Rabbitfish (Siganidae) are morphologically conservative Perciforme Fish found on Coral reefs in the Indo-Pacific Region. They get their name from their prominent front teeth, which are used scrape algae from Coral reefs and other hard substrates. All Rabbitfish conform to three basic shapes, with deep bodied forms, slender bodied forms and streamlined spindle-shaped forms. There are thought to be about 27 species, which can be separated on a mixture of colouration and genetic data. It is likely that the group contains many cryptic species.
The species name Siganus lineatus is currently used to describe Rabbitfish from southern India, Sri Lanka, the Maldives, Australasia, the Philippines and the west Pacific Islands. It has been thought for some time that the central Indain Ocean Populations are a separate species, but only limited data on these Fish has been available, based upon preserved specimens in museum collections that have lost their colouration
In a paper published in the journal Zootaxa on 30 May 2014, David Woodland of Zoology at the School of Environmental and Rural Science at the University of New England in New South Wales and Charles Anderson of Manta Marine Pvt Ltd in Malé in the Republic of Maldives, describe the Rabbitfish from southern India, Sri Lanka and the Maldives as a separate species, based upon genetic and colour information.
The new species is named Siganus insomnis, meaning ‘sleepless’, due to its nocturnal lifestyle. It is a blue Rabbitfish with a silvery belly and a distinctive pattern of bronze or golden bronze spots and stripes. It forms large schools in the waters around Sri Lanka, particularly around Coral and sandstone reefs and Sea Grass beds. The juveniles are found in brackish estuaries and lagoons. In India the species is found in Vembanad Kayal, a 200 km brackish lake running parallel to the coast in Kerala State, and in the Gulf of Mannar, where the juveniles are found in brackish estuaries and the adults on coral reefs. It was found on a number of coral atols in the Maldives, notably Faadhippolhu in the north and Kolhumadula and Addu in the south.
Siganus insomnis, subadults, about 15–20 cm long, Horubadhoo Island, Baa Atoll, Maldives. Dieter Grage in Woodland & Anderson (2014).
Siganus insomnis, large adults, about 35 cm SL, Komandoo Island, Lhavyani Atoll, Maldives. Dieter Grage in Woodland & Anderson (2014).
Siganus insomnis, adults, about 30 cm SL, Third Reef off Negombo, Sri Lanka. Susan Anderson in Woodland & Anderson (2014).
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