''Theromyzon tessulatum'' 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

Glossiphoniidae Glossiphoniidae are a family of freshwater proboscis-bearing leeches. These leeches are generally flattened, and have a poorly defined anterior sucker. Most suck the blood of freshwater vertebrates like amphibians, crocodilians and aquatic tu ...

. It is a

haematophagous Hematophagy (sometimes spelled haematophagy or hematophagia) is the practice by certain animals of feeding on blood (from the Greek words αἷμα ' "blood" and φαγεῖν ' "to eat"). Since blood is a fluid tissue rich in nutritious pro ...

(blood-sucking) leech, found in freshwater habitats in Europe.

Description

The cuticle of ''T. tessulatum'' is transparent, olive green or brownish in colour, with larger individuals often exhibiting six longitudinal rows of small yellow spots. This leech is active and frequently changes shape, being up to long when extended. The posterior sucker is broad and conspicuous but the anterior sucker is small, and invisible when the animal is viewed from above.

Distribution

This leech is found in freshwater habitats in Europe. It is common in the coastal flat parts of Holland which are visited by the

waterfowl Anseriformes is an order of birds also known as waterfowl that comprises about 180 living species of birds in three families: Anhimidae (three species of screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which in ...

that act as its

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 ( ...

. It is uncommon in Britain, where it has a discontinuous range, probably being distributed by movements of its bird hosts. It has also been recorded in North America from a number of locations.

Ecology

When parasitizing ducks and other waterfowl, ''T. tessulatum'' invades their mouths and respiratory passages. At other times, it is free-living in freshwater habitats. The adult broods its egg capsules on its under surface, where there may be as many as two hundred eggs. When the young are ready to emerge, the adult uses its sensilla organs to detect vibrations in the water and will move towards any disturbance that might be caused by a potential host. Suitable hosts are those with body temperatures of between . Although generally nocturnal and negatively

phototactic Phototaxis is a kind of taxis, or locomotory movement, that occurs when a whole organism moves towards or away from a stimulus of light. This is advantageous for phototrophic organisms as they can orient themselves most efficiently to receive li ...

(avoiding light), when the brooding adult is ready to release its young, it may swim in open water in the middle of the day. If it finds a suitable host, it attaches itself with its sucker to the nasal passages, the respiratory tract or inside the mouth. This leech is unique in that the adult attaches to the host but does not itself feed on it; instead, the young that it was brooding transfer to the host to take their first blood meal.

References

{{Taxonbar, from=Q150856 Glossiphoniidae Animals described in 1774 Taxa named by Otto Friedrich Müller