Eco-Physiological Studies of An Intertidal Crustacean, Pollicipes Polymerus (Cirripedia, Lepadomorpha)

Abstract

ABSTRACT Physiological responses to environmental stresses of the intertidal cirriped Pollicipes polymerus have been studied by combined field and laboratory experiments. The body temperature of air-exposed animals is always lower than expected from the heat load. Evaporation from the peduncle is responsible for the heat loss. The rate of water loss by evaporation from the peduncle cuticle is 1·5 μ l/cm2 h mmHg both at 21 and 27°C. The transpiration is proportional to the saturation deficit of the air. The water loss from the capitulum is negligible in comparison to that from the peduncle. The haemolymph osmolality of animals in the field increases during exposure to sunshine and decreases during exposure to rain. The increase in haemolymph osmolality during desiccation is equal to that calculated from the decrease in body water. The water loss during air exposure is adequately replaced during submersion, probably by osmosis. Pollicipes is an osmoconformer but is 5–20 m-osmoles hyperosmotic. It tolerates sea-water dilutions down to about 50 %. The hyperosmolality seems to be balanced by a high internal hydrostatic pressure. An excretory activity is observed. The excretion is isosmotic to the haemolymph and is possibly an ultrafiltrate of the latter. The muscle cells show volume regulation, but free amino acids seem to be unimportant in regulation of intracellular osmolality. The concentration of ninhydrinpositive substances in the muscle tissue is about 200 mm for animals in full strength sea water.