Ma lgorzata Proćków 1, Magda Drvotová 2,LucieJuřičková 2 &Elżbieta Kuźnik-Kowalska 3

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1 Biologia 68/1: , 2013 Section Zoology DOI: /s Field and laboratory studies on the life-cycle, growth and feeding preference in the hairy snail Trochulus hispidus (L., 1758) (Gastropoda: Pulmonata: Hygromiidae) Ma lgorzata Proćków 1, Magda Drvotová 2,LucieJuřičková 2 &Elżbieta Kuźnik-Kowalska 3 1 Museum of Natural History, Wroc law University, Sienkiewicza 21, Wroc law, Poland; mprockow@biol.uni.wroc.pl 2 Department of Zoology, Charles University, Viničná 7, CZ Praha 2, Czech Republic 3 Department of Invertebrate Systematics and Ecology, Institute of Biology, Wroc law University of Environmental and Life Sciences, Kożuchowska 5b, Wroc law, Poland Abstract: For the first time the life cycle of the common land snail Trochulus hispidus was completely described in Central Europe (Poland). This is a semelparous species predominantly with an annual life cycle and the reproductive period lasting from April till October. The first young snails hatch in spring, grow rapidly in summer and reach ca. 4 whorls until winter. In spring of the next year they mature and reproduce. After that they die. There is hardly any growth from late autumn till early spring. The average proportional growth rate is ca. 0.3 whorl/month in the wild. The fastest growth is present in the youngest snails and then gradually decreases over the course of their age. Laboratory and field observations allowed for establishing the following life cycle parameters: eggs calcified, almost spherical, ca. 1.5 mm, laid in spring and summer in batches of between 1 and 47. Time to hatching is 6 24 days, hatching is asynchronous; newly-hatched snails have approximately 1.5 whorls. Analysis of food preferences revealed, that T. hispidus tends to restrict its diet during the life. Generally the youngest snails equally consumed leaves of all four tree species offered (Fraxinus excelsior, Acer pseudoplatanus, Tilia cordata and A. platanoides) whereas adults preferred F. excelsior over A. pseudoplatanus and A. platanoides. Key words: life cycle; growth rate; population dynamics; feeding preference; Trochulus hispidus; Hygromiidae Introduction The land snail Trochulus hispidus (L., 1758) has a wide distribution range in Europe; in the north, along the Atlantic coast of Scandinavia it reaches the Arctic circle (Shileyko 1978; Kerney et al. 1983; Riedel 1988), in the east southern Ukraine, the Urals and St. Petersburg (Forcart 1965) and in the west the British Isles (Kerney et al. 1983). Its southern distribution border is not precisely known: it has been recorded in the central and north-eastern parts of Spain (Altonaga et al. 1994; Bragado et al. 2010) and northern Italy (Manganelli et al. 1995). There are a few records from Bulgaria and northern Croatia (Damjanov & Likharev 1975; Irikov & Mollov 2006; Irikov & Erőss 2008; Uherkovich et al. 2008). In Poland it is common in the whole country except the Carpathians; in the Sudetes it has been recorded up to 800 m a.s.l. (Wiktor & Wiktor 1968). It has long been known as an alien species in eastern and central Canada and the north-eastern part of the United States (Robinson 1999; Hotopp et al. 2010). It is the most widespread species in the genus Trochulus, most other species being restricted, especially to mountain ranges (Kerney et al. 1983). There are disputes about its relationship to, and the status of, a very similar species, T. sericeus (Draparnaud, 1801), often referred to as T. plebeius (Draparnaud, 1805) (Naggs 1985; Falkner et al. 2002). Significant shell variation within and between populations of T. hispidus has been reported and synonymisation of both names proposed (Proćków 1997, 2009). The main aim of this paper was to describe the life history and growth rate of T. hispidus based on laboratory observations and field studies. Although it is very common, very little is known about its ecology and life cycle except for some fragmentary data scattered in the literature. Jeffreys (1862), Taylor (1916) and Frömming (1954) provided some information on number of eggs and time to hatching and the latter author analysed the diet of the species. Cameron (1982) showed that the life-cycle was probably annual, most adults dying in autumn. It is found in a wide range of habitats, and may be found as high as 2000 m a.s.l. (Kerney et al. 1983). In addition, we asked whether juveniles and adults differ in their diet. Frömming (1954) gave the only c 2013 Institute of Zoology, Slovak Academy of Sciences

