Some aspects of the ecology of the land snail, Helicella virgata, in South Australia

1969 ◽  
Vol 17 (3) ◽  
pp. 495 ◽  
Author(s):  
DE Pomeroy
Keyword(s):  
Natural History ◽  
Natural Population ◽  
South Australia ◽  
Growth Curves ◽  
Land Snail ◽  
Food Resources ◽  
Winter Dormancy ◽  
Rate Of Growth ◽  
Length Of Life

H. virgata was introduced to South Australia from Europe and has since become remarkably numerous. Its natural history is described, including breeding, growth, and food. There is normally one generation per year, the eggs mostly hatching in autumn and the young growing rapidly until spring. Marking and recapture were used to determine growth curves in the field. Snails are only active when the ground is moist and the humidity high. Even in winter dormancy is frequent, and in summer it is prolonged. H. virgata is microphagous, feeding mainly on the topsoil and surface litter, avoiding places from which these are removed. It was shown experimentally that the numbers of young produced, their rate of growth, and the length of life of adults all decreased with increasing density. This was explained in terms of increasing starvation. A natural population was studied for nearly 2 years. In places the density of this population was high and there was evidence of a consequent shortage of food, which affected young and adults differently. "Effective fecundity" (p. 509) was inversely proportional to the density of the population. There were marked aggregations, apparently reflecting the distribution of food. However, the degree of "patchiness" (Lloyd 1967) remained fairly constant with time. Over most of its range H. virgata is relatively scarce and the numbers in these places are less likely to press upon the food resources. The effects of cultivation and trampling, lack of calcium in the soil, and other factors must explain this scarcity. Weather can certainly be important; the drought of 1965-66 reduced all populations severely.

Dormancy in the land snail, Helicella virgata (Pulminata : Helicidae)

1968 ◽  
Vol 16 (5) ◽  
pp. 857 ◽  
Author(s):  
DE Pomeroy
Keyword(s):  
Ambient Temperature ◽  
Evaporative Cooling ◽  
South Australia ◽  
Land Snail ◽  
The Sun ◽  
Winter Dormancy ◽  
Dormant State ◽  
The Family

H. virgata and other introduced snails of the family Helicidae spend much of their time in a dormant state. In winter, dormancy usually occurs daily, and lasts for a few hours only. In summer, when rainfall is rare, it may last for many days or even weeks, and is then referred to as aestivation. H. virgata aestivates in conspicuous positions, often fully exposed to the sun, at heights of up to 11 m from the ground. No appreciable heat is lost by evaporative cooling, and the temperatures of dormant snails may exceed the ambient temperature by as much as 10 degC, the amount of the excess being a function of height above the ground. Estimates are given of the temperatures experienced by aestivating snails over a whole summer; these exceed 30�C for three-quarters of the summer, and 40�C is reached quite commonly. The positions where H. virgata aestivate are discussed in relation to temperature, and it is concluded that their behaviour, which presumably evolved in their native European range, is less appropriate in the climate of South Australia; but despite this, their populations reach high densities in places.

New host records for ticks (Acari : Ixodidae) from the echidna (Tachyglossus aculeatus) revealed in Australian museum survey

2017 ◽  
Vol 65 (6) ◽  
pp. 379 ◽  
Author(s):  
Anna-Sheree Krige ◽  
Siew-May Loh ◽  
Charlotte L. Oskam
Keyword(s):  
Natural History ◽  
Tick Species ◽  
South Australia ◽  
Nationwide Survey ◽  
Australian Capital Territory ◽  
New Host ◽  
Australian Museum ◽  
First Time ◽  
New Host Records ◽  
Tachyglossus Aculeatus

