INTRODUCTION
Nemerteans or ribbon worms are soft bodied unsegmented worms. They are common and are often an abundant constituent of intertidal fouling communities, typically hidden in crevices or among sessile invertebrates and algae. They are basically carnivorous, feeding on small crustaceans, polychaetes and molluscs. To date, a total of 1275 species have been described and are grouped into 250 genera (Kajihara et al., Reference Kajihara, Chernyshev, Sichun, Sundberg and Crandall2008) and two classes.
In India, studies on the fauna of the phylum Nemertea are few and far between. The earliest report on Indian nemerteans is that of Ehernberg's (Reference Ehrenberg1831) brief account on Eupolia hemprichi (Punnett, Reference Punnett and Gardiner1903; Gravely, Reference Gravely1927). Another record of Gorgonorhyncus repeans from certain coasts of Indian was made by Coe (Reference Coe1947). There was also an account of some unidentified nemertean worms from the Gulf of Kachchh (Desai, Reference Desai2010); however, they were identified only up to the level of phylum. The heteronemertean Lineus mcintoshii has been reported by several workers from different coasts all over the world (Gibson, Reference Gibson, Costello, Emblow and White2001, Reference Gibson2005, Reference Gibson, Gibson, Costello, Bouchet, Boxshall, Arvantidis and Appeltans2010, Reference Gibson, Norenburg and Gibson2014). Here we report the occurrence of the heteronemertean Lineus mcintoshii (Langerhans, 1880) on the Kerala coast, which represents the first documented record of the species from the Indian coast. A comprehensive synonym list, as well as descriptions of features that will allow non-specialists to identify this species, are also included.
Lineus mcintoshii (Langerhans, 1880) (Figure 1)
Cerebratulus mcintoshii (unaccepted)
Lineus mintoshii (unaccepted)
Lineus mcintoshii (Langerhans, 1880). (A) Dorsal view of a living specimen; (B) a preserved specimen showing ventral view of head. 220 × 135 mm2 (96 × 96 DPI).
MATERIAL EXAMINED
The nemertean sample was incidentally observed in the intertidal region of the Mullur coast, Kerala. The nemertean was found associated with the green seaweed Bryopsis plumosa. The seaweed collected from the Mullur coast (8°22′N 77°00′E) was brought to the laboratory in sea water and the worms were sorted and examined for length, breadth and colour pattern in live condition and preserved in 4% formalin.
RESULTS
DESCRIPTION
In living condition, the length of the nemertean was about 8–9 cm, the breadth attained a maximum of 1 mm near the fore gut and tapered to the tail region. The body of Lineus mcintoshii can stretch a lot, up to five times its resting length. The body is slightly compressed ventrally. The body colour on the dorsal surface was yellowish white. The cephalic tip and the margins of the dorsal, as well as the ventral surface of the body, are almost colourless. The head was not demarcated from the neck. There was a flattened, triangular, reddish patch on the posterior portion of the cephalic tip. From the centre of this patch, a single reddish orange line extended along the dorsal median line to reach to the tip of the tail. On either side of this red line, numerous transverse dark brown patches were found rather regularly arranged. The distal ends of the patches marginally reached the ventral surface, while the proximal ends were connected with a longitudinal dark brown line, which was found abutting on each side of the longitudinal red line. The general shape of the patches appeared to be rather triangular, proximally wide and distally narrow. There were two small black dots in front of the reddish patch on the tip of the head. These dots were sometimes transformed into longitudinal short black lines that extended rather posteriorly. The cephalic grooves were long and reached the second transverse patches.
Lineus mcintoshii and Iwatanemertes piperata resemble each other but they can be distinguished by the reddish longitudinal stripe(s). In I. piperata, there are two, lateral red lines, one on each side of the body, which appear to represent a lateral nerve cord, a posterior continuation of the brain. On the other hand, L. mcintoshii has a mid-dorsal red stripe and the black markings are more solid and not so ‘amorphous’ as in I. piperata.
SYSTEMATICS
Phylum NEMERTEA, NEMERTINA; NEMERTINEA
Class ANOPLA
Sub class HETERONEMERTEA
Family LINEIDAE McIntosh, 1874
Genus Lineus Sowerby, 1806
Lineus mcintoshii (Langerhans, 1880) (accepted)
HABITAT
The worm was found associated with seaweeds.
DISTRIBUTION
Lineus mcintoshii has been reported by several researchers from different coasts all over the world. Gibson (Reference Gibson, Costello, Emblow and White2001, Reference Gibson2005, Reference Gibson, Gibson, Costello, Bouchet, Boxshall, Arvantidis and Appeltans2010, Reference Gibson, Norenburg and Gibson2014) reported its occurrence in the North Atlantic Ocean. Kajihara (Reference Kajihara2007) reported the presence of L. mcintoshii in Japanese waters.
REMARKS
The present report describes the distribution of this nemertean worm in Kerala, south-west coast of India. The record of this species in this location implies a new southernmost limit of distribution, extending the known distribution range in Pacific waters.
ACKNOWLEDGEMENTS
The authors are deeply grateful to Dr Bijukumar, Head of the Department of Aquatic Biology and Fisheries, University of Kerala, for providing adequate laboratory facilities in the department to carry out the research work. Financial support from the UGC (RGNF) is duly acknowledged. Thanks are due to Hiroshi Kajihara, Hokkaido University, Reviewing Editor of Zoological Science, Zoological Society of Japan and J.L. Norenburg, Research Zoologist at the Smithsonian National Museum of Natural History, Washington for confirming identification of the nemertean.
