List of echinoderms of Sri Lanka
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Sri Lanka is a tropical island situated close to the southern tip of India. The invertebrate fauna is as large as it is common to other regions of the world. So it is complicated to summarize the exact number of species found within the country.
Echinoderms belong to the phylum Echinodermata. They are deuterostomes that are closely related to chordates. Echinoderms are characterized by having a water vascular system, tube feet, radial symmetry, and undergo complete regeneration from a single limb. It is the largest phylum that has no freshwater or terrestrial members. There are five classes of echinoderms: Asteroidea (starfish), Ophiuroidea (brittle star), Echinoidea (sea urchin), Crinoidea (sea lily) and Holothuroidea (sea cucumber).
The following list provides echinoderms currently identified in Sri Lankan waters.
The first detailed work on irregular echinoids was carried out by Agassiz in 1872 and then by Clark & Rowe in 1971 where they compiled records of 24 species of irregular sea urchins in the "Ceylon area". However, some of these localities now belong to the Indian Territory. In 2017, a recent species list has been made by Arachchige et al., where he described 27 irregular echinoids from Sri Lankan waters.[1] The information on regular echinoids was listed by Agassiz & Desor in 1846 which continued to advance until the end of the 19th century. Then, there was a knowledge gap between the mid-20th and the beginning of the 21st centuries mainly due to a lack of systematic studies. However, in the latter part, two checklists have been published by the IUCN Red List in 2006 and 2012.[2]
Currently, in Sri Lanka, there are 39 regular echinoids belong to 28 genera, nine families, and five orders are recorded.[2] Meanwhile, there are 21 irregular echinoid species belong to four orders, nine families, and 15 genera in Sri Lanka.[1]
Irregular echinoids
Order: Echinoneoida
Family: Echinoneidae
Order: Echinolampadoida
Family: Echinolampadidae - Cassiduloids
Order: Clypeasteroida - Sand dollars
Family: Astriclypeidae
Family: Clypeasteridae
Family: Fibulariidae
Family: Laganidae
Order: Spatangoida - Heart urchins
Family: Brissidae
Family: Loveniidae
Family: Maretiidae
Regular echinoids
Order: Cidaroida
Family: Cidaridae
Order: Diadematoida
Family: Diadematidae
Order: Stomopneustoida
Family: Stomopneustidae
Order: Camarodonta
Family: Echinometridae
Family: Temnopleuridae
Family: Toxopneustidae
Starfish
The exact number of starfish in Sri Lankan waters is unknown. Many works came through the work done based on Indian echinoderms in and around Indian seas.[3][4][5][6][7][8]
Order: Valvatida
Family: Acanthasteridae
Family: Asterinidae
Family: Ophidiasteridae
Family: Oreasteridae
- Anthenea pentagonula
- Anthenea regalis
- Goniodiscaster scaber
- Siraster tuberculatus
- Stellaster equestris
- Stellaster incei
Family: Goniasteridae
Order: Forcipulatida
Family: Asteriidae
Order: Paxillosida
Family: Astropectinidae
Family: Luidiidae
Brittle stars
There is little works have done to identify the brittle star species around Sri Lanka. But, further detailed work is necessary to compile a checklist.[9][10]