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At least 145 records · Page 8Linked to original sources
PubMed2000

Molecular data from the 16S rRNA gene for the phylogeny of Pectinidae (Mollusca: Bivalvia).

The phylogenetic relationships among the species belonging to the family Pectinidae are still an issue of debate. The mitochondrial DNA sequences from the large ribosomal RNA gene may be of great value for systematic and phylogenetic studies within families. Partial sequences of the 16S rRNA gene were obtained for the scallop species Adamussium colbecki, Aequipecten opercularis, Chlamys glabra, C. islandica, C. varia, and Pecten jacobeus and compared with the published sequence of Pecten maximus. The present molecular data show that Chlamys are polyphyletic and do not support the assignment of these species to the two subfamilies Chlamydinae and Pectininae. Moreover, the minimal genetic distance between P. maximus and P. jacobeus suggests that they could belong to the same species.

Animals↗
PubMed1999

Development of the musculature in the limpet Patella (Mollusca, Patellogastropoda).

Whole-mount technique using fluorescent-labelled phalloidin for actin staining and confocal laser scanning microscopy as well as semi-thin serial sectioning, scanning and transmission electron microscopy were applied to investigate the ontogeny of the various muscular systems during larval development in the limpets Patella vulgata L. and P. caerulea L. In contrast to earlier studies, which described a single or two larval shell muscles, the pretorsional trochophore-like larva shows no less than four different muscle systems, namely the asymmetrical main head/foot larval retractor muscle, an accessory larval retractor with distinct insertion area, a circular prototroch/velar system, and a plexus-like pedal muscle system. In both Patella species only posttorsional larvae are able to retract into the shell and to close the aperture by means of the operculum. Shortly after torsion the two adult shell muscles originate independently in lateral positions, starting with two fine muscle fibres which insert at the operculum and laterally at the shell. During late larval development the main larval retractor and the accessory larval retractor become reduced and the velar muscle system is shed. In contrast, the paired adult shell muscles and the pedal muscle plexus increase in volume, and a new mantle musculature, the tentacular muscle system, and the buccal musculature arise. Because the adult shell muscles are entirely independent from the various larval muscular systems, several current hypotheses on the ontogeny and phylogeny of the early gastropod muscle system have to be reconsidered.

Animals↗
PubMed2004

Larval development of Aelurostrongylus abstrusus (Nematoda, Angiostrongylidae) in experimentally infected Cernuella (Cernuella) virgata (Mollusca, Helicidae).

The larval development of the cat lungworm Aelurostrongylus abstrusus was studied for the first time in the helicid mollusc Cernuella (Cernuella) virgata, in order to know its performance as intermediate host (I.H.). This snail is very common in the north-west of Spain. First-stage larvae (L1) of A. abstrusus were obtained by the Baermann-Wetzel method from the faeces of a naturally infected cat. Then, 120 specimens of C. (C.) virgata were infected with 500 L1/snail and maintained under laboratory conditions (20+/-2 degrees C). Every 2 days, from day 8 to day 76 post-infection (p.i.), three snails were killed in order to study the larval development of the parasite. Morphological features of the different larval stages were also recorded. The apparent rate of penetration of L1 into the snail foot was 65.5%, but only 4.78% completed their development to the infective stage (L3). The total number of larvae was 49.8+/-28.8 larvae/snail and the average number of L3 was 23.9+/-18.4 L3/snail. The first L2 and L3 were observed on day 12 and day 18 p.i., respectively. From day 52 p.i. onwards, all larvae were at the infective stage in the snail. Considering those results, it was concluded that C. (C.) virgata is a suitable I.H. for A. abstrusus.

Animals↗
PubMed1996

The metacercariae of sibling species of Meiogymnophallus, including M. rebecqui comb. nov. (Digenea: Gymnophallidae), and their effects on closely related Cerastoderma host species (Mollusca: bivalvia).

The morphology and ecology are described for four sibling species of digenean metacercariae: Meiogymnophallus minutus (Cobbold 1859), M. strigatus (Lebour 1908) from the estuarine cockle Cerastoderma edule L. and M. fossarum (Bartoli, 1965) and M. rebecqui (Bartoli, 1983) comb. nov. from the brackish water lagoon cockle C. glaucum (Poiret). Although occupying different sites within the two species of cockle, both M. minutus and M. fossarum infections result in pathological effects that may cause heavy host mortality. Remarkably, they also result in an inversion of the cockles in situ in the sand such that predation by the final host species is enhanced.

Animals↗
PubMed2003

Localization of serotonin and its possible role in early embryos of Tritonia diomedea(Mollusca: Nudibranchia).

A classical neurotransmitter serotonin (5-HT) was detected immunochemically using laser scanning microscopy at the early stages of Tritonia diomedea development. At the one- to eight-cell stages, immunolabeling suggested the presence of 5-HT in the cytoplasm close to the animal pole. At the morula and blastula stages, a group of micromeres at the animal pole showed immunoreactivity. At the gastrula stage no immunoreactive cells were detected, but they arose again at the early veliger stage. Antagonists of 5-HT(2) receptors, ritanserin and cyproheptadine, as well as lipophilic derivatives of dopamine blocked cleavage divisions or distorted their normal pattern. These effects were prevented by 5-HT and its highly lipophilic derivates, serotoninamides of polyenoic fatty acids, but not by the hydrophilic (quaternary) analog of 5-HT, 5-HTQ. The results confirm our earlier suggestion that endogenous 5-HT in pre-nervous embryos acts as a regulator of cleavage divisions in nudibranch molluscs.

Animals↗
PubMedDate not supplied

Zona localization of shell matrix proteins in mantle of Haliotis tuberculata (Mollusca, Gastropoda).

Organic matrix from molluscan shells has the potential to regulate calcium carbonate deposition and crystallization. Control of crystal growth thus seems to depend on control of matrix protein secretion or activation processes in the mantle cells, about which little is known. Biomineralization is a highly orchestrated biological process. The aim of this work was to provide information about the source of shell matrix macromolecule production, within the external epithelium of the mantle. An in vivo approach was chosen to describe the histologic changes in the outer epithelium and in blood sinus distribution, associated with mantle cells implicated in shell matrix production. Our results characterized a topographic and time-dependent zonation of matrix proteins involved in shell biomineralization in the mantle of Haliotis.

Animal Structures↗
PubMed1999

Primary cultures of heart cells from the scallop Pecten maximus (mollusca-bivalvia).

Primary cultures of Pecten maximus heart cells, isolated by an enzymatic procedure, were routinely obtained with a high level of reproducibility in a simple medium based on sterile seawater. Cells attached to the plastic substratum without the need to add a special factor. The number of adhering cells gradually increased with the time of culture. Two types of adhering cells were observed: epitheliallike cells and fibroblastlike cells, which were more numerous. The latter cells were identified as myocytes by electron microscopy and immunofluorescent staining. Results obtained by autoradiography, after incorporation of [14C]leucine, [3H]thymidine, and [14C]acetate, confirmed functional activity of the cells. These cultures were maintained viable in vitro during at least 1 mo.

Animals↗