Piona oryza

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: 81-82

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Piona oryza

n. sp.

Piona oryza  n. sp.

( Fig. 7View FIGURE 7)

Material examined. Holotype female, rice field, Yasothon Province, Thailand, 15° 44.688ʹ N, 104° 13.244ʹ E, 24- x-2010 ( RMNH)  . Paratype: One female, rice field, Amnat Chareon Province, 25-x-2010 ( RMNH)  ; one female, Rice field, Sisaket Province, 14° 59ʹ 28.4ʺ N, 104° 22ʹ 56.7ʺ E, 5-x-2010 ( RMNH)  .

Diagnosis. Genital field with one small platelet with 2–3 acetabula, located anteriorly to posterior two plates. The latter consisting of one plate with 7–9 acetabula and one with 20 acetabula. P4 with small setal tubercles.

Description. Female: Idiosoma; dorsal length 1045 (884–1025); width 810 (784–810). Posterior margin of fourth coxae slightly concave. Medial margin of fourth coxal plates as long as medial margin of third coxal plates. Genital field 454 (445) wide, sloping posteriorly (slope approx. 45°) with acetabula on weakly developed and fragmented platelets that are variable in shape and extending beyond the gonopore (fig 7A); one small platelet with (3–4) acetabula located anterior to two major posterior platelets (fig 7A); one posterior platelet with 7–9 acetabula, the other with 19 acetabula curved around an enlarged central acetabulum. Gonopore 186 (156) long. Pre-genital sclerite sickle-shaped, post-genital sclerite rectangular. Length of P1-5: 49, 219, 109, 186, 77. Ventral margin of P2 rugose and slightly convex, P4 stocky with small setal tubercles. Length of I-leg-4–6: 186, 194, 162. Length of IVleg-4–6: 235, 259, 211.

Etymology. Named for its occurrence in rice fields.

Remarks. The left and right large acetabular plates of the holotype differ, one being more fragmented. However, in the paratype both genital plates are similar, and are like the left genital plate of the holotype. The new species is similar to P. dadayi (Piersig, 1900)  , but differs in a less slender palp, and sloping posterior genital plates that extend well beyond the gonopore. Piona platyura Jin & Guo, 1992  has somewhat similarly shaped genital plates, but the small anterior platelet is fused to the posterior platelet, and P4 has a large ventral extension which is absent in the new species.


National Museum of Natural History, Naturalis