''Bothriocephalus gregarius'' is a tapeworm that parasitises the

turbot The turbot (''Scophthalmus maximus'') is a relatively large species of flatfish in the family Scophthalmidae. It is a demersal fish native to marine or brackish waters of the Northeast Atlantic, Baltic Sea and the Mediterranean Sea. It is an im ...

(''Scophthalmus maximus''). It has a complex life cycle including two intermediate hosts, a copepod and a small fish.

Distribution

The turbot (''Scophthalmus maximus'') is found in the northern

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

, the

Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden and the North and Central European Plain. The sea stretches from 53°N to 66°N latitude and from ...

and the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ea ...

, and ''B. gregarius'' occurs in the same range.

Life cycle

The life cycle of ''B. gregarius'' involves a definitive host, the turbot or other large flat fish, and two intermediate hosts, a

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

and a small fish. The adult tapeworm is an occupant of the turbot's gut. It lays eggs which pass with the fish faeces out into the sea and which hatch into free-swimming larvae, the coracidium. For development to proceed, the coracidium must be swallowed by a

, after which it develops into the infective stage, the

plerocercoid ''Plerocercoid'' refers to last larval form, the infective form, found in the second intermediate host of many Cestoda with aquatic life cycles. References

Cestoda Larvae {{Parasitic animal-stub ...

. If the copepod is then eaten by a small fish, such as a

goby Goby is a common name for many species of small to medium sized ray-finned fish, normally with large heads and tapered bodies, which are found in marine, brackish and freshwater environments. Traditionally most of the species called gobies have b ...

, the plerocercoid survives in its digestive tract. A turbot becomes infected when it swallows the infected small fish, and this completes the life cycle of the parasite. Off the coast of France, the plerocercoid larvae have been found in two species of goby, ''

Pomatoschistus marmoratus ''Pomatoschistus marmoratus'', the marbled goby, is a species of goby native to the eastern Atlantic from the Bay of Biscay down around the Iberian Peninsula through the Mediterranean Sea, the Black Sea and the Sea of Azov. It is also found in th ...

'' and '' Pomatoschistus minutus''. It seems that juvenile turbots feed on copepods, but these

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

s are too small to form a worthwhile part of the diet of larger turbot, and these bigger fish become infected after feeding on the infected gobies.

References

{{Taxonbar, from=Q49000426 Cestoda Parasitic helminths of fish Animals described in 1983