Atractides assimilis K.O.Viets, 1964

Pešić, Vladimir, Smit, Harry & Gerecke, Reinhard, 2011, New records of water mites of the genus Atractides Koch, 1837 (Acari: Hydrachnidia, Hygrobatidae) from South Africa, with descriptions of five new species, Zootaxa 2986, pp. 1-54 : 16-20

Atractides assimilis K.O.Viets, 1964

( Figs. 14–16 )

Material examined. South Africa: Mpumalanga province: DC 76 84 28/56/0 (0/1/0 mounted); DC 78 84 1/1 /0; DC 79 84 28/36/1 (2/2/0 mounted); DC 80 84 0/1/0; DC 81 84 2/1 /0; DC 83 84 3/2 /0; DC 84 84 0/2/0; DC 86 84 1/ 0/0; DC 87 84 5/21 /0 (0/1/0 mounted). KwaZulu-Natal province: DC 90 84 4/4 /0; DC 91 84 10/10 /0; DC 92 84 21/ 63/2; DC 93 84 0/1/0. Eastern Cape province: DC102 84 0/1/0.

General features. Dorsal integument striated; muscle attachments showing sexual dimorphism; genital field with 3-4 pairs of Ac - if three-acetabulate in triangular arrangement; if tetra-acetabulate three anterior pairs in triangular arrangement, Ac-4 located immediately behind the Ac-3. Palp: weak sexual dimorphism, ventral margins of P-2 and -3 straight or weakly concave, P-4 sword seta nearer to distoventral hair; capitulum with protruding and slender rostrum. I-L-5 little thickened, setae S-1 and -2 close to each other, blunt and similar in shape; I-L-6 stout, weakly curved, equal in H from base to claw furrow; leg claws with dorsal and ventral clawlets.

Morphology. Male (DC 79 84, n = 2): Extended dorsal shield including postoc and Dgl-3-6 ( Fig. 14A ), L/W 351–363/280–291; extended ventral shield ( Fig. 14B ) including coxae, genital field, excretory pore, all ventralia and Vgl, L/W 359–375/366; coxal field: completely fused, Cx-III W 255. Genital field: W between outer margins of the most lateral pair of Ac 101–103, L Ac 1-4: 19–20, 20–21, 17–21, 22–28; ejaculatory complex ( Fig. 14E ) L 72–79.

Palp ( Fig. 14C ): total L 198, dL: P-1, 22; P-2, 40-42; P-3, 40; P-4, 69; P-5, 25–27; L ratio P-2/P-4, 0.58–0.61; P-4 thickened; capitulum ( Fig. 14D ) ventral L 92–100; chelicera total L 170–184.

I-L ( Fig. 14F ): I-L-5 dL 82–85, vL 66–67, dL/vL ratio 1.22–1.3, HB 29, dL/HB 2.8–2.9, S-1 L 34–35, L/ W 7.4 –8.9, S-2 L 34–35, L/ W 6.6 –7.1, distance S-1-2, 1–2, L ratio S-1/2, 1.0; I-L-6 L 56–59, HB 18, L/HB ratio 3.1– 3.2; L ratio I-L-5/6, 1.45–1.46.

Female (DC 79 84, n = 2, in parentheses DC 87 84). Idiosoma L/W 560–600/478–481; muscle attachments ( Fig. 15B ): postoc on enlarged sclerite, D-2-5 not sclerotized but visible as granulated areas, Dgl-3-6 and Lgl round, without sclerotized extensions, glandularia maximum diameter 41; coxal field with extended borders of secondary sclerite, medioposterior margin of Cx-I+II rounded; medial margin of Cx-III+IV rounded, L 325–338 (314); Cx-III W 350–356 (375); Cx-I+II mL 100–111 (114), lL 216 (212). Genital field ( Fig. 15A , 16A ): L/W 142– 153 (168)/164–169 (187), pregen very robust, with extended secondary sclerite; genital plate L 89–92 (82–88), L Ac 1–4: 28–31 (29), 29–34 (35), 28–31 (22), 33–34 (33); excretory pore: sclerotized, Vgl-1 fused to Vgl-2.

