Acochlidium fijiense

Acochlidium fiiense is a small, soft, worm-like animal, with two tentacles but no shell. It is a shell-less freshwater gastropod of the subclass Opisthobranchia. It can grow up to 19mm in length and its foot may be longer than the visceral hump. This endemic freshwater gastropod has a cream-yellow background colour with wide brown stripes across the dorsal side. It also has shiny spicules on its visceral hump and foot.

Distribution

Acochlidium fijiense has only been recorded from the Nasekawa River (Vanua Levu) and Lami River (Viti Levu) despite searches in other rivers on these two islands.

 Acochlidium fiiense map

Acochlidium fiiense map

Habitat Ecology and Behaviour

Surveys conducted by Haynes and Kenchington between 1983 and 1988 showed thatA. fijiense lives under stones and rocks in shallow parts of streams (60 – 140 mm deep) influenced by the tide, but where there are no inflow of sea water. It is difficult to detect as it is well camouflaged, blending in with the stones under which it lives.  This species was most abundant in the months October and July, and individuals were also reproductively mature in the month of July. This is when their body hump enlarges to accommodate eggs, and the individual is therefore larger in size. It probably breeds between the months July and August, though this will have to be confirmed by further surveys and studies on this animal.Acochlidium fijiense is a hermaphrodite. Not much else is known on this species other than the information documented in the 1980s by the above authors.

Threat

The main threats toA. fijiense are river bed removal, the covering of the river bed with silt and grit during forest logging, mining, road making and the farming of very steep hillsides. The section of the Lami River which is home toA. fijiense on Viti Levu, runs through the Qauia settlement. This section of the river has undergone many changes such as increased houses and buildings along the river bank, and farming activities on the hill slopes since the 1980s. The impact of such changes on the only known Viti Levu population ofA. fijiense remains unknown.

Conservation Status

The conservation status of A. fijiense is unknown as there have been very limited studies conducted since the 1980s to assess its status. However, this species has been of more interest to overseas researchers than to locals. Collections of specimens from the known sites have been ongoing since the 1980s by Dr. P. Bouchet of the Natural History Museum, Paris in 2000 from the Nasekawa River; and by Michael Shrody of the University of Munich, Germany in 2006.

Remarks and Cultural Significance

The conservation status of A. fijiense is unknown as there have been very limited studies conducted since the 1980s to assess its status. However, this species has been of more interest to overseas researchers than to locals. Collections of specimens from the known sites have been ongoing since the 1980s by Dr. P. Bouchet of the Natural History Museum, Paris in 2000 from the Nasekawa River; and by Michael Shrody of the University of Munich, Germany in 2006.

References

Haynes (2001);
Haynes, A. (personal communication);
Haynes and Kenchington (1988);
Haynes and Kenchington (1991)