''Piscicola geometra'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

leech Leeches are segmented parasitic or predatory worms that comprise the subclass Hirudinea within the phylum Annelida. They are closely related to the oligochaetes, which include the earthworm, and like them have soft, muscular segmented bodie ...

in the family

Piscicolidae The Piscicolidae are a family of jawless leeches in the order Rhynchobdellida that are parasitic on fish. They occur in both freshwater and seawater, have cylindrical bodies, and typically have a large, bell-shaped, anterior sucker with which the ...

. It is an external parasite of marine, brackish and freshwater fishes. It was first described as ''Hirudo geometra'' by the Swedish naturalist

Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement in 1761 as Carl von Linné Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomial nomenclature, the ...

in his ''

Systema Naturae ' (originally in Latin written ' with the ligature æ) is one of the major works of the Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the system, now known as binomial nomen ...

'' in 1758.

Description

This leech can grow to a length of . It is pale brown, often with white transverse bands.

Distribution and habitat

This fish leech occurs in freshwater locations in the

Holarctic The Holarctic realm is a biogeographic realm that comprises the majority of habitats found throughout the continents in the Northern Hemisphere. It corresponds to the floristic Boreal Kingdom. It includes both the Nearctic zoogeographical region ...

and

Neotropic The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone. Definition In bioge ...

regions and is found in northwestern Europe and in North America. It is also present in some marine environments such as the Baltic Sea where it mainly parasitises

shorthorn sculpin ''Myoxocephalus scorpius'', typically known as the shorthorn sculpin or bull-rout, is a species of fish in the family Cottidae. It is a demersal species of the Northern Atlantic and adjacent subarctic and Arctic seas.

and

flounder Flounders are a group of flatfish species. They are demersal fish, found at the bottom of oceans around the world; some species will also enter estuaries. Taxonomy The name "flounder" is used for several only distantly related species, thou ...

s. It occurs in both moving and stagnant water, but seems to prefer well-oxygenated water at the wave-washed edges of lakes and rapidly flowing streams and rivers. Fish Leech imported from iNaturalist photo 187530624 on 2 December 2022

Fish Leech imported from iNaturalist photo 187530624 on 2 December 2022

Ecology

''P. geometra'' is an ectoparasite of various fish species. Hosts include

salmon Salmon () is the common name for several list of commercially important fish species, commercially important species of euryhaline ray-finned fish from the family (biology), family Salmonidae, which are native to tributary, tributaries of the ...

(''Salmo salar''),

brown trout The brown trout (''Salmo trutta'') is a European species of salmonid fish that has been widely introduced into suitable environments globally. It includes purely freshwater populations, referred to as the riverine ecotype, ''Salmo trutta'' morph ...

(''Salmo trutta''),

European eel The European eel (''Anguilla anguilla'') is a species of eel, a snake-like, catadromous fish. They are normally around and rarely reach more than , but can reach a length of up to in exceptional cases. Eels have been important sources of fo ...

(''Anguilla anguilla''), charr (''Salvelinus alpinus''),

gudgeon A gudgeon is a socket-like, cylindrical (i.e., ''female'') fitting attached to one component to enable a pivoting or hinging connection to a second component. The second component carries a pintle fitting, the male counterpart to the gudgeon, ...

(''Gobio gobio''),

bream Bream ( ) are species of freshwater and marine fish belonging to a variety of genera including ''Abramis'' (e.g., ''A. brama'', the common bream), ''Acanthopagrus'', '' Argyrops'', ''Blicca'', '' Brama'', ''Chilotilapia'', '' Etelis'', ''Lepo ...

(''Abramis brama''),

perch Perch is a common name for fish of the genus ''Perca'', freshwater gamefish belonging to the family Percidae. The perch, of which three species occur in different geographical areas, lend their name to a large order of vertebrates: the Percif ...

(''Perca fluviatilis''),

Prussian carp The Prussian carp, silver Prussian carp or Gibel carp (''Carassius gibelio''), is a member of the family Cyprinidae, which includes many other fish, such as the common carp, goldfish, and the smaller minnows. It is a medium-sized cyprinid, and d ...

(''Carassius gibelio'') and

common carp The Eurasian carp or European carp (''Cyprinus carpio''), widely known as the common carp, is a widespread freshwater fish of eutrophic waters in lakes and large rivers in Europe and Asia.Fishbase''Cyprinus carpio'' Linnaeus, 1758/ref>Arkive The ...

(''Cyprinus carpio''). The attachment site is on various parts of the body, on the gills or inside the mouth. This leech can swim well and is attracted by the presence of a suitable fish in its vicinity. It feeds periodically, attaching itself to the fish's body with its sucking disc before puncturing its skin with its proboscis and sucking its blood. When satiated, it releases its grip and sinks to the bottom, hiding among stones or submerged plants while digesting its meal. It needs several blood meals before it can reproduce. The mid-gut and adjoining mycetomes (pouches), contain

symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...

bacteria which help with the digestion of blood, provide additional nutrients, and prevent the entry of pathogens. Leeches are

hermaphrodite In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many Taxonomy (biology), taxonomic groups of animals (mostly invertebrate ...

and pair up to impregnate each other by hypodermic injection. The eggs are laid in dark brown cocoons which are cemented to submerged objects. After the eggs hatch, the juvenile leeches must seek out suitable fish

hosts A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places *Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman *Michel Host ( ...

. The whole life cycle takes about four weeks to complete.

References

External links

* {{Taxonbar, from=Q901837 Leeches Invertebrates of Europe Invertebrates of North Africa Animal parasites of fish Ectoparasites Animals described in 1761 Taxa named by Carl Linnaeus