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The use of shell features in age determination of juvenile and adult Roman snails Helix pomatia
Abstract
Features of the shell which can be used for aging Roman snails Helix pomatia L. are described. Field evidence suggests that growth breaks in the shell correspond to resting periods during the winter in the juvenile phase of shell growth. The microstructure of the shell is described and the structure of the juvenile breaks and layering in the lip of the adult snail are shown to be similar. It is concluded that the two are analogous, that the layers at the lip are annual, and that it is theoretically possible to trace the adult shell back to the year of hatching. In practice, errors may be made in recording, but the method can be of great value in population studies.
... A mollusk's shell potentially provides a record of environmental information in the form of bivalve shell growth bands, for example, which offer a precise chronological record as they change in response to environmental and physiological factors such as temperature (Nishida et al. 2012;Kubota et al. 2017), salinity (Schöne et al. 2013Shirai et al. 2014), and spawning (Nishida et al. 2012). Pollard et al. (1977) reported that the land snail Helix pomatia presents an annual growth break in its shell, corresponding to the winter season. Although L. pulchella has been known to spawn in temperatures of < 20 °C from September to November , the surface of the shell of L. pulchella is usually smooth, and no seasonal nor annual growth break has been observed on L. pulchella shells. ...
The Great East Japan Earthquake and accompanying tsunamis occurred on 11 March 2011, causing huge damage to marine organisms. The invasive naticid gastropod Laguncula pulchella (Euspira fortunei), which was introduced with the imported clam Ruditapes philippinarum from China and Korea, survived the earthquake. The “growth break line” observed on the shell surface in over 90% of the individuals collected in Matsushima Bay and Matsukawa-ura Lagoon after the tsunamis was examined by scanning electron microscopy. Each shell presented three layers before and three after the growth break. However, the fracture surface consisted of five layers—two prismatic and three crossed lamellar—around the growth break line. This suggests that shell formation temporarily ceased following the tsunamis and that the five-layered shell may have developed in response to the stress caused by the tsunamis. The newly formed middle layer became thinner after the “tsunami break,” which may be the result of a rapid change in the mineralization process, including rapid shell growth and/or repair. These results suggest that the damage to and forcible removal of habitats by the tsunamis was stressful for L. pulchella. A decrease in or the cessation of shell formation after a tsunami may be a common phenomenon in mollusks that inhabit tidal flats.
... In adult Cepaea age has been estimated from perio- stracum wear (Goodhart, 1962;Williamson, 1975Williamson, , 1976Williamson, Cameron & Carter 1977) and from relative shell weight (Williamson, 1979). Pollard (1973Pollard ( , 1975Pollard ( , 1977 and Falkner (1984) have suggested, that the lay- erings of the lip of Helix pomatia are formed annually. Similarly this paper shows that the layerings at the inner side of the lip of adult Arianta arbustorum and the growth breaks in the juvenile and subadult phase are formed annually. ...
The pulmonate snail Arianta arbustorum from the Swiss Alps was aged using thin sections of the shell margins cut from marked individuals. Shell layers at the apertural
lip and growth breaks in the juvenile can give a reliable estimate of age.
... Since snail activity and therefore growth rate and shell size are highly dependent on environmental factors such as humidity and soil calcium content (Goodfriend 1986), attempts were made to see the effect of these factors on shell size. Age distribution – External features of the shell (growth breaks and lip layering as described by Pollard et al. 1977 were used for categorising snail age. Four age groups were defined: Age IV – adults older than 4 years; Age III – adults of 3–4 years that were newly matured or ready to mature; Age II – young specimens of 2–3 years, Age I – juveniles of 1–2 years old. ...
Helix pomatia L., the Roman snail, is a species faced with growing commercial interest in Moldova. Its life history characteristics (slow
maturation and recruitment, high mortality among juveniles and low fecundity) along with its strong spatial aggregation, makes
it especially vulnerable to exploitation. In this study, differences in density, shell size and age distribution were assessed
in 7 unexploited and 10 exploited sites in the northern and central parts of Moldova. A significant impact of exploitation
on snail population densities, shell size of adult snails and age distribution was revealed. Exploited sites had much lower
densities than unexploited ones and in two places no live snails were found. This may suggest that exploitation is currently
carried out at an unsustainable level, but additional information on the demography of populations and intensity of exploitation
is required in order to make inferences regarding sustainability and long-term population management. There was a higher proportion
of adult snails in exploited sites than in non-exploited, because of the collection strategies: not only adults, but also
all other age groups are gathered. Bigger adult shell size in exploited sites may be related to lower population density,
but further study is required to confirm this. Establishing of well-organized population monitoring systems and development
of snail breeding enterprises are proposed in order to conserve the species in Moldova.
