Anacaena okinawana, 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 okinawana sp. nov.

Figs 2 , 3B-D, G, H, K, L , 4C-F, G , 5A-G , 6C-E

Anacaena sp.: Kamite and Aoyagi 2018: 26.

Paracymus orientalis : Kamite et al. 2019: 23 [misidentification, see Kamite 2020: 42].

Type locality.

Japan, Okinawa-ken (Prefecture), Okinawa-jima I., Kunigami-son, Benoki, tributary of Benoki Dam.

Type series.

Holotype: Japan • male, "JAPAN: Okinawa Pref.," / "Okinawa-jima I.," / "Kunigami-son, Benoki," / "tributary of Benoki Dam;" / "26.VII.2015; Y. Kamite leg." // “spec.#” / “20-47” // “HOLOTYPE” / “ANACAENA” / “okinawana” / "des. YN Minoshima 2021"; KMNH. Paratypes: Japan - Okinawa Pref., Okinawa-jima I. • 1 male, 4 females, 3 exs; same data as holotype; KMNH, YKC • 2 males, 3 females, 1 ex.; Benoki, Kunigami-son; 16 Oct. 2020; M. Moriguchi leg.; KMNH • 1 male, 1 female; Nishime-dake, Uka, Kunigami-son; 3 Oct. 2020; M. Katô leg.; KMNH • 2 exs; same locality; 27 Oct. 2020; J. Nakajima leg.; JNC. - Aka-jima I. (Kerama Is.) • 3 males, 1 female, 2 exs; Aka; 15 Mar. 2019; Y. Kamite leg.; small stream; KMNH, YKC • 2 males; Aka; 16 Mar. 2019; Y. Kamite leg.; small stream; KMNH, YKC • 1 female; Aka; 17 Mar. 2019; Y. & N. Kamite leg.; marsh, slow water flow; YKC. - Geruma-jima I. (Kerama Is.) • 1 male; Geruma; 15 Mar. 2019; Y. Kamite leg.; YKC. - Zamami-jima I. (Kerama Is.) • 1 male, 2 exs; upstream of Zamami Dam; 16 Mar. 2018; Y. Kamite leg.; KMNH, YKC • 1 ex.; Ama; 17 Mar. 2018; Y. Kamite leg.; KMNH • 2 males, 1 female, 1 ex.; Zamami; 17 Mar. 2018; Y. Kamite leg.; KMNH, YKC • 1 male; same locality; 19 Mar. 2018.; YKC.

Diagnosis.

Pronotum and elytra variable in colour, black to light yellowish brown. Pronotum with yellowish lateral margin. Antenna with eight antennomeres; antennomere 3 narrow. Maxillary palpus uniformly yellowish or with infuscate apex. Pronotum with very fine and sparsely distributed ground punctation consisting of uniformly-sized punctures. Metafemoral pubescence with horizontal hairline. Median lobe wide, elongate triangular with narrow basal apophyses. Gonopore large, situated at apex. Parameres slightly attenuated apically, rounded apically with weak inner angle; lateral margin of paramere weakly sinuate in dorsal view. Phallobase longer to slightly longer than parameres, almost parallel-sided in basal half, then narrowing to narrow and short manubrium.

Differential diagnosis.

The species is most similar to A. kumejimana . Dorsal colouration and the morphology of the aedeagus separate this species from A. torikaii and A. kumejimana .

Light brown individuals (Fig. 2A ) are not known in A. torikaii and A. kumejimana so far. In dark coloured specimens, yellowish margin on pronotum is narrower in A. okinawana than in A. torikaii (Fig. 3F ). The median lobe (Fig. 4C-F ) is wider in A. okinawana than in A. torikaii (Fig. 4B ). Lateral face of the paramere is weakly convex at base in A. okinawana , the convexity ends more apically (at basal third) in A. kumejimana (Fig. 4A ). This results in a different lateral sinuation of the lateral margin of the paramere in dorsal view. The median lobe is slightly longer in A. okinawana than in A. kumejimana , in which the apex of the median lobe does not reach close to the parameral apices (Fig. 4A ).

The pale specimens of A. okinawana resemble A. maculata Pu, 1964 distributed in southeast Asia and China: A. maculata has distinctly speckled elytra (with very small blackish spots) and a different morphology of the aedeagus (fig. 12 in Komarek 2012). For other similar species in Asia, see Differential diagnosis of A. kumejimana .

Description.

