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At least 253 records · Page 14Linked to original sources
PubMed2004

Planorbidae, Lymnaeidae and Physidae of Ecuador (Mollusca: Basommatophora).

In the course of a trip to Ecuador I had the opportunity of collecting topotypic specimens of the following nominal species of pulmonate molluscs: Biomphalaria cousini Paraense, 1966; Planorbis equatorius Cousin, 1887; P. canonicus Cousin, 1887; Lymnaea cousini Jousseaume, 1887 and P. boetzkesi Miller, 1879. Additional findings were: Helisoma trivolvis (Say, 1817), Biomphalaria peregrina (Orbigny 1835), Drepanotrema anatinum (Orbigny, 1835), D. kermatoides (Orbigny, 1835), D. lucidum (Pfeiffer, 1839), D. surinamense (Clessin, 1884), Lymnaea columella Say, 1817 and Physa acuta Draparnaud, 1805. P. boetzkesi and P. canonicus are considered junior synonyms of Gyraulus hindsianus (Dunker, 1848) and Biomphalaria peregrina (Orbigny, 1835), respectively.

Animals↗
PubMed2002

Comparative morphology of Astraea latispina (Philippi, 1844) and Astraea olfersii (Philippi, 1846) (Mollusca, Gastropoda, Turbinidae).

The present study examines comparatively the soft parts of turbinids Astraea latispina and Astraea olfersii. The characters of soft parts of these species, in agreement with Trochoidea organization, allow a differential diagnosis on the cefalic lappets, appendix of eye-stalk, hypobranchial glands, jaws, radulae, and stomach spiral caecum, which information will be helpful in taxonomic studies.

Anatomy, Comparative↗
PubMed2005

Applying weight gain in Pomacea lineata (SPIX 1824) (Mollusca: Prosobranchia) as a measure of herbicide toxicity.

Pomacea lineata, an extremely ubiquitous snail and pest to rice farmers throughout Asia, holds promise as a valuable resource for monitoring water quality in northeast Brazil. In this paper, we present data demonstrating the rate of weight gain in P. lineata neonates as a consistent measure of the stress imposed by sublethal concentrations of the herbicides Paraquat and Round-up. Our secondary agenda is to demonstrate the feasibility of incorporating bioassay into the standard municipal and state procedure of monitoring water quality. Growth data to assess chronic toxicity were generated in experiments of four and four, eight, twelve and sixteen days for Paraquat and Round-up, respectively. We estimated a 96 h no observed effect concentration (NOEC) and lowest observed effect concentration (LOEC) for Paraquat of 0.12 and 0.25 mg/L. The 96 h Round-up data yielded NOEC and LOEC values, respectively, of 0.25 and 0.5 mg/L. All concentrations of Round-up tested for the 192 h exposure yielded significantly lower growth than the control. Consequently, no NOEC could be derived. The LOEC was < 0.12 mg/L. Furthermore, there was no mortality during the test. At the lowest concentrations of Paraquat tested (0.005 mg/L) there was a significant increase in growth compared with the controls, suggesting a hormetic effect.

Animals↗
PubMed2001

Description of a new species of Thais (Mollusca: Neogastropoda: Muricidae) from Taiwan, based on morphological and allozyme analyses.

Thais keluo sp. nov. is described from intertidal shores of southwest Taiwan. The new species is differentiated from five other closely related species, namely T. bitubercularis (Lamarck), T. jubilaea Tan and Sigurdsson, T. clavigera (Küster), T. luteostoma (Holten) and T. rufotincta Tan and Sigurdsson, all of which occur in the South China Sea, on the basis of shell, radula and penis morphology. Thais keluo is also distinguished from the latter three species based on allozyme electrophoresis. The shell of T. keluo is characterized by four raised, spiral bands on the last whorl, one or two small, oblique columellar plica(e) on the inner lip, a finely crenate, thin, narrow, reddish-brown outer lip edge and four white, papillate denticles inside the outer lip of the aperture. In males, the penis is curved with a long, simple flagellum. The UPGMA cluster analysis based on 9 enzyme loci revealed that T. luteostoma is more closely related to T. clavigera than to T. keluo n.sp. The Nei's genetic distance (D) obtained between the new species and T. clavigera/T. luteostoma was 0.31, while T. clavigera and T. luteostoma were separated by a distance of 0.16. Thais rufotincta was separated from the other species by a distance of 0.78. In contrast, phylogenetic analysis of morphological data by maximum parsimony suggested that T. luteostoma was more closely related to T. keluo than to T. clavigera. However, both analyses indicated the close relationship amongst T. clavigera, T. luteostoma and the new species in relation to T. rufotincta.