2 132 M. Proćków et al. Table 1. Characteristics of sampling localities: CZ Czech Republic, Pl Poland. Site Coordinates Altitude a.s.l. Original biotope Age No of individuals Velká Javořina, CZ Velký Šenov, CZ Skryje, CZ Wroc law, Pl Březí, CZ Březí, CZ Březí, CZ Březí, CZ Rymaně, CZ Rymaně, CZ Cvikov-Drnovec, CZ N E N E N E N E N E N E N E N E N E N E N E 930 m primeval ash forest in mountains adults m village human impacted habitat adults m village human impacted habitat adults m Botanical Garden in the city human impacted habitat adults m garden in the village human impacted adults 10 habitat 330 m 18 weeks old m 17 weeks old m 15 weeks old m brook floodplain shrubs 22 weeks old m 13 weeks old m village human impacted habitat 15 weeks old 7 published account of diet in T. hispidus. Analysis of the excrements of just captured adult and juvenile individuals showed that the natural diet of the species is highly dependent on the food sources available in a particular site. Most European land gastropods are thought to be nonspecific herbivores or detritivores; detailed studies including faecal analysis have shown that even some of these species have developed distinct food preferences (Mason 1970; Williamson & Cameron 1976; Hatziioannou et al. 1994; Iglesias & Castillejo 1999). These preferences are not necessarily reflected in the places where snails are found by field observation; particular plant species also offer resting places, concealment and other favourable conditions (Iglesias & Castillejo 1999). Furthermore, some studies have shown that juveniles of some species show significantly less discrimination than adults (Wolda et al. 1971; Williamson & Cameron 1976). Material and methods Laboratory studies Life cycle, growth and fecundity The life history data were collected across various European populations of Trochulus hispidus. These comprised growth rate (Ehrmann s 1933 method of counting whorls), maturation, longevity, mating behaviour, fecundity, egg-laying, egg morphometrics and time to hatching. In order to collect these data we proceeded as follows: The material for the laboratory culture (79 individuals: 62 adults and 17 juveniles) was collected on 10 th April 2009 in Lubawka (Central Sudetes, SW Poland) and on 17 th May 2009 in Cheddar Gorge and Saltford (Somerset, W England). The laboratory observations lasted from 10 th April 2009 till 27 th November The individuals were kept in pairs and groups of 4 9. They were distributed as follows: Lubawka (9 pairs, 3 groups of 4 snails, 2 groups of 6 snails, 1 group of 7 snails, 1 group of 9 snails); Cheddar Gorge (4 pairs and 1 group of 9 snails); Saltford (2 pairs). The snails were kept in plastic boxes of a size depending on the number of individuals per box (6 7 7 cm, cm and cm). Initially, damp tissue paper with litter brought from the habitat were used as substratum but after 7 th June 2009 moss had been added as a shelter and a substratum for egg-laying. The data on clutch sizes include only records in the presence of moss. The snails were fed with lettuce, carrot, cucumber, apple and occasionally also parsley. Chicken egg shells or pieces of chalk were provided as a supplementary source of calcium. The temperature in the room varied from 17 Cinwinterto25 C in summer. The relative humidity in the dishes was constant, ca. 80%. The boxes were checked and cleaned at least once a week and during periods of intense observations (e.g., reproductive period) every day or two. Water and food were supplied as needed. Eggs and newly hatched snails were removed to separate boxes to prevent double counting on subsequent occasions. Food preferences Food preferences were tested using 6 and 5 populations of juveniles and adult individuals, respectively (Table 1). Each population was kept in one Petri dish. The populations of juveniles were kept in their original groups, as they hatched in the laboratory culture and were fed with ash leaves until the experiment began. The experiment was run at the same time for all snails. Moist tissue paper was placed at the bottom of each dish as an underlay. Each dish was supplied with cuttlebone as a source of calcium. In each trial four equal (3 3 cm) sized squares of decaying dead leaves of Fraxinus excelsior, Acer platanoides, Acer pseudoplatanus and Tilia cordata were placed onto the dishes on the first day of the experiment. All tree species involved in the experiment were chosen as supposedly preferable food for most land snail species, in contrast to leaves of Quercus species or Fagus sylvatica (Wäreborn 1969, 1970; Waldén 1981). The percentage of leaf area consumed was

3 Feeding, growing and life-cycle in Trochulus hispidus 133 Table 2. Age classes of T. hispidus. Age class No of whorls I II III IV V measured at 24-hour intervals on a daily basis. The experiment was finished after seven days. The data on the consumed proportion of leaves were then standardised by total percentage consumed (sum of the percentage of consumed leaves across all tree species). The reason is that various populations consumed various total amount of leaves, which would result to artificial difference between more and less hungry populations. Afterwards we transformed the proportion data using the square-root arcsin transformation. We used the population that originated from Březí to test the difference between adults and juveniles, and all the populations listed in Table 1 to test the differences between the sites. The differences between sites were tested in adults and juveniles separately. Each of four tree species were tested (12 tests altogether). We employed General Linear Model (GLM) to test effect of adults vs. juveniles being controlled for day, then we tested (GLM) for the effect of different sites being controlled for day. We used Bonferroni correction so that our level