This study evaluated the influence of rearing system (cultured vs. wild rearing systems), and fish sex on carcass and flesh traits of A. rivulatus, raised in Ecuador. Three hundred mature specimens from A. rivulatus were captured, 150 from each origin. Slaughter yield and dress-out resulted similar for both rearing system, and average fillet yield for cultured fish was significantly higher than for wild fish, while cooking loss was significantly lower. Dress-out was significantly higher in females. Significant differences were found in wet percentage, ash, fat and protein content in both rearing systems, but only wet percentage was significantly affected by sex. Palmitic, oleic and arachidonic acids had the maximum percentage of saturated (SFA) and mono/poly unsaturated (MUFA/ PUFA) fatty acids, respectively. In cultured and wild fish, differentiations were also found in PUFA/SFA, docosahexaenoic acid (DHA)/eicosapentaenoic acid (EPA), atherogenicity (IA), and thrombogenicity (IT) indices, along with P, K, Mg, Cu and Fe. Sex and rearing system significantly influenced most of the analyzed characteristics of carcass and flesh of A. rivulatus. Fillet high yield and its proximate composition categorize A. rivulatus as a suitable food. These results provide valuable nutritional information about native species for consumers in Ecuador. Highlights: The rearing system (cultured vs. wild rearing systems), and fish sex affect the carcass and flesh traits of A. rivulatus. Fillet high yield and its proximate composition categorize A. rivulatus as a suitable food. The proximate composition of fillet from cultured A. rivulatus is more adequate than those of wild A. rivulatus. The cultured A. rivulatus contains higher n-3 and n-6 PUFA percentages and adequate n-3/n-6 ratio.
An integrated rearing system for Cantareus aspersus under environmental conditions in an experimental orchard is proposed. In this study, the natural behaviour, circadian rhythms and suitable rearing conditions of the edible snail were optimised to produce homogeneous growth and low variability. The growth was stand-ardised, and growth pattern fit was assessed with various models. One thousand fry were cultured in the orchard, and a random sample of 100 snails were measured weekly for 23 weeks. The rearing system had the following characteristics: snails and earthworms were included in the experimental rearing orchard; a homogeneous group of juvenile snails of the same age and size and high rearing density (500 snails/m 2) was used; snails were fed with layers mash ad libitum; and mixed and fringes vegetation was planted in the orchard. A commercial size of 60% of snails was achieved in 21 weeks and 95% in 23 weeks. The different models showed a good fit, and the quadratic model obtained the best fit. This experimental snail orchard proposal can be extended to other areas, although it must be corrected according to different environmental conditions and fit to other species of interest. This experimental model could constitute a viable alternative to traditional models of animal experimentation with mammals, and given its high adaptability, it could be applied in different fields of science.
The rare carnivorous land snail Paryphanta busbyi watti was investigated by following marked snails over a study period of 6.3 years. Large snails were fitted with harmonic radar transponders to aid in locating them. This species is iteroparous and has determinate growth. Shells had maximum diameters of 49.6–61.2 mm. Two to eight large eggs, representing 5%–23% of the live weight of a snail, were laid at a rate of one to two per day over 2–5 days. These eggs were deposited in one to three holes dug in soil by the snails. A newly laid egg was surrounded by an adhesive membrane, which disappeared after a few days, exposing the calcareous shell. The eggs took 5–7.3 months to hatch and the young snails remained underground for a minimum of up to 2.8 months. The shells of these snails increased in size while underground. A non-linear mixed-effects model was used to combine data from 31 snails that were monitored for different lengths of time. Only an approximate estimate could be made of the development rate for young snails. Growth to the adult shell stage was estimated to take 3–4.3 years and fast-developing individuals tended to become larger adults. The maximum time that a snail with an adult shell was monitored was 4.1 years, whereas most snails with an adult shell were monitored for 1–2 years.
Fossil land snail shells constitute a valuable source of paleoenvironmental information for the Quaternary. They can be dated by a variety of methods, including radiocarbon, amino acid racemization and epimerization, and perhaps also and ESR. The vast majority of paleoenvironmental studies based on land snail shells have examined the faunal composition of fossil assemblages, from which a variety of paleoenvironmental characteristics such as biome, temperature, and moisture conditions have been reconstructed. Still, there are a number of problems involved in using this approach and these are discussed. Shell morphology has occasionally been used to reconstruct such factors as rainfall and temperature. Stable isotope studies on Quaternary land snails include: analysis of δ18O values of organic matter in the shells, to reconstruct C4 plant distributions from which rainfall amounts can be inferred, and analysis of δ18O values of shell carbonate, from which trends in the oxygen isotope composition of rainfall can be reconstructed. Stable carbon isotopes of shell carbonate have also been studied but their interpretation is not clear. Amino acid epimerization analysis ( ratios) of land snail shells has been used for estimation of paleotemperatures. Some potential uses of land snail shells for paleoenvironmental reconstruction include the study of stable isotopes of H and N, periodic growth lines, and deposits of pedogenic carbonates on the shells.
