Larval energy metabolism and physiological variability in the Asian shore crab Hemigrapsus sanguineus

Abstract

Larvae of the Asian shore crab Hemigrapsus sanguineus were reared in the laboratory during zoeal devel- opment (Stages I to V, ~15 d at 25°C and 30 ‰ S). Measure- ments of respiration rates, lactate dehydrogenase activity (LDH) and total protein content were made daily on indivi- dual larvae (n = 181) in order to assess the level of individual variance in energy metabolism during development. On aver- age, zoeal development in H. sanguineus was estimated to require 43.8 J of metabolic energy to reach a megalope stage; however, the level of individual variance in metabolic rates resulted in a range of 23.8 to 67.9 J (~3-fold difference). LDH specific activities also evidenced a wide range in individual values during development (12 to 785 µU µg -1 protein). Although respiration rates were correlated with LDH specific activity (r 2 = 0.628), it is more interesting to note the negative correlation between the variance in these measurements (r 2 = 0.796), indicating a substantial degree of individual differences in metabolic activities among these larvae. At present, phenotypic variations in physiological rate processes are not considered in life-history models of larval develop- ment, which could be an important variable determining the survival and dispersal of a larval cohort.