Relationships of gymnomorph gastropods (Mollusca: gastropoda)

The gastropod families Onchidiidae, Vaginulidae, Rathouisiidae and Rhodopidae have been classified in a subclass Gymnomorpha, in which the genus Smeagol has been more recently included, on the basis of characters related with limacization which should not be used for classification at suprafamilial levels. When only characters not related with limacization are taken into account, the onchidiids are very similar to the ellobiids; Smeagol may be considered an otinid slug; vaginulids and rathouisiids form a monophyletic group of pulmonates, the Rathouisioidea. It is proposed to reject the Rhodopidae from the Pulmonata, and to include the onchidiids and the Rathouisioidea in the order Archeopulmonata, together with the ellobiids, the otinids and the Amphiboloidea.     

中国复套蛞蝓科一新种：肺螺亚纲：鞋形目

现已知我国复套蛞蝓科,复套蛞蝓属共计6种,主要分布于我国台湾、广东、海南、浙江、广西、上海、安徽、四川等省市以及香港、澳门等地区。作者在云南省玉溪地区峨山彝族自治县采得复套蛞蝓科一新种:玉溪复套蛞蝓Vaginulus yuxiensis。本文对该新种的外部形态和内部构造,尤其对生殖系统和齿舌的形态结构作了较详细的描述,其齿式为:(3:1:3)/152。并且作者与其近似种中国复套蛞蝓 Vaginulus chinensis Moellendorrf,1881;和佛尔复套蛞蝓 Vaginulus fargcsianus Heude,1885进行了比较。     

Morphology and aestivation behaviour in some Madagascan acavid land snails

Nine species of Madagascan acavid land snails were compared in a phylogenetic context. The two most plesiomorphic, Clauator johnsoni and C. moreleti, differ from the others by their high-spired shells, short tentacles, short tails, long necks, and crawling mode of hitching the shell along the ground. In the seven more apomorphic species, the crawling mode is smooth, with the shell resting on the tail, and the relative lengths of tail and shell correlate significantly. Among these seven species, three pairs of closest relatives (Helicophanta petiti and H. uesicalis, H. farafanga and H. souuerbiana, Ampeltta decaryi and A. julii) show evidence of phylogenetic constraints on ranked shell size. Aestivation site (as tentatively inferred from rare data) does not correlate with shell shape or size: burrowers have H/D = 2.7 to 0.6 and D = 70 to 25 mm; arboreals have H/D = 0.8 to 0.5 and D = 70 to 30 mm; the species with both the highest spire and the smallest diameter (C. moreleti) is neither a burrower or an arboreal, but stays on the ground surface. Inferred aestivation sites are randomly distributed phylogenetically. Climate shows no correlation, except that the arborcals are only from humid to wet regimes. Uniform shell colouration occurs only in burrowers (C. johnsoni, H. petiti, H. uestcalis), but disruptive shell colouration occurs in all others, including burrowers (H. farafanga, A. decaryt), ground-surface aestivators (C. moreleti), arboreals (H. souuerbiana, A. julii), and semi-arboreals (Ampefita subfunebris). Among all nine species, burrowers have significantly thicker shells (than their close relatives of similar size), wider bodies, and longer snouts than non-burrowers (H. souuerbiana is exceptional in being arboreal despite its huge size and in having the broad foot and snout of a burrower). Thus, although there is some evidence for phylogenetic constraints, natural selection for aestivation and crawling behaviours seems to have dominated the evolution of external body morphology and of shell thickness (but not shell size and shape) in these snails.     

Degradation of the radula in the snails Biomphalaria glabrata say and Limnaea stagnalis L. (Gastropoda,Pulmonata)

Summary The radula of snails is formed at the posterior end of the radular gland or pocket, and degraded at the same rate at its anterior end. Degradation is due to different secretory activities of the inferior epithelium of the radular gland. Its secretions seem to degrade enzymatically the matrix of the radular membrane and basal plates of teeth, leaving only chitin containing microfibres and degradation products. The sclerotized parts of the teeth remain unchanged, but as they are now only loosely connected with the radular membrane. they are torn off easily during feeding movements. The rest of the degraded and frayed radular membrane and the subradular membrane are also lost by abrasion during feeding. The cells of the inferior epithelium are connected with each other by septate desmosomes and an elaborate system of deep lateral interdigitation which may provide tensile strength. Extrusion of degraded cells of the inferior epithelium into the subradular membrane takes place, although the thick basal lamina forms a continuous sheath which is closely adjoined to the basal parts of the inferior epithelium. Nerve fibres containing vesicles with electron dense neurosecretory material (deduced from the diameter of 200–250 nm) are attached to this sheath or penetrate into it; they may be involved in the regulation of production and degradation processes during radula replacement. Problems of the forward transport of radula and inferior epithelium are discussed.     

Gastrocopta (Mollusca,Gastropoda, Pupillidae) in?the?Pilbara region of Western Australia

Six species of Gastrocopta have been identified from the Pilbara region, Western Australia, by means of comparative analyses of shell and mtDNA variation. Three of these species, Gastrocopta hedleyi, Gastrocopta larapinta and Gastrocopta servilis, have been recorded in the Pilbara for the first time. Gastrocopta sp. CW1 is probably new to science and might be endemic to the region. By contrast, Gastrocopta hedleyi, Gastrocopta larapinta and Gastrocopta mussoni are shown to be widespread.     

