Conchological variation in Pomacea canaliculata and other South American Ampullariidae (Caenogastropoda, Architaenioglossa).

Universidad Nacional del Sur, Departamento de Biología, Bioquímica y Farmacia, San Juan 670, 8000 Bahía Blanca, Argentina.
Biocell: official journal of the Sociedades Latinoamericanas de Microscopía Electronica ... et. al (Impact Factor: 0.58). 09/2006; 30(2):329-35.
Source: PubMed
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    ABSTRACT: The aim of this study was to test the hypothesis that positive rheotaxis and anti-detachment behaviors contribute to the persistence of Pomacea canaliculata in lotic environments. This invasive apple snail is commonly considered a lentic dweller. In a first series of trials in a laboratory flume, current velocity was gradually increased until snails’ detachment. Detachment velocity was highly variable, with some snails able to withstand strong currents during short periods. Sexually undifferentiated snails were the most resistant to detachment; most of the snails that resisted high velocities were facing flow before detachment. In a second series of trials, snails’ net displacement was estimated at three fixed velocities (0, 0.15, and 0.30 m s-1). Current velocity did not influence mean net displacement, which was not different from zero. Marked snails were released in a stream and recaptured 24 h later estimating their net displacement. Most recovered snails dispersed a short distance from the release point and crawled through sites with very low current velocities. A small proportion of snails drifted downstream, indicating the existence of different dispersal mechanisms. Snails were able to resist current velocities that are among the highest recorded in streams in the Pampas region. P. canaliculata did not show a positive rheotactic response; in flowing water, snails crawl more often upstream, but at a slower pace than downstream. At the population level, a slow upstream spread seems possible in plain’s streams, probably being enough to compensate drift, but not to colonize headwaters. Irrigation systems are feasible pathways for the spread of this species in invaded regions.
    Aquatic Ecology. 01/2012; 46(1-46):129-142.
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    ABSTRACT: Phenotypic plasticity in life history traits favors the establishment of invaders and may magnify their ecological impacts. Pomacea canaliculata, the only freshwater snail listed among the 100 worst invaders worldwide, is able to complete its life cycle within a wide range of conditions, a capacity attributed to its life history plasticity. Using snails from their native range in Argentina we investigated the changes in fecundity, egg mass traits, offspring quality, and efficiency of food conversion into eggs in response to different levels of food availability throughout different life stages. Pre-maturity mortality was not affected by chronic reductions of up to 80% in food availability. Females fed ad libitum demonstrated no significant reproductive output differences when mated with males raised at different food availability levels. For females, the number and total weight of eggs and the size of egg masses decreased at high levels of food deprivation. Their efficiency of conversion into eggs of the food ingested during the reproductive period increased with deprivation, as did the survival time of their offspring. In contrast, the egg mass laying rate and the individual egg weight did not differ under different food availability regimes. Reductions in food availability have been suggested as a control method but our results indicate that fecundity would be lessened only at deprivation levels higher than 50% and would be partially compensated by an increase in hatchling survival. KeywordsWetlands–Paddy fields–Plasticity–Life history–Maternal effects–Efficiencies
    Biological Invasions 01/2011; 13(10):2351-2360. · 2.51 Impact Factor
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    ABSTRACT: 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.
    Malacologia 02/2010; · 1.59 Impact Factor


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