Eubonellia noratlanticum DattaGupta 1981

Eubonellia noratlanticum DattaGupta, 1981

(Fig. 2 A-D)

MATERIAL EXAMINED. — Porcupine Abyssal Plain, BEN- GAL 2, Discovery 226, stn 13078#11, 48°53.19’N, 16°35.98’W, 4844 m, 12.III.1997, 2 ♀♀.

DESCRIPTION

Colour of proboscis and trunk of preserved specimens is light pink. Distal tip of proboscis of larger specimen is damaged. In smaller specimen only basal stump of proboscis is still attached to trunk. Proximally, lateral margins of proboscis curl inwards giving it a tubular appearance (Fig. 2A). Trunk of larger specimen measures 66 mm in length and 12 mm across broadest part. Corresponding measurements of smaller specimen are 40 and 10 mm. Integument is thick and opaque at extremities of trunk where longitudinal muscles are arranged in bands, but thin and transparent in middle region of trunk. To unaided eye integument appears smooth but under magnification elongated papillae are visible in contracted regions of trunk, aligned roughly in transverse rows. Proboscis and trunk covered with elongated finger-like outgrowths, occurring either singly or in clusters (Fig. 2A). Genital pore is a transverse slit located about 8 mm away from anterior end of trunk (Fig. 2A).

Gonoduct single, sac-like, located on right side of nerve cord (Fig. 2B). Gonostome terminal, resembling short flared vase on a long stalk (Fig. 2B). Alimentary canal long and coiled forming several loops. Contents of gut fine sand not moulded into faecal pellets. Dorsal and neurointestinal vessels arise from wall of foregut without ring sinus (Fig. 2C). Dorsal vessel prominent, passing anteriorly dorsal to oesophagus and pharynx and entering proboscis. Neurointestinal vessel is single throughout (Fig. 2C). Anal vesicles small and branching (Fig. 2D).

REMARKS

The genus Eubonellia is distinguished by the presence of a bifurcate proboscis, absence of ventral setae, and a single gonoduct (right) with a distally located gonostome. The species Eubonellia noratlanticum is based on specimens from the North Atlantic collected at a depth of 3800 m. The present specimens closely approach the description provided by DattaGupta (1981) except for minor differences in the papillae and anal vesicles. The elongated outgrowths on the proboscis and trunk in the present specimens are probably epizoans. Some epizoans have been reported to occur on soft-skinned animals such as polychaete worms. Eubonellia noratlanticum appears to be close to E.valida, described by Fisher (1946). According to DattaGupta, the proboscis of E.valida is long, broad and flat and distally ends in two narrow limbs.