INTRODUCTION
Nudibranchs are molluscan groups, commonly known as ‘sea hares’ and are best known for displaying a fascinating range of colours and body forms. The Ragged Sea Hare Bursatella leachii is a marine opisthobranch gastropod mollusc belonging to the family Aplysiidae and the order Anaspide. They are circumtropical, found worldwide in warm temperate to tropical marine environments (Rudman, Reference Rudman1998). Kruczynski & Porter (Reference Kruczynski and Porter1969) have listed North Carolina as the northern limit of this species along the US east coast. Information on sea hare distribution and description from the Indian subcontinent is scanty and, therefore, an investigation into this aspect is necessary and important. B. leachii is the only species described under the genus Bursatella. The distribution of this species has generally been reported from the inter-tidal zone and down to depths of at least 10 m in coastal areas of the Indo-West Pacific oceans, the Caribbean Sea and the Mediterranean Sea. A significant number of reports on the opisthobranch fauna of India have been made during recent times. The purifying and anti-HIV properties of the protein from the purple fluid of sea hare samples collected in India have been recorded (Rajaganapthi et al., Reference Rajaganapathi, Kathiresan and Singh2002). The occurrence of the sea slug Kalinga ornate along the inshore waters of the Bay of Bengal off Chennai, India was reported by Sethi & Pattnaik (Reference Sethi and Pattnaik2012). Similarly, there have been new records of the occurrence of the black-margined nudibranch Doriprismatica atromarginata from the inshore waters of the Bay of Bengal along the Karaikal coast (Sethi and Otta, Reference Sethi, Ranhith and Kannan2014). Specimens of the Wedge Sea Hare Dolabella auricularia from Kayalpatinam, Gulf of Mannar, on the south-east coast of India (Sethi et al., Reference Sethi, Ranhith and Kannan2014), and the side-gilled slug Pleurobranchus mamillatus off the coast of Tuticorin (Ranjith et al., Reference Ranjith, Sethi and Kannan2014) have been described. The present finding is the first record of the B. leachii species from the east coast of India.
MATERIALS AND METHODS
While carrying out a general survey on marine molluscs in Pulicat Lake, we noticed the presence of the sea hare Bursatella leachii along with other molluscan species, which is uncommon for this part of the coast. The specimens were caught approximately 3 km from the south-east side of Pulicat lake (13°33′57″N 80°10′29″E) in a sandy substrate. They were identified based on the presence of their characteristic taxonomic features. The collected specimens were preserved in 70% (v/v) ethanol and deposited in the National Biodiversity Referral Museum at CMFRI, Kochi. For photographic documentation, a Cyber-Shot Sony 16.2 megapixel camera was used.
RESULTS
Based on the specific taxonomic features of this mollusc, it was identified as Bursatella leachii.
SYSTEMATICS
Phylum MOLLUSCA
Class GASTROPODA
Clad EUOPISTHOBRANCHIA
Super-family APLYSIOMORPHA
Genus Bursatella
Bursatella leachii Blainville, 1817
The samples were found near to the estuaries with higher frequencies on sandy bottoms (Figure 1). While less numbers of specimens were recorded at depths of about 1 m, the maximum occurrence was found at depths of approximately 20 cm. Dense concentrations, as high as 14–25/m2 and in groups (Figure 2), were also observed. The specimens were found on seaweed beds of Gracilaria verrucosa. The eggs of this sea hare, found in long green strings resembling spaghetti noodles, were also observed to be attached to seaweed (Figures 3–5).
Study sites of Ragged Sea Hare Bursatella leachii collected from Pulicat Lake, the Bay of Bengal, along the east coast of India.
Density of Ragged Sea Hare Bursatella leachii at Pulicat Lake.
Live Ragged Sea Hare Bursatella leachii collected at Pulicat Lake from the Gracilaria verrucosa seaweed beds.
Mass spawning of Ragged Sea Hare Bursatella leachii at Pulicat Lake from Gracilaria verrucosa seaweed beds.
Ragged Sea Hare Bursatella leachii Blainville, 1817 from Pulicat Lake: (A) Adults of B. leachii involved in the spawning process with green spaghetti-like egg strings; (B) Green- and yellow-coloured egg mass of B. leachii.
SPECIES DESCRIPTION AND MORPHOMETRIC MEASUREMENTS
The body of Bursatella leachii is greyish-green to white-tan with dark brown blotches and spots throughout the body. The body is compact and rounded, but the head and neck are distinctly separated. The head part is broad and short. The mantle has a network-like pattern with blue eyespots (ocelli) within black spots and green areas. The body is covered with numerous long, branching fleshy papillae, giving the animal a ragged appearance. The gill is covered by a pair of fleshy parapodia. Two long retractile olfactory tentacles called rhinophores lie on the head and two fleshy enrolled oral tentacles appear at each side of the mouth. As it has been reported, we also observed that adults are completely devoid of an internal shell (Voss, Reference Voss1980; Kaplan, Reference Kaplan1988; Rupert & Fox, Reference Rupert and Fox1998). In the present collection, the maximum length and weight of the animals recorded were 75 mm and 23 g, respectively. The average length and weight were 53.82 ± 6.32 mm and 15.2 ± 3.88 g, respectively.
Sea hares are not collected for human consumption in India and are, therefore, less popular. They are generally considered as low-value by-catch in trawls and, hence, are either discarded or used as manure or as an ingredient for fish feed. They are known to possess anti-cancer, anti-tumour and anti-viral compounds and are extensively used in pharmacological industries in other parts of the world. Soblidotin (Dolastatin-10 derivative), Synthadotin/ILX651, Cemadotin and Kahalalide F are marine natural compounds with anti-cancer qualities, derived from the sea hare, which are under various stages of clinical trials (Avila, Reference Avila2006; Haefner, Reference Haefner2003). An anti-HIV protein, bursatellanin-P, has been isolated from the purple ink secretion of the species, although it remains to be seen whether there will be tangible biomedical and economic benefits derived from this discovery (Rajaganapathi et al., Reference Rajaganapathi, Kathiresan and Singh2002).
ACKNOWLEDGEMENTS
The authors are grateful to Dr Gary Cobb, Sea Slug Forum, Australia and Dr Deepak Apte, BNHS, Mumbai for providing necessary information and help with the validation of the specimen.
