Research Article |
Corresponding author: Ko Tomikawa ( tomikawa@hiroshima-u.ac.jp ) Academic editor: Charles Oliver Coleman
© 2017 Sachi Matsukami, Takafumi Nakano, Ko Tomikawa.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Matsukami S, Nakano T, Tomikawa K (2017) A new species of the genus Nicippe from Japan (Crustacea, Amphipoda, Pardaliscidae). ZooKeys 668: 33-47. https://doi.org/10.3897/zookeys.668.12181
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A new species of the pardaliscid amphipod, Nicippe recticaudata, from off Cape Toi, Japan, is named and described. This is the first record of Nicippe Bruzelius, 1859 from the western Pacific coast of the Japanese archipelago. Additionally, nucleotide sequences of nuclear 28S ribosomal RNA and histone H3 as well as mitochondrial cytochrome c oxidase subunit I (COI) and 16S ribosomal RNA from the holotype and paratypes were determined. The morphological characteristics and the COI distance values enforced the distinctiveness of N. recticaudata sp. n. among the known Nicippe species. Nicippe recticaudata sp. n. closely resembles N. tumida Bruzelius, 1859 in having a two-dentate posterior margin of usoromite 1. However, the former is distinguished from the latter by the posterior margin of merus of pereopod 4 with 5–6 setae, anterior margin of merus of pereopod 5 with 9–10 setae, and telson with straight inner margin, tapering proximally. A key to the species of Nicippe is provided.
COI, cryptic species, Gammaridea , Nicippe tumida , North Pacific
The amphipod genus Nicippe Bruzelius, 1859 has been recorded from 35–1398 m deep, and currently consists of four species: N. tumida Bruzelius, 1859, N. buchi Andres, 1975, N. rogeri Lörz & Schnabel, 2015, and N. unidentata KH Barnard, 1932. Its type species N. tumida has been diagnosed by the two-dentate posterior margin of urosomite 1. Originally, this species was described based on specimens collected from Drøbak, Norway (
Contrary to the cosmopolitan cryptic species complex N. tumida, the other three species had been recorded from the type localities: N. buchi was collected from lava tubes off Lanzarote, North Atlantic Ocean (
Recently, unidentified specimens belonging to Nicippe were obtained from off Cape Toi, Miyazaki Prefecture, Japan, at a depth of 265–367 m. This is the first record of the genus from the western Pacific coast of the Japanese archipelago. Following a detailed examination of the specimens and their genetic data, these amphipods are described as a new species herein.
The present specimens were collected from off the southern tip of Kyushu (St-12) during a research cruise of the T/S Toyoshio-Maru (Hiroshima University) to Kyushu and the Nansei Islands, southwestern Japan in 2006 (Cruise # 2006-03). Specimens were collected with a sledge-net (mouth opening 145 cm × 15 cm, mesh opening 328 µm). The gear was towed along the bottom at a speed of 2 knots for 20 minutes. Samples were immediately fixed and preserved in 99% ethanol on-board ship. In the laboratory, specimens of Nicippe were sorted from amphipod samples under a stereomicroscope. For DNA extraction, muscle tissue was removed from the dorsal side of the pleon of each of three specimens.
All appendages of the examined specimen were dissected in 70% ethanol and mounted in gum-chloral medium on glass slides under a stereomicroscope (Olympus SZ61). The specimens were examined using a light microscope (Olympus BH2) and illustrated with the aid of a camera lucida. The body length from the tip of the rostrum to the base of the telson was measured along the dorsal curvature to the nearest 0.1 mm. The specimens are deposited in the Tsukuba Collection Center of the National Museum of Nature and Science, Tokyo (
The extraction of genomic DNA from pleon muscle followed
The PCR reaction and DNA sequencing were performed using the modified methods mentioned in
To calculate genetic diversity between the present specimens and the other Nicippe sample, one COI sequence (CMBIA134-11.COI-5P) of the amphipod identified as N. tumida was obtained from BOLD (
The COI sequences were manually aligned, because no indels were observed. Pairwise comparisons of uncorrected p-distances for three COI sequences obtained in this study (658 bp) and that obtained from BOLD (651 bp) were calculated using MEGA7.0.16 (
New Japanese name: Miko-yokoebi-zoku
Nicippe
tumida
:
Holotype: male (8.4 mm),
Dorsal margin of urosomite 1 with 2 pointed teeth; posterior margin of merus of pereopod 4 with 5–6 setae; anterior margin of merus of pereopod 5 with 9–10 setae; telson with straight inner margin, tapering proximally.
