Nicomachinae Arwidsson, 1906
Micromaldane Mesnil, 1897
Micromaldane sp. 1 (larva?)
Voucher. VINSON WEST: station 3MFB.
Diagnosis. Extremely small specimen, probably a larval stage as segmentation is not fully completed; chaetae developed; body spindle shaped (widest in the middle and narrowing anteriorly and posteriorly); 2mm long, 0.12mm wide; preserved specimen pale yellow.
Prostomium fused to peristomium, rounded anteriorly, forming a slight arched dorsal keel (resembling head of Rhodine).
Notochaetae of two types: straight, smooth, appearing narrowly limbate under light microscopy, 2 per fascicle observed, and single short, spatulate, lancet-shaped chaetae in each fascicle. Neuropodia not observed in first chaetiger with notochaetae, but present in all other chaetigers , very few per ramus – chaetiger 2 with 1 uncinus increasing to maximum number of 3 uncini in mid body chaetigers, thereafter decreasing to 1 in the last chaetiger. Uncini strongly curved with long shafts and swelling on the breast; main fang surmounted with few (number not clearly observed) smaller teeth; with large rostrated tooth below the main fan, fibrils not observed. Pre-anal achaetigerous segment/s likely present, but not clearly visible. Anal plaque likely not fully developed yet (larval character) or alternatively missing.
Remarks. Recently, Darbyshire (2013) described a new species Micromaldane shackletoni from Falkland Islands, intertidal depths and provided comparative table to all know species in this genus.
However Falkland Island specimen collected here, from slope depths (~1000m) is not the same species as M. shackletoni as it clearly has spatulate, lancet notochaeta, rather than narrow ones. Only two of the known species of Micromaldane possess spatulate chaetae – the type species of the genus M. ornithochaeta Mesnil, 1897 (type locality: France, know considered cosmopolitan, including the records of Fauvel (1916) from the Southern Ocean) and M. jonesi Achari, 1968 known from India.
Given the extremely small size, low number of chaetigers and incomplete segmentation, it is likely that this specimen represents the advanced larval stage (see discussion in Darbyshire, 2013) and it is not assigned to any species until more specimens become available.