Samythella sp. 1

Ampharetinae Malmgren, 1866

Samythella Verrill, 1873

Samythella sp. 1

Voucher. TOROA: station T4FB

Diagnosis.  Voucher is the only specimen collected in this study; a complete specimen, slender, body tapering posteriorly;  pale yellow in alcohol; length 9.5mm, width 1mm (at widest point of the thorax). Thorax composed of 15 chaetigers, of these 12 uncinigers, between chaetiger 3 and 4 with indistinct dorsal crest; abdomen with 27 uncinigers. Prostomium almost pentagonal shaped; without glandular ridges or eyespots.  Buccal tentacles smooth. Paleae absent. Three pairs of branchiae, inserted in a transverse row on a ridge; two groups separated by a median gap; branchial styles long, cylindrical, smooth but with ventral surface of the innermost branchiae ridged (visible only after staining). Anterior notopodia well developed, without cirri. Notochaetae few, smooth, narrowly limbate. Thoracic uncini with 5 teeth above rostral tooth and basal prow arranged in a single vertical row; tori without cirri. Abdominal uncinigers very long with rudimentary notopodia.  Abdominal uncini with many small teeth, arranged in 4 regular horizontal rows. Pygidium with 5 short, fleshy, rounded lobes of similar size; arranged in 1 (median) + 2 lateral pairs with median lobe slightly shorter than others.

Remarks. Characters of taxonomic importance in genus Samythella are number of abdominal segments and number and form of anal cirri (Fauchald, 1972). There are currently 6 recognised species in this genus and the combination of the characters mentioned above suggest that FI specimen represents a new species (see comparative table below). Additionally, S. affinis Day, 1963 differs from all its congeners in having paleae and lacking rudimentary notopodia in abdomen and Falkland Island specimen differs in having dorsal crest between chaetigers 3 and 4 (although indistinct, best noticeable after staining). The presence of dorsal crest also suggest affiliation with genera Melinnampharete Annenkova, 1937 and Eusamythella Hartman, 1971 (Eusamythella is considered a synonym of Melinnampharete by Jirkov, 2011), but within this group, FI specimen would also represent a new species given its much higher number of abdominal uncinigers, lack of paleae and the presence of rudimentary notopodia in abdomen. The generic placement of FI specimen is clearly tentative at present. Greater number of specimens is desirable in order to formally describe this species. Further, another species placed in this genus Samythella sp. 2 has been encountered in this study (see Remarks section for Samythella sp. 2 and comparative table below).

Comparative table of known Samythella Verrill, 1873 species.