Journal of Molluscan Studies - current issue

Discovery of the fourth species of the enigmatic chiroteuthid squid Asperoteuthis (Cephalopoda: Oegopsida) and extension of the range of the genus to the South Atlantic

Arkhipkin, A. I., Laptikhovsky, V. V. — 2008-07-30

A new species of deepwater squid Asperoteuthis nesisi is described based on a single specimen from the Southwest Atlantic. The new species is characterized by rather thin but muscled mantle and arms, and a wide ovoid funnel-locking apparatus with weak tragus and well-developed antitragus. Peculiar integumental tubercles are present both on the mantle and head. The largest arm suckers have chitinous rings with 12–14 separate sharp triangular teeth distally and a flat thin ridge proximally. Based on the external morphology, A. nesisi n. sp. is more closely related to A. acanthoderma than to A. mangoldae. Two specimens of ‘Mastigoteuthis? A’ reported previously from waters of South Georgia probably belong to A. nesisi n. sp. Our finding extends the range of the genus Asperoteuthis from the tropical and temperate Pacific to the sub-Antarctic Atlantic, supporting a cosmopolitan distribution of this genus of deepwater squid.

A photogrammetric methodology for size measurements: application to the study of weight-shell diameter relationship in juvenile Cantareus aspersus snails

Perea, J., Garcia, A., Acero, R., Valerio, D., Gomez, G. — 2008-07-30

A photogrammetric methodology is proposed to measure the diameter of snail shells on digital pictures. Digital photographs were taken of juvenile Cantereus aspersus snails. AutoCAD image analysis software was used for the measurements and the results were contrasted with data obtained using a digital caliper in the same snails to compare the accuracy of both methods. The snails were individually weighed and the shell diameter was measured once a week, for a total of 7 weeks. After the third week, there were no significant differences between both methods, whereas in the first 2 weeks the measurements obtained with a digital caliper scored larger diameters than the photogrammetric measurements. This is probably due to the difficulty to define the end of the shell with the caliper, whereas the photogrammetric analysis does not involve any risk for the snail. To test the reproducibility and repeatability of both methodologies seven snails were measured five times by three different examiners. Using the variance components analysis, the repeatability was 4.8% of the total variation for the photogrammetric methodology and 6.9% for the conventional methodology, while the reproducibility was 0.0% and 2.7% for the photogrammetric and conventional methodology, respectively. These findings indicate that the photogrammetric methodology can be used with confidence to measure the diameter of snail shells. The great advantage of this method is the ability to magnify the images to make more precise measurements from snails of any size, which is especially useful in the early stages of development. The growth data were used to construct a model for live weight (LW) estimation based on shell diameter. The snails showed high growth rates both in terms of shell diameter and LW. The shell diameters showed a low individual variation (16.2% CV) and were normally distributed, whereas the LWs showed greater variability (36.8% CV) and were not normally distributed. The best model for estimating LW from shell diameter in juvenile snails is the multiplicative model, with a high determination coefficient (96%).

A molecular phylogeny of the Rapaninae and Ergalataxinae (Neogastropoda: Muricidae)

Claremont, M., Reid, D. G., Williams, S. T. — 2008-07-30

The previous phylogenetic hypotheses for Rapaninae, a large and taxonomically perplexing subfamily of the Muricidae, have been based on morphological characters. These studies concluded that the subfamily is distinct from the Ocenebrinae and that some ‘ergalataxine’ muricids are contained within the Rapaninae. We tested these hypotheses using DNA sequence data (one mitochondrial and one nuclear gene) from 35 species across the Muricidae. The monophyly of the Rapaninae and Ergalataxinae is supported, but relationships among these and other muricid subfamilies are not resolved. We discuss phylogeny of the sampled genera within the Rapaninae and Ergalataxinae, and show that Thais (Rapaninae) and Morula (Ergalataxinae) are polyphyletic.

Three new species of Simrothiellidae (Solenogastres) associated with the hot-vent biotope

von Salvini-Plawen, L. — 2008-07-30

Solenogastres specimens collected during three French cruises at different hydrothermal vent sites represent three undescribed species, all belonging to the family Simrothiellidae (order Cavibelonia): Helicoradomenia parathermalis n. sp. comes from five stations of the Southeast Pacific Rise, Sensilloherpia pholidota n. sp, n. gen., is recorded from two stations of the Northeast Pacific Rise, and Diptyaloherpia insolita n. sp, n. gen., originates from one station of the Northeast Pacific Rise. The organization of the three species is systematically compared, and the two new genera are defined; they enlarge our knowledge of the organizational diversity of Solenogastres. The definitions of Simrothiellidae and of the order Cavibelonia are emended correspondingly. The common characters of all hot vent Solenogastres and adaptations in relation to this particular biotope are discussed; these include a particular anterior sense organ, solid mantle sclerites, latero-ventral foregut glandular organs of the clustered type, and a non-cnidarian diet, probably of polychaetes.