of significance was (= 0.01/12). A series of 12 t-tests (all six combinations of four tree species in case of adults and juveniles were tested separately) was employed to test food preferences. The differences between consumption of leaves deposited on the same Petri dish (see Table 1 for list of populations) were tested. Proportions of leaves consumed by five adult and six juvenile populations were arcsin square-root transformed before the test. Bonferroni correction suggests level of significance (= 0.01/12). Field studies Field observations on T. hispidus were carried out in Lubawka (Central Sudetes, N, E, 420 m a.s.l.) in a nettle (Urtica dioica) patch with a single tree of Acer platanoides and shrubs of Symphoricarpos albus growing on one side. The site was visited each month from April till October in 2009 and from May till October The aim of the field observations was to describe the life span, growth rate and seasonal changes in the population age structure. In order to estimate the growth rate and lifespan, individuals collected during a two-hour search, on each occasion from the same area of 9 m 2,weremarked and released in the place where they had been found. Marking involved painting a narrow stripe using nail-varnish each month a different colour on the upper side of the whorl s body, just next to the aperture, so that the shell increment could be read on recapture. Population size (N) and corresponding standard error (SE) were estimated using Bailey s modification of Petersen s mark recapture index (Seber 1982), separately for all snails and the snails with more than 3 whorls. The following formula was used: N = M(C +1)/(R +1), where M is the number of snails marked and released on each sampling occasion, C is the number of the snails from the next sample and R is the number of recaptured snails. In order to estimate the age structure there were five age classes distinguished based on the number of whorls (Table 2). The shell growth rate and standard statistics (mean, variance, standard deviation and median) of whorl increment in the consecutive classes were calculated on the basis of all marked-recaptured snails. Results Laboratory observations Egg-laying and hatching One of the captive snails was directly observed producing 22 eggs over the course of 4.5 hours (9:03 13:30 hours) on 5 th June Before laying the first egg it seemed as if the snail was looking for a suitable place by touching substratum and encountering objects, such as pieces of chalk or food, with its tentacles. The eggs were laid on the litter, lettuce leaves or directly on the tissue paper in 8 25 minutes intervals when the snail was occasionally motionless. Their number per batch ranged from 1 to 8. Later, when moss was added to the boxes, the snails laid their eggs in it preferentially. The mean clutch size was eggs per clutch (range 1 47, SD = 16.6, n = 79), excluding three batches that contained 65, 66 and 90 eggs, respectively, which most likely include more than one clutch (Fig. 1). Newly laid eggs were partly calcified, white and almost spherical. Initially they were shiny as a result of the covering mucus layer; after 4 7 days they became translucent, so that the young snail could be seen, surrounded only by a translucent membrane. Mean egg diameter, recorded across six clutches, was 1.5 mm (SD = 0.11 mm, n = 86), with size ranging mm. Time to hatching among 27 selected clutches originating from 9 different boxes lasted from 6 to 24 days (mean 13.89, SD = 5.07, n = 405). Hatching was asynchronous; juveniles of the same batch hatched over 1 5 days. Newly hatched juveniles had translucent shells and bodies; their shells had whorls (mean 1.5, SD = 0.17, n = 55). The protoconchs of the juveniles were smooth, whereas the following whorls were covered by periostracal hairs. Hatching success among the offspring was 82% (range 0 100%, SD = 24%) which was calculated based on the same 27 clutches. Reproduction was most frequent at the end of May and at the beginning of June (Fig. 2). Then it decreased sharply. The last four clutches were found on: 21.VIII.2009 (7 eggs and 2 clutches of 4 eggs) and 16.IX.2009 (4 eggs). Egg production per snail left alive during the observations was sevenfold higher in May and June (21 eggs/snail) than in July (3 eggs/snail). Growth and maturation Juvenile snails suffered very high mortality in the laboratory cultures. Although 82% of eggs hatched successfully, none of the 451 juveniles survived to reach maturity. 120 days after hatching, only 41 (9.1%) of juveniles were still alive and after 240 days there were only 21 (4.7%) left (Fig. 3). The largest snail had 4.8 whorls and

4 134 M. Proćków et al. Fig. 1. Number of eggs per batch recorded for 79 clutches in T. hispidus. Fig. 2. Reproduction output of T. hispidus in laboratory. Fig. 3. Temporal trend in survivorship of 451 T. hispidus hatchlings. reached this size at death (321 days). It had grown at the rate of 0.45 whorl/month. The longest living snail (377 days) reached only 4.0 whorls (0.32 whorl/month). ThecompletelifespanofT. hispidus could not be identified due to the fact that no specimen matured in lab conditions. The snails brought from the field started dying after 50 days. The longest living specimen died after 249 days (mean 118.3, SD = 46.4, n = 79). Food preferences We found significant effect of age stage on consumed leaves for all four tree species (P < , df = 1, n = 28, snails from one site of origin, 7 days for one population of adults and 7 days for 3 populations of juveniles, in all cases of the four tree species). Data were controlled for the day of the experiment. Fig. 4 shows that adults feeding behaviour was more uniform

