Effects of sediment type on burrows of Callianassa californiensis Dana and C. gigas Dana

Two species of thalassinid ghost shrimp, Callianassa californiensis Dana and C. gigas Dana, co-occur at high densities in the sand and mud flats of Bahia de San Quintin, Baja California, Mexico. Polyester resin casts of burrows made in the field reveal a shallow, branched, and voluminous burrow morphology for C. gigas in mud sediments and a deep, less voluminous, and “Y”-shaped burrow for C. californiensis in sand sediments. Laboratory experiments were used to test the hypothesis that sediment type influences burrow size. Larger burrows were created in mud than in sand, and C. gigas created larger burrows than C. californiensis. In contrast to current models of thalassinid burrow morphology which attribute much of the variation in burrow morphology and size to differences in feeding modes, the morphological differences in burrows created by the two species may be responses to environmental factors related to sediment type, in addition to reflecting various feeding patterns.