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

Abstract

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.