5 Feeding, growing and life-cycle in Trochulus hispidus 135 Fig. 4. Food preferences of adults (A) and juveniles (B) of T. hispidus. Squares, diamonds, triangles and circles show medians for F. excelsior, A. platanoides, A. pseudoplatanus and T. cordata, respectively. Boxes 50% confidence intervals, whiskers 95% confidence intervals. during the whole experiment (Fig. 4A), whilst preferences of juveniles (Fig. 4B) varied as the experiment proceeded. In adults, A. platanoides, A. pseudoplatanus and T. cordata were consumed differently at different sites (P < , df = 4, n = 35, 7 days for five populations in all cases) and F. excelsior was likely to be equally consumed at all the sites (no significance was detected P > 0.3). Unlikely in adults, in juveniles only F. excelsior was consumed differently between the sites (P < , n = 42, 7 days for six populations, three of them from one site of origin). Adults generally preferred (P < , df =8, n = 10) leaves of F. excelsior (Fig. 4A) over leaves of A. platanoides and A. pseudoplatanus. On the contrary, juveniles did not show significant preferences (Fig. 4B). Field observations In the field T. hispidus was found directly on plants and litter although in early spring, late autumn and during sunny days also inside curled dry leaves. The number of individuals marked (M) on each sampling occasion ranged from 51 to 276, and in all cases, except for April 2009 and May 2010 (when snails were still inactive due to the prolonged winter), it exceeded 130 (Table 3). There were many fluctuations in the estimate of population size (N) during the study period, though considerable rises in density (D) appeared in May and September 2009, and June Densities were lower in May and September 2010 (Table 3). Additionally, it has to be taken into consideration that emigrations and immigrations to the patch, as well as mortality,

6 136 M. Proćków et al. Table 3. Population estimates for all snails/snails with more than 3 whorls of T. hispidus in the study area of 9 m 2. Sampling occasion Year Month M R N SE D 2009 IV 51/ / / /172 V 181/174 5/5 3324/ / /355 VI 201/197 10/ / / /110 VII 185/181 36/ / / /186 VIII 276/268 30/ / / /125 IX 163/158 38/ / / /300 X 239/117 13/ / / / V 108/78 17/17 846/ /131 94/68 VI 140/117 17/ / / /276 VIII 190/189 8/8 1550/ / /171 IX 203/201 24/24 755/747 83/82 84/83 X 222/222 59/59 Explanations: M number of snails marked on each sampling occasion, R recaptured snails, N population size, SE standard error, D density (individuals/m 2 ). Table 4. Whorl increment per month in T. hispidus at the study site. Comparison of age classes expressed by number of whorls. No of whorls mean min-max SD median n certainly violate the assumptions of these estimates. Another such a problem is that by becoming larger, snails get easier to find. Although, when the smallest size classes were excluded from the calculation, population density, compared to that estimated for all snails, declined almost twice only in October 2009, in other months it varied slightly (Table 3). Population age structure and growth rate As can be seen in Fig. 5, T. hispidus overwinter in all size categories. By comparing the population structures in October 2009 and May 2010 it has been observed that young specimens grow also from late autumn till early spring. In May 2009, most snails collected were adult while only few adults were recorded in the same time the following year. The majority of the juveniles were recorded in October Throughout spring until autumn 2010 the population grew older but the percentage of adult specimens is still low. Mark-recapture technique revealed four adults that survived over two breeding seasons. Of the 2,159 marked juveniles and adults 257 (11.9%) snails were recaptured: 236 were recaptured once (10.9%), 20 (0.9%) twice and 1 (0.05%) three times. Among the recaptured adults (n = 122) 66 were dead on recapture, which represents ca. 54%. During the lifetime of the snails, proportional growth rate declined with age. Snails with whorls have the fastest growth, followed by those with whorls and then by the snails with more than 5 whorls (Table 4). Given the fact that T. hispidus, when hatching, had approximately 1.5 whorls the average growth of snails was estimated during both growing seasons (Fig. 6). Thus it equalled to 0.23 whorl per month. From late autumn till early spring, the maximum whorl increment was very small and reached only 0.1 whorl during the period of six months (from late October till early May). Discussion Life history of Trochulus hispidus All the available data on the life history of T. hispidus aresummarizedintable5.wherethesamefeatures have been studied, there is a broad measure of agreement among studies; this