Monatractides oman, Gerecke, 2004

Gerecke, Reinhard, 2004, Water mites from spring- and ground-water habitats in the Sultanate of Oman, Journal of Natural History 38 (22), pp. 2833-2849 : 2834-2837

Monatractides oman sp. nov. ( figures 1 , 2 )

Type series. HOLOTYPE: „, OMAN 96-68. Wadi Al Fara , Rustaq, B. -Rh. pump in gravel, probe at 60 cm; UTM 0545970/2595453 (23‡28'06̎N, 57‡27'00̎E), 28.0‡C, 1.134 mS cm 21, 1 April 1996, slide mounted in Hoyer’s fluid . Further material (not included in the type series): 2””, mounted on slides in Hoyer’s fluid, 4””, one deutonymph, undissected on a slide in Euparal.

Diagnosis. Male: idiosoma slender and elongated due to the extremely extended postgenital area; insertions of IV-L close to the median line; genital field relatively small; gnathosoma elongated.

Description. Male: idiosoma L/W 900/540 (ventral view: figure 1E ); gnathosomal bay L/W 189/54; glandular openings on tips of coxae with short hyaline extensions, two tubercles on each side of the gnathosomal bay; coxal field elongated, in particular due to increased L of Cx-2 z 3: Cx-1 total L 297, median L 108, Cx-2 z 3 median L 121, ratio Cx-1 total L/Cx-2 z 3 median L 2.5, ratio Cx-1 median L/Cx-2 z 3 median L 0.9; insertions of IV-L approached to the median line (distance between the insertions 324, versus 60% W idiosoma); genital field minute in dimensions and slender: L/W 143/112, ratio 1.3, about 20% of total idiosoma L; genital skeleton L 180, in shape typical for the genus (as given by Di Sabatino et al., 1992); posteromedial margins of Cx-4 close to each other, forming an acute angle at their insertion on the caudal margin of the genital field; postgenital field elongated (distance genital field-excretory porus 193, distance genital field-caudal idiosoma margin 320); dorsal shield ( figure 1D ) L/W 694/515 (ratio 1.3), dorsal plate L 627, L/W ratio 1.22; shoulder plate L/W 247/ 85 (ratio 2.9); frontal plate L/W 121/76 (ratio 1.6), L ratio shoulder plate/frontal plate 2.0; gnathosoma ( figure 1A ) elongated, in its anterior part with weakly concave ventral margin, ventral L 196, dorsal L 230; chelicera basal segment L/H 190/31, claw L 40, basal segment/claw ratio 4.8, L/H ratio 7.4; palp ( figure 1B, C ) total L 227, segment L (in parentheses L/H ratio) P-1 25 (0.8), P-2 72 (1.8), P-3 45 (1.3), P-4 58 (2.3), P-5 27 (2.5); L ratio P-2/P-4 1.24; P-2 and P-3 with very fine denticulation on the mediodistal segment margin and rather short ventrodistal setae, P-4 with a well-developed denticle near the short ventral hairs.

Females: idiosoma L/W 750/560 (ventral view: figure 2 ), gnathosomal bay L/W 184/58; coxal field elongated as in the male, Cx-1 total L 292, median L 108, Cx- 2 z 3 median L 100, ratio Cx-1 total L/Cx-2 z 3 median L 2.9, ratio Cx-1 median L/ Cx-2 z 3 median L 1.1; genital field L/W 157/153, ratio 1.0; posteromedial margins of Cx-4 as in males forming an acute angle at their insertion on the caudal margin of the genital field; postgenital field relatively short, but distance genital fieldexcretory porus remarkable (193, distance genital field-caudal idiosoma margin 195); dorsal shield L/W 616/450 (ratio 1.4), dorsal plate L 560, L/W ratio 1.24; shoulder plate L/W 225/81 (ratio 2.8); frontal plate L/W 117/81 (ratio 1.4), L ratio shoulder plate/frontal plate 1.9; gnathosoma and appendages as in male, ventral L 225, dorsal L 247; chelicera basal segment L/H 192/31, claw L 38, basal segment/ claw ratio 5.1, L/H ratio 7.4; palp total L 226, segment L (in parentheses L/H ratio) P-1 25 (0.7), P-2 71 (1.6), P-3 44 (1.2), P-4 58 (2.3), P-5 28 (2.2); L ratio P-2/P-4 1.22.

Discussion. Most probably, the females caught together with the holotype male belong to the same species, as they display high similarity in the elongated median suture line of Cx-2 z 3, the shape of the posterior margins of Cx-4 and the shape of the mouthparts. The difference in the shape of the genital field is a typical dimorphism in all species of Monatractides , the short postgenital area is due to the obviously juvenile age of all females from this population (indicated by weak sclerotization with large pores and absence of eggs). For this reason, the females are probably atypical in idiosoma shape and therefore not included in the type series.

Monatractides oman is closely related to M. balneatoris Di Sabatino and Gerecke, 2003 ( Di Sabatino et al., 2003) described from the Dead Sea area in Israel. Common features include the elongated idiosoma and gnathosoma, presence of relatively large shoulder plates (in M. oman still more elongated than in M. balneatoris which has a L ratio shoulder plates/frontal plates of 1.8) and dimensions and proportions of mouthparts. The most conspicuous difference is found in the shape of the Cx-4 (in M. balneatoris starting from the posterior margin of the genital field in a wide open obtuse angle); furthermore, the male genital field is less slender in M. balneatoris (L/ W 1.1 –1.2), the insertions of IV-L are more distanced (344, versus 64% W idiosoma) and the postgenital area is less extended (distance genital field-excretory pore v 130, genital field-caudal idiosoma margin v 240).

The character combination of an elongated idiosoma with large postgenital area and posteromedial margins of Cx-4 forming an acute angle at their starting point on the genital field is found also in M. lintriculus Di Sabatino and Gerecke, 2003 , a species only known in the female sex from the Golan Heights in Israel. This species differs from M. oman in a shorter median suture line of Cx-2 z 3, the mediocaudal margins of Cx-4 starting more distant from each other from the outer edges of the genital field, a less elongated gnathosoma and a more stout palpus without a distinct ventral denticle on P-4.

Figures

FIG. 1. Monatractides oman sp. nov., male (OMAN 96-68). (A) Gnathosoma, lateral view; (B) right palpus, lateral view; (C) left palp, medial view; (D) dorsal shield; (E) idiosoma, ventral view. Scale bars: 100 Mm.

FIG. 2. Monatractides oman sp. nov., female (OMAN 96-68), idiosoma, ventral view. Scale bar: 100 Mm.