1. The pleopods of C. californiensis, a potential site for extrabranchial oxygen exchange, do not contribute significantly to oxygen consumption. 2. C. californiensis has a gill surface area of 4.13 +/- 0.72 cm2/g wet body weight, the lowest value yet reported for a totally aquatic crustacean. 3. C. californiensis, when placed in simulated burrow conditions, regulates the PO2 very loosely in its immediate microhabitat, using its pleopods. 4. Field studies of pH and PO2 values in burrows of C. californiensis indicate that animal movement may play a large part in water exchange between the surface and burrow. 5. Activity studies suggest that oxygen is not critical to C. californiensis on a short term basis. Perception of oxygen after long deprivation may signal the possibility of renewed feeding and activity at the surface of its burrow.

A quantitative plankton net sampler with a multicompartment cod-end for use with deep submersible vehicles was developed. This cod-end protects samples from surface temperatures so that deep-sea animals can be recovered alive. The DSV Alvin used it to sample the benthopelagic faunas forms, a group dominated by copepods and larger crustaceans, were more uniformly distributed and ranged from 2.1 to 7.9 mg wet wt m-3. Abundances of Scotoanassa sp., but not the other categories, varied greatly between years and between basins. Scotoanassa sp. had a low oxygen consumption rate of 0.0009 ~1 O2 (mg wet wt)-' h-l; the near-bottom crustaceans had rates similar to those of bathypelagic crustaceans. Total metabolism of the sampled groups was dominated by Scotoanassa sp. and nongelatinous plankton near the bottom with other gelatinous plankton becoming dominant higher. Scotoanassa sp. may be a rapid growing, opportunistic species that can respond reproductively to short-term environmental changes.

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