(holotype,
Antenna 1 (Fig.
Antenna 2 (Fig.
Nicippe recticaudata sp. n., holotype, male, 8.4 mm,
Mouthparts. Upper lip (Fig.
Gnathopod 1 (Fig.
Gnathopod 2 (Fig.
Pereopod 3 (Fig.
Pereopod 4 (Fig.
Pereopod 5 (Fig.
Pereopod 6 (Fig.
Pereopod 7 (Fig.
Nicippe recticaudata sp. n., holotype, male, 8.4 mm,
Coxal gills on gnathopod 2 and pereopods 3–5 broad, longer than those of bases; gill on pereopod 6 ovate, length 0.5 × basis; gill on pereopod 7 slender, length 0.2 × basis.
Pleopods 1–3 (Fig.
Uropods. Uropod 1 (Fig.
Telson (Fig.
(paratype,
Antenna 2 (Fig.
Gnathopod 1 (Fig.
Gnathopod 2 (Fig.
Pereopods 6 and 7 (Fig.
Telson (Fig.
Callynophore on antenna 1 well developed (3 males, NMST-Cr 25458,
Color in life unknown; faded in preservative (Fig.
The specific name is a compound adjective derived from the Latin words rectus, and caudatus referring to the fact that the inner margin of the telson of this species is straight, a diagnostic character of the species.
In total nine nucleotide sequences were determined: holotype (
The obtained three COI sequences (LC214958–LC214960) were completely identical to each other. Based on the 651 bp aligned sequences, the COI uncorrected p-distance between N. recticaudata and the eastern North Pacific “N. tumida” was 17.1%.
Although the present specimens showed two characteristics in the degree of callynophore of male antenna 1 and the length of peduncular article 5 of male antenna 2, the obtained genetic data revealed that these morphological variants (specimens with strongly developed callynophore and long peduncular article 5 of antenna 2, e.g.,
According to the conventional classification of Nicippe species, this species would be identified as N. tumida based on the possession of the two-dentate posterior margin of urosomite 1. However, Nicippe recticaudata clearly differs from the “true” N. tumida defined by
A Nicippe specimen identified as N. tumida was recorded from the East China Sea (
1 | Dorsal margin of urosomite 1 smooth | N. buchi |
– | Dorsal margin of urosomite 1 dentate | 2 |
2 | Dorsal margin of urosomite 1 with 2 teeth | 3 |
– | Dorsal margin of urosomite 1 with 1 tooth | 4 |
3 | Posterior margin of merus of pereopod 4 with many (more than 10) setae; anterior margin of merus of pereopod 5 with numerous (more than 20) setae; telson with sinuous inner margin, weakly expanding proximally | N. tumida |
– | Posterior margin of merus of pereopod 4 with 5–6 setae; anterior margin of merus of pereopod 5 with 9–10 setae; telson with straight inner margin, tapering proximally | N. recticaudata |
4 | Pereonites 1 and 7 the widest, pereonites 2–6 shorter, subequal; uropod 3 peduncle with unarmed distodorsal lobe | N. rogeri |
– | Pereonites 1–4 subequal, shorter than 5–7 with segment 5 the longest; uropod 3 peduncle with 3 pointed distodorsal process | N. unidentata |
The authors express their sincere thanks to Professor Susumu Ohtsuka (Hiroshima University; HU), and the captain and crews of the T/S Toyoshio-Maru (HU) for their cooperation in the field. We also thank to Edward A. Hendrycks (Canadian Museum of Nature), Dr Anna-Nina Lörz (National Institute of Water and Atmospheric Research, New Zealand) and Dr Charles Oliver Coleman (Museum für Naturkunde) for their critical comments on this manuscript. This study was partly supported by JSPS KAKENHI Grant Numbers JP25242015, JP25840140, JP15J00720.