study adds precision and more features. While conditions in the laboratory were clearly not ideal (see below), the combination of field and laboratory data enable us to provide a general account. Seasonal changes in the age structure of the studied population, combined with the growth rate, make it possible to reconstruct the life cycle of the species. Juveniles hatch from April to October. The earliest hatched snails grow to ca. 4 whorls until winter. The growth rate then is ca. 0.3 whorl/month. Wintering juveniles have shells of whorls. After winter the snails resume their growth at a slower rate, to reach whorls in spring and they nearly all reproduce in the same year. After that they die. Those hatched in autumn hibernate as juveniles and reach their sexual maturity in late spring or summer. It is evident that the vast majority of individuals have only one breeding season during their life time. Additionally, a few adults over-

7 Feeding, growing and life-cycle in Trochulus hispidus 137 Fig. 5. Changes in size class distribution over the activity seasons 2009 and 2010 in the study site in Lubawka. Fig. 6. Average growth rate of T. hispidus during two activity seasons, expressed by whorl increment. wintered to breed once more. This places T. hispidus in a group of semelparous species which have an annual life cycle. This mode of reproductive strategy has also been observed in other species of the Hygromiidae family, i.e., Monacha cantiana (Montagu, 1803), M. cartusiana (O.F. Müller, 1774) (Chatfield 1968) and Candidula unifasciata (Poiret, 1801) (Hänsel et al. 1999), and agrees with the results for T. hispidus from Benthall Edge Wood near Ironbridge, England (Cameron 1982). In areas with dry and wet seasons some life cycle variations have been evidenced in a few semelparous hygromiid species. For example Xeropicta derbentina (Krynicki, 1836) or Xerolenta obvia (Menke, 1828) are able to switch from an annual life cycle to a biennial cycle in response to a population density or climate conditions (Kiss et al. 2005; Lazaridou & Chatziioannou 2005). As in many other land snail species, the reproductive season of T. hispidus is relatively long. In laboratory conditions it is limited to spring and summer, extending to autumn in only few individuals. Although in the field the individuals from the youngest age class were only observed in July, September and October

8 138 M. Proćków et al. Table 5. Life history traits of T. hispidus. Jeffreys (1862) Taylor (1916) Frömming (1954) this study Number of eggs/clutch Egg size about 1 mm mm mm Incubation time days days days 6 24 days Reproductive season April September April September April September April October Hatched juveniles Reproductive lifespan Growth rate 1 whorl, more than half of shell covered with minute red and straight hairs 1whorl,morethan half of shell covered with short and straight red hairs 1.5 whorls with characteristic hairs whorls, shell apex without hairs, many rows of hairs on the body whorl days, few adults overwinter 0.23 whorl/month (average); 0.3 whorl/month (to 5.0 whorls); 0.06 whorl/month ( 5.1 whorls) (Fig. 5), the presence of a second age class ( whorls) recorded in the period from May till October gives a direct indication of a breeding process occurring from spring till autumn. The conflict in the observations might be caused by the fact that newly-hatched snails are very small and difficult to find. Moreover, the general number of the individuals living on the patch was very high in some months and it was impossible to collect all of them. Data about reproductive period of hygromiid species inhabiting Central Europe are very scarce. Perforatella bidentata (Gmelin, 1791) has one reproductive period in summer (Kuźnik- Kowalska & Roksela 2009) and the helicellinids C. unifasciata and Helicella itala (L., 1758) have two reproductive periods in spring and autumn (Hänsel et al. 1999). T. hispidus, similarly to Cernuella virgata (Da Costa, 1778) investigated in Australia (Baker 1991), has a reproductive season extended to up to seven months. This may help spread the risk within a season, rather than between the seasons as seen in interoparous species and it can be related to the history of this species. T. hispidus was a common species of the glacial steppe (Ložek 1964) hence the semelparous life cycle can be the answer of this species to a harsh climate. For instance such adaptations, which favoured a switch from iteroparity to semelparity, have been evidenced for a small rodent, Neotoma lepida Thomas, 1893 (Smith & Charnov 2001). The life history of T. hispidus fits into general picture of our knowledge of the life histories in the species of similar size and habitat requirement, e.g., Vitrina pellucida (O.F. Müller, 1774) (Umiński 1975) or Succinea putris (L., 1758) (Jackiewicz 2003). Generally they breed when they are one year old and live through only one winter. In contrast, Discus rotundatus (O.F. Müller, 1774) was considered to be annual (Cameron 1982) but detailed studies revealed that its life span is years and time to reach maturity ca. 4months(Kuźnik-Kowalska 1999). This implies that it is an interoparous species with the reproductive period falling in