Monatractides polyhymnia Pešić & Smit, 2014, n. sp.
Creators: name: Pešić, Vladimir
name: Smit, Harry
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Trombidiformes
Torrenticolidae
Monatractides
Monatractides polyhymnia

description: Monatractides polyhymnia n. sp.
(Figs. 30A–F, 31A–C, 37E–F, 38E–F)
Type series. Holotype male, dissected and slide mounted, Ghana: Kue River, Kyabobo NP, 8º 31.087 N, 0º 36.049 E, alt. 208 m asl., 25.ii.2013, Smit. Paratypes: 1/1/0, same data as holotype, 0/1/0 dissected and slide mounted.
Diagnosis. P-3 ventral margin concave, sexual dimorphism of P-3, P-4 bowed, ventral margin with setaebearing protrusion in distal half of segment. Male: genital field oval (L/W ratio 1.26); P-3 with three stout, medially orientated setae at the ventrodistal margin. Female: genital field elongated trapezoid (L/W ratio 1.2); P-3 distally with ventrolateral seta.
Description. General features —Idiosoma roundish; frontal platelets shorter than shoulder platelets (shoulder/ frontal platelets L ratio 1.1–1.2); frontal margin with flat protrusions medial to the eyes (Fig. 31A); the tips of Cx-I orientated to the lateral side. Cxgl-4 located far anteriorly, near insertion of I-L; gnathosomal bay deep U-shaped, proximally wide box-shaped; posterior suture lines of Cx-IV extending posteriorly beyond posterior margin of genital field and directed posterolaterally; excretory pore and Vgl–2 away from the line of primary sclerotization, Vgl–2 posterior to excretory pore; gnathosoma nearly triangular in lateral view, with short, cone-shaped rostrum (Fig. 30F); palp compact, ventral margin of P-2 proximally with sharp bend, distally straight, bearing ventral seta, P-3 ventral margin concave, sexual dimorphism of P-3, P-4 bowed, ventral margin with setae-bearing protrusion in distal half of segment. Male: medial margin of Cx-II/III relatively short; genital field small and oval in shape; P-3 ventrodistally bearing three stout (short and thick) setae, orientated medially and one ventrolateral seta (Figs. 30C–D). Female: suture lines Cx-I/II complete, not meeting in the medial line, but separately ending at anterior genital field margin (Fig. 31B); genital field pentagonal; P-3 distally with ventrolateral seta (Fig. 31C).
Measurements. Male (holotype)—Idiosoma (ventral view: Figs. 30A, 38E) L 665, W 499; dorsal shield (Figs. 30B, 37E) L 559, W 418, L/W ratio 1.34; dorsal plate L 516; shoulder platelets L 142–147, W 69–70, L/W ratio 2.07–2.09; frontal platelets L 120–127, W 58–59, L/W ratio 2.03–2.2; shoulder/frontal platelets L ratio 1.12–1.22. Gnathosomal bay L 131, Cx-I total L 281, Cx-I mL 150, Cx-II+III mL 22; ratio Cx-I L/Cx-II+III mL 12.8; Cx-I mL/Cx-II+III mL 6.8. Genital field L/W 106/84, ratio 1.26; distance genital field-excretory pore 175, genital fieldcaudal idiosoma margin 241. Gnathosoma vL 184; palp total L 232–233, dL/H, dL/H ratio: P-1, 21–22/28, 0.78; P- 2, 68/47, 1.43; P-3, 49/43, 1.15; P-4, 68/28, 2.4; P-5, 26/13, 2.0; P-2/P-4 ratio 1.0; dL of I-L-5–6 (Fig.): 122, 128; I-L-6 H 58–59, dL/H I-L-6 ratio 2.2.
Female (paratype from Kue River, n = 1)—Idiosoma (ventral view: Figs. 31B, 38F) L 731, W 584; dorsal shield (Fig. 37F) L 641, W 494, L/W ratio 1.3; dorsal plate L 594; shoulder platelets L 156–159, W 78–81, L/W ratio 2.0; frontal platelets L 131–134, W 67, L/W ratio 1.95–2.0; shoulder/frontal platelets L ratio 1.19. Gnathosomal bay L 147, Cx-I total L 267. Genital field L/W 173/145, ratio 1.19; distance genital field-excretory pore 209, genital field-caudal idiosoma margin 284. Gnathosoma vL 199; chelicera total L 240; palp total L 229, dL/H, dL/H ratio: P-1, 23/28–29, 0.81; P-2, 69/48, 1.43; P-3, 48/38–39, 1.24; P-4, 64/29, 2.16; P-5, 25/12, 2.06; P- 2/P-4 ratio 1.09; dL of I-L-2–6: 69, 92, 111, 122, 131; I-L-6 H 55, dL/H I-L-6 ratio 2.4.
Etymology. The species is named after Polyhymnia (Ancient Greek: Πολυύμνια), one of nine Muses from Greek mythology, who was a patron of sacred poetry and song. The species name is a noun in apposition (in the nominative case).
Discussion. The new species shows a remarkable sexual dimorphism, as in the male P-3 has a group of three stout, medially orientated setae at the ventrodistal margin, while these setae are lacking in the female. Due to the shape of P-3 with stout, medially oriented setae at the ventrodistal margin, the new species from Ghana seems to be closely related to M. spinipalpis (K.O. Viets, 1981) a species described by K.O. Viets (1981) based on a single male from South Africa. Later on, Goldschmidt & Smit (2009) reported a single male of M. spinipalpis from Kwazulu- Natal Province and provided an additional description of this species. In the original description, K.O. Viets (1981) described this species as close to M. mitchelli (K.O. Viets, 1965), but differing in a stout, medially oriented setae at the ventrodistal margin of P-3 lacking in the latter species. Obviously, he was not aware that the difference in the shape of P-3 might be results of the sexual dimorphism, as the latter species was known only from two females from Transvaal (K.O. Viets 1965). It is possible that M. mitchelli represents a senior synonym of M. spinipalpis but this should be checked by finding additional material, including the male, from the locus typicus of M. mitchelli.
Monatractides spinipalpis differs from the new species from Ghana in larger idiosoma dimensions, a more elongated genital field (L/W ratio 1.41–1.55, data taken from K.O. Viets 1981 and Goldschmidt & Smit 2009), P-2 shorter than P-4 and by having a well developed ventrodistal protrusion on P-3. The female of M. mitchelli can be separated by the more elongated genital field, strongly tapering to the caudal end (see K.O.Viets 1958, Fig. 9).
Remarks. No ejaculatory complex of Monatractides spinipalpis has been described yet (see: K.O. Viets 1981, Goldschmidt & Smit 2009) Also in males in the present study this organ was not found, but sclerotized framework immediately above the genital field can be hardly visible.
Habitat. A sandy/bouldary streams, shaded by riparian vegetation (see Fig. 45 C in Pešić et al. 2013).
Distribution. Ghana; known only from the type locality.
description: Published as part of Pešić, Vladimir & Smit, Harry, 2014, Torrenticolid water mites (Acari: Hydrachnidia: Torrenticolidae) from Ghana, pp. 1-80 in Zootaxa 3820 (1) on pages 46-49, DOI: 10.11646/zootaxa.3820.1.1, http://zenodo.org/record/286303