Hemioniscus balani
Encyclopedia
Hemioniscus balani is a species
of isopod
crustacean
that is a widespread parasitic castrator
of barnacles in the north Atlantic Ocean
. Its range
extends from Norway
to the Atlantic coast of France
, and as far west as Massachusetts
.
adults of several species of barnacles, including Semibalanus balanoides
, Chthamalus fissus, Chthamalus dalli, and Balanus glandula
. It is rare to find more than one H. balani parasitizing the same host, but under conditions of heavy infestation a single barnacle may contain as many as seven H. balani.
Both the isopod parasite and its barnacle host are hermaphroditic crustaceans with a free-swimming larva and a sessile adult. H. balani is a protandrous hermaphrodite that develops into a female only after attaching to its adult host. While in its male swimming form, it resembles a typical isopod with antennae, jointed limbs, and a segmented exoskeleton. When fully mature, the adult female form of H. balani is reduced to a bloated, star-shaped egg sac, up to 8 mm in length inhabiting the mantle cavity of its barnacle host.
The barnacle host species are simultaneous hermaphrodites, with both male and female gonads in each adult. H. balani feeds on its host's ovarian fluid, so that the barnacle loses female reproductive ability but can still produce sperm.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of isopod
Isopoda
Isopods are an order of peracarid crustaceans, including familiar animals such as woodlice and pill bugs. The name Isopoda derives from the Greek roots and...
crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
that is a widespread parasitic castrator
Parasitic castration
Parasitic castration is the strategy, by a parasite, of blocking reproduction by its host, completely or in part. For example, Hemioniscus balani, a parasitic castrator of hermaphroditic barnacles, feeds on ovarian fluid, so that its host loses female reproductive ability but still can function as...
of barnacles in the north Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
. Its range
Range (biology)
In biology, the range or distribution of a species is the geographical area within which that species can be found. Within that range, dispersion is variation in local density.The term is often qualified:...
extends from Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
to the Atlantic coast of France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
, and as far west as Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
.
Life history
H. balani parasitically castratesParasitic castration
Parasitic castration is the strategy, by a parasite, of blocking reproduction by its host, completely or in part. For example, Hemioniscus balani, a parasitic castrator of hermaphroditic barnacles, feeds on ovarian fluid, so that its host loses female reproductive ability but still can function as...
adults of several species of barnacles, including Semibalanus balanoides
Semibalanus balanoides
Semibalanus balanoides is a common and widespread boreo-arctic species of acorn barnacle. It is common on rocks and other substrates in the intertidal zone of north-western Europe and both coasts of North America.-Description:...
, Chthamalus fissus, Chthamalus dalli, and Balanus glandula
Balanus glandula
Balanus glandula is one of the most common barnacle species on the Pacific coast of North America, distributed from the U.S. state of Alaska to Bahía de San Quintín near San Quintín, Baja California. It is commonly found in intertidal waters on mussels, rocks and pier pilings.It is a moderate-sized...
. It is rare to find more than one H. balani parasitizing the same host, but under conditions of heavy infestation a single barnacle may contain as many as seven H. balani.
Both the isopod parasite and its barnacle host are hermaphroditic crustaceans with a free-swimming larva and a sessile adult. H. balani is a protandrous hermaphrodite that develops into a female only after attaching to its adult host. While in its male swimming form, it resembles a typical isopod with antennae, jointed limbs, and a segmented exoskeleton. When fully mature, the adult female form of H. balani is reduced to a bloated, star-shaped egg sac, up to 8 mm in length inhabiting the mantle cavity of its barnacle host.
The barnacle host species are simultaneous hermaphrodites, with both male and female gonads in each adult. H. balani feeds on its host's ovarian fluid, so that the barnacle loses female reproductive ability but can still produce sperm.