Influence of egg cannibalism on growth, survival and feeding in hatchlings of the land snail Helix aspersa Muller (gastropoda, pulmonata, stylommatophora)

Under controlled conditions, growth, survivorship and several nutritional parameters (ingestion, egestion and assimilation) were measured weekly in hatchlings that either ate a conspecific egg after birth (cannibalistic) or not (non-cannibalistic) and in food-deprived individuals (control group). Subsequently, the snails were fed on Taraxacum officinale. After 4 days, cannibalistic snails were 1.3 times heavier than food-deprived snails and 100% survived (75.8% in the control group and 40% of the non-cannibalistic individuals). Mortality, particularly in smaller snails, might be a consequence of food deprivation. Nutritional and energetic gains of oophagy increased both future survivorship and growth. After 11 weeks, cannibalistic snails were 1.4 times heavier and had higher survival rates than food-deprived ones although ingestion, egestion rates and assimilation efficiency were similar in both groups. The larger wet weight of cannibalistic snails after 4 days induced a higher food consumption and thus a higher growth rate. The influence of oophagy on life-history traits is discussed in relation to costs and benefits.