The distribution, respiration and gills of a low oxygen tolerant crab, Munida quadrispina (Benedict, 1902) (Galatheidae, Decapoda) in an intermittently anoxic fjord
Date
1983
Authors
Burd, Brenda Jean
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Aspects of the ecology of the galatheid crab Munida quadrispina were examined as part of an overall study of the cliff community in Saanich Inlet, an oxygen depleted fjord. Using submersible and trap sampling, distributions of M. quadrispina were measured in Saanich and two other B.C. fjords. Respiration and gill measurements were made to examine possible low oxygen adaptations, and to compare with field information.
In Saanich, crabs were tolerant of oxygen levels ≥O.l to O.15 ml/1, where population density was always highest. Density distributions and total population estimates suggest that epibenthic crabs remained within these limits by vertical migration. Carapace length of adults increased significantly (p = 0.01) with decreasing oxygen, such that only the largest animals were present at limiting oxygen levels. This size gradient was not significantly different (ANCOVA p = 0. 01) from that predicted by the relationship of carapace length and critical oxygen level (Pc) from respiration experiments, indicating that the size gradient was based on metabolism (rate of oxygen consumption). In large crabs from oxygen poor areas of Saanich, gill weight increased exponentially with body weight. However, gill weight increased linearly in M. quadrispina from other areas, and in M. gregaria. M. quadrispina from Saanich Inlet had a greater percent gill weight in low oxygen areas than in high oxygen areas, indicating that a cause and effect relationship exists between gill size and habitat oxygen.