Egg retention and ovoviviparity in clausiliids of the genus Vestia P. Hesse (Gastropoda: Clausiliidae)

Abstract

The reproductive biology of three Carpathian clausiliids of the genus Vestia [V. gulo (E.A. Bielz, 1859), V. elata (Rossma¨ssler, 1836) and V. turgida (Rossma¨ssler, 1836)] was studied using two methods: (1) the presence of eggs was examined in uteri of snails collected in the wild; and (2) the reproduction of snails was observed for 2-4 years under laboratory conditions. All three species retained eggs (ovoviviparity sensu lato), but there was a variation in the stage of the development of embryos among the species: V. gulo retained embryos to a size of c. 1.3 embryonic whorls, then laid eggs that hatched after 7-10 days; V. elata retained embryos to a size of 1.8 whorls, then laid eggs that hatched after 2-4 days; and V. turgida retained the largest embryos with up to 2.9 embryonic whorls. Oviposition was observed rarely in the latter species so that most embryos probably hatched inside the parent (ovoviviparity sensu stricto). The number of retained eggs in a uterus differed significantly between V. gulo and V. turgida. The reproductive period of V. turgida was longer than that of V. gulo, with two distinct reproductive peaks in June and August. Eggs were spherical or slightly oval, partly calcified and resilient, but eggs of V. turgida were elongated and less resilient. Mean numbers of eggs in a single batch were: V. gulo, 9.44 + 3.73; V. elata, 4.50 + 2.07; and V. turgida, 3.83 + 2.12. Egg cannibalism was most intense in V. gulo, but was not observed in V. turgida. Under laboratory conditions V. gulo produced 1-4 batches, V. elata 1-7 batches and V. turgida 1-6 batches of eggs. The three species each produce up to 30-34 juveniles per reproductive season, but the interspecific variation and between-season variation were very high. A possible relation of the reproduction mode with habitat preferences of the species is proposed.

Oviparous reproduction of Vestia ranojevici moravica confirms taxonomic value of life history characters in carpathian clausiliids (Gastropoda: Pulmonata)

“…14 days). The eggs of other Vestia species kept at the same laboratory hatched after shorter time of external development (V. gulo: 7-10 days; V. elata: 2-4 days; V. turgida: 0-2 days), and immediately after egg deposition big, shelled embryos were visible through the egg envelopes (Sulikowska-Drozd 2008, 2009). In the Carpathian Vestia species anatomical examination of adults revealed the presence of developing embryos in reproductive tract, thus confirming their egg retaining reproductive mode.…”

“…Larger egg batches were recorded in V. gulo and B. fallax indicating a correlation with adult size which is larger in these species (Table 3). Among medium sized clausiliids (V. r. moravica, V. turgida, V. elata and B. stabilis) the size of egg batch/litter varied slightly: oviparous P. stabilis and V. r. moravica laid usually 5-8 and 4-6 eggs, respectively; egg-retaining V. elata produced 2-7 eggs at a time, while V. turgida delivered 2-5 neonates (Sulikowska-Drozd 2009;Sulikowska-Drozd & Maltz 2012b). Mean values of batch/litter size indicated that brooding species produced usually fewer offspring per reproductive event than oviparous clausiliids (Table 3).…”

“…To sum up, variation in reproductive modes was found in Vestia and Balea (Pseudalinda) (Piechocki 1982;Sulikowska-Drozd 2008, 2009, 2011Maltz & Sulikowska-Drozd 2010, 2011Sulikowska-Drozd & Maltz 2012a, b;Sulikowska-Drozd et al 2012). B.…”

“…Life history strategies of clausiliids are only fragmentarily known, yet recent studies point to some common traits such as determined growth, delayed maturation, iteroparity, longevity, ability for selfing and continuum of reproductive modes from egg-laying to live-bearing (Heller & Dolev 1994;Wirth et al 1997;Maltz & Sulikowska-Drozd 2008, 2011Sulikowska-Drozd 2009, 2011Szybiak 2010, etc.). It was noticed that closely related species may exhibit different reproductive strategies (e.g., short egg retention and viviparity, sensu Blackburn 1999), on the other hand, brooding species are classified in different genera which suggests that among clausiliids the evolutionary shift from oviparity, which prevails in land snails (see Heller 2001), towards the embryos retention in reproductive tract occurred more than once.…”

“…moravica (Brabenec, 1952). The data were compared to the results of breeding of Carpathian species of Vestia and Balea (Pseudalinda) in the same laboratory (Sulikowska-Drozd 2008, 2009Maltz & SulikowskaDrozd 2008;Sulikowska-Drozd & Maltz 2012a, b) to evaluate whereas differences in life history traits mirror the present taxonomy of the group (see Falkner et al 2001;Nordsieck 2007) or if similar reproductive strategies evolved independently.…”