Phenotypic plasticity in the growth of the self-fertilizing hermaphroditic fish Rivulus marmoratus

Temperature, salinity, food ration and interactions among them had significant effects on overall growth of hatchlings of the self-fertilizing hermaphrodite Rivulus marmoratus. Low temperature (19 degrees C) suppressed growth. At 26 degrees C, the treatment groups at 12 and 40 parts per thousand salinity had higher final wet masses than the group at 1 parts per thousand. When provided with high food ration, individuals whose parents were provided with low food had a significantly higher specific growth rate in the first month than those whose parents were provided with high food ration. This effect was also found in the final wet masses. It appears that genetic variation in this species occurs only between strains, yet within a strain there is considerable scope for phenotypic plasticity. The combination of a fixed genotype: and plastic expression, along with a suite of specialized physiological characteristics, may explain how a self-fertilizing hermaphrodite can thrive in such an abiotically stressful and Variable habitat as an estuary. (C) 1999 The Fisheries Society of the British Isles.