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The function of the excretory system of the teredinid bivalve Nausitora fusticula is discussed on the basis of new information on histology and ultrastructure. The wall of the auricles is lined with podocytes that allow haemolymph ultrafiltration to the pericardial cavity. These podocytes also show apical microvilli with absorptive activity. The primary urine is drained from the pericardial cavity to the afferent ducts by a citiated bulb-like structure. Theafferent and efferent ducts together form the kidney body. The afferent duct shows structures related to absorption, excretion and conduction of the urine. The efferent ducts, however, have structures concerned only with urine absorption and conduction. [ABSTRACT FROM AUTHOR]

The shell morphologies of the highshore littorinids, Littorina unifasciata Gray and Nodilittorina pyramidalis (Quoy & Gaimard) have previously been shown to vary at a variety of spatial scales, including among replicate sites at the same height, from height to height and from shore to shore. In this study, the relationships between morphology of the shell, the reserves of water held within the shell, the size of the foot and survival on different shores and rates of growth in different habitats were examined for L. unifasciata and, to a lesser extent, N. pyramidalis. Reserves of water were not consistently related to size or shape of the shell, but did increase as relative weight of shell increased. This may be due to the relatively smaller body providing more internal volume for extra-corporeal water. Water reserves and the amount of free water held in the shell were also not related to loss of water or survival during extended periods of emersion. Although the shape of the shell on sheltered and exposed shores was correlated with size of the foot, with the snails on an exposed shore having larger apertures and feet than those on a sheltered shore, transplant experiments did not show differential mortality between morphs from the different shores. All translocated and transplanted snails disappeared from the exposed shore at a greater rate than from the sheltered shore, but this was probably due to the snails dispersing out of the experimental areas rather than due to mortality. Therefore, many of the large-scale models that have previously been used to describe patterns of shell shape in intertidal gastropods do not appear to be important in these highshore littorinids. Finally, field experiments on growth of juvenile L. unifasciata indicated that rate of growth, largely governed by opportunity to feed rather than type and quantity of food, is the most likely explanation for the small- and large-scale patterns of shell shape that have been previously described in this species. [ABSTRACT FROM AUTHOR]

The nudibranch Dendrodoris nigra (Stimpson, 1855) has hitherto been considered as a single, highly poly-chromic species. Our investigations of external morphology, anatomy and colour variation have revealed more than one species exists. This conclusion gives credibility to the previous discovery of differing developmental patterns within D. nigra. Besides D. nigra, we recognise Dendrodoris fumata (Rüppell & Leuckart, 1830) which has three distinguishable colour forms. The occurrence of D. nigra is confirmed to be extensive, however, the species was not found to be circum-Australian as previously reported. The presence of D. fumata in Australia is confirmed and the species is also reported from Hong Kong and Fiji for the first time. The clear separation of these two species and recognition of the different colour forms will permit a more accurate picture of their distribution. [ABSTRACT FROM AUTHOR]

The nudibranch Discodoris indecora shows a perfect camouflage on its prey, the dictyoceratid sponge Ircinia variabilis. Shape and colour of the nudibranch are remarkably similar to that of the sponge which is widespread in the shallow waters of the Mediterranean Sea. The metabolite pattern of I. variabilis is dominated by unusual molecules, the sesterter-penoids palinurin and variabilin, containing 25 carbons and displaying at the ends a β-substituted furan ring and a tetronic acid. However, a chemical polymorphism has been recently described for I. variabilis. Some specimens contain either palinurin or variabilin whereas others possess a mixture of both sestertepenoids. During the study of Mediterranean sponges, a linear sesterterpenoid related to palinurin and variabilin was found in Ircinia fasciculata, that from a taxonomic point of view is closely relatedto Ircinia variabilis. Discodoris indecora shows a typical defence behaviour when it is disturbed, secreting a copious white slime that contains large amounts of palinurin and variabilin. Most likely the animal is able to transfer the sponge metabolites from the digestive glands to mantle glands. Electron micrographs of the nudibranch mantle showed the presence of unicellular glands characterized by a cylindrical vacuole with a big nucleus on the basis. The glands were concentrated in the most conspicuous tubercles of the dorsal mantle. Probably, the sponge metabolites are stored in these glands.Comparative chemical analysis of mucous secretions, dorsal tubercles, mantle, foot, digestive glands and hepatopancreas of D. indecora confirmed this hypothesis. Palinurin and fasciculation were, of course, present in the digestive glands but they were also found in the mucus and in the mantle sections enriched by the above described unicellular glands. The defensive role of palinurin and variabilin, strongly suggested by their anatomical location, was supported by recording the induction of feeding-deterrence in the fresh-water fish Carassius auratus and in the marine fish Chromis chromis and Sparus auratus. [ABSTRACT FROM AUTHOR]

