Spiochaetopterus M Sars, 1856
Spiochaetopterus sp. 1
Voucher. LOLIGO: station 3FA and INFLEXIBLE: station 3MFB.
Note: The morphological description of chaetopterids is structured in 3 different body regions following Bhaud (1998): anterior (region A), mid-body (region B) and posterior (region C) (e.g. A4 = chaetiger 4 in region A, B1= chaetiger 1 in region B).
Diagnosis. Small-sized species, specimen with well preserved region A, but damaged region B and C (specimens incomplete), annoculate species with the following count of chaetigers: 9A, 2B and at least 5C (specimens incomplete); measuring 4mm long and 0.3mm wide for 16 chaetigers. Eyes absent. Chaetiger A4 with a single large modified spine, spine rhomboid (?) in distal view, amber coloured. Long and short lanceolate chaetae present in region A. Red/brown band ventrally on A6 and very distinct white band on A7. Structure of region B and C not clearly observed due to damage of the specimen. Tube unbranched, smooth (no articulations) and translucent.
Remarks. Two species previously reported from the region are Spiochaetopterus patagonicus Kinberg, 1866, (no description available at the time of writing) and S. costarum (see Hartmann-Schroder, 1991), which differs from FI specimen in having much larger number of mid-body (region B) segments (29 reported by Hartman-Shroder, 1991) and articulated tube. Bhaud (1998) eastablished two groups of Spiochaetopterus, based on comparison of five species of the genus Spiochaetopterus: S. typicus, S. bergensis, S. costarum, S. oculatus, and S. solitarius. Group A, with boreal biogeographic affinity, consisting of S. typicus and S. bergensis. Representatives of group A have a middle region of two segments, modified setae of segment A4 are distally rhomboid and the tubes are without articulations. Group B, with temperate biogeographic affinity, consisting of S. costarum, S. solitarius and S. oculatus. Representatives of group B have a middle region of many, always more than 2 segments; modified setae of A4 are distally cordate, and the tubes are with articulations. Falkland Island specimens clearly belongs to group A, which species have boreal distribution. It is therefore likely that Falkland Islands specimens represent a new species, but better preserved material will be necessary to compare and diagnose this species. For now, we suggest morphospecies name Spiochaetopterus sp. 1.
