Sinaxonopsis laosensis, 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 : 424-427

Sinaxonopsis laosensis n. sp.

( Figures 20-21 )

Type material — Holotype male, dissected and slide mounted, Laos, 15-33-1, Kouangxi Waterfall , lentic bay within a pool behind a travertine barrier within the main brook, 19°44’55.9"N, 101°59’33.4"E, alt. ca. 490 m a.s.l., water depth 0.5 m, substrate: travertine mud covered by some leaves.

Diagnosis — Dorsal posterior plate bearing six pairs of glandularia (Dgl-2-4, and Lgl-2-4); Cx-IV with distinct medial suture line; Palp slender (L/H P-2, 2.2; P-4, 5.0); IV-L-4 distally with a strong bifurcated seta, IV-L-5 distally with a strong pennate seta; IV-L-6 anteriorly slightly enlarged, posteriorly with three strong, laterally flattened setae.

Description — Male: Idiosoma colourless; dorsal and ventral shield present; dorsal shield formed by a large posterior plate bearing six pairs of glandularia (Dgl-2-4, and Lgl-2-4) and one pair of anterior platelets bearing the lateral eyes, postocularia, A2 and Dgl-1 ( Figure 20A ); excretory pore projecting, located at the posterior end of dorsal shield; dorsal shield colour indistinct, eye pigment well developed. Ventral shield ( Figure 20B ) oval, slightly truncate at anterior end; tips of Cx-I not extending beyond frontal margin. Cx-IV with distinct medial, posterior and lateral suture lines, medial suture line straight, suture line Cx-III/IV developed only laterally, ending medial to IV-L insertions and not reaching the medial line; genital field triangular, gonopore elongated, acetabula numerous (approximately 30 pairs of acetabula, but due to rugosity of idiosoma some of these not visible in ventral view) and extend in parallel to the coxal plate margin as indistinct strips from the gonopore to the posterolateral idiosoma edge.

Palp: P-2-3 ventral margin slightly concave, P-4 longer than P-2, basally and distally concave, in centre convex with a pair of long setae ( Figures 20 D-E).

Legs: ventral margin of I-L-6 and II-L-6 with small denticles and a dense hair-like setae ( Figures 21 A-B); III-L-4 with dorsal and ventral margins diverging from base to tip, distal margin bearing two sword setae and two strong simple setae; III-L-5 slightly curved, distally with one strong sword seta, slightly set off from distal margin, and several slen- der simple setae; III-L-6 not bearing modified setae, claws modified and heteromorphic as illustrated in Figure 21C (inset); IV-L-4 with dorsal and ventral margins diverging from base to tip, in the enlarged distal half a group of strong, variously modified setae, one strong bifurcated ( Figure 21D , arrow), two strong sword setae, and two simple slender setae; IV-L-5 ventral margin almost straight, distally not remarkably thicker distally than proximally, distally in addition to one strong sword seta, slightly set off from distal margin, one pennate and two slen- der simple setae; IV-L-6 slightly curved, anteriorly slightly enlarged, posteriorly with three strong, laterally flattened setae; claws of I-III legs with a dorsal and ventral clawlets ( Figure 21A inset).

Measurements — Idiosoma L/W 581/43, dorsal shield L/W 550/438; posterior plate L/W 475/438, anterior platelets L/W 260/85; ventral shield L/W 556/463; gnathosomal bay L 141; gonopore L/W 78/9, ratio 8.5; ejaculatory complex L 172. Palp: total L 328, dL/H, dL/H ratio: P-1, 46/20, 2.3; P- 2, 80/37, 2.16; P-3, 46/29, 1.58; P-4, 111/22, 5.0; P- 5, 45/14, 3.2; L ratio P-2/P-4, 0.72; gnathosoma vL 132; chelicera total L 162, claw L 49, basal segment L 123, L basal segment/claw ratio 2.5. Legs: dL of I- L-2-6: 57, 75, 115, 145, 157; dL of II-L: 63, 65, 86, 125, 159, 169; dL of III-L: 77, 59, 89, 89, 181, 159; dL of IV- L: 120, 129, 188, 109, 212, 142. Female: Unknown.

Remarks — This is the third Sinaxonopsis species , the first one ( S. unicucrus Yi & Jin, 2012 ) was described by Yi and Jin (2012) from a pool in a stream in Anhui Province, China. The species from China, known from both sexes, differs from Sinaxonopsis laosensis n. sp. in: 1) Cx-IV medially forming pronounced angle, 2) palp segments comparatively more stout (L/H P-2, 1.65; P-4, 4.5; calculated from figures), IV-L-4 distally without strong bifurcated seta, IV-L-5 distally without strong pennate seta, IV- L-6 anteriorly strongly enlarged, with a pair of welldeveloped dorsal projections.

Recently, Smit (2016) described, based on a single female, the second species Sinaxonopsis siamicus from Thailand, a species clearly differing in Lgl-2 not on large posterior dorsal shield, a different configuration of Dgl-1 and A2 and comparatively more stouter palp.

Distribution — Laos; known only from the locus typicus ( Figure 25A ).

Figures

FIGURE 20: Sinaxonopsis laosensis n. sp., male, Kauangxi Waterfall, Laos: A – idiosoma dorsal view; B – ventral shield; C – ejaculatory complex; D-E – palp; F – gnathosoma. Scale bars – 100 µm.

FIGURE 21: Sinaxonopsis laosensis n. sp., male, Kauangxi Waterfall, Laos: A – I-L-2-6 (inset: claw); B – II-L (inset: ventral denticulation of II-L-6); C – III-L-2-6 (inset: claws); D – IV-L (inset: distal margin of IV-L-6) (arrow showing strong bifurcate seta). 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