Anacaena torikaii, Minoshima & Kamite & Fikáček, 2023

Minoshima, Yusuke N., Kamite, Yuuki & Fikacek, Martin, 2023, The genus Anacaena Thomson from the Ryukyu Archipelago of Japan (Coleoptera, Hydrophilidae), Deutsche Entomologische Zeitschrift 70 (1), pp. 143-157 : 143

Anacaena torikaii sp. nov.

Figs 1D-F , 3E, I, M , 4B , 6F

Type locality.

Japan, Kagoshima-ken (Prefecture), Amami-ôshima I., Amami-shi, Naze, Kinsakubaru.

Type series.

Holotype: Japan • male; "AMAMI JPN" / “Kinsakubaru” / “Naze” // “Amami-shi” / "17. VII. 2006" / "Y. Kamite leg." // "JAPAN: Amami Is.," / “Amamiôshima I.," / "Amami-shi, Naze," / “Kinsakubaru;” / "17.VII.2006; Y. Kamite" // “spec#” / “20-66” // “HOLOTYPE” / “ANACAENA” / “torikaii” / "des YN Minoshima 2021"; KMNH. Paratypes: Japan •1 male, 1 female; same collection data as holotype; KMNH, YKC.

Diagnosis.

Pronotum dark brown with broad yellowish lateral margin; elytra brown, weakly speckled, slightly paler at base. Antenna with eight antennomeres; antennomere 3 narrow. Maxillary palpus uniformly yellowish. Pronotum with very fine and sparsely distributed ground punctation consisting of uniformly sized punctures. Metafemoral pubescence with horizontal hairline. Median lobe elongate, tapering apically. Gonopore large, situated at apex. Parameres widest in basal third, rounded apically with inner angle. Lateral margin of paramere weakly sinuate in dorsal view. Phallobase as long as paramere, nearly parallel-sided in basal half, then narrowing to short and wide manubrium.

Differential diagnosis.

This species can be distinguished from other Ryukyu species by the slender, ca 3 times longer than wide, median lobe (Fig. 4B ). In addition, examined specimens have broader yellowish margins on pronotum (Fig. 1D, F ) than in dark-coloured specimens of A. okinawana (Fig. 2 ); examination of additional specimens is, however, needed to understand the variation of dorsal colouration of A. torikaii . Anacaena kumejimana has a yellowish patch on the base of elytra (Fig. 1C ), whereas the area is only slightly paler in A. torikaii (Fig. 1F ).

Outside of the Ryukyus, Anacaena jiafenglongi Komarek, 2012 known from China and A. hajeki Komarek, 2013 from Laos are similar to A. torikaii based on the morphology of the aedeagus. The maxillary palpomere 4 of A. jiafenglongi is stout (fig. 29 in Komarek 2012), whereas it is slender in A. torikaii . The basal piece is distinctly longer than the parameres of A. hajeki (fig. 5 in Komarek 2013) and separates the species from A. torikaii .

Description.

Body (Fig. 1F ) 2.1-2.5 mm in length, oval, slightly attenuated posteriad. Colour (Fig. 1D-F ). Head black, lateral part of clypeus yellowish. Pronotum dark brown with broad yellowish margins. Elytra brown, weakly speckled, slightly paler at base. Ventral face dark brown. Maxillary palpus uniformly yellowish.

Head. Labrum with a fringe of long erect setae. Ground punctures of clypeus and frons fine, densely arranged; interspace between punctures ca. 2-4 times the width of a puncture. Presence of fine setae on clypeus ambiguous (possibly already broken when collected or during preparation). Frontoclypeal sulcus indistinct. Systematic punctures on clypeus and frons slightly larger than ground punctures, each bearing a fine seta. Systematic punctures of clypeus sparsely distributed, especially on anterior part. Systematic punctures of frons on anterolateral and posterolateral parts close to compound eye and frontoclypeal sulcus.

Antenna with eight antennomeres. Scape stout, moderately long. Antennomere 2 stout, somewhat conical, ca. as long as antennomeres 3 and 4 combined; antennomere 3 narrow; antennomere 4 wider than 3; antennal club longer than antennomeres 2-5 combined. Maxillary palpus short (Fig. 3E ); palpomere 2 stout, longer than palpomere 3; palpomere 3 short, slightly shorter than palpomere 4; palpomere 4 longest, shorter than palpomeres 2 and 3 combined. Labial palpus short, shorter than width of mentum. Mentum (Fig. 3I ) ca. 1.7 times wider than long, subtrapezoidal, rounded anteriorly with median depression, with indistinct lateral angle (this character was observed without dissection of head appendages, thus not very accurate). Ground punctation on mentum fine, rather sparsely distributed. Lateral margin of mentum with fringe of fine setae.

Thorax. Pronotum with very fine and sparsely distributed ground punctation consisting of uniformly sized punctures. Systematic punctures on pronotum arranged as irregular transverse row along anterolateral and posterolateral parts. Prosternum weakly and evenly convex.

Ground punctation on elytra coarser than that of head and pronotum; punctures rather densely distributed; interspaces between punctures ca. 1-3 times the width of a puncture. Mesoventrite with median process pointed apically; process as subtrigonal pyramid with posterior transverse and anterior median longitudinal carinas. Metaventrite with inverted triangular medially elevated portion with small oval glabrous area. Metafemora (Fig. 3M ) pubescent in basal part and anterior half excluding apical area with horizontal hairline; hairline indistinct along basal part.

