During the INDEMARES/CHICA 0610, 0211 and 0412 expeditions, carried out in the northern Spanish sector of the Gulf of Cádiz, eleven mud volcanoes and their adjacent bottoms were sampled. Chemoautotrophic communities were found in 9 mud volcanoes, with the presence of a rare decapod callianassid, Calliax sp. (related to the Mediterranean infralittoral species C. lobata (De Gaillande and Lagardère 1966)) in three of them. Data on its morphology, biogeographical distribution, vertical distribution within the burrows, sediment composition, pH and redox potential values (each 5 cm intervals) are given. Finally, information on the chemoautotrophic communities associated with this callianassid is provided.