Sacculina

Sacculina
Scientific classification
Kingdom: Animalia Phylum: Arthropoda Subphylum: Crustacea Subclass: Cirripedia[?] Family: Sacculinidae[?] Genus: Sacculina
Species
S. atlantica S. bicuspidata S. bourdoni S. carcini S. gerbei S. gibbsi S. gonoplaxae S. inflata Ref: ITIS 89755 (http://www.itis.usda.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=89755) 2002-12-14

Sacculina is a barnacle parasitic on crabs. The adult bears no resemblance to the barnacles that cover ships and piers; it is classified as a barnacle because its larval form resembles one.

The female Sacculina larva finds a crab and walks on it until it finds a joint. It then molts, injecting its soft body into the crab while its shell falls off. The Sacculina grows in the crab, emerging as a bump on the underside of the crab's rear thorax, where the crab's eggs would be incubated.

The male Sacculina looks for a female Sacculina adult on the underside of a crab. He then enters and fertilizes her eggs. The crab cares for the eggs as she would have her own, having been castrated by the parasite.