Animals↗
PubMed2005

Phylogenetic relationships among major species of japanese coleoid cephalopods (Mollusca: Cephalopoda) using three mitochondrial DNA sequences.

Phylogenetic relationships among 36 species of major coleoid cephalopods from Japanese waters were studied using partial sequences of three mitochondrial genes, 16S rDNA, 12S rDNA, and cytochrome c oxidase subunit I gene. Octopoda and Decapoda were monophylic groups. Within Sepioidea, Sepiadariidae and Sepiolidae were not closely related to Sepiidae, but rather related to Teuthoidea. Sepiidae with a distinct calcareous shell formed a single cluster. Myopsida was closely related to Oegopsida. Within Octopoda, Opisthoteuthis depressa and Argonauta argo diverged earlier than Octopodiidae. The common octopuses in Japanese waters were separated into three clusters. The first cluster occupied a basal position, and includes large-sized octopuses, such as Enteroctopus dofleini and Octopus (Paroctopus) conispadiceus from the continental shelf and upper slope. The second cluster consisted of long-armed octopuses, such as O. ornatus, O. minor, and O. sasakii. The third cluster contained small- to medium-sized octopus, such as Amphioctopus fangsiao, A. areolatus, O. cyaneus, and O. vulgaris, in which several species possess ocelli on the web. The second cluster formed the sister group to the third cluster.

Animals↗
PubMed2000

Genetic diversity of oceanic island Lasaea (Mollusca: Bivalvia) lineages exceeds that of continental populations in the northwestern Atlantic.

Direct-developing lineages of the intertidal marine bivalve Lasaea have colonized both upstream mainland (southeastern Florida) and downstream oceanic island (Bermuda) locations in the western North Atlantic. Replicate samples from these two regional populations, separated by about 1500 km of open ocean, were sequenced for a 655-nucleotide portion of the mitochondrial (mt) cytochrome oxidase subunit I gene. Twelve haplotypes (2 Floridian and 10 Bermudan) were obtained that differed by a maximum of four substitutions among pairwise comparisons. Phylogenetic analysis yielded a parsimony network within which the mainland lineages clustered in one of the terminal branches; a mirror image of a priori expectations based on regional surface-current polarity. It is difficult, however, to envisage a plausible countercurrent dispersal mechanism. This tree topology may stem from divergent demographic processes operating on these two evolutionarily recent regional populations. The starlike phylogenetic pattern of Bermudan lineages is consistent with a history of rapid population growth. The restricted genetic repertoire and relative ecological scarcity of Floridian lineages imply either a recent founder event by unstudied Caribbean source populations or else a history of pronounced bottlenecks in population size. Bermuda's impoverished Caribbean marine biota may allow western North Atlantic Lasaea lineages to escape severe competitive interactions impacting other parts of their geographic range.

Animals↗
PubMed2000

Fertilization in Callochiton castaneus (Mollusca).

A fine-structural study of fertilization in Callochiton castaneus has revealed that the mechanism of sperm penetration into the egg is intermediate between the primitive condition found in members of the order Lepidopleurida and the more derived condition found in the Chitonida. C. castaneus sperm have the long needlelike nuclear filament and reduced acrosome that characterizes all Chitonida, but they have retained several plesiomorphic features such as an unspecialized mid-piece and a lack of flagellar reinforcement. As in some Lepidopleurida but unlike any Chitonida, the egg hull in this species comprises a thick, smooth jelly coat permeated by pores that permit sperm rapid access to the vitelline layer. The jelly coat is delicate and quickly dissolves when a sperm concentrate is used, suggesting that excess acrosomal enzymes may be responsible. Once the sperm have penetrated the vitelline layer, the long nuclear filament bridges the gap to cups in the egg membrane. However, once the fertilization membrane is raised, the perivitelline space exceeds the length of the nuclear filament, preventing other sperm from penetrating the egg. A fertilization cone forms around the nuclear filament of the penetrating sperm, but it does not appear to engulf the body of the sperm. Rather, the nuclear chromatin is injected into the egg as a long thread. The remaining sperm organelles are apparently abandoned on the egg surface. If this is the case, it would be a significant departure from fertilization in other molluscs and many other metazoans, in which sperm organelles, such as centrioles and mitochondria, enter the egg. New sperm and egg characters, as well as significant differences in fertilization, indicate that Callochitonidae are basal to all other members of the order Chitonida and may warrant separation as the sister taxon to the suborders Chitonina and Acanthochitonina.