A nationwide survey was conducted for ticks (Ixodidae) removed from echidnas, Tachyglossus aculeatus (Shaw, 1792), that had been previously collected between 1928 and 2013, and archived within Australian national (Australian National Insect Collection, Australian Capital Territory) and state (Queensland, South Australia, Victoria, and Western Australia) natural history collections. A total of 850 ticks from 89 T. aculeatus hosts were morphologically identified to determine instar, sex and species. Seven larvae, 349 nymphs and 494 adults were identified; 235 were female and 259 were male. The most common tick species was Bothriocroton concolor (Neumann, 1899) (89.2%). In addition, ticks previously recorded from T. aculeatus were identified, including Amblyomma australiense Neumann, 1905 (1.8%), Amblyomma echidnae Roberts, 1953 (0.1%), Bothriocroton hydrosauri (Denny, 1843) (1.4%), Bothriocroton tachyglossi (Roberts, 1953) (1.5%) and Ixodes tasmani Neumann, 1899 (1.2%). For the first time, 22 Amblyomma fimbriatum Koch, 1844 (2.6%) and 19 Amblyomma triguttatum Koch, 1844 (2.2%) ticks were recorded from T. aculeatus. This is the first survey to utilise archived Australian tick collections for the purpose of acquiring new data on tick species that parasitise T. aculeatus.

Energy flux in a natural population of the land snail Eobania vermiculata (Müller) (Gastropoda: Pulmonata: Stylommatophora) in Greece

1991 ◽  
Vol 69 (4) ◽  
pp. 881-891 ◽  
Author(s):  
Maria Lazaridou-Dimitriadou ◽  
Marios E. Kattoulas
Keyword(s):  
Mortality Rate ◽  
Natural Population ◽  
Energy Flux ◽  
Assimilation Efficiency ◽  
Land Snail ◽  
Metabolic Energy ◽  
Adult Density ◽  
Net Reproductive Rate ◽  
Rate Of Increase ◽  
Eobania Vermiculata

Survivorship, production, mortality rate, consumption rate, assimilation, and growth and ecological efficiencies were studied in a natural population of the land snail Eobania vermiculata in Greece. Eobania vermiculata may take 5 years or more to reach maximum size (33 mm). Mortality rate and life expectancy decreased with age. Net reproductive rate was 3.4 and per capita rate of increase was 1.0. Energy flux in E. vermiculata was studied using Urtica dioica and Lactuca sativa as food. The highest daily consumption and assimilation rates (weight specific) were observed in newly hatched animals and the lowest in adults. Assimilation efficiency, mean monthly production, and gross growth and ecological or net growth efficiencies fluctuated with the season and the physiology of the snails. Snails fed U. dioica showed higher assimilation, gross growth, and net growth efficiencies than those fed L. sativa. Energy flow through the E. vermiculata population was 78.9 cal∙m−2∙year−1 (1 cal = 4.1868 J), mean assimilation efficiency was 52% if the snails were fed U. dioica only, and the ingestion rate was 19.5%. When E. vermiculata was fed U. dioica during its lifetime, 4.26% of the total assimilated energy was used for egg production, 10.2% for growth, and 87.8% for metabolic energy. Annual secondary production gave a mean adult density of 4.1 individuals/m2, a mean annual standing crop (biomass) of 6.8 g∙m−2, and an annual production of 13.9 ± 1.8 g∙m−2 or 2859.5 mg C∙m−2. The annual turnover ratio, or productivity rate constant, was 2.0.

scholarly journals Demography of the land snail Tikoconus (Tikoconus) costarricanus (Stylommatophora: Euconulidae) in tropical low montane and premontane forests, Costa Rica

2019 ◽  
Vol 67 (6) ◽  
Author(s):  
Zaidett Barrientos
Keyword(s):  
Costa Rica ◽  
Natural History ◽  
Leaf Litter ◽  
Secondary Forest ◽  
Land Snail ◽  
Egg Laying ◽  
Land Snails ◽  
Tropical Species ◽  
Spearman Correlation ◽  
Mature Forest

