Leeches (Family: Hirudinidae)
Leeches are segmented worms that belong to the phylum Annelida and comprise the subclass Hirudinea. Like the oligochaetes, such as earthworms, leeches share a clitellum and are hermaphrodites. A clitellum is a thickened glandular and non-segmented section of the body wall near the head in earthworms and leeches that secretes a viscid sac in which the eggs are deposited.
Leeches do not have bristles like earthworms and some like the medicinal leech, Hirudo medicinalis have two suckers, one at each end, called the anterior and posterior sucker two suckers. The anterior (oral) sucker consisting of the jaw and teeth is where the feeding takes place. This anterior sucker secretes an anti-clotting enzyme, hirudin and an anaesthetic into the host's blood stream to prevent the host from feeling pain while it sucks blood. It uses a combination of mucus and suction to stay attached. The posterior sucker (acetabulum) is mainly used for leverage. During locomotion directional movement of the body is done by successive attachment and detachment of the oral sucker and the acetabulum.
The majority of leeches live in freshwater environments, while some species can be found in terrestrial and marine environments. The best-known leeches, such as the Hirudo medicinalis, are hematophagous, feeding on vertebrate blood and invertebrate hemolymph. Most leech species, however, are predatory, feeding primarily by swallowing other invertebrates. Almost 700 species of leeches are currently recognized, of which some 100 are marine, 90 terrestrial and the remainder freshwater taxa.
The medical leech Hirudo medicinalis
New Zealand has a native blood sucking leech in the Genus: Richardsonianus with the scientific name of Richardsonianus mauianus. It is commonly called the Tiger leech and is easily recognised by its longitudinal stripes. It is a rare leech and is found in some slow-flowing weedy streams, ponds and lakes in Northern New Zealand and south to the Waikato. They will latch on to the bare legs of humans wading in their habitats. When removed they leave a distinctive triangular bite mark on the skin. It takes the leech about nine months to digest its food before it needs another meal.
How to remove leeches http://www.wikihow.com/Remove-Leeches
The NZ leech Richardsonianus mauianus. Copyright photo courtesy of Neil Fitzgerald (www.neilfitzgeraldphoto.co.nz)
The mouth of Richardsonianus mauianus
Though most leeches live in fresh or saltwater environments New Zealand has three known native species of terrestrial leeches that are adapted to life out of the water. They feed on the blood of seabirds, particularly penguins and shearwaters. To obtain blood the leeches after dark nestle into the webbing on the feet of ground nesting birds. All New Zealand’s terrestrial species are now endangered, and confined to rat-free offshore islands except one specimen found under a log in Fiordland.
A terrestrial species called the ‘Taumaka leech’ or the ‘Open Bay Island leech’ (Hirudobdella antipodium) was only known to live on Taumaka Island off the West Coast near Haast. It hasn’t been seen since 1995, despite extensive searches. Weka the were introduced to the island in early last century probably eat leeches and that’s a worry for the survival of this population.
NZ terrestial leech Hirudobdella antipodium
There is a terrestrial species called Ornithobdella edentula that live on the Snares Islands, Little Solander Island in Foveaux Strait and on Kaimohu Islands near Stewart Island.
NZ terrestrial leech Ornithobdella edentula
The foreign, freshwater, jawless leech Helobdella europaea is present here in New Zealand. It has been found in Taupo and Auckland and its habitat are slow streams, irrigation ditches, drainage ditches. It is a small flat leech with a body length of 10–25 mm and can be easily recognized by its five lines of distinct conical black–tipped papillae of the dorsum. H. europaea is a predator of mainly of freshwater snails. It is also a scavenger feeder. It is no threat to humans as it does not feed on blood.
The foreign leech Helobdella europaea
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