Variation with habitat in Cepaea nemoralis: the Cain & Sheppard diagram

Cook, L. M. — 2008-07-30

In the 1950s Cain and Sheppard showed that in mature agricultural landscape in southern England samples of the polymorphic snail Cepaea nemoralis (L.) from woods had more unbanded, non-yellow individuals and fewer yellow bandeds than those from hedgerows and grassland. They considered mid-banded shells to be visually unbanded. This pattern was interpreted as resulting from selective predation acting on the phenotype rather than on specific genotypes. Evidence from this and 18 further data sets has been re-analysed. The association of yellow banded with open habitats and non-yellow, unbanded with woods is confirmed. The distribution of mid-banded is not consistent, and inclusion of other effectively unbanded phenotypes makes little difference to the result. The association therefore depends on the colour/banding system, but very little on other aspects of the phenotype. It is not incontrovertible evidence of selective predation; non-visual differences in fitness could also be involved. Further direct observation of the action of predators is needed to assess the argument for selective predation.

Choosy males in a littorinid gastropod: male Littorina subrotundata prefer large and virgin females

Zahradnik, T. D., Lemay, M. A., Boulding, E. G. — 2008-07-30

Mate choice has been considered to be a uniquely female behaviour. However, recent studies suggest that males strategically allocate their sperm among females with the greatest reproductive value. We investigated mating behaviour in the direct-developing Northern Pacific gastropod, Littorina subrotundata. Our field survey showed significant sexual dimorphism and the presence of size-assortative mating in our study population. Laboratory studies demonstrated that larger males may physically out-compete smaller males for access to females. Additional laboratory mate-choice experiments showed that males preferentially copulated with larger females. We also found that males were significantly more likely to copulate with virgin females than with females that had recently copulated. This suggests that males can detect the presence of sperm from rival males within a female's reproductive tract.

Ipunina, a new genus perhaps of Litiopidae (lower Caenogastropoda), from the Neogene of southern Chile

Nielsen, S. N., Frassinetti, D. — 2008-07-30

A new genus and species of lower caenogastropod, Ipunina vladimiri, is described from Neogene sediments of the islands Chiloé and Ipún, southern Chile. Ipunina has a protoconch with strong axial ribs on the upper side and a pattern of boxes on the periphery of the whorls, and a thin-shelled bucciniform teleoconch with strong spiral cords. Neither larval nor adult shell-morphology completely resolves the systematic placement. Affinities with Litiopidae, Planaxidae and Provannidae are discussed and placement in Litiopidae is favoured based on protoconch sculpture. This is the first record of Litiopidae from the Neogene of south-western South America.

Urate cells and tissues in the south american apple snail Pomacea canaliculata

2008-07-30

Intracellular urate concretions are known to occur in some insects, crustaceans and gastropods. Crystalloid-containing urate cells and tissues are widespread in many organs of the apple-snail Pomacea canaliculata. The occurrence of three different urate tissues (perivascular, compact and nodular) correlated well with uric acid concentrations found in the organs containing them. The highest uric acid concentrations were found in the coiled gut (showing both perivascular and compact tissues), the style sac (compact tissue), the testis, the midgut gland and the lung (perivascular tissue) and the aortic ampulla (nodular tissue). Lower concentrations were found in organs with perivascular tissue associated only with their main supplying vessels (anterior kidney and ctenidium), while organs devoid of urate tissues had minimal concentrations (mantle skirt, posterior kidney, albumen gland and heart). Transmission electron microscopy of urate cells revealed a process of sequential differentiation and death, accompanied by the formation and resorption of urate crystalloids. This process occurred asynchronously in cells within the same tissue, suggesting an active turnover of uric acid in the organs containing them.

