Molluscs show a wide diversity of sexual systems and strategies. There are both gastropod and bivalve families that are each primarily dioecious, simultaneous hermaphrodites, or sequential hermaphrodites, and other families in which almost every sexual strategy occurs. The multiple evolutionary transitions of sexual systems within molluscs would allow comparative analyses of the associated ecol...

This Paper reports a study on the benthic faunal abundance and diversity of tiger shrimp P. monodon culture ponds in Perak, west coast of Malaysia Peninsular. Sampling was carried out at three weeks interval throughout the 116 days culture period. In addition, water temperature, dissolved oxygen, salinity, transparency, pH and organic matter of soil were also measured. Results showed that the m...

The proportion of body mass devoted to skeleton in marine invertebrates decreases along latitudinal gradients from large proportions in the tropics to small proportions in polar regions. A historical hypothesis-that latitudinal differences in shell production costs explain these trends-remains untested. Using field-collected specimens spanning a 79°N to 68°S latitudinal gradient (16,300 km), we...

Sperm ultrastructure is examined in representatives of five genera of the nudibranch gastropod family Chromodorididae: (Chromodoris, Hypselodoris, Glossodoris, Risbecia and Pectenodoris) and the results compared with previous work on other gastropods, especially other nudibranchs. As chromodoridid phylogeny is still incompletely understood, this study partly focuses on the search for new and as...

Herbivore effects on diversity and succession were often studied in plants, but not in cryptogams. Besides direct herbivore effects on cryptogams, we expected indirect effects by changes in competitive interactions among cryptogams. Therefore, we conducted a long-term gastropod exclusion experiment testing for grazing effects on epiphytic cryptogam communities. We estimated the grazing damage, ...

This study aims at a better understanding of the evolutionary significance of viviparity in some freshwater gastropods. We use a phylogeny based on partial sequences of the mitochondrial 16S gene of representatives of the limnetic and pantropical Pachychilidae to infer the relationships within this particular group of cerithioideans and the evolution of reproductive strategies. The phylogeny pr...

Antarctic marine invertebrates from the Western Antarctic Peninsula (WAP) are generally stenothermal, with three-month survival and activity limits above the average maximum summer seawater temperature (1.08C) of 1–68C and 1–38C respectively. For many of these species to survive the warmer maximum temperature at the sub-Antarctic island of South Georgia (58C), they require either greater therma...

Forty gastropod species of the subclass Heterobranchia are described from Upper Jurassic (Upper Kimmeridgian) reefal limestones South Germany, including ten in open nomenclature and further uncertain identity. Six new to science: Ceritella convexa sp. nov. , Nerinea donosa Endoplocus acutus inflatus Pseudonerinea ? pseudomelaniformis Itieroptygmatis cylindrata A lectotype is designated for Ptyg...

The in ̄uence of soil exchangeable cations and aluminium content on the distribution of various terrestrial gastropods was investigated. Calcium was the most important factor, though aluminium and magnesium content also had some effect. Potassium and sodium had no signi®cant in ̄uence on distribution. The species most sensitive to the factors analysed were Cochlicopa lubrica, Vertigo pygmaea and ...

Common gastropods such as snails crawl on a solid substrate by propagating muscular waves of shear stress on a viscoelastic mucus. Producing the mucus accounts for the largest component in the gastropod’s energy budget, more than twenty times the amount of mechanical work used in crawling. Using a simple mechanical model, we show that the shear-thinning properties of the mucus favor a decrease ...