Lord Howe Island Earthworm (Pericryptodrilus nanus)

# Pericryptodrilus nanus (an earthworm) - endangered species listing

## NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. *Pericryptodrilus nanus* was first described by B. Jamieson in 1977, from Mount Gower Ridge, Mount Gower, Lord Howe Island.

2. *Pericryptodrilus nanus*, which is found on Lord Howe Island, was described in the Records of the Australian Museum 1977 vol 30:272-308 Figs. 1-7 by Jamieson 1977 as: Length 25-32 mm. Width (mid-clitellar) 1.0-1.5 mm. Segments 111-123. Prostomium broadly epilobous. First dorsal pore 6/7 or 10/11. Setae perichaetine, >30 per setiger. Nephropores 3 straight series on each side. Clitellum annular, in segments 1/2 XIII, XIV- XVI. Small slit-like combined male and prostatic pores a pair in XVIII approximately in b on prominent papillae. Accessory genital markings 2 midventral presetal circular glandular areas, with indistinct porelike centres, one in XX, the other in XXI. Female pore unpaired, midventral, anteriorly on XIV. Spermathecal pores 2 pairs, in 7/8 and 8/9, between the third and fourth setal rows. Dorsal blood vessel single. Hearts 3 pairs, in X-XII. A rudimentary gizzard in segment V; calciferous glands at least extramurally absent; intestine commencing in XVI. Three subspherical slightly bilobed nephridial bladders present on each side per segment, those in the tenth setal lines large, the others (above and below) small. The nephridia of the intermediate series each with a preseptal funnel near the nerve cord; no funnels demonstrable for the dorsal and ventral series. Pharyngeal, or other enteronephric nephridia, and tufted nephridia absent. Testes and funnels in X and XI; seminal vesicles in IX and XII. Ovaries and oviducal funnels in XIII. Large multiloculate ovisacs in XIV. Prostates thickly tubular, in XVIII and extending into XIX; ducts median, slender; vas deferens joining each gland at its junction with the duct. Penial setae absent. Spermathecae in VIII and IX; each with a subspherical ampulla, conical, and a large clavate inseminated lateral diverticulum which joins the duct at midlength; the diverticulum with or without a subsidiary less well developed or knoblike diverticulum of similar width at its base or all simple. This earthworm can be easily distinguished from all other earthworms on the island by the presence of the median accessory genital markings and three rows of nephridiopores.

3. *Pericryptodrilus nanus* is restricted to Mount Gower, Lord Howe Island, New South Wales. Sampling at many other sites at Lord Howe Island specifically for earthworms, has failed to extend the range of this species. The species is known from 10 specimens, lodged in the Australian Museum. They were all collected from the ridge of Mount Gower in deep leaf litter in moist environments close to streams.

4. *Pericryptodrilus nanus* requires a constant moist environment for survival. Disturbance to its leaf litter habitat, in particular trampling and camping, resulting in changes to the micro environment is likely to adversely affect the species.

5. Exotic earthworms have displaced native species in many areas in Australia because disturbance and modification of the habitat favours them over native species. (The highly deleterious effects of introduced earthworms on leaf litter, with accompanying devegetation, has recently been documented for North America. Exotic species are already present on Lord Howe Island around the settlement including Allobophora caliginosa, and Amynthas diffringens (later synonymized with A. corticis) (Jamieson, 1977 and Australian Museum collections), and the spread of these species or introductions of others could have deleterious impacts on Pericryptodrilus nanus.

6. In view of 3, 4 and 5 above the Scientific Committee is of the opinion that this species is likely to become extinct in nature in New South Wales unless the circumstances and factors threatening its survival or evolutionary development cease to operate.

Proposed Gazettal date: 16/03/01

Exhibition period: 16/03/01 - 20/04/01