CYPRID ULTRASTRUCTURE AND ADULT MORPHOLOGY IN PTYCHASCUS BARNWELLI, NEW SPECIES, AND P. GLABER (CIRRIPEDIA: RHIZOCEPHALA), PARASITES ON SEMITERRESTRIAL CRABS

Abstract

ABSTRACT Larval and adult morphology is studied in rhizocephalan parasites of the genus Ptychascus (Sacculinidae) infesting semiterrestrial crabs of the families Ocypodidae and Grapsidae. A parasite population from fiddler crabs (Uca) in Costa Rica represents a new species. Its cyprids have a sensory armament on the antennules that is distinct from that found in cyprids of Ptychascus glaber Boschma, the only previously described member of the genus. It is argued that larval characters will prove useful in rhizocephalan taxonomy. The main adaptations to life on semiterrestrial hosts in the genus Ptychascus are the lack of nauplii and the male cyprid's ability to settle and metamorphose almost immediately after release from the parasite. This abbreviated development probably ensures that the larvae can settle before being carried away from the habitat of the host crabs. Cyprid morphology is similar to that found in other sacculinid rhizocephalans. Furthermore, a TEM study shows that male cyprids metamorphose into a spine-covered trichogon as in other members of the Sacculinidae. It therefore seems that most features of the typical sacculinid life cycle are maintained.