Research Article |
Corresponding author: Hiroyuki Yoshitomi ( hymushi@agr.ehime-u.ac.jp ) Academic editor: Adam Brunke
© 2019 Hiroyuki Yoshitomi, Haruki Karube, Masakazu Hayashi.
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:
Yoshitomi H, Karube H, Hayashi M (2019) A new species of the genus Ochthebius (Coleoptera, Hydraenidae) from the Ogasawara Islands, Japan, with a description of the larva. ZooKeys 855: 95-107. https://doi.org/10.3897/zookeys.855.35677
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A new species of the genus Ochthebius, O. (O.) sasakii sp. nov., is described from the Ogasawara Islands, Japan, with a description of the larva. This record is the first of the family Hydraenidae from the Ogasawara Islands. This species belongs to the punctatus species group and is similar to two Japanese species, O. (O.) inermis Sharp, 1884 and O. (O.) danjo Nakane, 1990, but it differs from them in both adult and larval characters. The larva of O. (O.) inermis is also described for comparison.
Ochthebiinae, Ochthebiini, Bonin Islands, chaetotaxy, Staphylinoidea
The Ogasawara Islands (= Bonin Islands) are oceanic islands that were never connected to the continental mainland (
The genus Ochthebius Leach, 1815 (Ochthebiinae, Ochthebiini) is distributed in the Palaearctic, Oriental, Nearctic, Neotropical, Afrotropical, and Australian regions, and includes 540 species within 10 subgenera (
In the present paper, we describe a new species of the genus Ochthebius from the Ogasawara Islands, with a description of the larva. This record is the first of the family Hydraenidae from the Ogasawara Islands. The larva of O. inermis Sharp, 1884 is also described for comparison with the larvae of the new species and O. danjo Nakane, 1990.
The material examined in this paper is preserved in the Ehime University Museum, Matsuyama, Japan (
General observations, dissections, and microstructures of dissected parts were made under a Leica MZ95. After observation, the dissected parts were mounted on the same card with the specimen. Photographs were taken under a Leica MZ95.
The terminology follows
Morphological abbreviations used in this study are as follows:
EL elytral length from anterior margin to elytral apex;
EW maximum elytral width;
HL head length;
PL pronotal length in median line;
PW maximum width of pronotum;
TL total length (PL + EL + HL).
The average is given in parentheses after the range.
Holotype (
Ochthebius (Ochthebius) sasakii belongs to the punctatus species group (sensu
Measurement of three Japanese species of the Ochthebius punctatus species group.
O. sasakii | O. inermis | O. danjo | |
no. | 13 | 16 | 6 |
TL (mm) | 1.83–2.16 (2.00) | 2.20–2.55 (2.37) | 2.42–5.47 (2.99) |
HL (mm) | 0.30–0.42 (0.39) | 0.45–0.52 (0.48) | 0.45–0.55 (0.50) |
PW (mm) | 0.55–0.63 (0.60) | 0.67–0.76 (0.70) | 0.68–0.74 (0.71) |
PL (mm) | 0.40–0.48 (0.44) | 0.46–0.55 (0.50) | 0.50–0.55 (0.54) |
EL (mm) | 1.03–1.28 (1.17) | 1.25–1.50 (1.39) | 1.40–4.45 (1.96) |
EW (mm) | 0.72–0.90 (0.83) | 0.45–0.52 (0.48) | 0.90–1.00 (0.97) |
PW/PL | 1.21–1.50 (1.36) | 1.34–1.50 (1.40) | 1.29–1.36 (1.33) |
EL/EW | 1.31–1.53 (1.41) | 0.35–3.26 (2.32) | 1.42–4.49 (2.01) |
EL/PL | 2.29–2.98 (2.66) | 2.60–3.09 (2.81) | 2.58–8.09 (3.63) |
EW/PW | 1.24–1.50 (1.39) | 0.61–0.72 (0.68) | 1.29–1.41 (1.36) |
TL/EW | 2.17–2.75 (2.42) | 4.64–5.35 (4.98) | 2.50–5.53 (3.08) |
Chaetotaxy of 3rd instar larvae of Ochthebius spp. (after Delgado and Matsui for O. danjo). Cross: present; dash: absent.
