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A new species of Atractides Koch, 1837 (Acari, Hydrachnidia) is described from Ethiopia. The world number of Atractides now tallies 297 species. The diversity of the genus Atractides in the Afrotropical region is briefly discussed.
Water mites, taxonomy, new species, Africa, biodiversity
Water mites of the genus Atractides Koch, 1837 have been found in all biogeographical regions except Australia and Antarctica.
The aim of our paper is to describe a new Atractides species from Ethiopia. Additionally, the worldwide biodiversity of the genus Atractides Koch, 1837 of the world, with an emphasis on the Afrotropical region, is briefly discussed.
Material and methodsWater mites were collected by hand netting, sorted on
the spot from the living material, preserved in Koenike fluid and
dissected as described elsewhere (e.g.
All measurements are given in μm. For a detailed description and discussion of the characteristics of the genus Atractides and a detailed methodological introduction, see
The following abbreviations are used: Ac-1 = first acetabulum, alt. = altitude, asl. = above sea level, Cx-I = first coxae, dL = dorsal length, H = height, HB = central height, L = length, I-L-6 = Leg 1, sixth segment (tarsus), lL = lateral length, mL = medial length, P-1 = palp, first segment, S-1 = large proximal ventral seta at I-L-5, S-2 = large distal ventral seta at I-L-5, Vgl = ventroglandulare, vL = ventral length, W = width.
Systematicsurn:lsid:zoobank.org:act:E968E96B-BAF1-4641-8DB4-3490FC07C28C
Figs 1–3Holotype, male (ZMAN), dissected and slide mounted, Ethiopia, Roby River, 21.x.2006, 9°44.996N, 38°59.743E, 2507 m a.s.l. Paratypes: two males, one female (ZMAN, one female dissected and slide mounted), same data as holotype.
Dorsal integument striated, palp slender with P-2 straight in the both sexes, S-1 in female ending in a fine hair-like tip, excretory pore surrounded by distinct oval sclerite, Vgl-1 fused to Vgl-2.
General features. Dorsal integument: striated, muscle attachment plates unsclerotized. Coxal field: extended secondary sclerotization, caudal margin Cx-I broadly convex. Genital field: Ac in a weakly curved line. Excretory pore: sclerotized; Vgl-1 fused to Vgl-2. Palp: ventral margin of P-2 and ventral margin of P-3 slightly concave, ventral margin of P-4 straight, sword seta between ventral hairs, nearer to the distoventral hairs. Legs: I-L-5 S-1 and S-2 pointed, interspaced, S-2 basally enlarged, bluntly pointed; I-L-6 slender, curved, with maximum H proximally; leg claws with dorsal and ventral clawlets (Fig. 2C).
Male: Idiosoma L/W 669-684/541-556; coxal field L 420; Cx-III W 484; Cx-I+II mL 156; lL Cx-I+II 265. Genital field (Fig. 1): anterior margin convex, with a border of secondary sclerotization convexely protruding, anterior margins of gonopore and Ac-1 considerably distant from anterior margin of genital field; L/W 150/150; L Ac 1–3: 38–41, 39–45, 39–41.
Atractides ethiopiensis sp. n., male: idiosoma, ventral view. Scale bar = 100 μm.
Palp (Fig. 2A): total L 369, dL: P-1, 35; P-2, 72; P-3, 92; P-4, 131; P-5, 39; L ratio P-2/P-4, 0.55; P-4 club-shaped, with maximum H near distoventral hair.
Atractides ethiopiensis sp. n., (A–C male, D female) A, D palp, medial view B I-L-5 and -6 C leg claw. Scale bar = 100 μm.
I-L: I-L-5 dL 243, vL 169, dL/vL ratio 1.44, HB 50, dL/HB 4.86, S-1 L 121, L/W 11.2, S-2 L 95, L/W 5.6, distance S-1-2 23, L ratio S-1/2 1.27; I-L-6 L 166, HB 16, L/HB ratio 10.3; L ratio I-L-5/6 1.46.
Female. Idiosoma L/W 1106/928; coxal field L 473; Cx-III W 644; Cx-I+II mL 147; lL Cx-I+II 284. Genital field (Fig. 3B): L/W 181/209; genital plate bean-shaped, with slightly concave medial margins, L 139; L Ac 1–3: 44, 47, 43.
Atractides ethiopiensis sp. n., female A = coxal field B = genital field, excretory pore and Vgl-1 and -2 C = I-L-5 and -6. Scale bar = 100 μm.
Palp (Fig. 2D): total L 417, dL: P-1, 48; P-2, 80; P-3, 115; P-4, 132; P-5, 42; L ratio P-2/P-4, 0.6; P-4 not club-shaped, with maximum H near proximoventral hair; chelicera total L 250, claw L 83.
