Hexaxonopsis (Hexaxonopsis) cambodiensis, Pešic & Smit, 2016

Pešic, V. & Smit, H., 2016, New records of water mites from Southeast Asia (Acari: Hydrachnidia) with the description of two new genera and 12 new species, Acarologia 56 (3), pp. 393-433 : 414-420

Hexaxonopsis (Hexaxonopsis) cambodiensis n. sp.

( Figures 15 C-D, 16-17)

Type material — Holotype male, dissected and slide mounted, Cambodia, 15-35-1 Angkor , moat around the main Angkor temple, 13°24’54.0"N, 103°51’34.8"E, alt. 26 m a.s.l., depth 0.4- 0.2 m, substrate: red sand covered by detritus . Paratypes: 2/1/0, same data as holotype, one male and one female dissected and slide mounted .

Diagnosis — Colour pattern consisting of a central elongated patch of dark-blue; two pairs of glandularia in region between genital field and opening for insertion of IV-L separated from each other; posterior setae on gnathosoma enlarged.

Description — Dorsal and ventral shields fused anteriorly; dorsal shield with seven pairs of glandularia (the seventh pair inconspicuous, flanking the excretory pore); postocularia well distanced from anterior margin; excretory pore projecting, located at the posterior end of dorsal shield; anterior portion of dorsal shield with 14-15 pairs of triangular, posteriorly-directed denticles ( Figure 16A ); dorsal shield with colour pattern as illustrated in Figures 15 C-D; eye pigment well developed. Ventral shield oval, slightly truncate at anterior end, lateral margins rounded. Lateral margins of Cx-I/II with 2-3 strong, hook-like, posteriorly-directed projections; two pairs of glandularia in region between genital field and opening for insertion of IV-L, these are well separated from each other; a relatively short longitudinal ridge posterior to IV-L insertions. Genital field with three pairs of Ac, arranged in an arc. Palp: ventral margin of P-2 convex, distal margin of P-3 with well developed hyaline extensions, P-4 ventrally dilated near insertions of a pair of hairlike setae, and with a more robust seta near distal end of the segment; posterior setae on gnathosoma enlarged ( Figure 16E ). Legs: numbers of swimming setae: II-L-4, 1; II-L-5, 2-3; III-L-4, 2; III-L-5, 3; IV- L-4, 2; IV-L-5, 2-3. Male: Gonopore elongated. Female: Gonopore relatively large ( Figure 17A ).

Measurements — Male (holotype, in parentheses paratype): Dorsal shield L/W 372 (372)/266 (259), ratio 1.4 (1.44); ventral shield L/W 381 (399)/301 (294); gnathosomal bay L 103 (102); distance between most lateral pair of Ac 129 (128), gonopore L/W 38 (41)/31 (39), ratio 1.22 (1.05); ejaculatory complex L 99. Palp: total L 195 (200), dL/H, dL/H ratio: P-1, 30/17, 1.8 (31/16, 1.9); P-2, 45/35, 1.28 (45/34, 1.3); P-3, 25/23, 1.07 (25/23, 1.1); P-4, 66/16, 4.1 (69/15, 4.5); P-5, 29/11, 2.6 (30/11, 2.7); L ratio P-2/P-4, 0.69 (0.65); gnathosoma vL 51 (55), with apodemes 78 (80). Legs: dL of I-L: 32 (34), 32 (32), 29 (27), 49 (49), 65 (68), 72 (75); dL of IV-L: 43 (42), 65 (62), 58 (57), 71 (71), 79 (82), 86 (92).

Female: Dorsal shield L/W 384/272, ratio 1.41; ventral shield L/W 403/320; gnathosomal bay L 100; distance between most lateral pair of Ac 139, gonopore W 86. Palp: total L 189, dL/H, dL/H ratio: P-1, 29/14, 2.1; P-2, 44/33, 1.33; P-3, 25/23, 1.1; P-4, 63/15, 4.1; P-5, 28/10, 2.8; L ratio P-2/P-4 0.7; gnathosoma vL 57, with apodemes 82; chelicera total L 104. Legs: dL of I-L: 31, 32, 29, 46, 62, 68; dL of IV-L: 42, 62, 57, 69, 78, 88.

Etymology — Named after the country where the new species was found.

Remarks — The combination of posteriorly directed denticles on the dorsal shield, a short longitudinal ridge posterior to IV-L insertions, and absence of the lateral projections on the sides of the ventral shield, makes the new species most similar to Hexaxonopsis paxillatus ( Uchida & Imamura, 1951) , a species described by Uchida and Imamura (1951) from central China. The latter species can be separated in different arrangement of dorsal glandularia and the two pairs of glandularia located between genital field and insertions of the IV-L are more closely approached to each other. In the original description Uchida and Imamura (1951) did not mention the colour pattern. Moreover, at the illustrated figure of gnathosoma of A. paxillatus enlarged posterior setae which are so characteristic of the present new species are completely missing (see Uchida and Imamura 1951, figure 8d).

Distribution — Cambodia; known only from the locus typicus ( Figure 25D ).

Figures

FIGURE 15: Photoghraphs of dorsal shield. A-B Hexaxonopsis laosensis n. sp.: A – male holotype; B – female paratype. C-D H. cambodiensis n. sp.: A – male holotype; B – female paratype. E – H. angkoriensis n. sp., female holotype.

FIGURE 16: Hexaxonopsis (Hexaxonopsis) cambodiensis n. sp., male, Angkor Wat, Cambodia: A – dorsal shield; B – ventral shield; C – palp (P-1 lacking); D – palp; E – gnathosoma (arrow showing enlarged posterior setae); F – ejaculatory complex; G – I-L. Scale bars – 100 µm.

FIGURE 17: Hexaxonopsis (Hexaxonopsis) cambodiensis n. sp., female, Angkor, Cambodia: A – ventral shield; B – palp; C – chelicera. Scale bars – 100 µm.

FIGURE 25: Photoghraphs of sampling sites: A – Laos, Kauangxi Waterfall (locus typicus of Monatractides laosensis n. sp., Hexaxonopsis laosensis n. sp., Sinaxonopsis laosensis n. sp. and Africasia purpurea n. sp.); B – Laos, Kouangxi Waterfall, pond behind artifical barrier (sampling site of Hygrobates hamatus K. Viets, 1935, H. henni Wiles, 2004 and locus typicus of Forelia gereckei n. sp.); C – Vietnam, Bach MAE National Park, brook with a pool (sampling site of Monatarctides sp. and locus typicus of Limnesia scharfi n. sp., Schwoerbelia pioniformis n. sp. and Arrenurus contortus n. sp.; D – Cambodia, moat around the main Angkor temple (locus typicus of Hexaxonopsis