O. sasakii sp. nov. | O. inermis | O. danjo | ||
present study | present study | Delgado & Matsui 2000 | ||
pronotum | A1–A4 | × | × | × |
L1–L3 | × | × | × | |
P1–P4 | × | × | × | |
Da1, Db1, Dc1 | × | × | × | |
C1 | × | × | × | |
C2, C3 | – | × | × | |
C4, C5 | × | × | × | |
Da'–Dc', Dc'' | × | – | – | |
mesonotum | A1–A4 | × | × | × |
L1–L3 | × | × | × | |
P1–P4 | × | × | × | |
Da' | × | – | – | |
tergum I | A1, A3–A4 | × | × | × |
L1–L3 | × | × | × | |
P1, P3–P4 | × | × | × | |
P2 | × | – | – | |
DP1, DP2 | × | × | × | |
C1–C2, C4 | – | – | – | |
C3, C5 | × | × | × |
Adults. Body oblong, slightly convex dorsally, weakly shiny in dorsal surface. Coloration of body black, with weak bluish lustre; ventral surface of body blackish brown; antennae, maxillary palpi and legs yellowish brown, but fuscous in antennomeres IV–IX, terminal palpomere of maxillary palpi and femur.
Head (Fig.
Male. Sternite X (Fig.
Female. Sexual dimorphism indistinct in elytral gutter and elytral apices. Capsule of spermathecal duct (Fig.
Measurements (n = 13). TL 1.83–2.16 (2.00) mm; HL 0.30–0.42 (0.39) mm; PW 0.55–0.63 (0.60) mm; PL 0.40–0.48 (0.44) mm; EL 1.03–1.28 (1.17) mm; EW 0.72–0.90 (0.83) mm.
(based on a damaged specimen collected with adults from Chichi-jima). Body about 2.0 mm in fully expanded specimen. Coloration of body blackish brown, weakly shining; legs infuscate. Head (Fig.
All the specimens (both adults and larvae) were collected from the surface of littoral rocks covered with a film of sheeting fresh water (depth ca 1–2 mm; Fig.
The fauna of the Ogasawara Islands was seriously affected by a long drought in 2016–2017. In addition, a serious drought occurred from autumn to winter 2018/2019. In February 2018, HK found many individuals of O. sasakii sp. n. at the Ani-jima site (Fig.
Ogasawara Isls. (Chichi-jima, Ani-jima, Otouto-jima).
20 exs (mature larvae,
Body about 3.0 mm in fully expanded specimens. Coloration of body black, strongly shining; legs cream (see
The new species is closely related to two Japanese species, viz., O. inermis distributed in Japan (Honshu, Shikoku, Kyushu), Kunashir, and Taiwan, and O. danjo distributed in southern Kyushu (including Danjo Islands and Yakushima). The former species inhabits mainly stagnant or flowing water along rivers, usually associated with filamentous green algae (
1 | Elytra subparallel-sided, bearing long setae; anterior margin of labrum excised; apex of median piece short ( |
O. danjo |
– | Elytra arcuate laterally, bearing short setae; anterior margin of labrum gently arcuate or almost straight in dorsal view; apex of median piece long | 2 |
2 | Body larger (2.2–2.6 mm); anterior margin of labrum gently arcuate; elytral setae longer; median groove of pronotum distinct; median piece strongly curved; distal lobe expanded apically ( |
O. inermis |
– | Body smaller (1.8–2.2 mm); anterior margin of labrum shallowly concave in antero-dorsal view; elytral setae shorter; median groove of pronotum shallow; median piece gently curved; distal lobe slender (Fig. |
O. sasakii sp. n. |
Field research and collection in the Ogasawara Islands was done with the permission of the Japan Environmental Agency, Ogasawara Board of Education, Tokyo Metropolis, and the Agency for Cultural Affairs. We thank Tetsuro Sasaki, who discovered this new species with HK, Reiko Kaga, Yoshie Kaga, and Shoubu Yamada for their kind support in HK’s field research, and Dr Manfred A. Jäch (NMW) and Dennis Murphy (The United Graduate School of Agricultural Sciences, Ehime University) for their critical reading of the manuscript.
Part of this study was supported by joint research expenses from the Hoshizaki Green Foundation.