Shell variation in Helicodonta obvoluta (O.F. Muller, 1774) (Gastropoda: pulmonata: Helicidae s. lato)

Biometrical analysis of the material of 668 adult shells of Helicidonta obvoluta (Müll.) from Great Britain, Spain, Italy, Switzerland, Germany, Poland, the Czech Republic, Slovakia and Hungary showed a high inter-population variation. Similarity analysis revealed two clusters of populations: one from the centre of the range, another inhabiting its fringes. Snails from the Abruzzi Mts (Central Apennines) had shells similar to those from the central populations, though the area is located on the southern fringe of the distribution range

Molluscan fauna of abandoned crystalline limestone quarry in Rogozka (Lower Silesia, Krowiarki Range, Stronie Slaskie commune)

The paper deals with succession in an abandoned quarry of crystalline limestone, located in the village of Rogóżka (Krowiarki Mts near Konradów, the northern extension of the Śnieżnik Massif). Its bottom is covered by synanthropic communities of unspecified systematic rank and communities of limestone screes as well as clumps of Alnus incana and Betula sp. The following communities, gradually entering the quarry, have been distinguished: Dentario-Fagetum, Aceri-Tilietum and Carici remotae-Fraxinetum. The malacofauna collected in the quarry (45 species) constitutes 50.6% of the terrestrial snails recorded from the OEnieżnik Massif (89 species) and 43.7% of those collected in the Kłodzko Region (103 species). Seven of the 15 clausiliid species recorded from the Kłodzko Region were found in the quarry (47%), which indicates considerable diversity of the microhabitats. The most important species include Eucobresia diaphana, Semilimax semilimax, Macrogastra tumida, Helicigona lapicida, and most of all Clausilia parvula; for the last species the quarry in Rogóżka is the only extant locality in the Kłodzko Region. The fate of the quarry’s malacofauna is uncertain, since formally it has not been exluded from exploitation; measures need be taken to establish a nature reserve there

Helicodonta obvoluta (O.F. Muller, 1774) (Gastropoda: Pulmonata: Helicidae) - up-dated distribution in Poland, threats and conservation status

H. obvoluta is endangered within its whole distribution range. It is a C. European species, distributed from the Pyrennees and the Atlantic coast of France to southern Slovakia and northern Hungary; it occurs also in Great Britain, Schleswig-Holstein, southern part of Moravy, Albania, Bosnia, northern Serbia and in Italy. In Poland it has few localities in the central Sudetes. It is a typical forest-dweller of montane areas, associated with dead timber which is necessary for its reproduction, feeding and hibernation. Its presence in ten sites in Poland has been confirmed. The main threats for the species are clear-felling and removal of dead timber

Reproductive system development and annual cycle of gonad activity in Helicodonta obvoluta (O.F.Muller, 1774) (Gastropoda: Pulmonata: Helicidae s. Lat.)

The reproductive system structure in H. obvoluta follows the helicid pattern except for the dart sac which is absent. In juvenile snails the gonad is the first to develop; the later development of male and female reproductive organs is synchronous. At the stage of lip formation the reproductive system is fully developed. At an initial stage of the gonad development (3 and 4 whorls) mitotically dividing cells prevail, and the first pools of oocytes and spermatocytes in meiotic prophase appear. At the stage of 5 whorls the number of mitoses decreases, while the number of cells in meiotic prophase increases considerably, resulting in an increase in the gonad volume. The first growing oocytes appear, while spermatids and mature spermatozoa are absent. The gonad in lip-building snails contains all the cells characteristic of mature hermaphroditic gland. In mature gonad oocytes and spermatozoa are present throughout the year. The number and size of oocytes vary seasonally. Large vitellogenic oocytes are present from April till the beginning of July and from the end of August till October. The pool of growing oocytes appears in August and in November-December. The intensity of divisions leading to formation of the respective gametes changes in a similar way. The development of female lineage cells seems to determine the timing of reproduction, since spermatozoa are present throughout the year

Life cycle and population dynamics of Helicodonta obvoluta (O.F.Muller, 1774) (Gastropoda: Pulmonata: Helicidae)