Abstract. Introduction: Ecology and natural history of neotropical land snails is almost unknown. Objetive: In this paper I analyse the population dynamics of Tikoconus (Tikoconus) costarricanus Barrientos, in prep., an understory endemic euconulid. Methods: I compared T. costarricanus’ demography patterns in tropical montane forests in central Costa Rica in three habitats with different restoration techniques: a mature forest, a secondary forest and a Cuppressus lusitanica plantation. I collected data in three month periods during a year. I analysed population size in relation with habitat, sampling date, leaf litter humidity, depth and quantity; and specimen size in relation with habitat and sampling date. I also kept some specimens in terraria and described part of their natural history. Results: The species is more abundant in mature forest (Ø = 0.174 ind/m2). The number of specimens in each habitat was constant throughout the year (Kruskall-Wallis = 2.0118, p = 0.57, NS) and hatching occurs in the middle and last months of the rainy season (Kruskall-Wallis = 17.3061, p = 0.00061, **). Number of specimens is related with leaf litter humidity (Spearman correlation, r = 0.3524, n = 232, p = 0.000, **), amount (Spearman correlation, r = 0.3922, n = 232, p = 0.000, **) and depth (Spearman correlation, r = 0.2543, n = 232, p = 0.000, **). This relationship is explained by the high and stable humid environment provided by leaf litter. During the drier months some specimens migrate from the foliage to the leaf litter. Eggs (Ø = 1mm) are laid on moss or soil and the young spend the first 2 or 3 weeks of their life on moss. Egg masses are small (Ø = 4 eggs), and shells look bubbly. Egg development time (20 days) was longer than in other tropical species. Adult pigmentation appears around two months after hatch. In the only case observed egg laying began 5 months after hatching and the specimen lived 9 months. Conclusions: Although no conclusive, these data point to a fragile species susceptible to habitat and climate change. Restorations techniques should consider leaf litter features in order to protect endemic neotropical humid dependent diversity.

scholarly journals THE GROWTH AND DURATION OF LIFE OF CELOSIA CRISTATA SEEDLINGS AT DIFFERENT TEMPERATURES

1934 ◽  
Vol 17 (6) ◽  
pp. 763-781 ◽  
Author(s):  
Thomas I. Edwards ◽  
Raymond Pearl ◽  
Sophia A. Gould
Keyword(s):  
Growth Rate ◽  
Maximum Yield ◽  
Total Duration ◽  
Growth Curves ◽  
Growth Period ◽  
Hypocotyl Length ◽  
Rate Of Growth ◽  
Life Duration ◽  
Celosia Cristata ◽  
The Mean

Daily measurements of hypocotyl length were made on Celosia cristata seedlings cultured in darkness under aseptic conditions at six constant temperatures between 14.5° and 40.5°C. At 40.5° roots did not penetrate the agar and only the hypocotyls that were supported by the wall of the test tube could be measured. The growth curves were of the generalized logistic type, but of different degrees of skewness. The degree of symmetry of the growth curves was influenced by temperature. At the lower temperatures the maximal growth rate came relatively late in the grand period of growth; at successively higher temperatures it came progressively earlier. The mean total time rate of growth (millimeter per diem) was found to be a parabolic function of the temperature. The maximum rate of growth was found from the curve to be at 30.48°C. The maximum observed rate of growth, and the maximum yield, were found to be at 30°C. At all temperatures above 14.5° the maximum growth activity fell in the second quarter of the whole growth period. At all temperatures tested other than 30°, and at all parts of the growth cycle, the growth yield as measured by height of hypocotyl at any given equivalent point was less than at 30°. The total duration of life of the seedlings, and the duration of life after the end of the growth period (intermediate period) were inversely proportional to the mean total growth rate. The observations on Celosia cristata seedlings are thus in accord with the "rate of living" theory of life duration. The optimal temperature for life duration is the minimum temperature, within the range of these observations.

Age and growth studies of Gummy Shark, Mustelus antarcticus Gunther, and School Shark, Galeorhinus galeus (Linnaeus), from Souther Australian Waters

1992 ◽  
Vol 43 (5) ◽  
pp. 1241 ◽  
Author(s):  
PL Moulton ◽  
TI Walker ◽  
SR Saddlier
Keyword(s):  
South Australia ◽  
Growth Curves ◽  
Growth Patterns ◽  
Growth Equation ◽  
Von Bertalanffy ◽  
Fishing Mortality ◽  
Male And Female ◽  
Length Data ◽  
Von Bertalanffy Growth Equation ◽  
Galeorhinus Galeus

