Amage imajimai, Reuscher, 2015

Reuscher, Michael G., 2015, Amage imajimai sp. nov., a new species of Ampharetidae (Annelida: Polychaeta) from Japanese waters, European Journal of Taxonomy 154, pp. 1-7 : 3-5

Amage imajimai sp. nov.

urn:lsid:zoobank.org:act:CCA76C94-C953-418D-AFC9-DDBBD7D99C6D

Fig. 1 A–G

Diagnosis

Four pairs of branchiae. Twelve thoracic uncinigers. Notopodia without ventral cirri. Eleven abdominal uncinigers.

Etymology

The species is dedicated to the distinguished Japanese polychaete taxonomist Minoru Imajima.

Specimens examined

Holotype

JAPAN: SMF 24087 , Sagami Bay , 35°00.9’ N, 139°35.7’ E – 35°00.7’ N, 139°36.0’ E, 990–1060 m, KT-66-12, St. 7, Jul. 1966 (1 cs).

Paratypes

JAPAN: SMF 24086, same locality as holotype (3 cs); NSMT-Pol. P-600, same locality as holotype (3 cs, 1 af).

Description

Length of holotype 3.2 mm, width 0.4 mm. Prostomium with middle lobe bearing anterolateral frontal horns, delimited by incision from inflated surrounding lobe ( Fig. 1A ); prostomium without glandular ridges or eyes. Single tip of smooth buccal tentacle visible in buccal cavity. Four pairs of branchiae in L-shaped arrangement in segments II–IV ( Fig. 1B ), separated by wide median gap; all branchiae detached from specimen, cirriform, without conspicuous ciliation or annulations; innermost branchiae of anterior transverse row (1) originating from segment II, outermost branchiae of anterior transverse row (2) originating from segment III, median branchiae of longitudinal row (3) originating from segment IV, posterior branchiae of longitudinal row (4) originating from segment V ( Fig. 1B ). Segment II without chaetae. Notopodia with capillary chaetae from segment III, present in 15 chaetigers; first three notopodia in close succession due to shortness of segments and slightly elevated above following notopodia ( Fig. 1C ); first notopodia small, increasing in size from first to third pair; notopodial cirri absent. Neuropodial tori with uncini from segment VI, present in 12 thoracic uncinigers; tori without cirri. Continuous ventral shields conspicuous from anterior thorax to thoracic unciniger 9. Modified notopodia or segments absent. Intermediate uncinigers absent. Eleven abdominal uncinigers with small tuberculate rudimentary notopodia. Pinnules with minute tuberculate dorsal cirrus. Rudimentary notopodia and pinnules connected by glandular fold. Pygidium with one pair of digitiform, ventrolateral anal cirri. Left anal cirrus broken off. Thoracic uncini with 7 teeth in 2 staggered row over basal prow and rostral tooth ( Fig. 1 D–E). Abdominal uncini with numerous teeth in several rows over basal prow and rostral tooth. Tube parchment like with needle like spicules embedded.

Remarks

In four of the paratypes the buccal tentacles are better visible and clearly smooth. The tuberculate dorsal cirri of the abdominal pinnules are much better developed in the larger paratype specimens ( Fig. 1F ). The anal cirri are longer and cirriform in the larger paratypes ( Fig. 1G ). However, they also seem to break off easily as three of the six complete paratypes lack both anal cirri.

The two other Amage species with twelve thoracic uncinigers are A. benhami Reuscher, Fiege & Wehe, 2009 from the northeast Pacific and the Ross Sea and A. longitorus Reuscher, Fiege & Imajima, 2015 from Japan. The latter species differs from A. imajimai sp. nov. by the possession of only three pairs of branchiae, the very long tori in the first two thoracic uncinigers and the larger number of abdominal uncinigers (13). A. benhami differs from the new species by the presence of club shaped notopodial cirri and the higher number of abdominal uncinigers (15–16).

Among the other Japanese Amage species A. auricula , A. delus , A. ehlersi and A. scutata have 11 thoracic uncinigers, A. cf. adspersa has 14 thoracic uncinigers. A. cf. adspersa , A. auricula and A. delus differ from A. imajimai sp. nov. by the presence of notopodial cirri. A. scutata is unusual for the presence of rudimentary notopodia in the anterior segments. A. imajimai sp. nov. has a higher count of abdominal uncinigers (11) than A. auricula (8) and A. ehlersi (10) and a lower count than A. delus (12) and A. longitorus (13).

Distribution

Sagami Bay on the Southeastern Pacific coast of Honshu, in 990–1060 m.

Figures

Fig. 1. Amage imajimai sp. nov. A. Anterior end of holotype, dorsal view. B. “ID card”. C. Anterior end of holotype, lateral view. D. Thoracic uncinus, lateral view. E. Thoracic uncinus, frontal view. F. Abdominal uncinigers, lateral view (from paratype SMF 24086). G. Posteriormost abdominal uncinigers and pygidium, ventral view (from paratype SMF 24086).