Raup's model of shell growth, now in standard use, is operational only for strictly conispiral shells. The pertinence of evolutionary interpretations of the distribution of existing shells in the morphospace defined by Raup's parameters is questioned. A simple, more general model accounts for the non-isometric growth of many shells. Some aspects of the distribution of existing shells in the morphospace derived from the new model are discussed. [ABSTRACT FROM AUTHOR]

The development and morphology of the pallial and pulmonary cavities of various gastropods has been investigated using epoxy-resin serial sections. In the veliger larvae of Cellana sandwicensis (Patellogastro-poda), Gibbula adansonii (Vetigastropoda), Modulus tectum (Caenogastropoda) and Ovatella myosotis (Pulmonata) the formation of the pallial cavity is nearly identical. After shell formation a shallow dorsal pallial groove develops beneath the mantle edge. During the late veliger stage, the ectoderm forms a deep invagination along the bottom of the pallial groove on the right side of the larva, giving rise to the pallial cavity. In the ellobiid O. myosotis the pallial cavity becomes the lung (=pulmonary cavity), without any major post-metamorphic modification. Thus, the lung of this species is clearly homologous with the pallial cavity of prosobranchs. The lung of pulmonates with veliger development, as well as of fresh water basommatophorans and stylommatophorans, can be shown to be homologous by comparison of adult morphology. In contrast to previous views, the pulmonate lung should be regarded as truly homologous with the pallial cavity of prosobranchs and opisthobranchs. In the onchidiid pulmonate Onchidium cf. branchiferum, the larval pallial cavity shifts posteriorly after metamorphosis, where it gives rise to a lung and a cloaca. Contrary to previous interpretations, it can be shown that the onchidiid lung is homologous with at least part of the pallial cavity. Smeagol climoi has only a small pallial cavity and no separate lung. The previously described ‘lung’ is shown to be a gland. The re-evaluation of the development and morphology of the pulmonate lung has important systematic implications: (1) The pulmonary cavity does not represent a synapomorphic character of pulmonates. (2) The gymnomorphs cannot be separated from the remaining pulmonates based on lung development. (3) The lack of a lung in the smeagolids might give reason to reconsider this group's systematic placement within the pulmonates. [ABSTRACT FROM AUTHOR]

The taxonomic status of Bulinus globosus and B. nasutus as separate species remains unclear, espécially in areas of East Africa where their distribution overlaps. In order to throw further light on this question, a study was carried out on snails collected from the islands Unguja and Pemba, collectively known as Zanzibar, which lie in the Indian Ocean close to mainland Africa. In total, 169 snails from 22 sample sites were characterised by three methods: morphometric analysis of 15 shell measurements, enzyme analysis involving three enzyme systems and analysis with random amplified polymorphic DNA (RAPD). Enzyme analyses indicated that both B. nasutus and B. globosus were present on each island and their distribution was allopatric. Shell variation was considerable but did not clearly differentiate these taxa. Similarly, RAPD analysis indicated substantial genetic variation with in and between samples; more often than not, no two RAPD profiles were identical within the sample. On Pemba, B. globosus is more widely dispersed than B. nasutus which is confined to the eastern coast of the central region. On Unguja, B. globosus is found in more northern areas than B. nasutus. [ABSTRACT FROM AUTHOR]

