FISHERY BULLETIN: VOL. 79, NO. 2 



Figure 7. — A male specimen of Lithodes couesi (a 100 mm bar is included for scale). Generally, L. couesi are bright red with the 

 carapace being somewhat lighter than the legs; however, occasional specimens will be light pink. Great variability was found in the 

 length of the spines along the lateral margins of the carapace. The above specimen has especially long spines. 



those of crabs living on the shelf. The degree of 

 branchial inflation was quantified by Takeshita 

 et al. (1978) for three anomuran crabs in the fam- 

 ily Lithodidae — P. camtschatica, L. aequispina, 

 Paralomis uerrilli — and four brachyuran crabs in 

 the genus Chionoecetes — C. bairdi, C. opilio, C. 

 japonicus , C. tanneri — using moire photography. 

 For both the anomuran and brachyuran crabs, the 

 branchial chambers were more inflated in the 

 species living at greater depths. In the present 

 study, a similar type of assessment was not made 

 for L. couesi due to a lack of suitable photographic 

 equipment; however, the inflation of the branchial 

 chambers appears to be greater than L. aequispina 

 (a shallower species) and less than P. uerrilli (a 

 deeper species). Although I lack data to demon- 

 strate that enlarged gills are associated with 

 inflated branchial chambers, Rathbun (1893), in 

 the original description of C. tanneri (a deep 

 species), remarked that "The carapace is much 

 swollen at the branchial regions" compared with 

 C. opilio (a shallower species) and that the gills of 

 C. tanneri are about two-fifths longer than the 

 gills of an equal-sized specimen of C. opilio. 



The inflation of crab branchial chambers with 

 increasing depth is related to the distribution of 

 oxygen in the sea. Typically, the concentration of 

 dissolved oxygen decreases with depth until an 



oxygen minimum zone is reached, then increases 

 thereafter. In the region of the Gulf of Alaska near 

 the major seamounts, a minimum oxygen concen- 

 tration of 0.5 ml/1, roughly 7% of the surface 

 concentration, occurs at 1,000 m (Favorite et al. 

 1976). Since the combined depth ranges of the 

 species considered by Takeshita et al. (1978) 

 extend from 1,400 m to the inter tidal, the deeper 

 these species occur, the lower the oxygen concen- 

 trations they must deal with. Inflated branchial 

 chambers or unusually large gills have been 

 reported for a brachyuran crab, Lophorochinia 

 parabranchia (Garth and Haig 1971), and a mysid, 

 Gnathophausia ingens (Childress 1971a), both of 

 which are primarily restricted to oxygen mini- 

 mum zones. 



Lithodes couesi has two additional morpholog- 

 ical features allowing respiration in low oxygen 

 concentrations: large exhalent openings and large 

 scaphognathites (appendages located in the ex- 

 halent openings and used for pumping water over 

 the gills). Enlargement of these features, com- 

 pared with related shallow-water lithodid crabs, 

 implies that a relatively greater volume of water 

 is pumped over the gills. Gnathophausia ingens 

 was also found to have a large ventilation volume 

 compared with related shallow-water species 

 (Childress 1971a). 



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