July/August (Kuźnik-Kowalska 1999). Another exception is Aegopinella nitidula (Draparnaud, 1805), which is biennial (Mordan 1978; Cameron 1982). Based on the data of the growth rate collected through field observations it can be stated that the fastest proportional growth is present in the youngest snails and then gradually decreases over the course of their age (Table 4). The growth phases recorded in T. hispidus (fast phase followed by slow phase) seem to be typical for helicids and hygromiids (Maltz 2003; Kuźnik-Kowalska & Roksela 2009). The slow growth phase in such species is associated with a development of a reproductive system which has been discussed in Maltz (2003) and Maltz & Sulikowska-Drozd (2008). In the case of growth in the field, environmental factors such as variable temperature or humidity associated with a particular season should be considered. They may have a significant effect on the growth of the snails forcing them to hibernate or aestivate. The potential reproductive capacity of T. hispidus is great, and it is no surprise to find that this is matched by high juvenile mortalities. The changes in the age class proportion depend on the rate of the surviving adult individuals. Although, a high proportion of eggs may hatch, data obtained from field and laboratory work proves a high mortality in the first month in case of hygromiids (Chatfield 1968). There is also a large natural mortality within adults just after their reproduction, as evidenced by many empty shells found in the habitat (MP pers. observ.) and recaptured adults among which more than 50% were dead. It is noteworthy that in 2009 adults dominated from May till July in the studied area while in 2010 it changed and during the whole growing season juveniles comprised the bulk. Variations that occurred from one year to the next, implied considerable fluctuations in reproductive success and mortality. It is that combinations of environmental factors such as weather or climate conditions are important in controlling growth and longevity of the snails (Sulikowska-Drozd 2011; Proćków et al. 2012). There are few long-term studies of population fluctuations in land snails, though Williamson et al. (1977) found population density in a Cepaea nemoralis (L., 1758) population fluctuated fivefold over a six year pe-

9 Feeding, growing and life-cycle in Trochulus hispidus 139 riod, with big changes in recruitment among years. In the case of our studies the difference between years is very striking and might be strongly connected with the weather conditions when in August 2010 the precipitation was extremely high in the Sudetes (Miętus et al. 2010). This resulted in a flooding in many places. Admittedly, this phenomenon did not take place on the studied area but heavy rainfall may have had a catastrophic effect mainly on laid eggs but also on the newly hatched and young snails (Fig. 5). Much lower density recorded then in September 2010 supports this hypothesis (Table 3). Time to hatching in T. hispidus varies widely from 6 to 24 days; the difference cannot be entirely attributed to the temperature, since it pertained to some batches hatched at the same time in the same dish. In Punctum pygmaeum (Draparnaud, 1801) (Baur 1989), Helicodonta obvoluta (O.F. Müller, 1774) (Maltz 2003) or Perforatella bidentata (Kuźnik-Kowalska & Roksela 2009) similar variation has been observed. In P. pygmaeum it can be explained by possible egg retention, but T. hispidus and the latter two species are considered strictly oviparous species. Shells of hatchlings vary considerably in the numberofwhorlsasinp. bidentata (Kuźnik-Kowalska & Roksela 2009) and young T. hispidus immediately after hatching are very similar in appearance to M. cantiana (Chatfield 1968). The shell apex in both species is free of hairs, but many rows of hairs are present on the body whorl and are distributed in a lattice pattern (Kaiser 1966; Chatfield 1968). The degree of development prior to hatching is variable, and gives a clue as to the evolution of ovoviparity. The heavy mortality of juvenile T. hispidus in laboratory conditions is a serious problem in gaining insights into its biology. Falkner (1973) was unable to keep successfully the culture of T. graminicolus Falkner, 1973 despite his attempts to reconstruct the natural habitat. Our experiences are similar and concern not only T. hispidus but also T. villosulus (Rossmässler, 1838) and T. striolatus (C. Pfeiffer, 1828) brought from various locations in Poland, the Czech Republic and Great Britain (unpublished data). Furthermore, Cain (1959) mentioned difficulties in rearing T. striolatus. Of many half-grown individuals brought from the field only few became mature and one pair reproduced. High mortality of juveniles was also noticed and actually there is no information how long he kept the hatchlings and whether they finally matured. Mortality of very young snails (2.5 mm) of Monacha cantiana and M. cartusiana made it impossible to rear the snails to the adult state (Chatfield 1968). The species are found in similar ruderal environments. Given the ease with which breeding colonies of other snails also found in such environments [e.g., Cepaea species, Arianta arbustorum