''Sacculina'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of barnacles that is a parasitic castrator of crabs. They belong to a group called ''

Rhizocephala 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 Thoracic ...

''. 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 Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differentl ...

Cirripedia A barnacle is a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosiv ...

. The prevalence of this crustacean parasite in its crab host can be as high as 50%.

Habitat

''Sacculina'' live in a marine environment. During their larval stage they are pelagic, but as they form into adults they live as

ectoparasites Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

on crabs. Their primary host is the green crab, which is native to the Eastern Atlantic Ocean. Though these crabs have spread to other bodies of waters, it is not believed that ''Sacculina'' barnacles have traveled with them to these new localities.

Anatomy

The body of the adult parasite can be divided into two parts: one part is called the "externa" where the bulbous reproductive organ of the parasite sticks out of the abdomen of the host. The other part is called the "interna" which is inside the host's body. This part is composed of root-like tendrils that wrap themselves around the host's organs, which gives its group name of Rhizocephala, meaning "root-head". Through

microCT X-ray microtomography, like tomography and X-ray computed tomography, uses X-rays to create cross-sections of a physical object that can be used to recreate a virtual model ( 3D model) without destroying the original object. The prefix ''micro- ...

scans, these roots have been discovered to wrap around certain organs of the body, with most around the

hepatopancreas The hepatopancreas, digestive gland or midgut gland is an organ of the digestive tract of arthropods and molluscs. It provides the functions which in mammals are provided separately by the liver and pancreas, including the production of digestive ...

of crustaceans. This area is primarily for absorbing nutrients, which would explain why most concentrate in that region. In a similar species called ''Briarosaccus'' roots were seen extending to the brain and central nervous system, which could help explain how parasites like these can manipulate their hosts' behavior.

Life cycle

The female ''Sacculina''

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. ...

finds a crab and walks on it until she finds a joint. She then

molt In biology, moulting (British English), or molting (American English), also known as sloughing, shedding, or in many invertebrates, ecdysis, is the manner in which an animal routinely casts off a part of its body (often, but not always, an outer ...

s into a form called a kentrogon, which then injects her soft body into the crab while her

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses ** Thin-shell structure Science Biology * Seashell, a hard o ...

falls off. The ''Sacculina'' grows in the crab, emerging as a sac, known as an ''externa'', on the underside of the crab's rear

thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...

, where the crab's

egg An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell (a zygote) and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the a ...

s would be incubated. Parasitic ''Sacculina'' destroy a crab's genitalia, rendering the crab permanently infertile. After this invasion of the ''Sacculina'', the crab is unable to perform the normal function of molting. This results in a loss of nutrition for the crab, and impairs its overall growth. The natural ability of regrowing a severed

claw A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or tarsus ...

that is commonly used for defense purposes is therefore lost after the infestation of ''Sacculina''. The male ''Sacculina'' 'larva' looks for a female ''Sacculina'' on the underside of a crab. He then implants his cells into a pocket in the female's body called the "testis", where the male cells then produce spermatozoa to fertilize eggs. When a female ''Sacculina'' is implanted in a male crab, it interferes with the crab's hormonal balance. This sterilizes it and changes the bodily layout of the crab to resemble that of a female crab by widening and flattening its abdomen, among other things. The female ''Sacculina'' then forces the crab's body to release hormones, causing it to act like a female crab, even to the point of performing female mating dances. If the parasite is removed from the host, female crabs will normally regenerate new ovarian tissue, while males usually develop complete or partial ovaries instead of testes. Although all energy otherwise expended on reproduction is directed to the ''Sacculina'', the crab develops a nurturing behavior typical of a normal female crab. The natural hatching process of a crab consists of the female finding a high rock and grooming its brood pouch on its abdomen and releasing the fertilized eggs in the water through a bobbing motion. The female crab stirs the water with her claw to aid the flow of the water. When the hatching larvae of ''Sacculina'' are ready to emerge from the brood pouch of female ''Sacculina'', the crab performs a similar process. The crab shoots them out in pulses, creating a large cloud of ''Sacculina'' larvae. The crab uses the familiar technique of stirring the water to aid in flow.