1.1. The protected gastropod, Elona quimperiana, is essentially limited to western Brittany.2.2. The snail does not possess a complete uricolytic enzyme chain, allantoicase are absent.3.3. Variation in uricase and urease activity is more or less appreciable and related to age and season. Uric acid, urea and ammonia, nitrogenous catabolites are present, but uric acid is predominant. Elona quimperiana should be considered uricotelic.
The rare carnivorous land snail Paryphanta busbyi watti was investigated by following marked snails over a study period of 6.3 years. Large snails were fitted with harmonic radar transponders to aid in locating them. This species is iteroparous and has determinate growth. Shells had maximum diameters of 49.6-61.2 mm. Two to eight large eggs, representing 5%-23% of the live weight of a snail, were laid at a rate of one to two per day over 2-5 days. These eggs were deposited in one to three holes dug in soil by the snails. A newly laid egg was surrounded by an adhesive membrane, which disappeared after a few days, exposing the calcareous shell. The eggs took 5-7.3 months to hatch and the young snails remained underground for a minimum of up to 2.8 months. The shells of these snails increased in size while underground. A non-linear mixed-effects model was used to combine data from 31 snails that were monitored for different lengths of time. Only an approximate estimate could be made of the development rate for young snails. Growth to the adult shell stage was estimated to take 3-4.3 years and fast-developing individuals tended to become larger adults. The maximum time that a snail with an adult shell was monitored was 4.1 years, whereas most snails with an adult shell were monitored for 1-2 years. M R02010 I. A. N. St r in ger et al .
Shells were examined from immature snails (Helix pomatia) that had been treated with DDT or deprived of access to calcium carbonate. Exposure to DDT resulted in shell thinning with the thickness of each of the three structural layers being inversely related to the body burden of DDT. The normal crossed lamellar structure was distorted in some of the thin shells. Withholding calcium carbonate led to similar changes, and DDT may cause thin shells by impairing calcium metabolism.
Tidal cycles are reflected in daily growth-increment sequences in shells of many Recent and fossil mollusks. Living specimens of the bivalve Mercenaria mercenaria were notched at the growing edge of the shell and planted intertidally in Barnstable Harbor, Massachusetts. Shells from two lots, killed at intervals of 368 and 723 days after planting, show the same number of small growth increments as there were days from notching to killing. Superimposed on daily growth record are effects of winter (thin daily increments) and tides (14-day cycles of thick and thin daily increments). Comparison of Barnstable tide record with the first year's growth shows that, for each 14-day cycle, thin daily increments form during neap tides and thicker daily increments form during spring tides. Although tidal patterns are present in subtidal Mercenaria shells, they are rarely as pronounced as in intertidal ones. Spawning patterns differ from winter patterns; they are expressed in the shell by an interruption of regular deposition followed by a series of thin daily increments. Continuous sequences of bidaily patterns, one thick daily increment followed by a relatively thin one, are common in M. mercenaria.
The clearest 14-day cycles of deposition were seen in shells of the bivalve Tridacna squamosa. Each daily neap-tide increment is a simple layer consisting of a dark and light zone. Each daily spring-tide increment is a complex layer consisting of two light-dark alternations separated by a depositional break that is more pronounced than the breaks delimiting daily intervals. Preliminary results of growth-increment counts in fossils show a generally decreasing trend of the mean values of days per lunar month toward the Recent. The Pennsylvanian value is 30.07 ± 0.08, a figure that is in general agreement with those of Scrutton (1964), who counted 30.59 days per month on Devonian corals, and Barker (1966), who reported more than 30 days per month in Pennsylvanian bivalves.