L., 1758, Cornu aspersum (O.F. Müller, 1774)] can be raised in captivity, this suggests some rather specific requirements for these hygromiid snails that are missing in standard laboratory conditions. Williamson & Cameron (1976) reported no mortality in juvenile C. nemoralis kept in the laboratory, even when fed less than optimum diets. Since the juveniles of T. hispidus survived very poorly, doubts may arise whether the decline of reproductive rate in wild-collected adults was real. However, our clutch-size data did not differ from those published by Taylor (1916) or Frömming (1954), as well as, the lifetime of adults in captivity was reasonably long. Moreover, decreasing mean egg production per snail indicates that the data seem to be reliable. Food preferences Our laboratory experiment confirmed that diet of T. hispidus is variable (Frömming 1954). The only F. excelsior species was universally preferred across all focal populations. It suggests that individuals from different, geographically determined populations show variability in their diet, regardless of variation in available sources (but see Iglesias & Castillejo 1999) and/or different feeding history (but see Wareing 1993). It is thus likely that (i) T. hispidus profits from its plasticity in feeding habits, which allows the species to occupy highly variable sites and that (ii) this plasticity is actually responsible for the variability in diet that was reported for wild populations (Frömming 1954, Wareing 1993, Iglesias & Castillejo 1999). Acknowledgements Thanks are due to Dr. J.M.C. Hutchinson for his critical, detailed remarks on the manuscript and the invaluable help with linguistic corrections. We are also immensely grateful to an anonymous reviewer for helpful comments, constructive suggestions and all alterations in the text structure and organisation which improved the manuscript considerably. References AltonagaK.,GómezB.,MartínR.,PrietoC.E.,PuenteA.I.& Rallo A Estudio faunístico y biogeográfico de los moluscos terrestres del norte de la Península Ibérica. Eusko Legebiltzarra/Parlamento Vasco, Vitoria-Gasteiz, 503 pp. ISBN: , Baker G.H Production of eggs and young snails by adult Theba pisana (Muller) and Cernuella virgata (Da Costa) (Mollusca, Helicidae) in laboratory cultures and field populations. Aust. J. Zool. 39 (6): DOI: /ZO Baur B Growth and reproduction of the minute land snail Punctum pygmaeum (Draparnaud). J. Mollus. Stud. 55 (3): DOI: /mollus/ Bragado D., Araujo R. & Aparicio T Atlas y Libro Rojo de los Moluscos de Castilla-La Mancha. Organismo Autonómo Espacios Naturales de Castilla-La Mancha, Junta de Comunidades de Castilla-La Mancha, 506 pp. ISBN: Cain A.J Inheritance of mantle colour in Hygromia striolata (C. Pfeiffer). J. Conchol. 24: Cameron R.A.D Life histories, density and biomass in a woodland snail community. J. Mollus. Stud. 48 (2): Chatfield J.E The life history of the helicid snail Monacha cantiana (Montagu), with reference also to M. cartusiana (Müller). Proc. Malac. Soc. Lond. 38:

10 140 M. Proćków et al. Damjanov S.G. & Likharev I.M Suchozemni ochljuvi (Gastropoda terrestria). Fauna na Bulgarija, 4. Bulgarska Akademija na Naukite, Sofija, 425 pp. Ehrmann P Mollusken (Weichtiere). In: Brohmer P., Ehrmann P. & Ulmer G. (eds), Die Tierwelt Mitteleuropas Vol. II., Lief 1, Quelle & Meyer, Leipzig, 264 pp. Falkner G Studien über Trichia Hartmann, I. Trichia (Trichia) graminicola n. sp. aus Südbaden (Gastropoda: Helicidae). Arch. Moll. 103: Falkner G., Ripken T.E.J. & Falkner M Mollusques continentaux de France. Liste de Référence annotée et Bibliographie. Patrimoines Naturels 52: ISBN: Forcart L New researches on Trichia hispida (Linnaeus) and related forms, pp In: Eales N.B. (ed.), Proceedings of the Malacological Society of London, Vol. 36, Part 4, April 1965, Blackwell Scientific Publications, Oxford, 266 pp. Frömming E Biologie der mitteleuropäischen Landgastropoden. Duncker & Humblot, Berlin, 404 pp. Hatziioannou H., Eleutheriadis N. & Lazaridou-Dimitriadou M Food preferences and dietary overlap by terrestrial snails in Logos area (Edessa, Macedonia, Northern Greece). J. Mollus. Stud. 60 (3): DOI: /mollus/ Hänsel N., Walther Ch. & Plachter H Influence of land use and habitat parameters on populations of Candidula unifasciata and Helicella itala (Gastropoda, Helicidae) on calcareous grassland. Verh. Ges. Ökol. 29: Hotopp K.P., Nekola J.C. & Schmidt K New land snail (Gastropoda: Pulmonata) distribution records for New York state. Proc. Acad. Nat. Sci. Phila. 159 (1): DOI: Iglesias J. & Castillejo J Field observations on the feeding of the land snail Helix aspersa Müller. J. Mollus. Stud. 65: DOI: /mollus/ Irikov A. & Erőss Z An updated and annotated checklist of Bulgarian terrestrial gastropods (Mollusca: Gastropoda). Folia Malacol. 