Pallial systems in the Athoracophoridae (Gastropoda: Pulmonata)

Abstract

Pallial systems are described for 10 athoracophorid species: Athoracophorus bitentaculatus, Pseudaneitea dendyi, P. gigantea, P. papillata, P. pallida, P. aspera, P. schauinslandi, P. multistriata, and Palliopodex verrucosus from the New Zealand and sub antarctic area; and Triboniophorus graeffei from Australia. In the New Zealand and subantarctic species the kidney is invariably bilobed, the ureter is extensively folded and connected to the intestine by an elongate tubule running initially through the lung, and the pneumostome, anus, and excretory pores are widely sepamted. Triboniophorus graeffei has the pneumostome, anus, and excretory pore closely associated, a compact kidney, and a more simply folded ureter. The New Zealand and subantarctic representatives are considered to be more advanced. Reasons for the development of the features they display are discussed, as is the function and evolution of the entire pallial system. An account of the variation in the pallial complex of Athoracophorus bitentaculatus is included.     

Waves of dispersal in island-hopping Chondrina species (Gastropoda, Pulmonata, Chondrinidae)

The aim of this study was to unravel the historical biogeography of the speciose land snail genus Chondrina. To this end phylogenetic hypotheses were tested using mitochondrial DNA sequence data.Mitochondrial DNA sequences of the Cytochrome Oxidase subunit I region were obtained for 89 individuals, representing just over 70% of the extant Chondrina species. The extent of molecular genetic diversity and phylogeographical patterns were investigated by using neighbour joining, parsimony and bayesian methods for phylogeny reconstructions. The resulting data were used to infer historical biogeographical patterns for the genus Chondrina.The three phylogenetic methods yielded congruent topologies for the phylogeny reconstruction. Six clades were identified, each of which with at least one taxon that is known from the Iberian peninsula. The most parsimonious scenario indicates at least three waves of dispersal out of the Iberian peninsula into the North and East of Europe and Northern Africa.The phylogenetic relationships combined with the distributional patterns of the various species, indicate that only vicariance events cannot explain the actual situation. Apparently, separate waves of dispersal and subsequent speciation occurred, each time starting from the southwestern part of the present generic range. Until recently, this was obscured by repetitive cases of parallel or convergent evolution in shell characters, as became evident with the use of molecular methods.     

Setocallosa—a new genus and species of land snail from Arnhem Land,Australia (Stylommatophora: Camaenidae)

The new, monotypic camaenid genus Setocallosa is described for the new species S. pathutchingsae from Arnhem Land, Top End of the Northern Territory. This camaenid is characterized by a combination of distinct morphological features, such as a small, weakly elevated shell with widely open umbilicus and thick callus on the parietal wall, a wide epiphallic flagellum, elongated penis and short bursa copulatrix with subglobose end. The relationships of Setocallosa with the other camaenid genera in the area are investigated by means of mtDNA, but its phylogenetic position remains ambiguous. S. pathutchingsae occurs in sympatry with Arnhemtrachia ramingining, but based on morphology the two camaenids can be readily differentiated.

http://zoobank.org/urn:lsid:zoobank.org:pub:1C50CF24-7FEE-446A-9724-A0A4E850B5AA     

中国红树林区的耳螺

耳嫘是一类特殊的原始有肺类软体动物,主要分布于热带、亚热带海陆交汇区的高潮带和潮上带.耳螺在红树林区广泛分布,且资源非常丰富,全世界已知的约240种耳螺中,至少有一半以上的种类在红树林区被记录.本文总结了耳螺与红树林的关系以及中国嗜盐耳螺的种类,综述了红树林区耳螺的种类组成、分布、生态功能、行为等的研究进展,报道了中国...     

Evolutionary relationships of euthyneuran gastropods (Mollusca): a cladistic re-evaluation of morphological characters

Morphological characters of the Euthyneura available from the literature were re-evaluated in terms of terminology and primary homology. A total of 77 characters and 75 taxa were retained in a data matrix. Several assumptions on character weights and types were tested. In the cladistic analyses, it appeared that the data matrix was highly homoplastic, and only robust nodes (those which were little modified by variations in weight and coding of characters) were retained in a concensus tree. The evolutionary histories of all characters and monophylies of higher euthyneuran taxa were discussed. The following interrelationships of the taxa were obtained in a consensus tree: the clade Heterobranchia includes paraphyletic allogastropod taxa which emerge basally, and the clade Euthyneura. The latter includes the clade Pulmonata and at least 10 opisthobranch clades of unresolved relationship (Thecosomata, Gymnosomata, Acochlidioidea, Pyramidelloidea, Runcinoidea, Cephalaspidea, Sacoglossa, Umbraculoidea, Pleurobranchoidea, Nudibranchia). The Pulmonata include basommatophoran paraphyletic taxa and the clade Geophila (Onchidiidae, Soleolifera, Stylommatophora). The position of the Sacoglossa and the monophyly of the Notaspidea are also discussed.  © 2002 The Linnean Society of London, Zoological Journal of the Linnean Society , 2002, 135 , 403–470.