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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.
Leeches, order Hirudinida, [4] mostly have flattened bodies, usually tapered at both ends. They have a fixed number of segments, 33, but the segmentation is not visible externally because the cuticle is marked with annulations. Leeches do not bear chaetae. The front few segments or head have been modified into a sucker that usually surrounds ...
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]
In leeches there are no septa, the connective tissue layer of the body wall is so thick that it occupies much of the body, and the two coelomata are widely separated and run the length of the body. They function as the main blood vessels, although they are side-by-side rather than upper and lower.
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.
Leeches like the one attached to Hall have multiple rows of tiny teeth which they use to securely attach themselves to skin and drink blood. It can be painful and dangerous to simply yank leeches ...
A prominent feature of Pontobdella leeches are the "wart-like" tubercles which cover their bodies all over. Pontobdella 's hosts are generally elasmobranchs – rays, sharks, skates, and sawfish. Each segment of the leech's body (and all leeches have 32) has three or four annuli .
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.