''Sacculina'' is a genus of

barnacle 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 eros ...

s that is a

parasitic castrator Parasitic castration is the strategy, by a parasite, of blocking reproduction by its host, completely or in part, to its own benefit. This is one of six major strategies within parasitism. Evolutionary strategy The parasitic castration strateg ...

crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...

s. 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 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. The l ...

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%.

Habitat

''Sacculina'' live in a marine environment. During their larval stage they are pelagic, but as they form into adults they live as ectoparasites on crabs. Their primary host is the

green crab ''Carcinus maenas'' is a common littoral crab. It is known by different names around the world. In the British Isles, it is generally referred to as the shore crab, or green shore crab. In North America and South Africa, it bears the name europ ...

, 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 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 digesti ...

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 finds a crab and walks on it until she finds a joint. She then molts into a form called a kentrogon, which then injects her soft body into the crab while her shell 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, 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 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 reproduction, 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 Carcinus maenas, 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 actaeae'' * ''Sacculina aculeata'' Boschma, 1928 * ''Sacculina ales'' Kossmann, 1872 * ''Sacculina americana'' Reinhard, 1955 * ''Sacculina amplituba'' Phillips, 1978 * ''Sacculina anceps'' Boschma, 1931 * ''Sacculina angulata'' * ''Sacculina anomala'' 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'' 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'' 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