Hirudobdella antipodum
| Hirudobdella antipodum | |
|---|---|
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Annelida |
| Class: | Clitellata |
| Subclass: | Hirudinea |
| Order: | Arhynchobdellida |
| Family: | Hirudinidae |
| Genus: | Hirudobdella |
| Species: | H. antipodum |
| Binomial name | |
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Hirudobdella antipodum (Benham, 1904) |
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Hirudobdella antipodum is a terrestrial leech found only on the Open Bay Islands in New Zealand. It preys on the feet of nesting seabirds. Its numbers have been reduced significantly by introduced weka, and the entire remnant population of the leech is now living beneath a single boulder.
The leech was discovered when botanist Leonard Cockayne and Walter Dunlop (an analytical chemist from Orepuki) visited Taumaka, the largest of the Open Bay Islands, in February 1903. Dunlop was looking for weta in muttonbird burrows when he was bitten on the wrist. As Benham put it, in his description of the new species, "Fortunately Mr Dunlop is keenly interested in natural history, and he carefully withdrew his hand and found a leech attached thereto”.
Subsequently weka (Gallirallus australis) were introduced to the Open Bay Islands, and by 1969 these were thought to have driven the leech to extinction. The species was rediscovered in 1987, however, living in waterlogged penguin burrows underneath a large (5 m × 2 m) glacial boulder. Repeated surveys of the boulder over the next decade confirmed that the leeches, the entire world population known at that time, were surviving and breeding.
Terrestrial leeches require damp or wet environments to keep their skin moist and dispose of excreted ammonia, and so are normally found in forest. On the Open Bay Islands, H. antipodum was found in wet burrows or in waterlogged piles of sticks.
Terrestrial leeches primarily feed on mammals, though the New Zealand species have adapted to rely on birds. The Open Bay Islands leech feeds primarily on the feet of nesting seabirds, especially Fiordland crested penguins (Eudyptes pachyrhynchus). Leeches are able to ingest several times their body weight in blood, and can take months to digest it. Outside of the breeding season, H. antipodum may feed opportunistically on other vertebrates, such as fur seals or even earthworms. New Zealand terrestrial leeches may have once been opportunistic feeders of even active forest birds, such as the extinct moa.
Leeches are hermaphrodites, with both male and female genital pores. Those in the order Arhynchobdellida lay 5–10 eggs in cocoons. When Cockayne and Dunlop discovered this species, their initial search located six more individuals and two empty cocoons, which were oval, 14 mm long, and dark brown with a horny texture.
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