First Record of Dorid Nudibranchs Chromodoris Geminus (Rudman, 1987) from the Palk Strait of South East Coast of India

Advances in Biological Research 6 (5): 182-185, 2012 ISSN 1992-0067 © IDOSI Publications, 2012 DOI: 10.5829/idosi.abr.2012.6.5.6417

First Record of Dorid Nudibranchs Chromodoris geminus (Rudman, 1987) from the Palk Strait of South East Coast of India

Ramar Vinoth and Sundaram Ravikumar

Department of Oceanography and Coastal Area Studies, School of Marine Sciences, Alagappa University, Thondi Campus, Thondi-623 409, Ramanathapuram District, Tamil Nadu, India

Abstract: Nudibranchs are soft bodied sea slugs diversified along tropical India oceans. It has derived defense chemicals since the upper Cambrian the sea slugs are reported in Gulf of Mannar of south India. The present study reports the first time distribution of sea slugs along Palk Strait region of south India.

Key words: First Record Sea Slugs Chromodoris geminus and Palk Strait

INTRODUCTION interesting study, because many of the typical marine snails have remained virtually unchanged for millions of Nudibranchs are sea slugs which are soft-bodied years, appeared in the Upper Cambrian [9]. The loss of the animals like clams, snails, squid and mollusks. There are restrictive shell has enabled the plasticity of the more than 3,000 known species of different colored molluscan body be exploited and many more ecological Nudibranchs from bright blue to pink to white with niches to be occurred. orange polka dots. The patterns of color are more Slug with a defensive chemical is dependent upon its vivid and varied than any coral fish forms and are food source. The ability to synthesize its own feeding diverse. Those Nudibranchs which thrive in the hard, inhibitor would have obvious advantages. As another changing environment of the shore tend to be tough, porostome, Phyllidia derives its metabolites from food unspectacular species. In the gastropod subclass synthetic capacity has evolved within the group [10]. In Opisthobranchia there has been a general trend India distribution or nudibranchs have been reported in toward loss of the shell, with many lineages evolving several parts of ocean [11-24], but the assessment of from snails into sea-slugs and hence it named as biodiversity of nudibranchs along Palk Strait of “naked gills”. The loss of the shell has been compensated southeast Coast of India is overlooked and hence the by various adaptations [1-6]. The molluscan order present study has undertaken. nudibranchia are capable of graceful swimming, passive floating in the plankton layers, creeping over hard rock MATERIALS AND METHODS surface or along delicate hydroid stems and burrowing into sand or mud. A specimen of the Chromodoris geminus Two most common groups of nudibranchs are the (Rudman, 1987) (Fig. 1a) were collected from 4 to 6m depth dorids and eolids. The dorids are broad footed, low on seagrass beds using snorkeling method at Thondi profiled with delicate organs of small and gills retractable coast along Palk Strait of Southeast Coast of beneath a tough mantle. The eolide form is narrow footed Tamil Nadu (Fig. 1b), Latitude 9° 44’ 01.78” N and with numerous dorsal projections which are unrelated to Longitude 79° 01’ 00.98” E) during Dec 2011 to Jan 2012 either sea slugs or dorids [7]. Among dorids Dendrodoris and the specimen was brought to the laboratory and the limbata is only a known species [8], which are belongs identification was made using the standard guidelines: to the specialized suborder Porostomata. The diversity of (http://seaslugs.free.fr/nudibranche/a_chromo_geminus form, color and ecology in the nudibranchia provides .htm,www.seaslugforum.net/showall/chrogemi and [25].

Corresponding Author: Sundaram Ravikumar, Department of Oceanography and Coastal Area Studies, School of Marine Sciences, Alagappa University, Thondi Campus, Thondi-623 409, Ramanathapuram District, Tamil Nadu, India. Tel: +91-4561-243470, Cell: +91-9003306959. 182 Advan. Biol. Res., 6 (5): 182-185, 2012

(a) (b)

Fig. 1: (a) Map of the Study area, (b) External Morphology characters, (c) Chromodoris geminus (d) Gill circlet (Simply pinnate).

RESULTS purple-brown spots or marks, usually ringed with white, an often reticulate brownish background and a purple The present study reported only one species border. C. geminus differs in having four color bands C. geminus of sea slugs during this study in the around the mantle edge, an outermost thinner than the Thondi Coast along Palk Strait of Southeast Coast rest is white, then translucent grayish purple, then of India. It belongs to Phylum: Mollusca, Class: another white band and finally a band of bright golden Gastropoda, Subclass: Opisthobranchia, Order: yellow. The other three have a distinct purple line at the Nudibranchia, Suborder: Doridina, Family: border, narrow in C. leopardus and R. tryoni, but broad in Chromodorididae and Species: Chromodoris geminus. C. kuniei. The shape of the body of R. tryoni was high The morphological features of presently observed with a reduced mantle overlap, is typical of the genus nudibranchs are given below: Risbecia. Chromodoris has a over lapped wide mantle with the purple mantle edge, C. leopardus and C. kuniei Similar Species: The C. geminus is looking more similar can be distinguished from R. tryoni by the broad purple to offer species like Chromodoris kuniei, Risbecia tryoni border, consisting of three slightly different colored and Chromodoris leopardus. bands in C. kuniei and by the leopard-like multiple spots, or marks, forming a hollow square, found in C. leopardus. Description: The C. geminus, R. tryoni, C. kuniei and C. The Rhinophore stalk is translucent white with pointed leopardus have oval body and wide mantle. Both have tips and the club is a translucent gold with a brownish purplish or brownish mantle with dark round spots with tinge to the lamellae. Gill circlets are simple pinnate white haloes in the mantle. They all have large purple or (Fig.1c and 1d).

183 Advan. Biol. Res., 6 (5): 182-185, 2012

Size: 5.8 cm In 2001, chemo-ecological studies on the opisthobranchiate fauna were also published from Locomotion: A sea slug “crawls” by gliding along on its this area [29]. Fourteen species of nudibranchs have foot. The foot is a broad, flat muscle. It also adheres to recently recorded from the Gulf of Mannar region rocks and other surfaces. Sea slug moves to the waves of including C. geminus [28]. The present study also fine muscular contractions sweep along the foot. The reported C. geminus from the Palk straight region and it is contractions lift the animal’s foot and then return it to the a new record to this area. surface a little farther ahead and pulling the animal forward. ACKNOWLEDGEMENT

Feeding: Sea slugs are nudibranchs have a radula - a The authors are thankful to the authorities of ribbon of curved, chitinous teeth. The radula functions to Department of Oceanography and Coastal Area Studies, scrape or tear food particles. Nudibranchs are grazing Alagappa University for providing facilities and UGC New carnivores that feed on sessile animals such as hydroids, Delhi for the award of Dr. K.S. Kothari post - post doctoral sea anemones, soft corals, bryozoans, sponges, barnacles Fellowships. and fish eggs. Each family of nudibranchs is usually restricted to one type of prey. REFERENCES

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