3) has been used to immunolocalize allatostatin-like peptides in the brain-retrocerebral complex ofLabidura ripariaadult females. Strongly stained immunoreactive cells are observed in thepars intercerebralis(14 cells) and mainly in thepars lateralis(32 cells). Fibres leading to thecorpus allatumare also stained. In the deutocerebrum, one cell is immunostained at the root of each antennal nerve. In the tritocerebmm two cells in each brain hemisphere are weakly immunostained. During the reproductive cycle, these cells and their axons show immunoreactivity at previtellogenic, ovulation and ovarian arrest periods. During vitellogenesis, immunoreactivity is restricted to only four perikarya in thepars intercerebralis.

ISSN:0792-4259    

DOI:10.1080/07924259.1998.9652661

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor