Seychelles Invertebrates

Introduction

Some 3,000 species of terrestrial invertebrate have been recorded in Seychelles.  The majority of these are known from isolated records or from a small number of specimens.  The Nature Protection Trust of Seychelles has ongoing research programmes evaluating the diversity of invertebrates in the islands.  These projects, mostly undertaken on a voluntary basis, aim to locate species which have not been recorded since their collection 100 years ago, to identify sites of special importance for invertebrate conservation and monitor the distribution of introduced species.

NPTS invertebrate research relies upon extensive collections of historical literature and a network of taxonomists providing identification and taxonomic reviews.  This has enabled the identification of large numbers of species not recorded since the major collection expeditions of 1892-1909 and many new species.  So far very few islands have been studied and only one large island (Silhouette) is being studied in detail.

Rediscoveries

The majority of 'rediscovered' species are small and inconspicuous.  One dramatic exception is the Seychelles bee-hawkmoth (Cephonodes tamsi).  This species was known from a single specimen from Mahe island in 1911 and was presumed extinct until several individuals were found on Silhouette in 1997.  This large, bright red species appears to be locally abundant but very patchily distributed.  Research into its distribution and ecology will re-evaluate its status.  Since 1997 further dramatic rediscoveries have been made: the Seychelles hummingbird hawkmoth (Macroglossum alluaudi) in 2000 and the Seychelles fineliner damselfly (Teniobasis alluaudi) in 2001.  These striking species will be the focus of major research initiatives in the future.

Fregate island invertebrates

The only conservation measures specifically for invertebrates are the captive breeding programme for the threatened species from Fregate island.  NPTS is working with the Zoological Society of London's Invertebrate Conservation Centre to maintain a viable captive population of Seychelles giant millipede (Sechelleptus seychellarum), giant tenebrionid beetle (Pulposipes herculeanus), Fregate island snail (Pachnodus fregatensis) and Seychelles giant scorpion (Chiromachus ochropus).  These are all threatened by brown rats (Rattus norvegicus) which invaded the island in 1995.  It was feared that rats will feed on these large invertebrates and as the rat population expanded the invertebrates may have become extinct.  The millipede is found on several other islands but may represent a separate sub-species.  The beetle is restricted to Fregate island (historically it was also found on Round island near Mauritius and probably on other Seychelles islands) as is the snail.  The scorpion is found on other islands in Seychelles but is only abundant on Fregate.  All four species are established in captivity, ensuring that a reservoir population is maintained.  Rats were eradicated from the island in 2000 and invertebrate population surveys were carried out by NPTS in 2002.  Field work on Fregate by NPTS discovered a new genus of snail in 1999, this species is also in need of conservation.

Taxonomy

A major research programme led by NPTS is the full revision of the taxonomy and conservation status of all Seychelles species.  This is producing several scientific publications, the most important of which are the Seychelles fauna monographs.