Higher level relationships within the Gastropoda are difficult to determine, in part due to the paucity of identified synapomorphic characters. Larval shell hydrophobicity may be a useful additional character for gastropod family systematics. A survey of 57 species indicates that larval shell hydrophobicity is common or ubiquitous in pyramidellids, opistho-branchs, and marine pulmonates but is unknown in patellogastropods, vetigastropods, and caenogas-tropods. The taxonomic distribution of hydrophobic larval shells is consistent with the hypothesis that it is a heterobranch synapomorphy. Unfortunately the condition in key ‘lower’ heterobranchs such as architectonicids and valvatoids is unknown. [ABSTRACT FROM AUTHOR]

The morphology of the mature spermatozoa of the closely-related freshwater pulmonates, Bulinus africanus and Bulinus globosus, was examined using scanning and transmission electron microscopy. A comparison showed no useful differences that could be used to distinguish the species though they did differ in one respect from Bulinus tropicus, the only other bulinid for which sperm morphology is known. [ABSTRACT FROM AUTHOR]

Parsimony analysis of 29 finned and finless octopod taxa considered 66 anatomical and morphological characters to discover synapomorphies that unite monophyletic groups. The resultant cladogram (177 equally parsimonious trees at 191 steps, CI 0.429) resolved all relationships except those among the 16 exemplars of the Octopodidae included and those among Tremoctopus, Ocythoe and Argonauta. Bootstrap values of over 90% support the monophyly of the finned and finless octopods, relationships among the finned octopods, the bolitaenids and the monophyly of Haliphron, Tremoctopus, Ocythoe and Argonauta; bootstrap values for other nodes range from 57 to 79%. Among finned octopods, specimens representing Grimpoteuthis are basal, as Voss (1988a) suggested. Specimens of Opisthoteuthis represent a distinct lineage, and are sister taxon, in this analysis, of Cirroteuthis (although specimens of Stauroteuthis could not be included). New definitions of the genera Opisthoteuthis and Grimpoteuthis are provided to reflect their separate evolutionary histories rather than their overt morphological similarity. Among finless octopods, bolitaenids are basal. The monophyletic Octopodidae is the sister taxon to the clade containing the sister taxa Vitreledonella and Amphitretus, and Haliphron, Tremoctopus, Ocythoe and Argonauta. The Ctenoglossa and Heteroglossa, families grouped by shared radular dentition, are diphyletic and paraphyletic, respectively. The cladistic relationships demonstrate that both the Vitrele-donellidae and Idioctopodidae are junior synonyms of the Amphitretidae; despite conspicuous morphological differences separating these taxa, they share a recent evolutionary history. [ABSTRACT FROM AUTHOR]

This study deals with the systematic status of the widespread nominal land snail Cochlicopa lubricella (Porro, 1838). Three putative, conchologically distinctive morphotypes of Cochlicopa (Pulmonata: Cochlicopidae) occur in central Europe: C. nitens, C. lubrica, and C. lubricella. Self-fertilization is the main breeding stretegy within each of these nominal species. These three morphotypes were studied with RAPD profiling and the results compared with those of previous investigations using isoenzyme electro-phoresis (Armbruster & Schlegel, 1994: J. Zool. Syst. Evol. Res., 32: 282–296). Both sets of molecular data provide evidence against the monophyly of the conchologically classified members of C. lubricella. The strain previously classified as C. lubricella type 1 on shell morphological grounds is genetically indistinguishable from C. lubrica. The strain termed C. lubricella type 2 constitutes a distinctive group. C. lubrica, C. lubricella type 1 and C. lubricella type 2 are more closely related to each other than either is to C. nitens. The molecular data demonstrate the shortcomings of shell morphometric characteristics for determining the taxonomic rank of nominal snail species. [ABSTRACT FROM AUTHOR]

