Anna Sulikowska-Drozd

Life Cycles of Clausiliids of Poland — Knowns and Unknowns

Abstract. Among the 24 native clausiliids, 15 were subject to laboratory observations. Eleven of them were found to be oviparous, three — egg retainers and one — ovoviviparous. Batches, containing most often one to about a dozen of partly calcified, ellipsoidal or spherical eggs, appeared usually in the spring and autumn (in non-hibernating individuals throughout the year). Probably the main factors determining the onset of reproduction are humidity and temperature while the photoperiod has no significant effect. The incubation period is ca. two weeks (room temperature), the hatching is synchronous or asynchronous. Cases of intra-batch and inter-batch cannibalism were observed. The minimum time from hatching/birth till adult size is ca. 3–9 months and after further 5–8 months the snails start producing eggs/babies. Clausiliids are iteroparous. Anatomical studies on the development of the reproductive system show that just before lip completion the reproductive system is still incompletely developed. Penis, epiphallus and spermatheca develop within the first month after growth completion (which would indicate attainment of ability to copulate), and the reproductive system becomes wholly mature only after a few months. The clausiliid development strategy is probably the following: the quickest possible growth and attainment of adult size, then development of the reproductive system and attainment of sexual maturity.

Woodland mollusc communities along environmental gradients in the East Carpathians

Mollusc communities were sampled quantitatively at eleven sites representing different environmental conditions in the Bieszczady National Park (East Carpathians Mts, Poland). Overall 61 species were recorded. Alder forest in the valleys (AF; Alnetum incanae carpathicum, Caltho-Alnetum, secondary alder forest) hosted the richest fauna, with up to 41 species occurring sympatrically on 100 m2 of forest floor and average density ca. 750 specimens m−2. Three important ecological controllers of species composition and community structure were found. The main predictor of mollusc assemblage composition was calcium content; the first DCA axis of molluscs most significantly and highly correlated with calcium content in the leaf litter and organic matter in the upper layer. The second axis significantly correlated with altitude and negatively with annual temperature, and thus can be explained as an elevational gradient. We observed slope aspect to constitute the third significant gradient. On the basis of forward selection in CCA analysis organic matter in the upper layer of soil was the best predictor of species composition, which explained 26% of total variance. It comes to prove that in mountain forest on non-calcareous bedrock molluscs obtain calcium mainly from leaf litter.

Life History of Alinda biplicata (Montagu, 1803) (Gastropoda: Pulmonata: Clausiliidae) Based on Five-Year Laboratory Observations

Abstract. The maturation, growth and reproduction of Alinda biplicata, in the laboratory were studied over a five-year period. The snails were kept in pairs and groups of a few individuals. The initial material came from two populations from SW. Poland. The snails reproduced during the whole year, more intensively in the spring and autumn. We confirmed the ovoviviparity of A. biplicata: the whole embrynic development takes place in eggs retained in the parents uterus. The snails gave birth to juveniles (no egg-laying was observed), and the uteri of dissected individuals contained from 3 to 15 eggs. The number of juveniles per litter was 1 to 8. The snails produced 3 to 20 juveniles in 2–9 batches per year. The neonate shells had 2.1–2.9 whorls and height of 1–1.6 mm. Growth to adulthood lasted 20 to 56 weeks and the time increased with increasing density of snails. The snails became sexually mature 5–6 months after completeion of shell growth and formation of the closing apparatus. The juvenile mortality ranged from 16.7% to 60.6% and increased with density. The life span in the laboratory was 220 to 295 weeks (4 to 6 years). These results are compared with those for other species; A. biplicata resembles other large ovoviviparous Clausiliidae species.

