Ampharetinae Malmgren, 1866
Samythella Verrill, 1873
Samythella sp. 2
Voucher. ENDEAVOUR: station E6FA
Diagnosis. Voucher is the only specimen collected in this study; a complete specimen, small and slender, body tapering posteriorly; pale yellow in alcohol; length 4.5mm, width 0.6mm (at widest point of the thorax). Thorax composed of 15 chaetigers, of these 12 uncinigers; abdomen with 17 uncinigers. Prostomium wide, pentagonal shaped lobe; without glandular ridges or eyespots. Buccal tentacles not observed. 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 6 short, fleshy, rounded lobes with the 2 dorsal ones largest and 2 ventral ones smallest.
Remarks. Characters of taxonomic importance in genus Samythella are summarised in remarks section of another species encountered in this study as Samythella sp. 1. The two FI species (each represented by one specimen only) are very similar, differing primarily in size and number of abdominal uncinigers. Samythella sp. 1 represents a larger species with 27 abdominal uncinigers and indistinct (but upon staining detectable dorsal ridge between thoracic chaetigers 3 and 4), while Samtyhella sp. 2 possess only 17 abdominal uncinigers and no ridge has been detected. The two species also differ in a form of abdominal uncini, in lateral view, the basal prow appears quadrate in Samythella sp.1 and rounded in Samythella sp. 2 (see Plates for each species). Samythella sp. 2 represents a new species, given the combination of characters such as number abdominal uncinigers and number and form and ventral cirri (see comparative table for known species of Samythella).
Comparative table of known Samythella Verrill, 1873 species.
|
No. of AUs |
No. of anal cirri |
Form of anal cirri |
|
|
Samythella sp. 1 |
27 |
5 |
small lobes of similar size arranged in 1 (median) + 2 pairs of lateral ones; median shortest |
|
Samythella sp. 2 |
17 |
6 |
small, rounded lobes; 2 dorsalmost largest, 2 ventralmost smallest |
|
S. elongata Verrill, 1873 |
at least 29 |
8 |
the 2 dorsalmost longest |
|
S. neglecta Wollebaek, 1912 |
at least 29 |
8 |
gradually increasing in size |
|
S. bathycola Uschakov, 1950 |
at least 29 |
14 |
7 long and 7 short, alternating |
|
S. affinis Day, 1963 |
11 |
? |
? |
|
S. interrupta Fauchald, 1972 |
13 |
6 + 1 median pad |
2 long, 2 short, 2 cushion-like |
|
S. pala Fauchald, 1972 |
20 |
6 |
2 longer, 2 short, 2 cushion-like and a single median pad |
|
AUs = abdominal uncinigers |
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