Direct evidence of parasitism by Copidognathus stevcici (Acari, Halacaridae) in crabs Maja squinadoand M. brachydactyla (Brachyura, Majidae) in the laboratory.

Marine mites belonging to the family Halacaridae were found associated with adult females of the spider crabs Maja brachydactyla Balss, 1922 and M. squinado (Herbst, 1788) held under laboratory conditions. Morphological study of collected samples identified the mites as Copidognathus stevcici Bartsch, 1976. C. stevcici was found on pleopods of ovigerous and post-ovigerous females in both crab species, with an intensity ranging from 10 to 326 mites per host. Mites were observed alive on their host for extended periods and direct evidence of feeding on crab's eggs is provided. The COI mtDNA sequence of these mites is reported as an addendum to the species description.