# Chtonobdella limbata

Chtonobdella limbata is a species of terrestrial blood-sucking leech, found in Australia. They are a common species of subtropical rainsforests. Contracted, the leeches are about 28 millimetres (1.1 in) long, but once extended they can reach 60 millimetres (2.4 in) or even 80 mm (3.1 in) in length. They have two saw-like jaws which they use to cut open their victims' skin. In colour, they are mostly dark, with some coloured stripes. Their rear suckers are oval-shaped and have a prehensile protuberance on their tips.
Chtonobdella limbata is found along the east coast of Australia, especially in the state of New South Wales. The leeches are adapted to withstand drought-like conditions by anhydrobiosis: they burrow into the ground and enter an inanimate state that resists dehydration. In this state they can survive for several months. They are exclusively ground-dwellers, and never enter water or climb onto forest vegetation.

## Classification

Chtonobdella limbata is the type species for the genus Chtonobdella and is classified in the family Haemadipsidae. Adolph Eduard Grube published about the species somewhat ambiguously under the name Hirudo limbata but with "the suggestion of Chtonobdella as a new genus". Confusingly, Grube later referred to the species again as H. limbata$_,$ a name kept by some other scholars. The name Chtonobdella is derived from two Greek elements: chton, meaning 'ground' or 'land'; and bdella, simply meaning 'leech'; thus, Chtonobdella is a 'land leech' – an appropriate name given its terrestrial habitat.

## Description

All members of the genus Chtonobdella have two jaws, which act like cutting saws against their victim's skin, opening a wound. Most leeches have three jaws, leaving a Y-shaped cut, but duognathous species leave V-shaped cuts.
When contracted, the leeches are about 25 to 30 millimetres (0.98 to 1.18 in) long, but their extended length reaches from 50 to 60 millimetres (2.0 to 2.4 in), and in a few cases as long as 85 millimetres (3.3 in).$^{:295}$ Meeting notes record Grube's original specimens as being 1 and 1.5 inches (25 and 38 mm) long. The body of C. limbata is widest at the back. The leeches have five pairs of conspicuous eyes laid out in the shape of an arch. In colour, the leeches are dark green with a yellowish stripe down the middle of their backs, with another stripe on each side. Their undersides are ruddy and covered with splotches and streaks of blackness.$^{:295}$
The leech's rear sucker is elliptical, longer than it is wide; it has 64 rays. Such rays help increase the suction provided by the sucker, and are present in all Haemadipsidae. The sucker's rearmost tip is slightly pointed and is adorned with a slightly hook-shaped and prehensile small protuberance. Haemadipsid leeches have another adaptation that helps increase their rear sucker's suction: liquids excreted from the nephridiopore are guided onto the sucker's surface, which maintains moisture and suction power.
In 1944, John Percy Moore, working from a single "poorly preserved" specimen from Dorrigo, New South Wales, and held in the British Museum, provided a detailed description of the species' morphology. All leeches have 32 segments, but they are all also covered with external rings called annuli; the gonopores of C. limbata are separated by nine and a half such rings, with the male pores on the sixth segment and the female ones on the thirteenth. Different segments have different annulation. The first four body segments have one annulus each; the fifth has two; and the sixth has three on the top but only two on the bottom. The next segment, the seventh, has three annuli all the way around; and eighth has four annuli. Segments nine to twenty-two are 5-annulate. In segment twenty-three, the number of annulations descends to four. The twenty-fourth is simpler with only two annuli, while the remaining eight segments – number twenty-five to thirty-two inclusive – have only one. Annulation was formerly widely used to identify species, but is used less today as the apparent number of annuli can vary.
* Diagram showing the annulation of C. limbata.
* C. limbata on a human thumb.

## Habitat

Leeches are often thought of as aquatic creatures, but Chtonobdella limbata, like all members of its genus, is terrestrial, and a common species of subtropical rainforest habitat. However, because of its habitat preferences it has a patchy distribution, preferring spots in canopy forest without underbrush that have been wetted by seepage. These spots usually have more stable moisture levels than the general forest floor, which the leeches do not inhabit.$^{:294}$ C. limbata is a terrestrial species, and do not enter water, nor can they swim, although they are able to survive underwater. They stick to the ground and do not even usually climb onto vegetation.$^{:295}$

### Anhydrobiosis

In dry times, the leeches bury themselves into the soil, and can enter an inanimate state that resists dehydration, in which they can survive for months given no water in their environment. However, the leeches revitalize themselves immediately when water re-appears. This is considered an example of anhydrobiosis.$^{:295}$ In 1968, Laurence R. Richardson coined the term to describe the leech's behaviour, and he defined it as "a category of cryptobiosis based on environmental stress due solely to the lack of water". Upon making his discovery, Richardson decided to perform an experiment. He placed a leech, well-fed, in a large jar. The jar contained moss, damp soil, a small fern, and some leaves – but no further water or moisture was ever provided. The leech made a small burrow in the soil and would emerge in the late morning or afternoon and move around the jar for some time. Richardson's experiment started in the middle of January, and in May the leech's activity suddenly dropped off. It was not seen again. By July, the plants were dead. Richardson opened the jar at the end of October. "The soil was powder dry," he wrote. He found the leech in the soil, very much contracted, firm, and rigid. "The skin was so dry dust fell from it." The leech did not respond to handling or to sunlight. Then the leech was returned to the soil, which was sprinkled with water; in less than ten minutes, the leech was alive, revitalized and active and resuming its routine. Richardson noted that no other land leech can survive such dehydration. He also later experimented with over-watering the soil so it became muddy; the leech avoided the soil and clung to the side of the jar.$^{:300}$

## Distribution

Chtonobdella limbata is found in all three eastern Australian states. It is most reported in New South Wales, but is also found in Queensland and Victoria. In New South Wales it is found along the coast and into the Blue Mountains; in Queensland it is similarly found along the coast, and has been reported as far north as near the Daintree River. In the state of Victoria, records are fewer and restricted to the vicinity of the Strzelecki Ranges and western Gippsland.