Marine biologists in the city are surprised by the sighting of a rare seven-armed sea star popularly known as star fish along the Chennai coastline.

The two specimen collected by the officials from the sea near Nochikkuppam area have been exhibited in Marine Biology Regional Centre (MBRC) aquarium at Foreshore Estate.

K. Venkataraman, Officer-in-Charge, MBRC, Chennai, said the marine aquarium in their office premises was inaugurated four years ago. “We used to collect specimen for the aquarium from the Rameswaram coast and exhibit them. A couple of days ago when a team of officials went to Nochikuppam area, they found two seven-armed sea star, which has not been recorded in the entire coastline of the subcontinent so far,” he said.

During 1930s researchers from the Madras University identified the presence of coral reef bed along the Chennai coastline. The reef bed was found running along the stretch from the present harbour area up to Mahabalipuram. After 1940s there were no studies or research work had been taken up. Again last year the Geological Survey of India authorities identified the presence of coral reefs near Mahabalipuram, Dr. Venkataraman said.

Explaining about the speciality of the seven-armed sea stars, he said like the house gecko, the seven-armed sea stars shed their arms when threatened by the predators, which would later grow automatically. The seven-armed sea stars do not have blood and eyes. Another speciality of the sea stars was that unlike the other marine organisms, they bring their stomach out and digest the feed externally.

A total of 2,000 species of sea stars are found world over of which 765 were found in the coral reef areas in the country, which included all different varieties of echinoderms, Dr. Venkataraman said. Available records showed that the seven-armed sea stars were found in Mauritius, Philippines and Hawaii Islands.

Coral reefs and associated organisms were found along the Chennai coastline at a depth of about 30 ft, Dr. Venkataraman said adding that the presence of reef bed provide livelihood for the fishermen, ensure protection of the coastline and help researchers to take up study on them.