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Leeches either have a pharynx that they can protrude, commonly called a proboscis, or a pharynx that they cannot protrude, which in some groups is armed with jaws. [38] In the proboscisless leeches, the jaws (if any) of Arhynchobdellids are at the front of the mouth, and have three blades set at an angle to each other.
These leeches have five pairs of eyes, with the last two separated by two eyeless segments. The family is monotypic, containing only the subfamily Haemadipsinae, though as the family can apparently be divided into two or three distinct lineages, at least one of the proposed splits, while not a distinct family, might be a valid subfamily. [1]
Rhynchobdellida (from the Greek rhynchos, mouth, and bdellein, sucking), [1] the jawless leeches [citation needed] or freshwater leeches, [2] are an order of aquatic leeches. [ 3 ] [ 4 ] Despite the common name "freshwater leeches", species are found in both sea and fresh water.
Some clitellates have sticky pads in the roofs of their mouths, and some of these can evert the pads to capture prey. Leeches often have an eversible proboscis, or a muscular pharynx with two or three teeth. [23]
The leech sometimes emerges from the water to hunt for earthworms. [4] [7] Like other leeches, Haemopis sanguisuga is a hermaphrodite. The testes mature first and the ovaries later in the organism's life. A pair of leeches will line up with the clitellar regions in contact, and sperm is passes by the one acting as male to the female gonopore.
Each segment of the leech's body (and all leeches have 32) has three or four annuli. [2] [3]: 236 They are large leeches; one species, Pontobdella novaezealandiae, can grow as long as 20 centimetres. [3]: 236 [4]
Arhynchobdellida, the proboscisless leeches, are a monophyletic order of leeches. They are defined by the lack of the protrusible proboscis that defines their sister taxon, the Rhynchobdellida . [ 1 ] [ 2 ] [ 3 ] Arhynchobdellida is a diverse order, compromising both aquatic and terrestrial , besides sanguivorous and predatory , leeches. [ 3 ]
As in other species of leech, a cocoon is secreted by the clitellum, a thickened glandular section of the body wall behind the head, and this moves forwards over the head, receiving fertilised eggs from the gonopore on the way. [5] In some areas, Erpobdella obscura has a semelparous life history, i.e., the leech dies after reproduction.