Eosentomon villare, Nakamura, 2021

Nakamura, Osami, 2021, Three New Species of the Family Eosentomidae (Protura) from the Nasu Imperial Villa, Central Japan, Species Diversity 26 (1), pp. 111-125 : 111-115

Genus Eosentomon Berlese, 1908 Eosentomon villare sp. nov. ( Figs 1 , 2 ; Table 1)

Eosentomon sp. NIV: Nakamura 2019: 18.

Diagnosis. Labral setae present; cephalic anterior additional setae absent; foretarsal sensilla b ′ 1 and c ′ absent; long empodium on hind tarsus; abdominal tergites V–VII with four pairs of anterior setae (A1, 2, 4, 5), P1a on VII short at posterior margin; sternite VIII with two anterior and seven posterior setae, IX–X with six setae.

Specimens examined. Holotype (NSMT-Ap 539): female, the Nasu Imperial Villa, Nasu-machi, Tochigi Prefecture, 37.1100°N, 140.0158°E, elev. 919 m, secondary forest dominated by Q. crispula and P. densiflora , 7 October 2011, K. Furuno et al. leg. Paratypes: two females (TPM-IV-14024; SMNH-Ap-36639), same data as for the holotype except sampling date, 15 October 2013.

Description. Body length. 663 (598–676) µm.

Head. 94 (91–94) µm long, 70 (71–73) µm wide. Posterior additional setae and seta m4 present, but anterior additional seta absent, anterior and posterior sensilla present ( Fig. 1A ); median subposterior seta (sp) subequal to median posterior seta (p) in length, 8 (8) µm; one pair of sensilla (pp) posterior to pseudoculus rudimentary. Labral setae present ( Fig. 1B ). Rostral seta normal, about equal to subrostral seta, 13 (12–13) µm in length ( Fig. 1B ). On maxillary palpus ( Fig. 1C ), dorsal sensillum length 7 µm, longer than lateral sensillum, 5 µm. On galea ( Fig. 1D ), digit O slightly longer than M and I. Mandible with two teeth ( Fig. 1E ). Clypeal apodeme distinct ( Fig. 1A, B ). Pseudoculus with a central mark ( Fig. 1F ), 10 (10) µm long, PR=9 (9).

Legs. Foretarsus length ( Fig. 1G, H ) 68 (68–70) µm; claw 12 (13–14) µm, TR=5.7 (4.9–5.3); empodium 11 (11) µm, EU=0.9 (0.8); sensillum s length 16 (14–16) µm, longer than claw. Sensillum t1 nearer to α3 than to α3 ′, BS=0.9 (0.8); t2 small, narrowly spatulate; t3 slightly broadened, reaching base of α7; a linear, not reaching base of γ2; b linear, reaching base of γ3; c linear, surpassing base of β5; d linear, reaching base of α5; e and g rounded spatulate and large; f1 and f2 thin, f2 shorter than f1; a ′ linear; b ′ 1 absent; b ′ 2s ame as t2, small, narrowly spatulate; c ′ absent. A pore between α1 and δ1, and between b and α3 ′. Length of middle tarsus 29 (28–33) µm, length of claw 10 (11) µm; empodium short and about 1/4 of claw in length ( Fig. 1I ), 3 (3) µm long; hind tarsus 36 (36–39) µm, claw 11 (12) µm; empodium longer than 2/3 of claw in length ( Fig. 1J ), 8 (8) µm long; on hind tarsus ( Fig. 1J ), D2 and D4 spine-like, more slender than D5.

Chaetotaxy. Chaetotaxy as in Table 1 and Fig. 2A–C . On thoracic tergites II–III ( Fig. 2A ), P1a and P2a seta-like, but shorter than P1; P1a posterior to P1-P2; P2a slightly closer to P2 than to P3; P1a, 7 (7–9) µm long, subequal or slightly longer than P2a, 7 (6–7) µm long. Abdominal tergites II– IV with five pairs of anterior setae (A1 to 5), V–VII with four pairs (A1, 2, 4, 5); P1a on tergite I, and P1a and P2a on II–VI delicate, longer than P1; P1a on VII short, about 1/2 of P 1 in length, 9 (9) µm long, at hind margin; P2a on VII subequal to P 1 in length ( Fig. 2B ); P1a on I–VI nearer to P1 than to P2; P2a on II–VII nearer to P3 than to P2; on VIII ( Fig. 2B ) P1a ′ normal and slightly anterior to P2, P2a ′ short, linear. Setae on thoracic and abdominal sternites all seta-like; sternite VIII with two anterior and seven posterior setae; sternites IX–X with six setae ( Fig. 2C ).

