Arrenurus (Micruracarus) monocavus, Smit, 2012

Smit, H., 2012, New records of the water mite family Arrenuridae from the Afrotropical region, with the description of 11 new species and two new subspecies (Acari: Hydrachnidia), Zootaxa 3187, pp. 1-31 : 23

Arrenurus (Micruracarus) monocavus n. sp.

( Figs. 57–62)

Material examined. Holotype male, Chobe River at Kasane, Botswana, 17° 47’ 43,34” S 25° 13’ 23,00 ” E, 17- vii-1996 ( RMNH) . Paratypes: one male, one female, same data as holotype ( RMNH) .

Diagnosis. Gonopore of male shifted caudally; dorsum with a hole with a complex structure inside; posterior margin with a closed cleft.

Description. Male: Idiosoma yellowish-brown, dorsally 502 (486) long and 356 (356) wide, ventrally 518 long. Dorsum with a small, incomplete dorsal shield, 176 (176) wide. Dorsal shield narrowed posteriorly. Cauda absent, posterior margin of idiosoma with a large, closed cleft. Dorsum posteriorly with a hole, with a complex structure inside; this hole extending internally. One dagger-like structure can be seen inside the hole near the anterior margin, with might be a rudimentary petiole. Moreover, two hyaline bowed, setae-like structures are present on the posterior margin. Capitular bay shallow. Anterior coxae extending beyond anterior idiosoma margin. Margins of coxae indistinct. Suture line between third and fourth coxae oblique. Gonopore shifted caudally, 10 long, and not visible in normal ventral view. Genital plates long, swollen laterally, extending to lateral idiosoma margin. Lengths of PI-PV: 26, 60, 52, 67, 32; palp rotated, PII anteroventrally with two setae and more dorsally one more seta. Lengths of I-leg-4-6: 70, 80, 86. Lengths of IV-leg-4-6: 116, 86, 64; IV-leg-4 without spur. Legs with swimming setae; also I-leg-5 with one swimming seta.

Female: Idiosoma yellowish-brown, 527 long and 535 wide. Dorsal shield incomplete, 340 wide. Beside glandularia D2 and D3 there is another glandularium on the dorsal shield, including associated seta. This must be considered as an aberration. Idiosoma truncated posteriorly. Anterior idiosoma margin convex. Anterior coxae extending beyond anterior idiosoma margin. Capitular bay shallow. Margins of coxae indistinct. Suture line between third and fourth coxae oblique. Gonopore 118 long and 130 wide, lying close to posterior idiosoma margin. Genital plates reversed wing-shaped, extending to lateral idiosoma margin, swollen laterally. Lengths of PI- PV: 34, 72, 46, 70, 34; palp as in male. Lengths of I-leg-4-6: 80, 72, 76; first legs without swimming setae. Lengths of IV-leg-4-6: 90, 98, 80.

Etymology. Named for the hole in the dorsum of the male.

Remarks. The most unusual character is the caudal shifting of the gonopore of the male. Within the family Arrenuridae , two other genera show a caudal shifting of the gonopore, i.e. Thoracophoracarus K. Viets and Hamappendix Walter and Bader. The new species is most close to members of Thoracophoracarus , but differs in the presence of a distinct dorsal shield. As Gerecke (2009) stated, presence of a dorsal shield would destroy the concept of a monophyletic genus Thoracophoracarus . The female shares the reversed wing-shaped genital plates with females of Thoracophoracarus . The rotation of the palp is found in other subgenera as well, e.g. Dadayella Koenike and Arrhenuropsis K. Viets , the latter subgenus only known from the female sex. This character probably developed independently in several clades. Due to the posterior median cleft of the male, the new species is assigned to the subgenus Micruracarus .