Life span

''Sacculina'' are primarily host dependent so their life span matches that of their hosts. Crabs usually have a life span anywhere from 1 to 2 years.

Biological control agents

''Sacculina'' has been suggested to be used as a type of biological control agent to help reduce the populations of the invasive green crab. This is controversial because ''Sacculina'' can also use native crab species as their host.

Species

More than 100 species of ''Sacculina'' are currently recognised: * ''

Sacculina abyssicola ''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 ...

'' * '' Sacculina actaeae'' * ''

Sacculina aculeata ''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 ...

'' Boschma, 1928 * ''

Sacculina ales ''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 ...

'' Kossmann, 1872 * ''

Sacculina americana ''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 ...

'' Reinhard, 1955 * ''

Sacculina amplituba ''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 ...

'' Phillips, 1978 * ''

Sacculina anceps ''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 ...

'' Boschma, 1931 * ''

Sacculina angulata ''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 ...

'' * ''

Sacculina anomala ''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 ...

'' Boschma, 1933 * '' Sacculina atlantica'' Boschma, 1927 * '' Sacculina beauforti'' Boschma, 1949 * '' Sacculina bicuspidata'' Boschma, 1931 * '' Sacculina bipunctata'' Kossmann, 1872 * '' Sacculina boschmai'' Reinhard, 1955 * '' Sacculina bourdoni'' Boschma, 1960 * '' Sacculina brevispina'' * '' Sacculina bucculenta'' Boschma, 1933 * '' Sacculina bursapastoris'' Kossmann, 1872 * '' Sacculina caelata'' Boschma, 1931 * '' Sacculina calappae'' * '' Sacculina calva'' Boschma, 1933 * '' Sacculina captiva'' Kossmann, 1872 * ''

Sacculina carcini ''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 w ...

'' Thompson, 1836 * '' Sacculina carpiliae'' * '' Sacculina cartieri'' Kossmann, 1872 * '' Sacculina cavolinii'' Kossmann, 1872 * '' Sacculina comosa'' Boschma, 1931 * '' Sacculina compressa'' Boschma, 1931 * '' Sacculina confragosa'' Boschma, 1933 * '' Sacculina cordata'' Shiino, 1943 * '' Sacculina crucifera'' Kossmann, 1872 * '' Sacculina curvata'' Boschma, 1933 * '' Sacculina cuspidata'' Boschma, 1949 * '' Sacculina dayi'' Boschma, 1958 * '' Sacculina dentata'' Kossmann, 1872 * '' Sacculina docleae'' Huang & Lützen, 1998 * '' Sacculina duracina'' Boschma, 1933 * '' Sacculina echinulata'' * '' Sacculina elongata'' Boschma, 1933 * '' Sacculina eriphiae'' Smith, 1906 * '' Sacculina exarcuata'' Kossmann, 1872 * '' Sacculina fabacea'' Shiino, 1943 * '' Sacculina flacca'' Boschma, 1931 * '' Sacculina flexuosa'' Kossmann, 1872 * '' Sacculina gerbei'' * '' Sacculina ghanensis'' Boschma, 1971 * '' Sacculina gibba'' Boschma, 1933 * '' Sacculina glabra'' * '' Sacculina globularis'' Boschma, 1970 * '' Sacculina gonoplaxae'' * '' Sacculina gordonae'' Boschma, 1933 * '' Sacculina gracilis'' Boschma, 1931 * ''

Sacculina granifera ''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 t ...