Animals↗
PubMed2002

Embryogenesis and development of Epimenia babai (Mollusca Neomeniomorpha).

Neomenioid aplacophorans (= Solenogastres) constitute one of the main lineages of molluscs. Developmental data of early embryogenesis and larval development of neomenioids are available for some species based on histological sections. I used other techniques to study the development of Epimenia babai Salvini-Plawen, 1997, and here I report new data on neomenioid development. The embryos of E. babai are lecithotrophic and cleavage is spiral, unequal, and holoblastic. Two polar lobes are formed, one at the first cleavage stage and one at the second cleavage stage. No evidence of external metameric iteration is visible through scanning electron microscopy or histology at any stage. A ciliated foot, a pedal pit, and aragonitic spicules develop from the definitive ectoderm. A spicule begins as a solid tip, continues to an open-ended hollow spicule, and finally becomes a closed-ended hollow spicule. The free-swimming trochophore larvae of E. babai have been considered unusual in lacking the characteristic neomenioid cellular test, an outer locomotory structure within which the entire definitive adult body develops. However, through the use of scanning electron and light microscopy, semithin sections, Hoechst nuclear staining, and programmed cell death staining to study the ontogeny and fate of the apical cells, I show that the entire pre-oral sphere (the apical cap) of the larvae is similar to the test of the other neomenioids. The results suggest that the test of the neomenioid larvae is an enlarged pre-oral sphere of a trochophore. The test morphologies of neomenioid larvae are compared to those of pericalymma larvae of protobranch bivalves, and the homology and evolution of molluscan larval tests is discussed.

Animals↗
PubMed2002

Evaluation of radiography, ultrasonography and endoscopy for detection of shell lesions in live abalone Haliotis iris (Mollusca: Gastropoda).

Radiography, ultrasonography and endoscopy were examined for their efficacy as non-destructive techniques for the detection of shell lesions in the marine gastropod Haliotis iris Gmelin. X-rays provided 69% correct diagnoses, with detection being restricted to those lesions which were mineralised. Ultrasound also showed potential to reliably detect lesions (83% correct diagnoses), but only where the lesions demonstrated a clear 3-dimensional relief. Lesion dimensions were underestimated using ultrasound. Endoscopy, applied to anaesthetised individuals, provided the most accurate method (92% correct diagnoses) for lesion detection and, although invasive, had no discernible effect on survival of the abalone 8 mo after screening.

Animals↗
PubMedDate not supplied

The cytoskeleton of chondrocytes of Sepia officinalis (Mollusca, Cephalopoda): an immunocytochemical study.

Our previous electron microscope study showed that chondrocytes from cephalopod cartilage possess a highly developed cytoskeleton and numerous cytoplasmic processes that ramify extensively through the tissue. We have now carried out a light microscope immunocytochemical study of chondrocytes from the orbital cartilage of Sepia officinalis to obtain indications as to the nature of the cytoskeletal components. We found clear positivity to antibodies against mammalian tubulin, vimentin, GFAP, and actin, but not keratin. The simultaneous presence of several cytoskeletal components is consistent with the hypothesis that cephalopod chondrocytes have the characteristics of both chondrocytes and osteocytes of vertebrates, which endow the tissue as a whole with some of the properties of vertebrate bone. We confirm, therefore, the presence in molluscs of the ubiquitous cytoskeletal proteins of metazoan cells that have remained highly conserved throughout phylogenetic evolution.

Animals↗
PubMedDate not supplied

The distribution of cells containing FMRFamide- and 5-HT-related molecules in the embryonic development of Viviparus ater (Mollusca, Gastropoda).

The timing and spatial distribution of cells containing FMRFamide- and 5-HT-related molecules in the embryonic development of the mollusc Viviparus ater are examined using immunohistochemistry. FMRFamide-like molecules emerge in the early stage E8 (8% of embryonic development) before the 5-HT immunoreactivity, and they are not only found during nervous system ontogeny. As the parts of the digestive tract differentiated, the pattern of the diffuse gut endocrine cells, present in adults, start to be established (E20-E30), and both open and closed cell types are immunoreactive to anti-FMRFamide antibody. From their appearance (E20), cells with a 5-HT-like phenotype are distributed in the central nervous ganglia and progressively assembled during embryonic development. The early occurrence of both these molecules in V. ater embryos reinforces the growing view that neurotransmitters play a regulatory role in embryogenic processes. In particular, the very early presence of FMRFamide-related factors suggests an involvement of these molecules in the regulation of basic, not only neuronal, cell behaviours, while 5-HT seems to be a more specific neural development signal.

Animals↗