Sacculina is a genus of barnacles that is a parasitic castrator of crabs. They belong to a group called Rhizocephala. The adults bear no resemblance to the barnacles that cover ships and piers; they are recognised as barnacles because their larval forms are like other members of the barnacle class Cirripedia. The prevalence of this crustacean parasite in its crab host can be as high as 50%.
Barnacles are a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and are hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile (nonmobile) and most are suspension feeders, but those in infraclass Rhizocephala are highly specialized parasites on crustaceans. They have four nektonic larval stages. Around 1,000 barnacle species are currently known. The name Cirripedia is Latin, meaning "curl-footed". The study of barnacles is called cirripedology.
Rhizocephala are derived barnacles that parasitise mostly decapod crustaceans, but can also infest Peracarida, mantis shrimps and thoracican barnacles, and are found from the deep ocean to freshwater. Together with their sister groups Thoracica and Acrothoracica, they make up the subclass Cirripedia. Their body plan is uniquely reduced in an extreme adaptation to their parasitic lifestyle, and makes their relationship to other barnacles unrecognisable in the adult form. The name Rhizocephala derives from the Ancient Greek roots ῥίζα and κεφαλή, describing the adult female, which mostly consists of a network of thread-like extensions penetrating the body of the host.
Cancer pagurus, commonly known as the edible crab or brown crab, is a species of crab found in the North Sea, North Atlantic Ocean, and perhaps the Mediterranean Sea. It is a robust crab of a reddish-brown colour, having an oval carapace with a characteristic "pie crust" edge and black tips to the claws. A mature adult may have a carapace width up to 25 centimetres and weigh up to 3 kilograms. C. pagurus is a nocturnal predator, targeting a range of molluscs and crustaceans. It is the subject of the largest crab fishery in Western Europe, centred on the coasts of the British Isles, with more than 60,000 tonnes caught annually.
Pagurus longicarpus, the long-wristed hermit crab, is a common hermit crab found along the Atlantic and Gulf coasts of the United States and the Atlantic coast of Canada.
Diogenes pugilator is a species of hermit crab, sometimes called the small hermit crab or south-claw hermit crab. It is found from the coast of Angola to as far north as the North Sea, and eastwards through the Mediterranean Sea, Black Sea and Red Sea. Populations of D. pugilator may be kept in check by the predatory crab Liocarcinus depurator.
Amphibalanus improvisus, the bay barnacle, European acorn barnacle, is a species of acorn barnacle in the family Balanidae.
Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The larvae of crustaceans often bear little resemblance to the adult, and there are still cases where it is not known what larvae will grow into what adults. This is especially true of crustaceans which live as benthic adults, more-so than where the larvae are planktonic, and thereby easily caught.
Hemioniscus balani, a species of isopod crustacean, is a widespread parasitic castrator of barnacle in the northern Atlantic Ocean. Its range extends from Norway to the Atlantic coast of France, and as far west as Massachusetts. It is also commonly found on the Pacific coast of North America; it is not known if the Pacific and Atlantic populations are the same species, or if the Pacific population exists following human-assisted introduction.
Pollicipes polymerus, commonly known as the gooseneck barnacle or leaf barnacle, is a species of stalked barnacle. It is found, often in great numbers, on rocky shores on the Pacific coasts of North America.
Pleurobrachia pileus is a species of comb jelly, commonly known as a sea gooseberry. It is found in open water in the northern Atlantic Ocean, the North Sea, the Baltic Sea and the Black Sea, and was first described by the Danish zoologist Otto Friedrich Müller in 1776.
Heterosaccus is a genus of barnacles in infraclass Rhizocephala. Like other taxa in this group, they parasitize crabs. Geoffroy Smith circumscribed the genus in 1906; he initially only included H. hians. Smith circumscribed a genus distinct from Sacculina due to a difference of the mesentery; in Heterosaccus, the mesentery does not stretch down to the mantle opening but rather only is present on the ring of attachment.
Sylon hippolytes is a castrating parasite that infects the shrimp Pandalina brevirostris.
Loxothylacus panopaei is a species of barnacle in the family Sacculinidae. It is native to the Gulf of Mexico and the Caribbean Sea. It is a parasitic castrator of small mud crabs in the family Panopeidae, mostly in the Gulf of Mexico, the Caribbean Sea and the eastern Atlantic Ocean.
Panopeus lacustris, the knot-fingered mud crab, is a true crab belonging to the infraorder Brachyura. It can be distinguished from related species by its exceptionally broad and knobbly main chela (claw).
Sacculina carcini, the crab hacker barnacle, is a species of parasitic barnacle in the family Sacculinidae, in particular a parasitic castrator, of crabs. The crab that most often is used as a host is the green crab, the natural range of which is the coasts of Western Europe and North Africa. It can be found attached to the crab's abdomen and affect consumption rates by humans.
Pagurus forbesii is a species of hermit crab in the family Paguridae. It is found in the northeastern Atlantic Ocean and the Mediterranean Sea.
Pagurus acadianus, the Acadian hermit crab, is a species of hermit crab in the family Paguridae. It is found in Western Atlantic Ocean.
Pagurus dalli, commonly known as the whiteknee hermit, is a species of hermit crab in the family Paguridae. It is found in the northeastern Pacific Ocean at depths down to about 276 m (900 ft). It usually lives in a mutualistic symbiosis with a sponge, or sometimes a hydroid.
Clistosaccidae is a family of parasitic barnacles belonging to the bizarre and highly apomorphic infraclass Rhizocephala, which is part of the barnacle subclass Cirripedia.
