Amage cf. ehlersi Reuscher, Fiege & Imajima, 2015

Reuscher, Michael G. & Fiege, Dieter, 2016, Ampharetidae (Annelida: Polychaeta) from cold seeps off Pakistan and hydrothermal vents off Taiwan, with the description of three new species, Zootaxa 4139 (2), pp. 197-208 : 198-199

Amage cf. ehlersi Reuscher, Fiege & Imajima, 2015

( Fig. 1 A–E)

Specimens examined. SMF 24134, Yonaguni Knoll IV Hydrothermal Field, low CO2 seepage site, Okinawa Trough, 24°50.802’N 122°42.094’E, 1382 m, SO 196, Station 40, TV-MUC, 14 March 2008 (1 cs).

Description. Length 3.5 mm, width 0.6 mm. Prostomium with middle lobe bearing anterolateral frontal horns ( Fig. 1 A), delimited by incision from inflated surrounding lobe; prostomium without glandular ridges or eyes. Buccal tentacles smooth. Four pairs of cirriform branchiae in L-shaped arrangement in segments II–IV ( Fig. 1 A), separated by wide median gap; innermost branchiae of anterior transverse row originating from segment II, outermost branchiae of anterior transverse row originating from segment III, median branchiae of longitudinal row originating from segment IV, posterior branchiae of longitudinal row originating from segment V. Segment II without chaetae. Notopodia with capillary chaetae from segment III, present in 14 chaetigers; anterior notopodia small, increasing in size from first to third pair; notopodial cirri absent ( Fig. 1 A). Neuropodial tori with uncini from segment VI, present in 11 thoracic uncinigers; tori without cirri. Continuous ventral shields conspicuous to thoracic unciniger 11, faint to abdominal unciniger 4. Elevated or modified notopodia absent. Intermediate uncinigers absent. Eleven abdominal uncinigers with large digitiform rudimentary notopodia ( Fig. 1 A). Pinnules with tuberculate dorsal cirrus. Rudimentary notopodia and pinnules connected by glandular stripe. Pygidium with crenulated terminal anus and one pair of short and thick lateral anal cirri ( Fig. 1 A). Thoracic uncini in lower torus with 4 teeth in 1 row over basal prow and rostral tooth ( Fig. 1 B), thoracic uncini in upper torus with one or two additional small teeth on top ( Fig. 1 C). Abdominal uncini with about 7 teeth in two staggered rows over basal prow and rostral tooth ( Fig. 1 D, E).

Remarks. The single specimen collected at the Yonaguni Knoll IV Hydrothermal Field has eleven abdominal uncinigers, whereas Amage ehlersi Reuscher, Fiege & Imajima, 2015 was described with only ten. Otherwise the specimen agrees well with the original description. Future sampling effort in the Yonaguni Knoll IV Hydrothermal Field may help to conclude, if this vent population belongs to Amage ehlersi , or if the description of a new species is warranted.

Distribution. Amage ehlersi has been found along the coast of Japan, in depths of 30–590 m ( Reuscher et al. 2015). The finding at the Yonaguni Knoll Hydrothermal Field is the species’ second record and the first one from the vicinity of a hydrothermal vent. It is also the deepest and southernmost record of the species.

Figures

FIGURE 1. Amage cf. ehlersi: (A) entire specimen, dorsolateral view; (B) uncinus from lower thoracic torus, frontal view; (C) uncinus from upper thoracic torus, frontal view; (D) abdominal uncinus, lateral view; (E) abdominal uncinus, fronto-lateral view.