Mactra veneriformis (Bivalvia: Mactridae) is one commonly cultured bivalve species in the western Pacific Ocean. In the current study, the complete mitrochondrial DNA (mtDNA) of the clam M. veneriformis was determined. The M. veneriformis mt genome is 16,854 bp in length and encodes 34 genes on the same strand, including 12 protein-coding genes (PCGs), 2 ribosomal RNA genes and 20 transfer RNA genes. The length of 12 PCGs is 11,358 bp, which accounts for 67.4% in whole mt genome. The proportion is similar to other clams' mt genomes and within those of bivalves mt genomes. Gene order (which is the same as that of RZ C. antiquata) of M. veneriformis mt genome is compared with that of other veneroids. Compared with the typical gene content of animal mt genomes, atp8 and two tRNA Ser genes are missing in the mt genome. All non-coding regions are 1978 bp in length, among them the longest one is speculated as the control region, which is located between the tRNA His and tRNA Arg. The secondary largest non-coding region (NCR664) between the tRNA Gln and tRNA Thr in the M. veneriformis mt genome contains one section of tandem repeats (125 nt × 5.2 or 249 nt ×  2.6). The tandem repeats account for 97.89% (650/664) of the NCR664, which is a unique characteristic of the M. veneriformis mt non-coding regions compared with those of other veneroids. [ABSTRACT FROM AUTHOR]

Mactra veneriformis (Bivalvia: Mactridae) is one commonly cultured bivalve species in the western Pacific Ocean. In the current study, the complete mitrochondrial DNA (mtDNA) of the clam M. veneriformis was determined. The M. veneriformis mt genome is 16,854 bp in length and encodes 34 genes on the same strand, including 12 protein-coding genes (PCGs), 2 ribosomal RNA genes and 20 transfer RNA genes. The length of 12 PCGs is 11,358 bp, which accounts for 67.4% in whole mt genome. The proportion is similar to other clams' mt genomes and within those of bivalves mt genomes. Gene order (which is the same as that of RZ C. antiquata) of M. veneriformis mt genome is compared with that of other veneroids. Compared with the typical gene content of animal mt genomes, atp8 and two tRNA Ser genes are missing in the mt genome. All non-coding regions are 1978 bp in length, among them the longest one is speculated as the control region, which is located between the tRNA His and tRNA Arg. The secondary largest non-coding region (NCR664) between the tRNA Gln and tRNA Thr in the M. veneriformis mt genome contains one section of tandem repeats (125 nt × 5.2 or 249 nt ×  2.6). The tandem repeats account for 97.89% (650/664) of the NCR664, which is a unique characteristic of the M. veneriformis mt non-coding regions compared with those of other veneroids. [ABSTRACT FROM AUTHOR]

The article focuses on the study of wafting of cerebrospinal fluid through the cilia of spinal cords and brain ventricles in mollusc, carried out by the researcher Yoshiteru Seo, from Dokkyo Medical University School of Medicine, Japan. It mentions the visualization of fluid motion of mollusc through magnetic resonance imaging (MRI). It presents the manipulation of flow of water across their gills.

Multiplacophorans are Palaeozoic (Silurian to Permian) stem group polyplacophorans with 17 shell plates in a particular arrangement of single terminal plates separated by three columns of plates forming five transverse rows. Their distinctive morphology has prompted disparate interpretations of their relationship to polyplacophorans. Some features are strikingly similar to crown group polyplacophorans and even to some living families. Here we describe two Devonian forms, Protobalanus spinicoronatus sp. nov., a hercolepadid from northeast Ohio, USA, and Hannestheronia australis gen. et sp. nov., a strobilepid from South Africa. Using the results from a Bayesian relaxed molecular clock to test competing scenarios of the relationship of multiplacophorans to crown group polyplacophorans, we demonstrate that multiplacophorans are stem group polyplacophorans in which certain characters of the crown group evolved convergently. [ABSTRACT FROM AUTHOR]