Porotaxy. Abdominal tergites IX–X with a pair of pores near seta 1. Abdominal sternites I–XI with one medial pore ( Fig. 2C ). Telson with two dorsal medial pores and one ventral medial pore.

Female squama genitalis ( Fig. 2D ). Caput processus blunt, slightly curved against median edge of stylus, corpus processus reduced except for well-developed alae processus; filum processus long and slender; proximo-lateral sclerotization present; stylus apex narrowly rounded.

Chaetotaxic variation. P4a on abdominal tergites III–IV and P2a on abdominal sternites VI–VII asymmetrically absent and asymmetrically present in one paratype female.

Remarks. The genus Eosentomon contains more than 280 species and is common in most areas of the world. Within this genus, the new species is similar to E. sociale Bernard, 1975 , E. erwini Copeland, 1978 and E. quapawense Tipping and Allen, 1994 from the USA, and to E. notiale Tuxen and Imadaté, 1975 from the Solomon Islands, according to a combination of important features such as the absence of foretarsal sensillum b ′ 1, the long empodium on the hind tarsus, and two anterior and seven posterior setae on sternite VIII ( Bernard 1975; Tuxen and Imadaté 1975; Copeland 1978; Tipping and Allen 1994). This new species differs from these four established species, however, by the anterior setae on abdominal tergite VII (six setae in the four established species), the setae on abdominal sternites IX–X (four setae in the four established species but six on IX in E. quapawense ), and the structure of the female squama genitalis.

Among the Japanese Eosentomon species , the new species is similar to E. udagawai Imadaté, 1961 , E. dubium Nakamura, 2010 , and E. inconditum Nakamura, 2010 in having a long empodium on the hind tarsus and two anterior and seven posterior setae on sternite VIII ( Imadaté 1974; Nakamura 2010). However, the new species differs from these three established species by the absence of foretarsal sensillum b ′ 1 (present in the three established species) and the structure of the female squama genitalis (duck’s head-type caput processus in the three established species). Moreover, this new species is distinguished from E. udagawai by the labral setae (absent in E. udagawai ) and the length of the empodium on the middle tarsus (about one-third of the claw length in E. udagawai ), from E. dubium by the anterior setae on abdominal tergites V–VII (ten setae on V–VI and six on VII in E. dubium ), and from E. inconditum by the anterior setae on abdominal tergite VII (six setae in E. inconditum ). The following eight Japanese Eosentomon species also lack foretarsal sensillum b ′ 1: E. kumei Imadaté and Yosii, 1959 , E. topochi Imadaté, 1964 , E. toi Imadaté, 1964 , E. brachychaetum Nakamura, 2010 , E. kantoense Nakamura, 2010 , E. spatulatum Nakamura, 2010 , E. calvum Nakamura, 2010 , and E. hiroshianum Nakamura, 2010 ; however, the new species is easily distinguishable from these as they have a short empodium on the hind tarsus ( Imadaté 1974; Nakamura 2010).

Distribution. Japan, known only from the type locality.

Etymology. The specific name is derived from the Nasu Imperial Villa, the type locality.

Figures

Fig.1. Eosentomon villare sp. nov., holotype, female (NSMT-Ap 539). A, Dorsal view of the head; B, labrum and rostral region; C, maxillary palpus; D, galea; E, mandible; F, pseudoculus; G, interior view of the foretarsus; H, exterior view of the foretarsus; I, distal part of the middle tarsus; J, dorsal view of the hind tarsus. Abbreviations: as, anterior sensillum; cs, clypeal seta; I, inner digit; lb, labral seta; M, median digit; md, dorsal sensillum; ml, lateral sensillum; O, outer digit; p, median posterior seta; pa, posterior additional seta; pp, a pair of sensilla posterior to pseudoculus; ps, posterior sensillum; rs, rostral seta; sp, median subposterior seta; sr, subrostral seta. Arrows show pores. Scale bars: 10µm.

Fig. 2. Eosentomon villare sp. nov., holotype, female (NSMT-Ap 539). A, Dorsal view of thorax III, right side; B, dorsal view of abdomen VI–VIII, right side; C, ventral view of abdomen VIII–X; D, female squama genitalis. Arrows show pores. Scale bars: 20µm.