NATURAL HISTORY AND POPULATION DYNAMICS OF THE LAND SNAIL HELIX TEXTA IN ISRAEL (PULMONATA: HELICIDAE)

1990 ◽  
Vol 56 (2) ◽  
pp. 189-204 ◽  
Author(s):  
JOSEPH HELLER ◽  
HAYA ITTIEL
Keyword(s):  
Population Dynamics ◽  
Natural History ◽  
Land Snail

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.

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.

scholarly journals Natural history, population dynamics, and habitat use of humpback whales over 30 years on an Alaska feeding ground

Ecosphere ◽  
2017 ◽  
Vol 8 (1) ◽  
pp. e01641 ◽  
Author(s):  
Christine M. Gabriele ◽  
Janet L. Neilson ◽  
Janice M. Straley ◽  
C. Scott Baker ◽  
Jennifer A. Cedarleaf ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Natural History ◽  
Habitat Use ◽  
Humpback Whales ◽  
Feeding Ground

scholarly journals The influence of diet and isolation on growth and survival in the land snail Bulimulus tenuissimus (Mollusca: Bulimulidae) in laboratory

2008 ◽  
Vol 25 (2) ◽  
pp. 224-227 ◽  
Author(s):  
Liliane M. O. Meireles ◽  
Lidiane C. Silva ◽  
Flávia O. Junqueira ◽  
Elisabeth C. A. Bessa
Keyword(s):  
Population Dynamics ◽  
Mortality Rate ◽  
Growth Rates ◽  
Land Snail ◽  
Land Snails ◽  
Laboratory Animals ◽  
Mixed Diet ◽  
Growth And Survival ◽  
Different Types

Feed influences directly growth and survival in land snails. Here, we investigate the influence of diet and isolation on growth and survival in Bulimulus tenuissimus (d'Orbigny, 1835) in the laboratory. Animals were maintained individually and in groups and three different types of diets: lettuce, ration and both lettuce and ration (mixed diet) for 210 days. Isolated animals, in all diet types, grew more rapidly than grouped animals. Also, snails fed with lettuce grew most slowly in isolated or grouped treatments. Within isolated or grouped treatments, growth rates were similar for the ration and the mixed diet. Mortality rate was higher in animals fed on lettuce only, in both density treatments. Thus, diet and density are important components of the population dynamics of B. tenuissimus.

scholarly journals Population dynamics of two troglobitic Troglorhopalurus (Scorpiones: Buthidae) scorpions from Brazil

2018 ◽  
Vol 1 ◽  
Author(s):  
Jonas Gallão ◽  
Maria Elina Bichuette
Keyword(s):  
Population Dynamics ◽  
Natural History ◽  
Reproductive Biology ◽  
Reproductive Period ◽  
Conservation Strategies ◽  
Population Estimates ◽  
Chapada Diamantina ◽  
Ecological Aspects ◽  
History Of

Population dynamics studies raise relevant data to understanding ecological aspects and natural history of species as well as better conservation strategies. Using two scorpions species, Troglorhopalurus translucidus Lourenço, Baptista & Giupponi, 2004 and Troglorhopalurus lacrau (Lourenço & Pinto-da-Rocha, 1997) from Chapada Diamantina, Bahia state, Brazil, we estimate populacional parameters through mark and recapture methodology, and Jolly-Seber estimator. In addition, data on both species as sexual ratio, reproductive biology, growth, longevity, feeding habitats, and seasonality were analyzed in the caves and afterwards compared to other scorpion species as well as other arachnids. We captured and marked 82 specimens of T. translucidus and 65 specimens of T. lacrau. Population estimates were 361 ± 199 individuals to T. translucidus and 333 ± 252 to T. lacrau. Population estimates were considered high for the troglobitic scorpions when compared to subterranean arachnids or even with epigean species of scorpions. Both troglobitic scorpions featured remarkable differences in relation to epigean scorpions as higher longevity, longer reproductive period, slower growth. Besides T. translucidus showed marked seasonality with populational variations in rainy seasons in contrast to T. lacrau with populational stability. Suppl. material 1

scholarly journals Inferring microevolution from museum collections and resampling: lessons learned from Cepaea

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3938 ◽  
Author(s):  
Małgorzata Ożgo ◽  
Thor-Seng Liew ◽  
Nicole B. Webster ◽  
Menno Schilthuizen
Keyword(s):  
Natural History ◽  
Common Species ◽  
Land Snail ◽  
Lessons Learned ◽  
General Direction ◽  
Cepaea Nemoralis ◽  
Natural History Collections ◽  
Evolutionary Changes ◽  
Long Term Trends

Natural history collections are an important and largely untapped source of long-term data on evolutionary changes in wild populations. Here, we utilize three large geo-referenced sets of samples of the common European land-snail Cepaea nemoralis stored in the collection of Naturalis Biodiversity Center in Leiden, the Netherlands. Resampling of these populations allowed us to gain insight into changes occurring over 95, 69, and 50 years. Cepaea nemoralis is polymorphic for the colour and banding of the shell; the mode of inheritance of these patterns is known, and the polymorphism is under both thermal and predatory selection. At two sites the general direction of changes was towards lighter shells (yellow and less heavily banded), which is consistent with predictions based on on-going climatic change. At one site no directional changes were detected. At all sites there were significant shifts in morph frequencies between years, and our study contributes to the recognition that short-term changes in the states of populations often exceed long-term trends. Our interpretation was limited by the few time points available in the studied collections. We therefore stress the need for natural history collections to routinely collect large samples of common species, to allow much more reliable hind-casting of evolutionary responses to environmental change.

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