Comparative gill characteristics of Munida quadrispina (Decapoda, Galatheidae) from different habitat oxygen conditions

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Abstract
The allometric (bilogarithmic) relationship between dry gill weight and organic body weight was compared for benthic galatheid crabs (Munida quadrispina Benedict, 1902) from a low-oxygen fjord and from a normal oxygen population. In the M. quadrispina from the low-oxygen fjord, the slope (b) of the allometric function of gill weight versus body weight was 1.00. This b value was significantly higher (ANCOVA, p < 0.01) than the corresponding slope for the same function in M. quadrispina from normoxic areas (b = 0.63). However, only the largest crabs from the low-oxygen fjord were living consistently in low-oxygen (< 0.15 mL/L) conditions; they also had significantly greater (twice as much) relative gill weight than their normoxic counterparts. This observation agrees with findings from previous studies that only the largest M. quadrispina are able to tolerate severe oxygen depletion. Small M. quadrispina from both the low-oxygen fjord and the normoxic area were always found in oxygen concentrations > 2.0 mL/L. There were no significant differences the relative gill sizes of the small crabs from different areas. It was concluded that gill development in M. quadrispina is affected by long-term habitat oxygen conditions. This factor could be important in comparison of inter- and intra-specific allometric gill functions and in the study of weight-specific oxygen consumption rates of decapod crustaceans.