Rhynchobdellida (from the Greek ''rhynchos'', mouth, and ''bdellein'', sucking), the jawless leeches or freshwater leeches, are an

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

of aquatic

leeches Leeches are segmented parasitism, parasitic or Predation, predatory worms that comprise the Class (biology), subclass Hirudinea within the phylum Annelida. They are closely related to the Oligochaeta, oligochaetes, which include the earthwor ...

. Despite the common name "freshwater leeches", species are found in both sea and fresh water. They are defined by the presence of a protrusible

proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elong ...

instead of jaws, and having colourless blood. They move by "inchworming" and are found worldwide. The order contains 110 species, divided into 41 genera and three families. Members of the order range widely in length, usually between 7 and 40 mm. They are hermaphrodite. The order is not

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

Appearance and eating habits

Smooth Turtle Leech imported from iNaturalist photo 3860130 on 27 November 2022

Instead of jaws and teeth, Rhynchobdellidae have protrusible proboscises, which they use to penetrate the host's skin. Mouths of Rhynchobdellidae species are small holes from which the proboscis can be protruded. The proboscis then sucks out the desired bodily fluid from the host: usually blood or coelomic fluid in the case of invertebrate victims. Rhynchobdellidae are either sanguivorous or

predatory Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

. Sanguivorous species usually feed on a variety of other animals, using their proboscis to host's skin. They generate

anticoagulants Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquitoes, where the ...

(like

mosquitoes Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning "gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "litt ...

) and natural anaesthetia to help the feeding. Predatory Rhynchobdellidae have digestive enzymes that help break down their prey, which usually consists of small invertebrates such as insect larvae or

amphipods Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far descri ...

Families

Glossiphoniidae (Freshwater jawless leeches)

The

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 ...

, the freshwater jawless leeches, or leaf leeches (due to their shape) are

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

leeches, flattened, and with a poorly defined anterior sucker. The family Glossiphoniidae contains one of the world's largest species of leech, the giant Amazon leech, which can grow up to 45 cm in length. Many species show extended parental care, keeping eggs in nests or pouches and caring for and feeding the young. They feed on both vertebrate and invertebrate animals.

Piscicolidae (Fish leeches)

The

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 ...

occur in both

and

seawater Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has appro ...

, have cylindrical bodies, and a usually well-marked, bell-shaped, anterior sucker. They are parasites of fish. The family was originally divided into three subfamilies based on species' pulsatile

vesicles Vesicle may refer to: ; In cellular biology or chemistry * Vesicle (biology and chemistry), a supramolecular assembly of lipid molecules, like a cell membrane * Synaptic vesicle ; In human embryology * Vesicle (embryology), bulge-like features o ...

, but the subfamilies were disbanded in 2006. Ozobranchus jantseanus cropped

Ozobranchidae (Turtle leeches)

Ozobranchidae are primarily parasitic on marine turtles, and are sometimes merged with the Piscicolidae.

References