Pseudoscalibregma sp. 1  

Pseudoscalibregma Ashworth, 1901

Pseudoscalibregma sp. 1

Voucher: VINSON WEST: station 5MFA.

Diagnosis.  A medium-sized species, body elongate, arenicoliform, expanded in anterior half then tapering to narrow abdominal region; voucher specimen incomplete with 26 chaetigers, 15mm long and 1.8mm wide at its widest. Colour in alcohol light pink. Body segments bi- or triannulate; annulations formed of large squared cells; body surface relatively smooth, the annulation faint. Pygidium missing.

Prostomium with well-developed narrow, elongated processes or horns, pointed anterolaterally; posterior margin of prostomium visible dorsally; eyes absent. Peristomium achaetous, not concealing posterior margin of prostomium, consisting of single ring complete dorsally; ventrally, both upper and lower lip of mouth composed of around 10 small lobes.

Branchiae absent. Parapodia biramous, reduced, inconspicuous anterior in chaetigers becoming large and well developed in middle and posterior chaetigers. Dorsal and ventral cirri present; small, conical; prominent from chaetiger 16. Interramal papillae small, in anterior chaetigers, becoming larger in middle and posterior parapodia.

All chaetigers with noto- and neuropodial fascicles of slender capillaries; in anterior region arranged into 2 rows, with chaetae of posterior row longest; capillaries of middle and posterior chaetigers arranged in 1 row. Lyrate chaetae present from chaetiger 2; tine very long, unequal, both tapering to very slender filamentous tip.

Remarks. The combination of the following characters – arenicoliform body shape, T-shaped prostomium, presence of dorsal and ventral cirri in posterior segments, absence of spines and absence of branchiae make this species consistent with genus Pseudoscalibregma (see Blake, 1981).

This genus is well represented in the region, with four species known: Pseudoscalibregma bransfieldium (Hartman, 1967); Pseudoscalibregma usarpium Blake, 1981; Pseudoscalibregma papilia Schüller, 2008 and Pseudoscalibregma palmeri Blake, 2015. Falkland Island specimen differs from these and likely represents a news species (see comparative table below).

Comparison of morphology of known Pseudoscalibregma species from the region and Falkland Island specimen.