Circannual Gonad Activity in Two Species of the Genus Vestia P. Hesse (Gastropoda: Pulmonata: Clausiliidae)

Abstract. Vestia gulo and V. turgida are iteroparous simultaneous hermaphrodites. In the wild they are active from April till October; they reproduce in the spring and summer (egg retention from May to August), and hibernate from November till March. Their gonads show the greatest activity in the spring and summer (maturation of oocytes, intensive vitellogenesis: March–May, numerous mature oocytes: May–July; production and maturation of spermatozoa: March–May; numerous packets of mature spermatozoa: May–October), which coincides with the reproductive season. The onset of reproduction is determined by the size of the pool of vitellogenic and mature oocytes; oocyte production starts in the summer of the previous vegetation season and lasts till next spring. Mature spermatozoa are present in the gonad from spring till autumn which indicates an ability to mate during the whole active period. During hibernation the gonads contain no spermatids, mature spermatozoa or advanced vitellogenic oocytes.

Selfing and brooding in Alinda biplicata (Gastropoda: Pulmonata: Clausiliidae) – life history traits of a good coloniser

Alinda biplicata is capable of uniparental reproduction (selfing). The snails need 18 to 24 weeks to reach their ultimate size, and the first reproduction takes place 26 to 39 weeks after shell growth completion. Besides giving birth to juveniles, which is typical of A. biplicata (39% of litters), the uniparentally reproducing individuals laid egg batches (38%) as well as mixed batches (eggs and juveniles; 23%). Within a few days the eggs decomposed, and in mixed batches they were often consumed by the accompanying neonates. In the next season, 70% of the remaining 20 snails reproduced (all of which had reproduced in the previous season). In the first season the neonate:egg proportion was 54:46, in the second 74:26. The egg-laying should be regarded as an anomaly – getting rid of eggs which were not fertilised or in which embryos died at early cleavage stages. The combination of selfing and brooding may explain the wide distribution and wide range of habitats occupied by A. biplicata.

Influence of Habitat Structure and Conditions in Floodplain Forests on Mollusc Assemblages

ABSTRACT: Alder floodplain forests are a rare and threatened forest type in Europe. These forests can be very rich in mollusc species. The intermediate disturbance hypothesis predicts that species richness should peak at intermediate inundation frequency, that is, at intermediate elevation above the river level. We additionally hypothesized that constantly high soil moisture can distort the usually positive correlation between the amounts of downed deadwood and snail richness, and that tree stems might be more favourable than deadwood because their vertical structure provides a better refuge during inundation events. To this end, we sampled molluscs from a core area of 20 × 20 m from eight alluvial forests with black alder in the surroundings of Łódź, Central Poland. In each core area, substrate was collected from eight random plots (0.25 m2 each). We also recorded soil pH, vascular plant species and mosses diversity, along with other structural variables. Plant indicator values were calculated according to Ellenberg. Soil quality (amongst others: soil pH, reactivity value, nutrient and moisture availability) decreased with increasing elevation above the river level. In the plot samples, we found a total of 18,497 individuals from 52 species. Mollusc species richness dropped stronger than densities with an increasing elevation above the river level. Main influences on mollusc richness and abundance originated from positive correlations with soil pH and moisture. An additional hand sampling campaign on tree stems and deadwood items in the core area revealed that coarse woody debris items on average carried twice as many individuals as did tree stems. Deadwood and tree stems supported similar numbers of snail species per item, but beta-diversity was higher on deadwood. Consequently, Jackknife 2 predicted that deadwood is utilized by about 46 species, whereas tree stems only support about 39 species. Our results indicate (1) that mollusc richness peaks at low elevations above normal water level in this type of forest, (2) that intact hydrological regimes are associated with high soil quality and mollusc biodiversity, and (3) suggest that coarse woody debris adds resources, refuges and a dispersal agent for the alder forest floor fauna.