Age-length data were derived from counting stained bands on whole vertebral centra obtained from gummy shark, Mustelus antarcticus, captured by gill-nets during 1973-76 in Bass Strait and from gummy shark and school shark, Galeorhinus galeus, captured during 1986-87 in Bass Strait and waters off South Australia. The data were fitted to the von Bertalanffy growth equation after adopting the Francis reparametrization and correcting for sampling bias caused by the selectivity effects of the gill-nets of various mesh sizes used to capture the sharks. The von Bertalanffy growth curves of male and female gummy shark were significantly different, but the growth curves of male and female school shark were not. The growth curves suggest that growth rates of male and female gummy shark in Bass Strait were lower during 1986-87 than during 1973-76 and that the growth rates of male and female gummy shark and school shark in Bass Strait during 1986-87 were lower than those in South Australia at the same time. These apparent temporal and spatial differences in growth patterns of gummy shark are explained by the 'Phenomenon of Apparent Change in Growth Rate'. It is concluded that the growth curves determined for 1986-87 are distorted by the effects of a long history of high and length-selective fishing mortality and that actual growth patterns of gummy shark are better represented by the von Bertalanffy growth equation determined for shark caught in Bass Strait during 1973-76, when fishing mortality was much lower. Verification of age estimates was attempted by comparing von Bertalanffy growth curves derived from age-length data with those derived from tag release-recapture length-increment data, but these comparisons highlight the limitations of using tag data for this purpose. Although reasonable agreement was found between such growth curves for gummy shark, it appears that school shark older than 11 years cannot be aged accurately from stained whole or sectioned vertebrae. Sectioned vertebrae from a school shark recaptured 35.7 years after being tagged and released and calculated as having an age exceeding 45 years gave estimates of only 18-20 years of age.

The Dispersal of Cernuella-Virgata (Mollusca, Helicidae)

1988 ◽  
Vol 36 (5) ◽  
pp. 513 ◽  
Author(s):  
GH Baker
Keyword(s):  
South Australia ◽  
Land Snail ◽  
Early Summer ◽  
Permanent Pasture ◽  
Roadside Vegetation ◽  
Mark Release Recapture

The dispersal of the land snail Cernuella virgata was measured in South Australia by mark-release- recapture. Dispersal was not influenced by the paint used for marking, displacement of the snails during the marking process or crowding at release points. Snails moved out of a well-grazed permanent pasture to adjacent weedy roadside vegetation in early summer. They returned to the pasture in autumn. Factors which might direct this movement are discussed. Average movements varied between 0.1 and 0.4 m day-'. Some snails moved more than 25 m in one month in spring-summer and 50 m in 3 months in autumn-winter.

scholarly journals Results of Research on the Active Species Protection of the Roman Snail (Helix Pomatia, Linnaeus, 1758) Using Farmed Snails in the Second Year of Life. First Season of the Study

2014 ◽  
Vol 14 (2) ◽  
pp. 377-389 ◽  
Author(s):  
Maciej Ligaszewski ◽  
Przemysław Pol ◽  
Iwona Radkowska ◽  
Krzysztof Surówka ◽  
Andrzej Łysak
Keyword(s):  
Natural Population ◽  
Brassica Rapa ◽  
Trifolium Pratense ◽  
Helix Pomatia ◽  
Active Species ◽  
Species Structure ◽  
Species Protection ◽  
Rate Of Growth ◽  
Second Year Of Life ◽  
Second Year

Abstract The effect of three forms of active species protection in the Roman snail were studied. On the “source plot” the natural population was supported by introducing hatchlings of farmed Roman snails aged 1+, bred from adult specimens of this population. These hatchlings (age 1+) from “source plot” population were also introduced to the following two natural plots: to the “empty plot”, where the population was formed by introduction of farmed Roman snails in the second year of life (1+) into a selected area which had been emptied of the natural population; to the “inhabited plot”, where farmed Roman snails aged 1+, originating from breeding snails of the foreign population from a “source plot”, were introduced to the local natural population. It was established that introducing Roman snails aged 1+ and bred under farm conditions has a clearly positive influence on the age structure of the natural population in the studied plots. The rate of growth of these snails adjusted to the rate of growth of the specimens in the same age group belonging to the natural population. The farmed Roman snails grew most rapidly in the “empty plot” sown with fodder vegetation, more slowly in the “source plot” with access to appropriate herbaceous vegetation, and most slowly in the “inhabited plot”. The attempt to create a naturalized population in a specially adapted “empty plot” without the natural population was successful. This was determined not only by a large number of hiding places from calcareous stones available to the Roman snails but above all by the species structure of the herb flora, which met their nutritional requirements as it contained high proportions of plants such as Brassica rapa × Brassica rapa subsp. chinensis, white clover (Trifolium repens), red clover (Trifolium pratense) and the hybrid of lucerne (Medicago × varia Martyn)

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