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Proceedings of Wayamba University Research Congress 2017, Senate Research & Higher Degrees Committee
95
The irregular echinoids of Sri Lanka
Arachchige G.M. a, Jayakody S. a* and Mooi R. b
a Department of Aquaculture and Fisheries, Wayamba University of Sri Lanka, Makandura, Gonawila,
Sri Lanka;
b Department of Invertebrate Zoology and Geology, California Academy of Sciences, 55 Music Concourse
Drive, San Francisco, CA 94118
*Corresponding author (email: sevvandi_jayakody@yahoo.com)
Abstract
Irregular echinoids are formally known as Irregularia, a group including forms such as lamp urchins
("cassiduloids", a non-monophyletic assemblage), sand dollars (Clypeasteroida) and heart urchins
(Spatangoida). The group is mainly infaunal and are important components of marine ecosystems
as both adults and larvae. The earliest information on irregular echinoids from Sri Lanka (formerly
Ceylon) comes from Agassiz (1872). Clark & Rowe (1971) compiled records of 24 species of
irregular sea urchins in the “Ceylon area” (some of these localities now belong to Indian Territory).
According to the most recent species list assembled by Arachchige et al (2017), 27 irregular
echinoids have been recorded from Sri Lankan waters. However, the current knowledge of diversity
and distribution of Sri Lankan species belonging to the Irregularia are poorly known. In addition,
there are no recent taxonomic studies or biodiversity surveys for Sri Lankan irregular echinoids, and
no illustrations or reference collections are available in Sri Lanka. This study was conducted as an
island-wide systematic sampling survey. Over 200 echinoid specimens were collected from 21
localities in Sri Lankan coastal waters by snorkelling, skin and SCUBA diving down to 33 m depth.
The collected specimens were identified using existing keys and authenticated with specimens
available at the Natural History Museum Vienna, Austria. This study recorded 21 irregular echinoid
species belonging to four orders, nine families and 15 genera. Among the identified irregular
echinoids, five species were new records from Sri Lankan waters. In addition, three unidentified
species belonging to the genera Fibularia and Metalia were reported and were kept as open
nomenclature. Also, 13 previously reported irregular echinoids were rediscovered during this study
(Table 1). For convenience of identification of all reported irregular sea urchins in Sri Lanka, a
dichotomous key was developed using information updated by the current study and published
information in the literature.
Proceedings of Wayamba University Research Congress 2017, Senate Research & Higher Degrees Committee
96
Table. 1. Identified sea urchin species, their families and orders (*New records from current study,
**species reported from current study but identified only to genus)
Order
Family
Species
Echinoneoida
Echinoneidae
Echinoneus cyclostomus
Echinoneoida
Echinoneidae
Koehleraster abnormalis
Echinolampadoida
Echinolampadidae
Echinolampas alexandri
Echinolampadoida
Echinolampadidae
Echinolampas ovata
Clypeasteroida
Astriclypeidae
Echinodiscus bisperforatus
Clypeasteroida
Astriclypeidae
Echinodiscus truncatus*
Clypeasteroida
Astriclypeidae
Sculpsitechinus auritus
Clypeasteroida
Clypeasteridae
Clypeaster humilis
Clypeasteroida
Clypeasteridae
Clypeaster reticulatus
Clypeasteroida
Fibulariidae
Echinocyamus megapetalus*
Clypeasteroida
Fibulariidae
Fibulariella angulipora*
Clypeasteroida
Fibulariidae
Fibularia sp1**
Clypeasteroida
Fibulariidae
Fibularia sp2**
Clypeasteroida
Laganidae
Jacksonaster depressum
Clypeasteroida
Laganidae
Peronella lesueuri
Clypeasteroida
Laganidae
Peronella oblonga*
Spatangoida
Brissidae
Brissus agassizii*
Spatangoida
Brissidae
Metalia sternalis
Spatangoida
Brissidae
Metalia sp**
Spatangoida
Loveniidae
Lovenia elongate
Spatangoida
Maretiidae
Nacospatangus alta
Species distribution maps for recorded species are also being prepared using the updated list. In
addition to the survey work, a broader study listing all species of irregular echinoids recorded from
both the shallow and deep waters of Sri Lanka has also been performed. Therefore, the diversity of
reported irregular sea urchins from Sri Lanka now stands at 35 species representing 11 families in
four orders.
Key words: Diversity; Irregular echinoids; Sri Lanka