Phyllodoce patagonica complex
Phyllodocinae Örsted, 1843
Phyllodoce Lamarck, 1818
Phyllodoce patagonica complex
Voucher. SEA LION: station 1MFC.
Diagnosis. Voucher is a large, almost complete (pygidium missing) specimen in good condition; 37mm long and 1.8mm wide (including parapodia); some light brown pigmentation present on dorsum of anterior segments, with segment 5 and 6 darkest, segments 7-10 lighter, thereafter pigmentation fading with faint horizontal line per segment present.
Prostomium anteriorly rounded, about as wide as long; with two pairs of prostomial appendages of similar form, short and cirriform: pair of antennae and pair of palps; with a pair of red, subdermal eyes near the posterior margin; nuchal papilla not observed. Proboscis not observed. Four pairs of tentacular cirri; cirri of segment 1, dorsal and ventral cirri of segment 2, and dorsal cirri of segment 3 cylindrical, with long, tapered ends; cirri of segment 1 reaching segments 4-5. Dorsal cirri of segments 2 and 3 reaching about segment 10. Ventral cirri of segment 2 reaching segment 4-5.
Parapodia uniramous; europodial lobes long, with both lobes of similar length. Dorsal cirri large, foliose, changing throughout the body in the following fashion: anterior – broad and rounded to ovoid (increasing in size posteriorly); mid body – distally distinctly truncated, acquiring subrectangular form (largest); posterior – decreasing in size, oval to rounded. Ventral cirri of similar throughout, elongated, tapering into pronounced tip; changing in size with those in mid body region largest. Chaetae compound spinigers with very slender blades, tapering into extremely long thing tips; rostrum of chaetal shaft number of fine serrations; anteriorly about 15 per fascicle; in mid-body about 25 per fascicle. Additionally, in midbody chaetigers a single, very thin simple capillary observed in the ventralmost position in the chaetal fascicle. Pygidium not observed.
Additional information. As part of taxonomic standardization exercise, other very similar specimens from Falkland Islands became available for examination. One specimen had an everted proboscis: proximal part with 12 rows (6 on each side) with about 8 papillae per row and single mid dorsal row with 4 papillae, subdistal part of proboscis with large irregular mounds; distally with circlet of ~17 small rounded papillae.
Remarks. Proboscis was not everted in otherwise well preserved voucher, but additional specimens became available for examination and proboscis of one individual was cleraly observed, confirming the presence of the single dorsomedian row of papillae as in P. patagonica (see separate entry with comments on genus Phyllodoce from the region). Distinctly truncated, subrectangular shape of dorsal cirri in median segments was confirmed in voucher specimen, specimens further suggesting similarities to P. patagonica, but also P. truncata (see separate entry with comments on genus Phyllodoce from the region). Unfortunately, the dorsal cirri in specimen with everted proboscis were mostly missing, with most posterior one present around segment 30, where the fully truncated shaped has not been yet developed. Further there is some variation in anteriormost dorsal cirri, which can be rounded, broadly oval to elongated oval (see comparative images). Molecular evidence may be needed to confirm if differences observed here represent different species. For now we suggest to include these under Phyllodoce patagonica complex.
