Pioneer Life of the Tadpole Shrimps, Triops Spp. (Notostraca : Triopsidae)

Abstract

Tadpole shrimps (Triops spp.) are aquatic animals which appear in paddy fields a few days after the flooding and ploughing. Their growth, oviposition, hatching of eggs, and the environmental conditions which stimulate egg hatching were analyzed especially in T. granarius and T. longicaudatus to test the hypothesis that tadpole shrimps are pioneer animals in a temporary water pool.Many eggs hatched soon after submergence and developed rapidly to maturity. The shrimps began oviposition on the 10th day after submergence, while still growing in body size, and deposited many eggs in the soil during their short life span. The eggs hatched very heterogeneously and intermittently, and many eggs remained in the dormant state for a long period under constant water temperature. Desiccation of eggs was effective to promote subsequent hatching, and the rate of hatching fluctuated with the length of desiccation period. Total hatching was not achieved, however, even by repeated treatments of desiccation and submergence. Hatching of eggs was sensitive to light. These ecological characteristics are considered to be highly adaptive to an irregularly disturbed aquatic habitat.