Reproductive biology and growth of two Vallonia species in laboratory conditions (Gastropoda: Eupulmonata: Valloniidae)

Abstract

Folia Malacologica is funded by the Ministry of Science and Higher Education, Republic of Poland under agreement no. 646/P-DUN/2016 allocated to the activities of disseminating scienceFolia Malacol. 24(4): 265-273 http://dx.abstract: Reproduction and growth of Vallonia pulchella (O. F. Müller) and V. costata (O. F. Müller) were studied in laboratory conditions. Their ellipsoid and singly laid eggs are among the smallest heavily calcified (mean size 0.68×0.67×0.52 and 0.69×0.67×0.54 mm in V. pulchella and V. costata, respectively). V. pulchella reached morphological maturity (lip completion) at 3.25-3.50 whorls (mean 3.35), 49 to 166 days after hatching (85). The first egg (sexual maturity) was laid at 3.25-3.50 whorls (3.35), 50-283 days after hatching (162). The life span ranged from 628 to 940 days (779), the time elapsing between the last egg and death was 12-184 days (111). In V. costata the lip was completed at 3.25-3.50 whorls (3.37), 42 to 183 days after hatching (120). The first egg was laid at 3.25-3.50 whorls (3.42), 131-290 days after hatching (193). The life span ranged from 360 to 841 days (709) and the time elapsing between the last egg and death was 11-692 days (210). The egg production rate and juvenile life span in individuals kept in isolation were the same as in those kept in pairs or larger groups. The growth pattern was similar in the two species: fast phase followed by slow phase. However, the formation of ribs on the shell surface of V. costata probably slowed down its growth rate. The life history traits shared by the two Vallonia species are determined growth, iteroparity, longevity and predominantly selfing reproductive mode. The greater lifetime fecundity, shorter incubation period, faster growth and longer life span predestine V. pulchella to be a better coloniser than V. costata.

Taxonomic and functional diversity of land snails reflects habitat complexity in riparian forests

“…The negative response of large snails, reaching later sexual maturity and having more offspring, is most probably explained by the preference of large helicid snails for less complex habitats. The number of eggs (and by default the number of offspring) is known to be small in minute species with short lifespans occurring in leaf litter 51 – 53 . Baur 51 issues two hypotheses concerning this convergence: it can be the result of specific natural selection processes in the leaf litter microhabitat or, a general constraint caused by the very small size of the animals.…”

Fitting competing models and evaluation of model parameters of the abundance distribution of the land snail Vallonia pulchella (Pulmonata, Valloniidae)

“…There have been few publications on the results of aut-and demecological research on the land snail V. pulchella. In the 1930s, research was carried out on the reproduction of this mollusc (Whitney, 1937(Whitney, , 1941, which was continued in this century (Kuźnik-Kowalska & Proćkow, 2016). It was revealed that the density of V. pulchella is affected by many soil physico-chemical properties, especially calcium and magnesium concentration and pH of water extract (Hermida et al, 1993(Hermida et al, , 2000.…”

Why pygmy snails lay giant eggs: the kiwi syndrome

“…Like kiwis (Bain, 2018), some small land snails need moist environments; are not agile; have unexpectedly long lifespans (Finch, 1994, p. 13;Kuźnik-Kowalska & Proćków, 2016); lay relatively large eggs with little individual variation (Baur, 1994); and invest resources in large offspring with better survival rates (Baur & Raboud, 1988). Perhaps kiwis, and snails with this list of characteristics, which I will call the "Kiwi Syndrome", have been exposed to evolutionary pressures that include low egg predation, heavy predation on the young, and a minimal viable size for hatchlings, forcing small snails to invest in relatively large offspring at the cost of reduced fecundity.…”