Rhodininae Arwidsson, 1906
Rhodine Malmgren, 1865
Rhodine cf. antarctica Gravier, 1911
Vouchers. LOLIGO: station L11FA.
Diagnosis. Small-sized species; voucher incomplete; composed of single, anterior fragment with 12 chaetigers, 10mm long and 1mm wide; colour in alcohol whitish to pale yellow.
Prostomium without cephalic plaque, but with high cephalic keel; prostomium together with peristomium fused with first chaetiger. Appearance of a shallow depression anterior to first chaetiger, giving slightly “humped” appearance to prostomium, but no true dorsal crest observed. Chaetiger 1-3 long (much longer than wide) with the first chaetiger longest and chaetigers 2 and 3 slightly shorter; chaetigers 4 to 9 short (about as long as wide), chaetigers 10-12 longer again. Chaetigers 2 and 3 with well-developed segmental collar; collar anteriorly entire, without any pronounced notches (at best with a wide, very shallow depression dorsally in large specimen); well-developed collars also observed on at least other fragmented body segments (likely from mid or posterior part of the body). From chaetiger 4-9 whitish, ventral glandular shields present on the anterior half of segment.
Chaetigers 1-4 with notochaetae only; notochaetae long and short narrowly limbate capillaries. Uncini from chaetiger 5 arranged in double, interlocking rows until the end of 12 chaetigers-long fragment, with about 23 uncini per row. The uncini have a large main fang surmounted by several rows of small teeth; breast of uncini with a stout subrostral spine above basal prow; with medium length handle.
Posterior part and pygidium not observed.
Tube: tube composed of small, tightly packed particles; speckled with mostly black particles mixed with fewer white particles and test of forams (refer to the image).
Remarks. Specimen is consistent with genus Rhodine in possessing collared segments, uncini from chaetiger 5, arranged in double rows on several anterior chaetigers. Rhodine is a small genus with some species considered to have a cosmopolitan distribution, the last description of new Rhodine species dates to 1911. Of the Rhodine species previously reported from the region: R. antarctica, R. intermedia and R. loveni, the FI specimens appear to be most similar to R. antarctica (see table below), mostly due to dimensions of body segments, lack of obvious dorsal crest and presence of ventral shields on chaetigers 4-9 (presumably, Gravier (1911) reported these as “Aux quatrième, cinquième, sixième, septième, huitième et neuvième sétigères, on observe des anneaux blancs”). However full distribution of uncini with double rows as well as characters derive from the posterior, particularly the form of pygidium cannot be established. Other species belonging to genus Rhodine were also encountered in Falkland Islands collection and these species are compared in table below.
Comparison of Rhodine species reported from the region (as reported in literature) and Falkland Island specimens.
|
Species |
Size category |
Prostomium |
Anterior segmental collars |
Uncini in double rows in chaetigers |
Ventral shields in chaetigers |
Relative lengths of chaetigers 1-4 |
|
R. antarctica |
small |
smooth |
present in chaetigers 2 and 3, entire |
5-12 |
4 - 9 |
1 very long, 2-3 long, 4 short |
|
R. intermedia |
medium to large |
with dorsal crest |
present in chaetigers 2 and 3, not notched or slightly notched mid-dorsally |
5-14 |
3-10? |
1 very long, 2-3 long, 4 short |
|
R. loveni |
medium to large |
with dorsal crest |
present in chaetigers 2 and 3, notched mid-dorsally |
5-14 |
3 - 9? |
1 very long, 2-3 long, 4 short |
|
Rhodine cf. antarctica (this study) |
small
|
slightly humped, but no true dorsal crest |
present in chaetiger 2 and 3, entire |
5 -12 (fragment is only 12 chaetigers long) |
4 - 9 |
1 very long, 2-3 long, 4 short |
|
Rhodine cf. intermedia (this study) |
medium |
with dorsal crest |
present in chaetigers 2 and 3, not notched or with shallow depression mid-dorsally |
5-14 (or end of 12 chaetiger long fragment) |
3 - 9 |
1 very long, 2 short, 3 long, 4 short |