Palp ( Fig. 16C ): total L 275–280, dL: P-1, 26–30 (26); P-2, 65 (62); P-3, 62 (57); P-4, 83–84 (84); P-5, 39 (32); L ratio P-2/P-4, 0.77–0.78 (0.74); P-4 slender than in males; capitulum ( Fig. 16B ) ventral L 117–134 (118), chelicera ( Fig. 16E ) total L 267 (244).

I-L ( Fig. 16D ): I-L-5 dL 111–115 (111), vL 92 (88), dL/vL ratio 1.2–1.26 (1.26), HB 37 (37), dL/HB 3.0–3.1 (3.0), S-1 L 42–44 (42), L/ W 7.3 –7.4 (8.0), S-2 L 37–41 (42), L/ W 5.1 –5.4 (6.2), distance S-1-2, 1.0–2.0 (3.0), L ratio S-1/2, 1.08–1.1 (1.0); I-L-6 L 69–72 (68), HB 19–22 (19), L/HB ratio 3.3–3.6 (3.5); L ratio I-L-5/6, 1.6 (1.6).

Remarks. Due to the similar shape of the palp, the capitulum with a slender and protruding rostrum, I-L-5 with setae S-1 and -2 close to each other, blunt and similar in shape, a stout and weakly curved I-L-6 and Ac arranged in a triangular position, the specimens examined show general conformity with Atractides assimilis , a species described by K.O. Viets (1964b) from headwaters of the Vaal River in the Mpumalanga province (the province from which originates most of the specimens of our study). A difference is found in I-L-6 relatively longer in the type specimens (L I-L-5/6 ratio 1.24–1.27, data taken from K.O. Viets 1964b). The type specimen has three pairs of Ac (see K.O. Viets 1964b, Fig. 8 ). In our material tri or – tetracetabulate specimens are found. Moreover, in the same populations, specimens with an asymmetric genital field bearing four Ac on one side and three on the other can be found regularly ( Fig. 16A ). For example, examination of 14 adult specimens from Krokodilspruit shows that five specimens have 4+4 (number of Ac left + right side), six specimens 3+3, two specimens 4+3 and one specimen 2+2. Thus far, only two female specimens of this species are known ( K.O. Viets 1964b), and this is the first description of the male.

Our specimens from South Africa closely resemble A. minutissimus (Lundblad, 1927) , a species known from Kenya. This species also has four pairs of Ac (see Lundblad 1927b: Figs. 85, 128–134). In the original description of A. minutissimus, Lundblad (1927b) mentioned that the capitular rostrum is quite short, but much longer and narrower (see Lundblad 1927b, Fig. 132) than in other Atractides species described by him in the same paper. The only differences compared with the original description and Lundblad’s (1927b) drawings of A. minutissimus are found in the ventral margin of P-2, which is slightly convex in A. minutissimus ( Lundblad 1927b, Fig. 130). Furthermore, in the figure given by Lundblad (1927b, Fig. 131) the leg claws are without dorsal clawlets. Additional material of A. minutissimus from the locus typicus is necessary to establish more clear differences between this species and A. assimilis .

Distribution. South Africa: Mpumalanga province: K.O. Viets (1964b), present study; Kwazulu-Natal and Eastern Cape provinces: present study.

Figures

FIGURE 14 A – F. Atractides assimilis K. O. Viets, 1964, male, Sterkspruit River just above dam at the fish hatchery at Lydenburg: A = idiosoma, dorsal view; B = idiosoma, ventral view; C = palp, medial view; D = capitulum, lateral view; E = ejaculatory complex; F = I-L- 5 and - 6. Scale bars = 100 μm.

FIGURE 15 A – B. Atractides assimilis K. O. Viets, 1964, female, Sterkspruit just above dam at the fish hatchery at Lydenburg: A = idiosoma, ventral view; B = idiosoma, dorsal view. Scale bar = 100 μm.

FIGURE 16 A – E. Atractides assimilis K. O. Viets, 1964, female (A = specimen from Krokodilspruit, B – E—specimens from Sterkspruit River just above dam at the fish hatchery at Lydenburg): A = genital field; B = capitulum; C = palp, lateral view; D = I-L- 5 and - 6; E = chelicera. Scale bars = 100 μm.

FIGURE 8 A – C. Atractides linearis (Lundblad, 1927), male, Pholelana River: A = genital field, excretory pore and Vgl- 1 and - 2; B = I-L- 5 and - 6; C = palp, medial view. Scale bar = 100 μm.