Blood Concentrations ofLimnoria(Isopoda) in Relation to Salinity

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Abstract
SUMMARY: Freezing-point measurements were made of blood samples taken from specimens of the marine wood-boring isopodLimnoriathat had been exposed to sea water of various salinities for 2-3 days. Most of the work was done withL.(L.)tripunctataMenzies, but some preliminary experiements were carried out withL.(L.)lignorum(Rathke) andL.(L.)quadripunctataHolthuis.It was found that the freezing point of the blood averaged 0·17°C above that of the external of medium in both hyp- and hyperosmotic environments. In the absence of any obvious factor which could explain this discrepancy, it is assumed thatLimnoriahas a certain degree of control over its blood concentrations.Further experiments showed that the blood concentration fell as soon as the animal was introduced to the reduced salinity and levelled off at the hyperosmotic value within a few hours. There was some evidence of a periodicity in the osmoregulation.The possible energetics of osmoregulation inLimnoriaare discussed and it is concluded that the amount of energy utilized in the process is unlikely to make any significant inroad into the energy resources available for boring activity.