Unionicola (Majumderatax), 1993

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 : 409

Unionicola (Majumderatax) sp.

( Figure 10 )

Material examined — Vietnam, 15-51-1 Mekong delta at Can Tho, Mekong River , shore, near ferry landing place, 10°03’43"N, 105°47’02"E, alt. 1 m a.s.l., water depth 0.2-0.5 m, substrate: grey-black sand, Eichhornia crassipes , 0/0/1 (mounted) .

Morphology — Deutonymph: P-2 with one serrate seta in ventral and proximomedial position; P- 4 with strongly developed cone-shaped, projections on ventral margin, two proximal, apically bearing a denticle-like seta, one distal, apically bearing a peglike seta; P-5 claw bifurcated into two very long, slender clawlets (length: dorsal 32, ventral 25 µm) ( Figures 10 B-C). Provisional genital field with two pairs of acetabula ( Figure 10A ). I-L-5 with a large (L 55µm) blade-like distoventral seta ( Figure 10D ).

Measurements — Idiosoma L/W 447/378; coxal field L/W 225/252; provisional genital plate L/W 37/26, Ac diameter 19-20. Palp: total L 196, dL/H, dL/H ratio: P-1, 12/25, 0.5; P-2, 60/35, 1.7; P-3, 19/34, 0.55; P-4, 65/28, 2.3; P-5, 40/-; dL ratio P- 2/P-4, 0.93; gnathosoma vL 95; chelicera total L 97.

Remarks — In addition to the type species, Unionicola hankoi Szalay, 1927 , known from the Palaearctic, the subgenus includes Unionicola crenipalpis Lundblad, 1969 from Burma. The combination of a well developed cone-shaped, projections on ventral margin of P-4 (absent in U. crenipalpis ) and one proximomedial serrate seta on P-2 (lacking in U. hankoi ), easily separates the single deutonymph from the Mekong delta from all other species of the subgenus Majumderatax . Most probably we are dealing with an undescribed species, but since adults are not available, a final decision can not be made.

Figures

FIGURE 10: Unionicola (Majumderatax) sp., deutonymph, Mekong River, Vietnam: A – idiosoma, ventral view; B-C – palp; D – I-L-5 and -6. Scale bars – 100 µm.