''Loxothylacus panopaei'' is a species 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 ...

in the family

Sacculinidae The Sacculinidae are a family of barnacles belonging to the bizarre parasitic and highly apomorphic infraclass In biological classification, class ( la, classis) is a taxonomic rank, as well as a taxonomic unit, a taxon, in that rank. It i ...

. It is native to the Gulf of Mexico and the Caribbean Sea. It 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 ...

of small mud crabs in the family Panopeidae, mostly in the Gulf of Mexico, the Caribbean Sea and the eastern Atlantic Ocean.

Taxonomy

''L. panopaei'' was first described by the American zoologist Charles F. Gissler in 1884; it was parasitizing the mud crab '' Panopeus lacustris'' and was collected at Tampa, Florida. The barnacle infects a number of species of mud crab and it seems likely that it is a species complex. Further taxonomic studies should clarify the position.

Description

The parasitic adult ''L. panopaei'' consists of an externa, a yellowish-orange mass of soft tissue, attached by a stalk to a host crab's abdomen; the stalk branches internally into tubes which surround the crab's gut.

Distribution

''L. panopaei'' is native to the Gulf of Mexico, the Caribbean Sea, the Atlantic coasts from

Cape Canaveral , image = cape canaveral.jpg , image_size = 300 , caption = View of Cape Canaveral from space in 1991 , map = Florida#USA , map_width = 300 , type =Cape , map_caption = Location in Florida , location ...

to Florida and those of Venezuela. It has increased its range northward, being found for the first time in Chesapeake Bay in 1964. It arrived in the bay because many oysters there were infected by ''

Haplosporidium nelsoni ''Haplosporidium nelsoni'' is a pathogen of oysters that originally caused oyster populations to experience high mortality rates in the 1950s, and still is quite prevalent today. The disease caused by ''H. nelsoni'' is also known as MSX (multinuc ...

'' and stocks were replenished by importing eastern oysters (''Crassostrea virginica'') from the Gulf of Mexico. Accompanying these oysters were some crabs ''

Eurypanopeus depressus ''Eurypanopeus depressus'', the flatback mud crab or depressed mud crab, is a true crab belonging to the infraorder Brachyura and the family Panopeidae. It is native to the western Atlantic Ocean and is often found in estuaries and lagoons, c ...

'' which were parasitized by ''L. panopaei'', the parasitic barnacle thus was inadvertently introduced to Chesapeake Bay where it found new species of crab to infect.

Ecology

The adult barnacle bears no resemblance to an acorn barnacle but the larval development is typical of a barnacle, with four nauplius larval stages and one cyprid larval stage. The female cyprid larva of ''L. panopaei'' has a spear-like stylet. When it settles on a suitable crab host, it pierces the

carapace A carapace is a Dorsum (biology), dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tor ...

and develops underneath as an endoparasite for about a month. It then extrudes an externa, or brood sac, beneath the crab's abdomen. This is fertilised by a free-swimming male cyprid larva. When the eggs in the brood sac have matured, the sac releases several thousand nauplius larvae at intervals. Female crabs care for their eggs by carrying them beneath their abdomen, keeping them well aerated and protecting them. ''L. panopaei'' manipulates the behaviour of both sexes of the crab on which it settles, so that the host treats the barnacle's brood sac as if it contained the crab's own eggs. In the case of male crabs, the parasite causes the ventral abdominal plate to widen, which makes it more suitable for brooding, and alters the crab's behaviour so that it looks after the brood sac, despite this not being a normal behaviour for a male crab. Reproduction is completely suppressed in both male and female crabs which are effectively castrated. The barnacle seems able to take control of the timing of the crab's moult, extruding its brood sac immediately after

ecdysis Ecdysis is the moulting of the cuticle in many invertebrates of the clade Ecdysozoa. Since the cuticle of these animals typically forms a largely inelastic exoskeleton, it is shed during growth and a new, larger covering is formed. The remna ...

, when the crab's shell is soft. Suitable host crabs include the flatback mud crab (''Eurypanopeus depressus''), the Say's mud crab (''Dyspanopeus sayi''), the knotfinger mud crab (''Panopeus lacustris''), P. obessus, the furrowed mud crab (''P. occidentalis''), the oystershell mud crab (''P. simpsoni''), the Harris mud crab (

Rhithropanopeus harrisii ''Rhithropanopeus harrisii'' ( common names include the Zuiderzee crab, dwarf crab, estuarine mud crab, Harris mud crab, white-fingered mud crab, and white-tipped mud crab), is a small omnivorous crab native to Atlantic coasts of the Americas, ...

), '' Tetraplax quadridentata'', and the inflated mud crab (''Tetraxanthus rathbunae''), all found in the western Atlantic Ocean, as well as the black-clawed crab (''Lophopanopeus bellus'') which is found in the eastern Pacific Ocean.

Notes

References

External links

* {{Taxonbar, from=Q7845976 Barnacles Parasitic crustaceans Crustaceans described in 1884 Endoparasites