Arrenurus (Megaluracarus) acuticoxalis

Smit, Harry, 2017, New records of water mites from standing waters in Thailand, with the description of nine new species (Acari: Hydrachnidia), Zootaxa 4312 (1), pp. 69-91: 85

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Arrenurus (Megaluracarus) acuticoxalis

n. sp.

Arrenurus (Megaluracarus) acuticoxalis  n. sp.

( Fig. 9View FIGURE 9)

Material examined. Holotype male, rice field, Amnat Chareon Province, Thailand, 16° 03.244ʹ N, 104° 38.105ʹ E, 25-x-2010 ( RMNH). 

Diagnosis. Cauda posteriorly with a rudimentary petiole, second coxae drawn out into a long pointed extension; posterior margin of Cx-IV nearly straight to lateral idioma margin.

Description. Male: Idiosoma green, 656 long and 413 wide. Anterior margin slightly concave, cauda relatively short, nearly as long as wide. Dorsal shield rounded, 267 long and 255 wide. Posterior part of cauda with complex structures, including a short, rudimentary petiole which is upturned (only visible in lateral view). L4 on short humps. Distal margin of first coxae drawn out to a point, second coxae with a large pointed extension extending well beyond the idiosoma. Medial margin of fourth coxae longer than medial margin of third coxae, posterior margin of Cx-IV concave. Gonopore 44 long. Genital plates long and narrow, extending to lateral idiosoma margin. Length of P1-5: 24, 44, 32, 58, 25; P2 medially with one seta. Length of I-leg-4–6: 87, 58, 146 (to tip). Length of IV-leg-4–6: 158, 80, 108 (to tip); IV-leg-4 without a spur. Third and fourth legs with numerous swimming setae.

Female: Unknown.

Etymology. Named after the very pointed first coxae.

Remarks. There are several species of Arrenurus  with extended anterior coxae and a rounded complete dorsal plate including A. celyonicus Daday, 1898  and A. egathus Cook, 1966  . The new species is most similar to A. cornutus Walter, 1929  recorded from Java. This species lacks the rudimentary petiole, and the posterior margin of the cauda is more concave in A. cornutus  . Lundblad (1969), who assigned his specimens from Burma to A. cornutus  , noted the absence of a rudimentary petiole but overlooked the differences in the shape of the fourth coxae.


National Museum of Natural History, Naturalis