Pomacea canaliculata is the only freshwater snail listed as one of the 100 worst invaders worldwide. Recent studies have demonstrated that small Pomacea snails have higher foraging and competitive abilities than larger snails and hence that ecological and agricultural damage of this invasive snail may be size-dependent. Furthermore, females of P. canaliculata usually reach larger sizes than males, a pattern that results from higher growth rates and not from higher survivorship in females; however, the proximal causes of the sexual dimorphic growth rates are unknown. In this study, we investigate the ingestion rates and growth efficiencies of P. canaliculata in order to explain the ontogenetic and sexual differences in growth and food consumption patterns. Two experiments were performed to study specific ingestion rates and the efficiency in food conversion to body mass at different feeding conditions. Ontogenetic and sexual differences were found in the specific ingestion rates. These decreased inversely with shell length and were higher for females than for males of comparable size. Conversion efficiencies decreased with age in both sexes, in males noticeably earlier than in females. Under high food availability conditions, the decrease is sharper than under low food availability. However, the effect of food availability almost disappeared when in the effect of size was removed. The sexual dimorphism of growth efficiencies and ingestion rates explain why females tend to reach a larger adult size than males, a pattern probably explained by development of the testicle and correlated reduction of mid-gut gland size. Our results on ontogenetic patterns of ingestion rates support predictions that during the reproductive season small snails may cause a great part of the damage to aquatic crops and natural wetlands.

North Pacific species of the family Solemyidae — Petrasma pusilla (Gould, 1861); Solemya valvulus Carpenter, 1864; Solemya panamensis Dall, 1908; Petrasma pervernicosa (Kuroda, 1948); Solemya reidi Bernard, 1980; and Solemya tagiri Okutani, Hashimoto & Miura, 2003 — and the type species of subgenera of the genus Solemya Lamarck, 1818, are re-examined. Five species of the genus Solemya are recognized from the North Pacific: Solemya (Solemya) pusilla (Gould, 1861); Solemya (Solemya) valvulus Carpenter, 1864; Solemya (Solemya) tagiri Okutani, Hashimoto & Miura, 2003; Solemya (Petrasma) panamensis Dall, 1908; and Solemya (Petrasma) pervernicosa Kuroda, 1948. The gutless S. reidi from the northeastern Pacific is synonymized with S. pervernicosa from the northwestern Pacific. Solemya pervernicosa was found in the Sea of Okhotsk and in the Sea of Japan near the coast of Sakhalin Island at the 300–800 m depth and was not previously recorded for Russia. A study of the materials of Acharax johnsoni (Dall, 1891) provided additional data on its distribution and ecology in the Pacific Ocean. This species was found in the Sea of Okhotsk (depth 370–1,515 m), as well as in the Monterey Canyon and Peru-Chile Trench (depth 3,040–4,200 m) in cold methane seep areas. The results of a comparative analysis of subgenera and species of the genus Solemya, descriptions of North Pacific species of the genus Solemya, and additional data on the distribution and ecology of A. johnsoni are presented.

The apple snail Pomacea canaliculata is a freshwater snail originating in tropical and temperate South America. We investigated the effect of temperature acclimatization, moisture levels, and food availability on the loss of cold hardiness in overwintering snails. Cold hardiness broke down by four days in snails maintained in aquatic condition at 25°C and by eight days at 20°C. However, snails held at 15°C retained their cold hardiness even after 64 days. In addition, the cold hardiness of snails kept moist (wrapped in wet towel) was maintained for at least 64 days even at 25°C. These results indicate that warm temperature together with increase of water availability decreases the cold hardiness of overwintering snails. Glycerol content reduced as cold hardiness decreased; supporting a previous hypothesis that glycerol has a major physiological role in the development of cold hardiness in this species.

This study provides a revision of the Magellanic and Antarctic species of Thyasira and Parathyasira. The status of all species previously reported from the area is revised and a new species described. Five species are recognized as valid: Thyasira falklandica (Smith, 1885); Thyasira scotiana, n. sp.; Thyasira debilis (Thiele, 1912), new combination; Parathyasira magellanica (Dall, 1901), new combination; and Parathyasira dearborni (Nicol, 1965), new combination. Cryptodon fuegiensis Dall, 1890, previously reported under the genus Thyasira, is reallocated into Conchocele Gabb, 1866. Loripes pertenuis Smith, 1881, and Thyasira bongraini Lamy, 1911, are considered nomen dubia.

Biological interaction between two ecologically related species in sympatry results mostly as character divergence, which is also known as ecological character displacement. However, there are reports of character convergence in areas of overlap. Here we present a case study of sympatric convergence and allopatric divergence in form between two species, Barnea Candida (Linnaeus, 1758), and Pholas orientalis Gmelin, 1791. They are members of closely related genera of marine bivalves from the eastern coast of India. So far as we know, this is the first report of a biological interaction between marine living bivalves. These two species are mud-boring deposit feeders. All of the characters here analyzed to show character shifting have adaptive significance or are proxy data for trophic apparatus. The present study involves more than 1,200 specimens collected from three sympatric and three allopatric sites that range over 1,000 km. Statistical analyses reveal that B.candida diverges more from its allopatric position than P. orientalis in sympatry. Character displacement generally takes place in sympatry to avoid or minimize competition for similar resources. The present two species have similar reproductive and feeding strategies. They also have similar ecological requirements for food and habitat. Because of these ecological and functional constraints, Barnea Candida and Pholas orientalis could not reduce competition by resource partitioning. Instead, they compete and hence converge.