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

Based on five-year observation of 36 snails collected in the Čeladná valley (Moravia, Czech Republic) and their progeny reared in laboratory, it was found that Vestia ranojevici moravica (Brabenec, 1952) is oviparous. The oviparity in V. ranojevici is in line with the previous assumption of its reproductive strategy based on anatomical studies alone. It supports the separate position of the species in the genus Vestiaa (subgenus Brabenecia). V. ranojevici was kept at room temperature (18–25°C) between March and October; in winter snails were stored at 3°C. The egg-laying period started in late March, ca. 1 month after raising the temperature, and lasted till September, with one maximum in spring. In the laboratory the snails laid eggs in batches (usually 4–6 eggs, max 11) or singly. The number of batches per pair per season was 1–8; the corresponding number of eggs — 3–40. The eggs were gelatinous, with separate calcium carbonate crystals in the external envelope. The average egg size was 1.80 × 1.51 mm, but actual size and shape were highly variable: larger and more elongated eggs were produced mainly by laboratory reared animals. Freshly deposited eggs did not contain shelled embryos nor the reproductive tract of dissected individuals contained eggs. At room temperature the eggs hatched after ca. 14–16 days, then the shell growth lasted 20–29 weeks; the snails laid eggs 30 weeks after completion of shell growth indicating one-year life cycle under laboratory conditions. Adult individuals collected in the field reproduced during 4–5 consecutive years. Comparison of V. ranojevici reproduction to the results of breeding of other Carpathian clausiliids in the same laboratory shows that similar reproductive strategies may have evolved independently in different lineages of the group: both the oviparous and egg retaining species belong to the genera Vestia and Balea.

The reproductive strategies of clausiliid land snails from Northern Vietnam (Gastropoda: Stylommatophora)

Under laboratory conditions we scrutinized the reproduction and development of two clausiliid land snail species from northern Vietnam: Phaedusa paviei (Morlet, 1892) and Oospira vanbuensis (Bavay and Dautzenberg, 1899). These species, very similar in shell size and shape, feature different reproductive modes. The former is viviparous, giving birth to one or two neonates on a single occasion, with the number of developing embryos retained in the reproductive tract ranging from 1 to 11. The embryonic shells are 1.8–4.7 mm in height. The latter species is oviparous and produces eggs in clutches (four to six per clutch). Hatching occurs 18–21 days after egg-laying. Both species exhibit a similar growth pattern: the ultimate shell size is attained after 6.5–8.5 months and reproduction starts 5–7 months later. The distribution of viviparous reproduction among the Phaedusinae and its taxonomic importance are discussed.

On the histology, ultrastructure and function of the spermoviduct and free oviduct in egg-retaining door snails (Pulmonata: Clausiliidae)

We studied the anatomical, histological and ultrastructural changes of the spermoviduct and free oviduct in three closely related clausiliid snails (Baleinae) in relation to their different reproductive strategies: oviparity in Laciniaria plicata, egg retention in Vestia gulo and viviparity in Alinda biplicata. Since egg retention occurs in the lower parts of the spermoviduct and free oviduct, these organs were studied in detail to determine their structural diversity. The results of anatomical studies showed that the length proportions of the free oviduct and spermoviduct are different between oviparous snails and egg-retaining/viviparous snails. The allospermiduct of the free oviduct displays significant morphological and ultrastructural dissimilarities in snails that differ in reproductive strategies. These differences mainly concern the type of subepithelial secretory cells and their secretory products. In egg-retaining snails, the subepithelial cells are serous and their secretory products create a suitable environment (oncotic pressure) for retained eggs, whereas in oviparous snails the serous cells are absent.

Reproductive strategy in rock-dwelling snail Cochlodina orthostoma (Gastropoda: Pulmonata: Clausiliidae)

Abstract To analyse the reproductive activity of the central-European clausiliid Cochlodina orthostoma we sampled monthly 30 adults from three sites comprising old stone walls of two abandoned castles and isolated limestone rocks. Out of the 395 dissected snails, 25.1% retained eggs. The number of eggs in the uterus ranged from 2 to 12. The highest percentages of gravid individuals were recorded in June–July, but reproductive intensity varied among populations. Almost half of the recorded eggs contained a shelled embryo. The largest embryonic shell featured approximately 1.3 whorls. The reproductive mode of the species was also studied in laboratory culture. Egg-laying was observed between May and November, the number of eggs laid on a single occasion ranged from 1 to 8, and the number of eggs produced per individual varied between 6 and 21 during the observation period. We found that eggs were laid in various developmental stages, accordingly, there were differences in egg sizes and the external incubation period varied between 6 and 15 days. Based on our results C. orthostoma should be regarded as brooding species with a short and flexible period of egg retention.