Amphisamytha Hessle 1917

Amphisamytha Hessle, 1917

Type species: Amphisamytha japonica Hessle, 1917 Synonym: Mooresamytha Williams, 1987: 256 –257.

Generic diagnosis (emended): Prostomium without glandular ridges. Buccal tentacles smooth. Four pairs of cirriform branchiae. Segment II without chaetae. Thorax with 17 chaetigers and 14 uncinigers. No modified segment. Glandular pads above abdominal neuropodia.

Remarks: The different interpretation of abdominal structures referred to as rudimentary notopodia, glandular pads or glandular rudimentary notopodia is confusing in this genus. Hessle (1917) erected the genus Amphisamytha for A. bioculata (Moore, 1906) and the type species A. japonica Hessle, 1917 - which have, according to Hessle, distinct abdominal rudimentary notopodia, a character later confirmed by Day (1964). The other species known so far, Amphisamytha galapagensis Zottoli, 1983 a, and Amphisamytha fauchaldi Solís-Weiss & Hernández-Alcántara, 1994, both described from Pacific hot vents, have been included in the genus although they do not have abdominal rudimentary notopodia. Instead, they are described as having glandular pads, an ad hoc expression coined by Zottoli (1983a) in order to describe puffy structures above the abdominal neuropodia. Indeed, the interpretation of the glandular pads as rudimentary neuropodia seems to be doubtful as our examination of the respective holotypes showed. The term "glandular pads" is also used in the description of Amathys lutzi Desbruyères & Laubier, 1996, the only ampharetid species currently known from Atlantic hot vents that shares many traits with Amphisamytha.

For A. bioculata, the rudimentary notopodia have been described as “small papillae” by Moore (1906), while Williams (1987) described the puffy structures (glandular pads) as rudimentary notopodia and considered their small papillae as cirri. Hilbig (2000) states that “the notopodial rudiments are reduced to distinct but low ridges with a very small distal part barely emerging from the dorsal body wall“ whereas the ridges correspond to the glandular pads and the small distal part to the cirri in A. galapagensis. In the new species described here, there are also glandular pads with minute dorsal papillae. As it is not clear, if the glandular pads or their small papillae can be related to rudimentary notopodia, we suggest avoiding this term for the genus Amphisamytha and use glandular pads and dorsal cirri, instead.

Williams (1987) erected a monospecific genus Mooresamytha for the species Amphisamytha bioculata based on arrangement of branchiae and the presence of dorsal cirri on abdominal glandular pads (rudimentary notopodia in Williams’ description). Hilbig (2000) considers Mooresamytha a junior synonym of Amphisamytha because of interspecific variability of both characters. This line of arguments is followed here, especially because we found dorsal papillae in this new species.

In his review of the Ampharetidae, Jirkov (2001) considers Amphisamytha as a junior synonym of Phyllocomus. His reasoning is not completely clear to us and we therefore decided to use the classical systematics from Day (1964) and Holthe (1986a, 2001).