Body (Fig. 2 ) 1.9-2.6 mm in length, oval, slightly attenuated posteriad (Fig. 2 ). Colour (Fig. 2 ). Head black, lateral part of clypeus yellowish. Pronotum and elytra light yellowish brown to black; margins of pronotum yellowish in dark-coloured specimens. Ventral face dark brown, legs slightly paler. Antenna yellow with infuscate antennal club. Maxillary and labial palpi uniformly yellowish or with infuscate apex.

Head. Labrum with a fringe of long erect setae. Clypeus and frons bearing densely arranged fine setae but very often setae missing (possibly already broken when collected or during preparation). Ground punctures of clypeus and frons fine, densely arranged; interspace between punctures ca. 2-4 times the width of a puncture. 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. 3B-D ); palpomere 2 stout, longer than palpomere 3; palpomere 3 short, about half or 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. 3G, H ) ca. 1.7 times wider than long, subtrapezoidal, rounded anteriorly with median depression; lateral margin with lateral angle but generally indistinct (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 areas. 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 portion medially elevated, with small, oval, glabrous area. Metafemora (Fig. 3K, L ) pubescent along basal area and anterior half excluding apical area, with horizontal hairline; hairline indistinct along basal part.

Abdomen. Aedeagus (Fig. 4C-F ; see also Fig. 5A-G ): Median lobe wide, elongate triangular with narrow basal apophyses, ca. 2.5 times longer than its greatest width, dully pointed apically, longer than parameres. Basal apophysis weakly incurved in proximal part. Gonopore large, situated at apex. Parameres rather variable, slightly attenuated apically, rounded apically with weak inner angle; apical third of dorsal face of paramere membranous or very weakly sclerotised. In dorsal view, lateral margin of paramere weakly convex to slightly sinuate in specimens from Okinawa-jima I. (Figs 4C, D ; 5A-C ), slightly sinuate from Kerama Is. (Figs 4E, F , 5D-G ). Lateral face of parameres convex basally; dorsal inner margin of parameres sinuated. Phallobase longer to slightly longer than paramere, almost parallel-sided in basal half, then narrowing to narrow and short manubrium; borderline between membrane and sclerite (unpigmented and pigmented area) of ventral face of phallobase generally indistinct, incision of anterior margin moderately deep.

Distribution.

Okinawa Is.: Okinawa-jima I. and Kerama Is. (Aka-jima I., Geruma-jima I., Zamami-jima I.).

Habitat.

Aquatic species. Examined specimens were collected from a small stream (Fig. 6C, D ) and from a marsh with a slow water flow. The specimen from Geruma-jima I. was collected from small pool on a concrete drainage (Fig. 6E ) ( Kamite and Aoyagi 2018; Kamite et al. 2019).

Etymology.

Named after the type locality: Okinawa Is., Japan.

Variation.

This species shows morphological variations partly correlated with geography (Fig. 5 ), indicating that the populations from Okinawa I. and Kerama Is. may be isolated from each other (see Discussion).

Colouration of pronotum and elytra. Dorsal colouration is highly variable, yellowish brown (Fig. 2A ) to black (Fig. 2B, C, E-H ). We examined two yellow individuals collected from Okinawa-jima I.; although they are females, we consider them conspecific with dark specimens from the same population based on external characters. The range of variation seems to be smaller in specimens from Kerama Is. (mostly black specimens) than in those from Okinawa-jima I. (yellowish to black).

Maxillary palpus. Two types of colourations of maxillary palpus were observed (Fig. 3B-D ): uniformly yellowish palpus and infuscate at apex. This variation seems not to be affected by geography.

Aedeagus of the species vary both within and between islands. Specimens of Okinawa-jima I. (Figs 4C, D ; 5A-C ) have slightly smaller aedeagus with not or weakly sinuate lateral face of parameres and slightly narrower median lobe in dorsal view. Aedeagus of the specimens from Kerama Islands (specimens from Aka-jima I., Geruma-jima I., and Zamami-jima I. were examined) is slightly larger, with weakly sinuate lateral face of parameres and slightly wider median lobe (Figs 4E, F , 5D-G ).

Figures

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 5. Map of the Central Ryukyus (Amami Is. to Okinawa Is.) and aedeagus of Anacaena species. A-G. Anacaena okinawana; A-C. from Okinawa-jima I., D-G. from Kerama Is. (D, E. Aka-jima I.; F. Geruma-jima I.; G. Zamami-jima I.); H, I. A. kumejimana.

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.