FRESHWATER FISH
'The two known species found in the lake; Anguilla obscura, an eel and Eleotris fusca, a bully, are usually found in fresh or brackish water. The eel migrates to the sea to breed.
MARINE FISH
The Templeton Crocker Expedition collected 36 species of marine fishes on Rennell, 20 on Bellona and three on both islands, including a new flying fish of the genus Cypselurus from Rennell. The Danish Expedition in 1951 added another 19 species to the Rennell list including two small blenniid species and one small Kraemeria which were new to science. With other visits from scientists, the fish list for Rennell has continued to grow.
HERPETOLOGY
Lake Tegano is the only location for the endemic sea krait, Laticauda crockeri. It is the second record of a sea snake living in a freshwater lake; the other is from Lake Taal, Luzon in the Philippines. The sea krait is thought to have evolved in isolation during one of the periods when Lake Tegano became cut off from the sea. The other species of sea snake in Lake Tegano, Laticauda colubrina, has a wide distribution throughout the region.
Laticauda colubrina often tends to come on land when not foraging and hides in rock crevices and holes but L. crockeri never comes on land. L. colubrina can often be found resting on the small islets in the lake. L. crockeri feeds on the native goby, Eleotris fusca, while L. colubrina prefers the eel, Anguilla obscura. Neither species of snake feeds on the introduced fish. Tilapia mossambica.
Both species forage by swimming near the bottom and investigating crevices. They forage at depths ranging from a few centimetres to about 13 metres. L. colubrina grows much larger then L. crockeri. All large females of L. colubrina weighed more than 1000g which is much more than the heaviest mature female of L. crockeri (280g). According to East Rennellese, L. colubrine is an egg-laying species while L. crockeri gives birth to live young. This has been confirmed for L. colubrina but not for L. crockeri as yet.
It is likely that L. crockeri represents a relict of a regional population of L. laticaudata which was either widespread in the Solomon Island region or was a geographical outlier of the principal population. L. crockeri has evolved a number of distinctive features, of which the most obvious are its small size at maturity and well-developed melanism.
No amphibians have been recorded from Rennell. This is unusual as the rest of the Solomon archipelago has a rich and peculiar frog and toad fauna. Their absence is probably explained by the topography i.e. the raised coral atoll and the absence of surface water except for Lake Tegano which has slightly brackis water, factors making invasion by amphibians impossible.
There are five species of geckos, four skinks, one monitor lizard (Varanus) and three snakes (two boas, Candoia and one blind-snake), all of which are species with widespread distributions and are typical of the region. LAND SNAILS Rennell has 27 species of land snails belonging to 15 families. Seven species are endemic and two species are restricted to Rennell and Bellona (total = 9, endemism = 33%). The genus Quirosella (Ariophantidae) is endemic and is related to snails found in the Admiralty Islands north of eastern New Guinea. Three species of Quirosella have evolved and at some sites, they occur together. Why they differentiated is hard to explain considering the fairly uniform environment on Rennell. CRUSTACEANS The coconut crab (Birgus latro) and two or three other species of land hermit crabs (Coenobita) occur on Rennell. Coconut crabs have been harvested by the local people since the opening of the road in 1995 and larger animals are becoming harder to find. Two large and two small species of land crabs are found throughout the forest. Coconut crabs have been eaten to extinction in some islands and need to be harvested with care as they mature slowly and reach harvesting size of two kg at 30 years. The crab is nocturnal and usually lives les than one kilometre from the sea. Their favourite food is the juicy flesh inside young coconuts. The crab has a large body cavity under its shell where it sores coconut oil for its annual hibernation. It is thought that the crabs climb coconut trees and break of a number of nuts which fall to the ground. Some will split open and the crabs work on these to get into the flesh. They may spend up to two days eating the coconut. INSECTS Moths (Lepidoptera) have the greatest number of species (total = 246) of the insect groups recorded from Rennell. Of these, 35 species and 25 subspecies are endemic to Rennell and 5 species and 6 subspecies are found only on Rennell and Bellona. When these figures are combined (total = 71), 29% of the moths are endemic. The intense scientific interest in Rennell over the years has resulted in many insect collections. The biological significance of recording 246 species of moths on Rennell is unknown but it may be linked to the composition of the forest as some bats and moths play an important role as plant pollinators. This number of moth species may be typical for an island of this size but without more scientific investigation, it is not possible to make comparisions. Also, the level of endemism cannot be put into context at this time because there is no comparative information for other islands in the Solomons group. THE FAUNA OF LAKE TEGANO A total of 78 species of animals were recorded from the lake. Of these, 56 were identified and there were 12 species and one subspecies that are endemic to the lake. Also, three genera of crustaceans are endemic to Lake Tegano. The fauna includes: two sea snakes, two fish species, six lake gastropods, 22 lake crustaeceans, 40 lake insects (20 in the larval stage only); one water mite, two annelids, two nematodes and one leech. Four additional mosquito larvae are known only from small pools of stagnant water. Only 18% (14 of the 77 species) are of marine origin.' Source; Nomination of EAST RENNELL, SOLOMON ISLANDS by the Government of the Solomon Islands for Inclusion in the World Heritage List Natural Sites.
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