Sacculinidae

Sacculinidae is a family of parasitic barnacles within the Rhizocephala, a group of endoparasitic crustaceans that infect mainly decapods such as crabs. Members of this family are obligate parasites of crustaceans and are found in marine environments worldwide.

Rhizocephalan sacculinids have a distinctive life cycle. Free-living larval stages, including nauplius and cypris, seek a crustacean host, attach, and inject tissue that forms an internal network called the interna, which grows through the host’s organs. An external reproductive body, the externa, then develops outside the host, containing the female reproductive system. The externa is connected to the interna by filaments and releases larvae to continue the cycle. The parasite draws nutrients from the host through its rooting system and often suppresses the host’s reproductive capabilities, sometimes altering host behavior to favor the parasite’s transmission.

Taxonomy and identification: Sacculinidae is the best-known family within Rhizocephala; the genus Sacculina is the type genus. The most studied species is Sacculina carcini, a parasite of the European shore crab Carcinus maenas, frequently cited as a classic example of parasitic castration and host manipulation. The family has a cosmopolitan distribution, with species described from temperate to tropical seas and various crustacean hosts.

Ecology and significance: Sacculinidae infections can influence host population dynamics and community structure, and may have implications for fisheries and aquaculture in cases of heavy infestation, though impacts are typically species- and context-specific.