Abdomen. Aedeagus (Fig. 4B ): Median lobe elongate tapering apically, ca. 3 times longer than its greatest width, dully pointed or nearly rounded apically. Basal apophyses narrow, weakly incurved apically. Gonopore large, situated at apex. Parameres widest at basal third, membranous in apical half dorsally, rounded apically with inner angle, attenuated apically at midlength of parameres; apical half of lateral margin and inner margin almost parallel-sided in dorsal view. In dorsal view, lateral margin of paramere weakly sinuated. Phallobase as long as paramere, nearly parallel-sided in basal half, then narrowing to wide and short manubrium; borderline between membrane and sclerite (unpigmented and pigmented area) of ventral face of phallobase very indistinct, incision of anterior margin possibly shallow.

Distribution.

Amami-ôshima I. Only known from the type locality.

Habitat.

Aquatic species. Examined specimens were collected in a small stream in a forest (Fig. 6F ).

Etymology.

Named after Mr. Hisahiro Torikai (Amami-shi), who kindly assisted with Y. Kamite’s field work on Amami-ôshima Island.

Checklist of the Anacaena species of Japan

1. Anacaena asahinai Satô, 1982 Hokkaidô, Honshû; Russia

2. Anacaena kumejimana sp. nov. Kumejima Island

3. Anacaena okinawana sp. nov. Okinawa Islands (Okinawa-jima Island, Kerama Islands)

4. Anacaena torikaii sp. nov. Amami-ôshima Island

Key to the species of Anacaena of Japan

The key is based on the selection of most reliable characters only and follows our understanding of the intraspecific variation based on material examined in this study (updates may be needed for coloration characters after additional specimens are collected). Additional quantitative characters may help with the identification, see the differential diagnoses of the respective species.

1	Metafemoral pubescence with horizontal hairline (Fig. 3J-M ). Endemic to Ryukyu Archipelago	2
-	Metafemoral pubescence extended with oblique hairline, covering basal two-thirds to three-quarters of femur. Honshû and Hokkaidô islands	A. asahinai
2	Median lobe of aedeagus slender, ca. 3 times longer than wide, attenuated towards apex with nearly straight lateral margins (Fig. 4B ). Amami-ôshima Island	A. torikaii
-	Median lobe of aedeagus wide, ca. 2.2-2.5 times longer than wide, triangular and attenuated towards apex in apical part, nearly parallel-sided in basal part (Fig. 4A, C-F ). Okinawa Islands (Okinawa-jima I., Kerama Is., and Kumejima I.)	3
3	Colouration of elytra dark, with yellowish spot anteromesally around scutellar shield (Fig. 1C ). Lateral face of paramere convex at basal third (Fig. 4A ). Kumejima Island	A. kumejimana
-	Colouration of elytra variable, yellowish to black but elytra without yellowish spot anteromesally around scutellar shield (Fig. 2 ). Lateral face of paramere convex at base (Fig. 4C-F ). Okinawa-jima Island and Kerama Islands	A. okinawana

Figures

Figure 1. A-C. Anacaena kumejimana, holotype; D-F. A. torikaii, holotype (D, E) and paratype (F).

Figure 2. Anacaena okinawana, holotype (C, D) and paratypes (A, B, E-H). A-D. From Okinawa-jima I.; E-H. From Kerama Is. (E, F. Aka-jima I., G, H. Zamami-jima I.).

Figure 3. A-E. Maxillary palpus; A. Anacaena kumejimana, paratype; B-D. A. okinawana, paratypes; B. from Okinawa-jima I., C, D. from Aka-jima I. (Kerama Is.); E. A. torikaii, holotype; F-I. Mentum; F. A. kumejimana, paratype; G, H. A. okinawana, paratypes; G. from Okinawa-jima I.; H. from Aka-jima I. (Kerama Is.); I. A. torikaii, holotype; J-M. Hind femora, indicating femoral pubescence but borderline of pubescence often not clear at base; J. A. kumejimana, paratype; K, L. A. okinawana, paratypes; K. from Okinawa-jima I.; L. from Aka-jima I. (Kerama I.); M. A. torikaii, holotype.

Figure 4. A-F. Aedeagus (A-F) and abdominal segment 9 (G), dorsal view. A. Anacaena kumejimana, holotype; B. A. torikaii, holotype; C-G. A. okinawana, holotype (C) and paratypes (D-G); C, D, G. from Okinawa-jima I.; E, F. from Kerama Is. (E. Aka-jima I.; F. Zamami-jima I.).

Figure 6. Collecting localities of the species of Anacaena on the Ryukyu Archipelago. A-B. Anacaena kumejimana; A. Daruma-yama, Kumejima I., 21 May 2007; B. Nakandakari, Kumejima I., 20 May 2007; C-E. A. okinawana; C. tributary of Benoki Dam, Kunigami-son, Okinawa-jima I., 26 Jul. 2015; D. Aka, Aka-jima I., 15 Mar. 2019; E. Geruma, Geruma-jima I., 15 Mar. 2019, after Kamite et al. (2019); F. A. torikaii; F, Kinsakubaru, Amami-oshima I., 17 Jul. 2006.