Graf and Cummings (2006), hereafter referred to simply as “G & C”, provided phylogenetic analyses of a three-partition data set in order to (1) examine the higher level evolutionary relationships within the Palaeoheterodonta, (2) estimate the history of character state change, and (3) develop a phylogenetic classification for the group. However, portions of the available COI DNA sequence data, for multiple terminals, were omitted from G & C's phylogenetic analyses, and no attempt was made to explicitly account for the documented saturation in the COI data partition. In order to evaluate the effects of these omissions, we performed Bayesian inference (BI) as well as maximum parsimony (MP) analyses on G & C's combined evidence (CE) matrix that included all of the ingroup COI sequences contained in G & C, plus the omitted outgroup COI sequences. We conclude that G & C's COI DNA sequence omissions, when combined with MP analyses not accounting for COI saturation, negatively affected the topologies of the best trees obtained from phylogenetic analyses of the CE matrix. This conclusion questions the utility of G & C's inferences regarding palaeoheterodont bivalve character evolution as well as the taxonomic classification drawn from its preferred topology. For example, counter to G & C's inferences, our BI and “transformed COI” MP analyses determined that unionoid oyster conchology has evolved multiple times, and all of our phylogenetic analyses indicate that the Etheriidae (sensu G & C) is not monophyletic. However, it should be noted that, to date, no phylogenetic analysis of this data set has robustly estimated all basal nodes within the Unionoida. Therefore, any inferences regarding unionoid bivalve character evolution, diversity and classification drawn from these topologies should be considered weakly supported.

The freshwater gastropod genus Posticobia Iredale, 1943, is found predominately in eastern Australia and is redefined using morphological and anatomical characters. The genus is found in a wide range of habitats from isolated springs in central Australia to the large coastal rivers and lakes of New South Wales and Queensland. The genus as currently recognised is considered to contain three species, Posticobia brazieri (E. A. Smith, 1882) from eastern Australia, Posticobia ponderi n. sp. from Mulligan Springs, South Australia, and Posticobia norfolkensis (Sykes, 1900) from Norfolk Island.

The invasive apple snail Pomacea canaliculata is known as an omnivorous species, but there are only few reports of its predation. This study examined the potential of this snail as a predator of common freshwater snails in southern China. Laboratory experiments were conducted to quantify the damage of the apple snail to both early stages (eggs and/or neonates) and adults of five species of freshwater snails (Austropeplea ollula, Biomphalaria straminea, Melanoides tuberculata, Physa acuta, Sinotaia quadrata). The apple snail caused significant mortality to all of the early stages of the five snails, as well as adults of the pulmonates A. ollula, B. straminea and P. acuta, but did not consume adults of the prosobranchs M. tuberculata and S. quadrata. Such differential survival of the prey might be explained by differences in shell hardness and structure, as the adult prosobranchs were well protected by a hard shell and an operculum, whereas the pulmonates had a relatively fragile shell and lacked an operculum. The apple snail was unable to detect its prey from a distance, but it crawled quickly, which could create opportunities for direct contact with potential prey. Apple snails may therefore influence invaded ecosystems through predation on other freshwater snails.

Ancient lakes are hotspots of biodiversity, often harboring a large number of endemic species that make them prime model systems for evolutionary biologists. Besides such well-recognized ancient or long-lived lakes as Baikal, Biwa, Ohrid, and Tanganyika, there are other potentially old and biodiverse lakes in the world with poorly specified ages and under-studied faunas. We here report on the mollusc fauna of one such lake, Lake Trichonis in continental Greece. This graben lake is situated in a highly tectonized area, characterized by karst features and probably of middle to late Pliocene origin. Lake Trichonis is deep, oligotrophic, and rich in such specific habitat types as macrophyte meadows, rocky shores and sublacustrine spring systems. Moreover, it is a hotspot of freshwater biodiversity in Greece, particularly in molluscs.

After reviewing newly collected material and the published mollusc records, we found that at least 33 mollusc species occur in Lake Trichonis, with 24 gastropod and 9 bivalve species currently being recognized. This is 24% of the total freshwater mollusc diversity of Greece; 21% of the gastropods (five species) are endemic to Lake Trichonis. If the whole Trichonis Basin is considered, which also includes neighboring Lake Lysimachia, eight species (33%) of the total fauna appear to be endemic. Taking lake surface areas into account, the index of gastropod endemism of 0.442 (log N_{endemic species}/log A_{surface area}) for the Lake Trichonis Basin resembles on a world-wide scale values known for Lake Baikal, Russia, and Lake Biwa, Japan, and is only exceeded by Lake Ohrid, Macedonia/Albania, and ancient lakes of Sulawesi, Indonesia.

Despite the limited knowledge about the lake's evolutionary history, the suggested age of origin, the palaeogeographical characteristics, and the potential timing of phylogenetic events reviewed here support the presumed status of Lake Trichonis as an ancient lake.

From a conservational standpoint, more research, management and conservation efforts are necessary because ancient lakes are among the most vulnerable and threatened ecosystems on earth. Effects of human-induced environmental change are already noticeable in Lake Trichonis. Recognition of Lake Trichonis as a unique system with an unusually high biodiversity may help promoting conservation efforts.