OSMOREGULATORY CAPACITIES OF CALLIANASSA AND UPOGEBIA (CRUSTACEA: THALASSINIDEA)

¹ Department of Zoology, University of California, Berkeley, California
² Department of Zoology, Oregon State University, Corvallis, Oregon

1. Callianassa californiensis and Upogebia pugettensis (Crustacea: Thalassinidea) have been studied with respect to their osmoregulatory capacities and selected aspects of their natural history. Upogebia affinis and Callianassa filholi have been studied with respect to their osmoregulatory capacities.

2. Upogebia pugettensis has a discrete, open and durable burrow system and is distributed further up the Yaquina estuary than is C. californiensis, which is without such a burrow system.

3. Resident species of thalassinids are exposed to brackish conditions in the winter and spring at Yaquina Bay.

4. The lower lethal salinity limit for U. pugettensis and U. affinis is approximately 10% SW; that for C. californiensis is 25%-30% SW; that for C. filholi is probably 35%-40% SW.

5. U. pugettensis and U. affinis are strong hyper-osmotic regulators below 75% SW. In full strength SW, U. pugettensis and U. affinis are iso-osmotic, and the former species conforms osmotically in 125% SW. In U. pugettensis the ions of Na⁺, K⁺, and Ca⁺⁺ are comparably regulated, while Cl^- is probably hypo-regulated in the higher salinities.

6. Callianassa californiensis conforms osmotically in the range 30%-125% SW. The ions of Cl^-, Na⁺, K⁺, and Ca⁺⁺ are relatively poorly regulated. Preliminary findings indicate that C. filholi conforms osmotically in the range 40%-100% SW.

7. The urine of C. californiensis and U. pugettensis is iso-osmotic to the blood.

8. The genera Callianassa and Upogebia are considered to be euryhaline, but the euryhalinity of the former is more limited.

9. The osmoregulatory capacities of Upogebia are considered adaptive to osmotic emergencies which arise, in part, from dependence upon an open burrow system; the osmolability and interstitial habits of Callianassa are an alternate adaptive response to its estuarine environment.

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