Rhythmic succinate dehydrogenase activity in the slug, Laevicaulis alte (Ferussac, 1821).

Succinate dehydrogenase (SDH) in central nervous system (CNS) and food muscle (FM) crested at 0400 h while in midgut gland (MG) it was out of phase. The average enzyme level (in per cent) was high during dark h half cycle (data points at 2000, 0000 and 0400 h) in CNS and FM and opposition prevailed for MG. Null hypothesis (Ho) was accepted (Ho = A = O) for CNS and rejected (Ho = A not equal to O) for MG and FM. The characteristics of the rhythm in CNS and FM correspond to motor functions, while in MG to energy source.