Molecular confirmation of species status for the rare cephalaspidean Melanochlamys lorrainae (Rudman, 1968), and comparison with its sister species M. cylindrica Cheeseman, 1881

Krug, P. J., Morley, M. S., Asif, J., Hellyar, L. L., Blom, W. M. — 2008-07-30

Colour polymorphisms, and phenotypic plasticity of traits such as shells and radulae, complicate the taxonomy of many invertebrate taxa. Recent field surveys in New Zealand yielded specimens of the white cephalaspidean opisthobranch Melanochlamys lorrainae (Rudman, 1968), not reported since the 1960s. We used an integrative approach to test whether M. lorrainae was a distinct species or an unpigmented morph of the more common black congener M. cylindrica Cheeseman, 1881. Molecular data were combined with analysis of shell morphology and observations of relative abundance and habitat preference for the two nominal species. Differences in the shape of the internal shell were congruent with body colour, but less extreme than previously reported. In field surveys, M. lorrainae was found on sand- or mudflats while M. cylindrica was primarily associated with rocky habitat and red algal turf. Molecular phylogenetic analyses were performed on three gene regions, the mitochondrial cytochrome c oxidase subunit I (COI) and large ribosomal subunit (16S) rRNA loci, and the nuclear large ribosomal subunit (28S) rRNA locus. In all analyses M. lorrainae and M. cylindrica were reciprocally monophyletic, with net genetic distances of 16.5% for COI, 2.4% for 16S and 0.9% for 28S, all comparable to distances between sister species of other cephalaspideans. The northeastern Pacific M. diomedea and an undescribed Australian species formed a clade with modest support in parsimony analysis of mtDNA, and strong support in Bayesian analysis of the nuclear 28S gene despite an unusually long branch for the Australian species. No strong phylogenetic affinity was detected between the New Zealand species and the other two Melanochlamys spp., which also differ in some morphological respects. Group mating via unilateral insemination is described for M. cylindrica.

Three new solar-powered species of the genus Phyllodesmium Ehrenberg, 1831 (Mollusca: Nudibranchia: Aeolidioidea) from the tropical Indo-Pacific, with analysis of their photosynthetic activity and notes on biology

Burghardt, I., Schrodl, M., Wagele, H. — 2008-07-30

Three new Phyllodesmium species, Phyllodesmium lizardensis n. sp. from Lizard Island (Australia), P. lembehensis n. sp. from Sulawesi (Indonesia) and P. koehleri n. sp. from the Philippines, are described. Phyllodesmium lizardensis n. sp. and P. lembehensis n. sp. are associated with octocorals of the family Xeniidae and are similar to other Xeniidae-feeding Phyllodesmium species. Nevertheless, unique combinations of cerata morphology and colour, tooth and jaw morphology, the position of the anal papilla, as well as the special digestive glandular branching system within the cerata clearly distinguish these new species from described ones. Phyllodesmium koehleri n. sp. probably feeds on octocorals of the genera Lemnalia or Paralemnalia; it shows a cactus-like cerata morphology that is unique among Phyllodesmium species. In vivo measurements of photosynthetic activities in P. lizardensis n. sp. and P. lembehensis n. sp. indicate a symbiotic relationship with zooxanthellae at least for some days. These results are discussed in comparison to the Xeniidae-feeding species P. jakobsenae Burghardt & Wägele, 2004 and P. rudmani Burghardt & Gosliner, 2006. Histological investigation of the digestive diverticula within the cerata of all new species also suggests a relatively high efficiency of the symbiosis.

A new method for marking slugs by ultraviolet-fluorescent dye

Foltan, P., Konvicka, M. — 2008-07-30

We introduce a new, cheap, fast and reliable method for marking slugs, using biologically inert UV-fluorescent dye. The dye remained visible for more than 3 months in all individuals marked. Use of the dye did not affect survival, spatial behaviour or daily activity of the slugs, nor the prey choice of the predatory beetle Pterostichus melanarius, under controlled semi-natural conditions. The new method will enable further investigations of absolute slug densities, diurnal activity, mobility and dispersal, using capture-recapture techniques. The resulting data would allow the construction of more exact forecasting models for the population dynamics of pest slugs, potentially leading to a reduction in the use of control agents, particularly chemical molluscicides.

Novel intermediate-term individual marking technique for slugs

Wallin, K. F., Latty, T. M. — 2008-07-30

Environmental cues trigger seasonal regression of primary and accessory sex organs of the mud snail, Ilyanassa obsoleta

Hotchkiss, A. K., Sternberg, R. M., LeBlanc, G. A. — 2008-07-30

Is self-fertilization possible in nudibranchs?

Pola, M., Gonzalez Duarte, M. M. — 2008-07-30