Euchone sp. 4  

Euchone Malmgren, 1866

Euchone sp. 4

Voucher specimens. VINSON WEST: station 1MFB.

Diagnosis. Small bodied, slender species; voucher specimen with body complete, but branchial crown missing; 3 mm long (body) and 0.25 mm wide, with 8 thoracic and 15 abdominal chaetigers with 5 of these associated with pre-pygidial depression; colour in alcohol pale yellow.

Collar well developed, flared; much higher ventrally than dorsally; mid-dorsal margins not overlapping; anterior margin entire without any notches (?). Glandular ridge present on chaetiger 2, very narrow.

Collar chaetae narrowly-limbate arranged in single longitudinal somewhat oblique row; superior notochaetae long, narrowly limbate, while inferior notochaetae short, broadly limbate (but not truly mucronate). Thoracic neuropodial uncini acicular, with main fang relatively slender in lateral view and with at least 6 small teeth. Companion chaetae absent. Abdominal neuropodial chaetae few, narrowly-limbate. Notopodia of anterior abdominal chaetigers with quadrate avicular uncini (not as robust as in other Euchone species); in frontal view resembling rasp-shaped plates of Amphicorina, with small teeth arranged in about 8 rows of approximately 15 teeth per row above the main fang; with well developed breast and very short handle.

Abdomen with a narrow pre-pygidial depression occupying 5 chaetigers, with high raised membranous lateral flanges connected anteriorly by a rounded membrane, flanges lower posteriorly. Pygidium well developed, triangular lobe. Tube not observed.

Mehtyl green staining pattern: refer to plate accompanying this description.

Remarks. Euchone sp. 4 shows similarities with Euchone southerni, which has been by now reported from different localities in the Atlantic Ocean - its type locality in Ireland; Gulf of Mexico (as Euchone cf. southerni) and Mediterranean Sea (Giangrande, 1989). This latter species is now considered as a new, but undescribed species (as Euchone sp. in Giangrande and Licciano, 2006). There are detectable differences relating to size, number of abdominal chaetigers, and incision of collar and staining pattern. Falkland Island specimen likely represents a new species; however, specimens with branchial crown (currently not available) will be necessary to fully diagnose this species.

Comparison of specimens assigned to Euchone southerni and similar species, including Falkland Islands specimen.