Prevalence and phylogeny of parasitic dinoflagellates (genus Blastodinium) infecting copepods in the Gulf of California.

Abstract

Plankton samples collected from Bahía de La Paz, Baja California Sur, Mexico in June 2008 revealed infection of copepods by Blastodinium spp. Of eight copepod genera encountered in the samples, only one (Paracalanus) was parasitized by Blastodinium. Infection prevalence was low, 0.6 % to 2.0 %, withall parasitized individuals being females tentatively identified as Paracalanus parvus. All but one infected host examined during the study was parasitized by Blastodinium crassum, the sole exception being a Paracalanus cf. parvus infected by Blastodinium contortum. A phylogeny constructed using a dataset of ~1.3 Kb sequences of the small subunit ribosomal DNA gene of B. contortum and B. crassum from Bahía de La Paz and 36 other dinoflagellate sequences available in GenBank, including all available for Blastodinium,placed Blastodinium as a monophyletic clade deep within the Dinokaryota. Sequence divergence among B. contortum ex Paracalanus cf. parvus from Bahía de La Paz, B. contortum ex P. parvus from the Mediterranean Sea, B. contortum ex Clausocalanus arcuicornis, B. crassum ex P. cf. parvus from Bahía de La Paz, and B. navicula ex Corycaeus giesbrechti supported separation of the three parasites as distinct species.