Amage imajimai sp . nov . , a new species of Ampharetidae ( Annelida : Polychaeta ) from Japanese waters

A new polychaete species of the family Ampharetidae, Amage imajimai sp. nov., is described from deep waters of sagami Bay, Japan. It is characterized by the possession of four pairs of branchiae, twelve thoracic uncinigers, eleven abdominal uncinigers, and the lack of thoracic notopodial cirri. The new species is named in honor of the renowned Japanese polychaetologist Minoru Imajima. An identification key for all Amage species from Japanese waters is provided.


Introduction
In a recent study on Ampharetidae from Japan many new species and new records were discovered (Imajima et al. 2012(Imajima et al. , 2013;;Reuscher et al. 2015aReuscher et al. , 2015b)).In the last publication of the series (Reuscher et al. 2015b), a list of all 58 ampharetid species recorded from Japan was provided.six of these species known to occur in Japanese waters belong to the genus Amage Malmgren, 1866: A. cf. adspersa (Grube, 1863), A. auricula Malmgren, 1866Malmgren, , A. delus (chamberlin, 1919)), A. ehlersi Reuscher, Fiege & Imajima, 2015, A. longitorus Reuscher, Fiege & Imajima, 2015and A. scutata Moore, 1923.During the examination of material from the National Museum of Nature and science in Tsukuba (Japan), I was able to identify another new species of Amage, which is described here.The new species was collected at a depth of about 1000 m in sagami Bay off the southeastern honshu coast.

Material and methods
The specimens examined in this study were collected in sagami Bay during a research cruise in July 1966.They were fixed in 7% formaldehyde seawater solution and preserved in 70% ethanol.
Preserved specimens were examined with an Olympus sZX7 stereo microscope and compound microscopes of the models Leica DMLB and Olympus cX41.Pencil drawings were made using a camera lucida, attached to the Leica DMLB.

R e s e a r c h a r t i c l e
urn:lsid:zoobank.org:pub:F9A2F05E-0F3A-4459-BB5F-FC8563DD683C The drawings were digitized with a Wacom Intuos drawing tablet and Adobe Illustrator, according to the methods of coleman (2003).shadings were added in Adobe Photoshop.The "ID card" (Imajima et al. 2012) was prepared in Adobe Illustrator.Full details for the material deposited at senckenberg can be found at http://sesam.senckenberg.de/.

Diagnosis (emended)
Prostomium with middle lobe surrounded by inflated lobe, lacking glandular ridges.Buccal tentacles smooth.Two to four pairs of cirriform branchiae.segment II usually without chaetae, or exceptionally with minute chaetae.Thorax with 9-14 uncinigers.Modified or intermediate segments absent.Abdomen with rudimentary notopodia.

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

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. 1D-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.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).

The two other
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.

Discussion
The variety of habitat types and complex interactions of different environmental gradients in the oceans surrounding the Japanese islands attract a variety of species with different physiological and ecological adaptations and thus form the basis of a diverse polychaete fauna.Japan has a wide variety of habitats that are colonized by polychaetes, including bays, deep-sea trenches, hydrothermal vents, and cold seeps, among others (e.g., Juniper & sibuet 1987;horikoshi et al. 1990).The northern part of Japan receives cold water from the Oyashio Current, whereas southern Japan is under the influence of the warm Kuroshio current (Imajima et al. 2012).Therefore, Japan's polychaete fauna includes Arctic and sub-Arctic species as well as tropical and subtropical species.In the recent series on Ampharetidae from Japan (Imajima et al. 2012(Imajima et al. , 2013;;Reuscher et al. 2015aReuscher et al. , 2015b)), 60% of the examined species were new to science and the number of species known from Japan more than doubled.This shows that the current knowledge of species diversity of ampharetid polychaetes from Japan is far from exhaustive and more sampling effort is needed to complete the picture.Amage imajimai sp.nov. is the 59 th species of the family Ampharetidae and the seventh species of the genus Amage recorded from Japan.
REUSCHER M.G., New Amage species from Japan Of the other Amage species from Japan, A. delus and A. scutata are known only from northern honshu, A. cf.adspersa and A. imajimai sp.nov.have only been recorded from sagami Bay, whereas A. auricula, A. ehlersi and A. longitorus have a wider distribution within Japanese waters.
Within Ampharetidae Amage is probably the most heterogeneous genus as it contains species with two (if the genus Egamella is considered a junior synonym), three and four pairs of branchiae, with nine (Egamella), eleven, twelve, and fourteen thoracic uncinigers, with and without notopodial cirri.
A revision is needed to determine if Amage can be upheld as a single genus, or if it should be split into multiple genera.
specimens are deposited in the following institutions: NsMT = National Museum of Nature and science, Japan sMF = senckenberg Museum Frankfurt, Germany