Occurrence of heterosaccus (cirripedia: Rhizocephala) in the new zealand crab metacarcinus novaezelandiae (decapoda: Cancridae) and distribution of other rhizocephala in the south pacific

Abstract

A sacculinid rhizocephalan parasite was recently rediscovered in New Zealand after original recordings from collections in 1931. This new species of Heterosaccus occurred in 93.5 of 1118 Metacarcinus novaezelandiae (Decapoda: Cancridae) collected from Wellington Harbour between May 2006, and March 2007. Of the parasitized crabs, 22.1 had a rhizocephalan externa, 62.7 had a scar, and 15.2 had only the interna. Prevalence of Heterosaccus sp. was similar for male and female crabs and all were castrated. Many of the infected males displayed major morphological changes, which included a wider pleon and extra pairs of biramous pleopods compared to uninfected males (feminisation). Newly emergent externa and externa filled with eggs or embryos were found throughout the year, which indicates a year-round reproductive cycle. However, virgin externae were more common at the beginning of the southern hemisphere summer. A literature survey of Rhizocephala in the South Pacific revealed overall few described species (n 20), records of nine genera, and several reported but unidentified species in new hosts. The South Pacific clearly has a rich rhizocephalan fauna, but little is known about the ecology of these parasites in this part of the world. © The Crustacean Society.