16 (4): Irikov A. & Mollov I Terrestrial gastropods (Mollusca: Gastropoda) of the Western Rhodopes (Bulgaria), pp In: Beron P. (ed.), Series: Biodiversity of Bulgaria 3. Biodiversity of Western Rhodopes (Bulgaria and Greece) I., Pensoft & Nat. Mus. Natur. Hist., Sofia, 974 pp. ISBN: Jackiewicz M Bursztynki Polski (Gastropoda: Pulmonata: Succineidae). Wyd. Kontekst, Poznań, 83 pp. ISBN: Jeffreys J.G British Conchology, or an account of the Mollusca which now inhabit the British Isles and the surrounding seas. Vol. 1 Land and Freshwater Shells. J. Van Voorst, London, CXIV+341 pp. DOI: title Kaiser P Bau, Entwicklung und Regeneration des Haarkleides von Trichia hispida (L.) zugleich ein Beispiel für eine einfache Musterbildung im Tierreich. Arch. Moll. 95 (3/4): Kerney M.P., Cameron R.A.D. & Jungbluth J.H Die Landschnecken Nord- und Mitteleuropas: Ein Bestimmungsbuch für Biologen und Naturfreunde. Paul Parey, Hamburg und Berlin, 384 pp. ISBN: Kiss L., Labaune C., Magnin F. & Aubry S Plasticity of the life cycle of Xeropicta derbentina (Krynicki, 1836), a recently introduced snail in Mediterranean France. J. Mollus. Stud. 71 (3): DOI: /mollus/eyi030 Kuźnik-Kowalska E Life cycle and population dynamics of Discus rotundatus (O. F. Müller, 1774) (Gastropoda: Pulmonata: Endodontidae). Folia Malacol. 7(1):5 17. Kuźnik-Kowalska E. & Roksela A Life cycle of Perforatella bidentata (Gmelin, 1791) (Gastropoda: Pulmonata: Helicidae). Folia Malacol. 17 (4): DOI: /v x Lazaridou M. & Chatziioannou M Differences in the life histories of Xerolenta obvia (Menke, 1828) (Hygromiidae). J. Mollus. Stud. 71 (3): DOI: /mollus/eyi032 Ložek V Quartämollusken der Tschechoslowakei. Rozpravy ústředního ústavu geologického, 31, 574 pp. Maltz T.K Life cycle and population dynamics of Helicodonta obvoluta (O. F. Müller, 1774) (Gastropoda: Pulmonata: Helicidae). Folia Malacol. 11 (3 4): Maltz T.K. & Sulikowska-Drozd A Life cycles of clausiliids of Poland knowns and unknowns. Ann. Zool. 58 (4): DOI: Manganelli G., Bodon M., Favilli L. & Giusti F Fascicolo 16. Gastropoda Pulmonata, pp In: Minelli A., Ruffo S. & La Posta S. (eds), Checklist delle specie della fauna italiana, Edizioni Calderini, Bologna. Mason C.F Food, feeding rates and assimilation in woodland snails. Oecologia (Berl.) 4 (4): DOI: /BF Miętus M., Ustrnul Z., Marosz M., Owczarek M., Biernacik D., Czekierda D., Kilar P. & Czernecki B Monthly Climate Monitoring Bulletin, August (accessed ). Mordan P.B The life cycle of Aegopinella nitidula (Draparnaud) (Pulmonata: Zonitididae) at Monks Wood. J. Conchol. 29: Naggs F Some preliminary results of a morphometric multivariate analysis of the Trichia (Pulmonata: Helicidae) species groups in Britain. J. Nat. Hist. 19 (6): DOI: / Proćków M Shell variation in some populations of Trichia hispida (L.) from Poland (Gastropoda: Pulmonata: Helicidae). Genus 8: Proćków M The genus Trochulus Chemnitz, 1786 (Gastropoda: Pulmonata: Hygromiidae) a taxonomic revision. Folia Malacol. 17 (3): DOI: /v Proćków M., Kuźnik-Kowalska E. & Lewandowska M Differences in population dynamics of Bradybaena fruticum (O.F. Müller, 1774) (Gastropoda: Pulmonata: Bradybaenidae) in a submontane and lowland area of Poland. Anim. Biol. 62: DOI: / X Riedel A Ślimaki lądowe Gastropoda terrestria. Seria: Katalog fauny Polski. Cz. 36, t. 1. PWN, Warszawa, 316 pp. ISSN Robinson D.G Alien invasions: the effects of the global economy on non-marine gastropod introductions into the United States. Malacologia 41 (2): Seber G.A.F The estimation of animal abundance and related parameters. 2nd edition. Charles Griffin & Company Ltd, London, 654 pp. ISBN: , Shileyko A.A Naziemnyje molljuski nadsemejstva Helicoidea. Fauna SSSR, N. S. 117, Molljuski tom. III, vyp. 6. Nauka, Leningrad, 384 pp. Smith F.A. & Charnov E.L Fitness trade-offs select for semelparous reproduction in an extreme environment. Evol. Ecol. Res. 3(5): Sulikowska-Drozd A Population dynamics of the Carpathian clausiliid Vestia gulo (E.A. Bielz 1859) (Pulmonata: Clausiliidae) under various climatic conditions. J. Conchol. 40: Taylor J.W Monograph of the Land and Freshwater Mollusca of the British Isles. Taylor Bros., Leeds, 160 pp. Uherkovich A., Purger D. & Csiky J First find of Pomatias rivularis (Eichwald, 1829) (Mollusca: Pomatiidae) in Croatia. Natura Croatica 17 (3): Umiński T Life cycles in some Vitrinidae (Mollusca, Gastropoda) from Poland. Ann. Zool. 33: Waldén H.W Communities and diversity of land molluscs in Scandinavian woodlands. I. High diversity communities in taluses and boulder slope in SW Sweden. J. Conchol. 30: Wareing D.R Feeding history a factor determining food preferences in slugs. J. Mollus. Stud. 59 (3): DOI: /mollus/ Wäreborn I Land molluscs and their environments in an oligotrophic area in southern Sweden. Oikos 20 (2): DOI: / Wäreborn I Environmental factors influencing the distribution of land molluscs of an oligotrophic area in southern Sweden. Oikos 21: DOI: /

11 Feeding, growing and life-cycle in Trochulus hispidus 141 Wiktor J. & Wiktor A Charakterystyka fauny mięczaków polskiej części Karkonoszy ze szczególnym uwzględnieniem Karkonoskiego Parku Narodowego. Ochr. Przyr. 33: Williamson P. & Cameron R.A.D Natural diet of the land snail Cepaea nemoralis. Oikos27 (3): DOI: / Williamson P., Cameron R.A.D. & Carter M.A Population dynamics of the land snail Cepaea nemoralis (L): A six-year study. J. Anim. Ecol. 46 (1): DOI: /3955 Wolda H., Zweep A. & Schuitema K.A The role of food in the dynamics of populations of the land snail Cepaea nemoralis. Oecologia (Berl.) 7 (4): DOI: /BF Received January 17, 2012 Accepted September 25, 2012