'' Boschma, 1973 * '' Sacculina granulosa'' Boschma, 1931 * '' Sacculina guineensis'' Boschma, 1971 * '' Sacculina hartnolli'' Boschma, 1965 * '' Sacculina herbstianodosa'' (Hesse, 1867) * '' Sacculina hirsuta'' Boschma, 1925 * '' Sacculina hirta'' Boschma, 1933 * '' Sacculina hispida'' Boschma, 1928 * '' Sacculina holthuisi'' Boschma, 1956 * '' Sacculina hystrix'' * '' Sacculina ignorata'' Boschma, 1947 * '' Sacculina imberbis'' Shiino, 1943 * '' Sacculina inconstans'' Boschma, 1952 * '' Sacculina infirma'' Boschma, 1953 * '' Sacculina inflata'' Leuckart, 1859 * '' Sacculina insueta'' Boschma, 1966 * '' Sacculina irrorata'' Boschma, 1934 * '' Sacculina jamaicensis'' Boschma, 1966 * '' Sacculina lata'' Boschma, 1933 * '' Sacculina leopoldi'' Boschma, 1931 * '' Sacculina leptothrix'' Boschma, 1933 * '' Sacculina lobata'' Boschma, 1965 * '' Sacculina loricata'' * '' Sacculina margaritifera'' Kossmann, 1872 * '' Sacculina micracantha'' Boschma, 1931 * '' Sacculina microthrix'' Boschma, 1931 * '' Sacculina muricata'' Boschma, 1931 * '' Sacculina nectocarcini'' * '' Sacculina nigra'' Shiino, 1943 * '' Sacculina nodosa'' Boschma, 1931 * '' Sacculina ornatula'' Boschma, 1951 * '' Sacculina ostracotheris'' Boschma, 1967 * '' Sacculina papposa'' * '' Sacculina pertenuis'' Boschma, 1933 * '' Sacculina phacelothrix'' Boschma, 1931 * '' Sacculina pilosa'' Kossmann, 1872 * '' Sacculina pilosella'' * '' Sacculina pinnotherae'' Shiino, 1943 * '' Sacculina pisiformis'' Kossmann, 1872 * '' Sacculina pistillata'' Boschma, 1952 * '' Sacculina pomum'' Kossmann, 1872 * '' Sacculina pugettiae'' Shiino, 1943 * '' Sacculina pulchella'' Boschma, 1933 * '' Sacculina punctata'' Boschma, 1934 * '' Sacculina pustulata'' Boschma, 1925 * '' Sacculina quadrialata'' Boyko & van der Meij, 2018 * '' Sacculina rathbunae'' Boschma, 1933 * '' Sacculina reinhardi'' * '' Sacculina reniformis'' Boschma, 1933 * '' Sacculina robusta'' Boschma, 1948 * '' Sacculina rotundata'' Miers, 1880 * '' Sacculina rugosa'' * '' Sacculina scabra'' Boschma, 1931 * '' Sacculina schmitti'' Boschma, 1933 * '' Sacculina scutigera'' Huang & Lützen, 1998 * '' Sacculina semistriata'' * '' Sacculina senta'' Boschma, 1933 * '' Sacculina serenei'' Boschma, 1954 * '' Sacculina setosa'' * '' Sacculina spectabilis'' Boschma, 1948 * '' Sacculina spinosa'' * '' Sacculina striata'' Boschma, 1931 * '' Sacculina sulcata'' * '' Sacculina surinamensis'' Boschma, 1966 * '' Sacculina teres'' Boschma, 1933 * '' Sacculina teretiuscula'' Boschma, 1931 * '' Sacculina ternatensis'' Boschma, 1950 * '' Sacculina upogebiae'' Shiino, 1943 * '' Sacculina vankampeni'' Boschma, 1931 * '' Sacculina verrucosa'' * '' Sacculina vieta'' Boschma, 1933 * '' Sacculina weberi'' Boschma, 1931 * '' Sacculina zariquieyi'' Boschma, 1947

References

Sources

* *: (cites many earlier papers by Boschma and others including other sources for the above list) * * *

External links

* {{Taxonbar, from=Q150610 Barnacles Parasitic crustaceans Parasites of crustaceans Mind-altering parasites Crustacean genera