Lifecycleof Helicodonta obvoluta (O. F. Müll.) was studied in the field and in laboratory. Mating lasts 2–3 hrs and includes: meeting of the partners, recognition, courtship dance, copulation, resting phase and parting. No spermatophores were observed upon dissection of a total of 90 adult individuals which seems to indicatethat H. obvoluta does not produce them. The egg-laying snail embeds anterior part of its body 4–6 mm deep in rotting timber. The egg-laying lasts from about a dozen hours to two days. Freshly laid eggs are white, calcified, slightly translucent and get opaque in a few days. They are slightly oval, of 2.10–2.85 mm major and 2.00–2.60 mm minor diameter. In laboratory, eggs are laid in spring (March-June) and autumn (August-November), in the field, the egg-laying periods are somewhat shorter (April-beginning of June, end of August-beginning of October). Most laboratory snails laid eggs only once in their lifetime, the maximum number of egglaying periods was four. The percentage of hatching eggs in laboratory is ca. 59%. The number of eggs per clutch ranges from 9 to 27. The incubation period ranges from 14 to 31 days, and is shorter for spring (14–18 days) compared to autumn (19–23 days) clutches. Hatching is asynchronous, lasting from 1 to 4 days. With approaching hatching, thewhitecolour of thee gg disappears, so that theyoung snail is surrounded only by a translucent membrane, which gets broken as a result of its movements. Newly-hatched snails have shells of 1 whorl, devoid of periostracal hairs. No egg cannibalism was observed. Out of 174 young hatched in laboratory, 159 reached maturity. During numerous dissections of adult individuals no eggs were found in the reproductive tracts; if there is an egg-retention, it must be very short-lasting. Placing eggs in rotting timber and covering them with mucus protects them from drying-out, ensures a more favourable temperature and limits accessibility to predators. The number, relative and absolute size of eggs, number of clutches per year and per lifetime, and the life span seem to be correlated with size rather than with phylogenetic position of the species. No uniparental reproduction was observed. In laboratory the time elapsing between hatching and maturity (lip completely formed) ranged from 140 to 624 days; it varied between individuals hatched in particular years and seasons, e.g. young of the spring 1997 grew much faster (mean 354 days) than those of the spring 1999 (mean 442 days). The time required to reach full size was not correlated with the ultimate number of whorls. The growth shows three distinct phases: a quick initial phase of 3–4 months, a slow phase, and a short quick phase preceding lip formation. The monthly increment depends on the growth phase: 1.15 whorl in phases 1 and 3, 0.30 whorl in phase2. Thegrowth ratein thefie ld is similar to that observed in laboratory, though with a wider scatter within growth phases and some differences between years and seasons. Depending on weather conditions, theyounge st ageclass (1) appears from April till Juneor from May till July, and from thee nd of August till the beginning of October. Thus each season two new generations are produced: spring and autumn. The spring generation, depending on the month of hatching, may complete its growth in the same season and winter as adults, or reach stage 4 or 5 and complete their growth next spring. The autumn generation always winters as immature snails which complete their growth in late spring next year. Adult snails (c. 1 year old) dominatein all themonthly samples, whileolde r individuals arefe w. In laboratory, thelifespan ranged from 516 to 1,187 days; thus thelifespan of someindividuals exceeds 3 years. Thee stimateof lifespan in the field, based on marking-release-recapture, is less exact, but on the whole the oldest snails in the field lived slightly over 3 years, whilelifespan of somewas only 2 years. In laboratory and in thefie ld, thesnails reproducein spring and autumn. In laboratory, they areactive(fe eding, crawling) throughout theye ar, but in winter resting periods of a few days at a time are observed, with the aperture covered by a thin epiphragm. In the field, the snails enter winter torpor at the end of October/beginning of November, having penetrated rotting logs from below, and stay in rotting wood with their apertures covered with thick, calcified epiphragms. Depending on weather, they get active at the beginning or end of April. Under conditions of constant temperature and humidity (indoors) adult snails show two activity peaks: late evening and early morning, with a resting period during theday . Immatureindividuals aremoreactive , with a constant high activity sinceafte rnoon till mid-morning, and most remain activeduring theday . In conditions of variablete mperatureand humidity (out- oors), the activity of all age classes depends on humidity and temperature, the immature snails, like in constant conditions, being generally more active. The mobility of H. obvoluta is rather high, individual snails cover the distance of 4–5 or even 7 metres during a month

Gastropods of the glen Kotlina Walbrzyska and highlands Pogorze Walbrzyskie

The gastropod fauna of the glen Kotlina Wa³brzyska and highlands Pogórze Wa³brzyskie was studied in 1993–1995. A total of 89 species were collected from 63 localities. The following species are rare in the Sudetes: Segmentina nitida (O. F. Müll.), Succinea elegans Risso, Vertigo antivertigo (Drap.), Arion silvaticus Lohmander, Vitrea contracta (Wstld), Daudebardia rufa (Drap.), Tandonia rustica (Millet), Clausilia parvula Fér., Balea perversa (L.), Helicodonta obvoluta (O. F. Müll.) and Causa holosericeum (Studer). The fauna of the glen KotlinaWa³brzyska differs from that of the highlands PogórzeWa³brzyskie, the former being much poorer as a result of the strong anthropopressure. Zoogeographically, widely distributed species (Holarctic, Palaearctic, Eurosiberian, European) constitute most of the studied fauna (51.6%)

Reproduction of Balea (Pseudalinda) fallax (Rossmassler, 1836) (Gastropoda: Pulmonata: Clausiliidae) kept under laboratory conditions

Balea fallax (Rossm.) collected from the Roztocze Upland (SE. Poland) was kept in the laboratory for four years. Observations were conducted between March and October when the snails were kept at room temperature (18-25°C); in winter they were stored at 3°C. The egg-laying period started in late March and lasted till October, with maxima in spring and early autumn. The snails laid oval, gelatinous eggs with separatecalcium carbonate crystals in the external envelope (average egg size 1.96 × 1.73 mm). The eggs were deposited in batches (up to 14 eggs at a time) or singly. The number of batches per snail per year ranged between 1and 4. Snails isolated before maturation laid defective eggs which failed to develop, which suggest that the speciesis incapable of uniparental reproduction or at least the ability is very limited. The reproduction rate decreased during consecutive years, probably as a result of the aging or the shortage of allosperm in isolated individuals.Compared to batches of typically oviparous clausiliids, eggs of B. fallax hatched slightly earlier (interval between oviposition and hatching lasted 8-10 days at room temperature). It is likely that the adults retained developing eggs in the uterus for a short time. The juveniles needed at least 6 months to attain the ultimates hell size