I-L: I-L-5 dL 279, vL 186, dL/vL ratio 1.5, HB 65, dL/HB 4.3, S-1 ending in a fine hair-like tip (Fig. 3C) L 162, L/W 11.3, S-2 L 117, L/W 4.8, distance S-1-2 29, L ratio S-1/2 1.38; I-L-6 L 210, HB 19, L/HB ratio 11.1; L ratio I-L-5/6 1.33.
Named after its occurrence in Ethiopia.
Due to the striated integument, a slender palp
with P-2 lacking ventrodistal projection and similar morphology of I-L-5
and -6, with S-1 in female ending in a fine hair-like tip Atractides ethiopiensis sp. n. resembles Atractides latisetus (K. Viets, 1916), a species known from Cameroon (K.
Ethiopia.
To get an overview of the biodiversity of the genus worldwide, we examined numerous papers,
Distribution of freshwater mite species of Atractides
per biogeographical provinces: PA–Palaearctic; NA–Nearctic;
NT–Neotropical; AT–Afrotropical; OL–Oriental; AU–Australasian;
PC–Pacific Oceanic Islands; AN–Antarctic. Biogeographical provinces are
given according to
Thus far, 47 species and 3 subspecies have been
recorded from the Afrotropical region, with large differences in the
state of knowledge of different regions. The number of known species
ranges from 14 from Kenya, 13 from South Africa and 9 from Liberia (
The Afrotropical members of Atractides belong to the following subgenera Atractides Koch, 1837 s.s., Megabates K. Viets, 1924, Tympanomegapus Thor, 1923 and Polymegapus K. Viets, 1926. However, the older data (
A critical analysis of the Afrotropical Atractides species, with the aid of the diagnoses and the revised key presented in
The subgenus Megabates K. Viets, 1924, includes two Afrotropical species, i.e., Atractides rectipes (K. Viets, 1924) and Atractides longicoxalis (Cook, 1974). According to
The other 35 species and subspecies are assigned to Atractides s. s. According to our present state of knowledge, slightly more than a half (54%) of these species are known from both sexes, i.e., Atractides comorosensis Smit & Pešić, 2010, Atractides contemptus (Lundblad, 1951), Atractides coriacellus K. Viets, 1956, Atractides damkoehleri (K. Viets, 1916), Atractides ethiopiensis sp. n., Atractides falcipes (Walter & Bader, 1952), Atractides kilimandjaricus Lundblad, 1952, Atractides latisetus (K. Viets, 1916), Atractides linearis (Lundblad, 1927), Atractides lundbladi lundbladi (Halik, 1947), Atractides madagascariensis K.O. Viets, 1964, Atractides minutissimus (Lundblad, 1927), Atractides processiferus (Walter & Bader, 1952), Atractides pusillus (Walter & Bader, 1952), Atractides scutelliferus K.O. Viets, 1964, Atractides splendidus splendidus (Lundblad, 1927), Atractides splendidus superbus (Lundblad, 1927), Atractides thoracatus Koenike, 1898 and Atractides valididens (Lundblad, 1951). Three species are known from the male only, i.e. Atractides africanus (Lundblad, 1951), Atractides baderi K.Viets, 1956 and Atractides invidendus K.O.Viets, 1964, while 12 species are known from the female only, i.e., Atractides assimilis K.O.Viets, 1964, Atractides callosus K.O.Viets, 1972, Atractides exiguus Lundblad, 1952, Atractides immodestus (Walter & Bader, 1952), Atractides irangiensis K.O. Viets & Böttger, 1972, Atractides kuhlmanni K.O.Viets, 1963, Atractides lundbladi curvitarsis K. Viets, 1955, Atractides pulcher K. Viets, 1956, Atractides rostellatus K.O.Viets, 1964, Atractides sudafricanus K. Viets, 1956, Atractides tenuipes tenuipes Lundblad, 1952 and Atractides tenuipes ambiguus K.O. Viets, 1971.
Three species are of doubtful status and merit attention during future taxonomical studies: Atractides africanus (Lundblad, 1951) – possibly a synonym of Atractides linearis (Lundblad, 1927) (see
In conclusion the current knowledge of the diversity of Afrotropical Atractides species is far from complete. Moreover, information on the diversity of Afrotropical Atractides among different freshwater habitats is unbalanced, and some important habitats are poorly (e.g., springs) or completely unexplored (e.g., hyporheic interstitial). Additional field work is highly needed for an appropriate evaluation of the extant diversity.
We are indebted to Johannes Postma (Ann Arbor) for reviewing the English.