Artacamella Hartman, 1955
Artacamella sp. 1
Voucher. VINSON WEST: station 1MFA and station 3MFB.
Diagnosis. Voucher 1MFA (too damaged for meaningful description, although extended proboscis clearly observed). Voucher 3MFB small, slender specimen 3mm, slender, incomplete (only 15 chaetigers longs = thoracic segments only, abdomen missing entirely); colour in alcohol pale yellow, no pigmentation. Eye absent. Anterior structures typical for the genus with prostomium inconspicuous lobe; tentacular membrane projecting anteriorly when fully expanded; upper lip projecting anteriorly, with pair of expanded peristomial lateral lobes forming 3-lobed structure; lower lip expanded, forming conical, longitudinally ridged, proboscis. Buccal tentacles short.
Branchiae missing (scars observed); 2 pairs, on segments 2–3; inserted laterally with posterior pair inserted more laterally than anterior pair, notochaetae and uncini begin on the same segment (=segment 6), thoracic uncini all acicular, of the same type on all thoracic segments. All notopodia of similar size. All notochaetae of similar size and structure, simple, smooth-tipped, narrowly limbate capillaries. All thoracic uncini long-handled hooks with large distal fang surmounted by crest of many denticles; uncini arranged in single rows throughout thorax. Abdomen and pygidium missing.
Remarks. The presence of conical ridged proboscis, thoracic long-handled uncini and 15 thoracic chaetigers assign Falkland Island specimens to genus Artacamella Hartman, 1955. While one specimen is badly damaged and the other is incomplete (abdomen is entirely missing), the comparison with only 4 known species of Artacamella suggest, that these represent a new species (see comparative table below). However better preserved material will be necessary in order to formally describe this species, which is here assigned to morphospecies Artacamella sp. 1. At the same time, this is a first record of genus Artacamella for the FI region, but also its first record from deeper waters as known species so far had only shallow water distribution (see table below). Artacamella can be easily confused with genus Trichobranchus Malmgren, 1866 when proboscis retracted (see Hutchings and Peart, 2000; Muir 2011).
Comparison of known species of Artacamella and Falkland Island specimens (modified from Hutchings and Peart, 2000).
Type/Voucher locality |
No. of branchial pairs |
Notopodial development |
Notopodia from segment |
Neuropodia from segment |
Arrangement of uncini |
|
A. dibranchiata |
Port Phillip Bay, Victoria, Australia, 20m |
2 |
1st pair smaller than subsequent pairs, compact, rectangular
|
6 |
5 |
in single rows throughout |
A. hancocki |
Off Los Angeles, California, USA, 20m |
3 |
1st-3rd pairs smaller than subsequent pairs |
5 |
5 |
? |
A. torulosa |
Halifax Bay, Queensland, Australia, |
2 |
1st-2nd pairs smaller than subsequent pairs |
6 |
6 |
in double rows on first 5 thoracic neuropodia, in single rows on all subsequent segments |
A. tribranchiata |
Jervis Bay, NSW, Australia, 11m |
3 |
all of similar size, compact, rectangular |
6 |
6 |
in single rows throughout |
Artacamella sp. 1 |
Falkland Islands, ~1000m |
2 |
all of similar size, compact, rectangular |
6 |
6 |
in single rows throughout (thorax) |