(1) Information on the distribution of Helix pomatia shows that while it occupies several different habitat types it is, in most of its range in England, largely restricted to aspects facing approximately south. (2) Intensive studies on a single population show the dependence of activity, mating and egg-laying on rainfall. The breeding biology is described. The growth rate of immature snails is very variable. (3) An earlier classification of adult snails into growth classes is shown to be into age classes. Older snails hide themselves amongst vegetation less than younger snails but are less mobile. (4) The adult snails in one site showed a regular seasonal pattern of movement, away from, and later back to, hibernation areas. The particular pattern of movement of individual snails seems to be repeated from year to year. The known `homing' ability is believed to be related to the existence of permanent hibernation areas. In a linear hedgerow individual snails returned to hibernation sites but there was no overall directional pattern of movement affecting the whole population in the hedge. The difference between the two sites was believed to be related to the availability of sites suitable for egg-laying. (5) Observations in the field showed a strong preference for feeding on two species of Centaurea. (6) Known predators of young and adult snails are listed and a possible disease briefly discussed.
The evidence at present available, although incomplete, gives rise to fears for the future of the edible snail Helix pomatia L. The scale of exploitation is increasing, particularly in Eastern Europe, to meet growing demand, mainly from the West. The growth of legislation to control collecting supports the evidence of declining numbers, but the legislation does not appear to be backed by sufficiently detailed population ecology studies. The need for co-ordinated international action on farming, legislation and ecological study is urged.
Roman snails (Helix pomatia) have been treated with pp′-DDT from 2 wk of age until hibernation. Taking snail size into account, relatively low doses of DDT significantly reduced shell and operculum weight whereas higher doses of DDT did not cause this response. After reemergence from hibernation, the incidence of operculum eating was significantly higher among snails hibernating late in the season, and as exposure to DDT increased so operculum eating became more prevalent.Shell thinning in snails due to pesticide is likely to have occurred in some heavily treated agricultural localities if the response of other species to DDT is similar to that of Helix pomatia.
a method of dividing adult Helix pomatia into growth classes, which are probably also age classes, is described. Differences in behaviour of individuals previously thought to be associated with their status in a population are probably differences between individuals of different age.
Egg shell characteristics and incidences of shell breakage have been studied for the grey heron Ardea cinerea at several colonies in eastern England.Eggs collected in the late 1960s and in the 1970s had shells which were significantly thinner than shells collected before 1946. For a sample taken in 1973, shell thickness, shell strength, mammillary layer thickness and palisade layer thickness were all inversely related to the concentration of pp'-DDE(+ pp'-DDT + pp'-TDE) in the egg contents. Shell thinning was considered to be due to a reduced availability of shell components leading to a depressed rate of shell formation. A separate mechanism resulted in increased mammillae height relative to mammillary layer thickness. For comparison, the structure of other types of thin shells was also examined.Incidence of egg shell breakage was positively related to the residue levels of pp′-DDE or dieldrin in intact eggs. Eggs with shells thinner than 240 μm were unlikely to survive incubation. Since such eggs tend to contain higher-than-average residues, sampling intact eggs leads to a mean egg residue figure that is lower than the real mean for the colony. Measuring shell thickness is suggested as a rapid and economical bioassay of DDE levels. Shell thinning leads to a proportionally greater reduction in shell strength, and breakage of shells less than 240 μm in thickness was probably due to a combination of shell fragility and aberrant behaviour by the brooding adults. Breakage of thicker shells was believed to be mainly due to deliberate destruction. Despite more than half of the pairs breaking their shells during some years, heron populations have not declined overall perhaps because of the ability of this species to lay repeat clutches. There are indications that egg residues of DDE and other organochlorines are decreasing, and shell thickness and the incidence of shell breakage are returning to normal.
Aus: Zeitschrift f. wissensch. Zool. Bd 113. Marburg, Phil. Diss. v. 4. Aug. 1915, Ref. Korschelt.
Fine structure of the normal and the regenerated shell of Helix has been studied by thin sectioning, replica technique, and scanning electron microscopy. Normal shell consists of four calcareous layers: innermost nacreous, two cross lamellar, and outermost prismatic. Crystals of the shell are well defined and are surrounded by intercrystalline organic matrix. Intracrystalline organic matrix is recognized, particularly in decalcified sections. Interrelationships between the organic and inorganic components have been studied in decalcified thin sections. Regenerated shell appears similar to nacreous layer of the normal shell. Crystals are large and stacked like bricks. Intracrystalline organic matrix is very prominent. Electron diffraction of the crystals of the regenerated shell generally gives calcite pattern whereas the normal shell gives aragonite. Surface topography of the normal and regenerated shell has been compared by replica techniques.
Till molluskernas biologi II
- Lundquist G.
Relationship of size to age in the cockles Cerastoderma edule and C. glaucum from the River Crouch estuary, Essex
- Boyden C. R.
Die Weinbergschnecke (Helix pomatia L.) Lebensweise, Verbrauch Handel und Zucht
- Hein G.
Die Weinbergschnecke
- G. Nietzke