Teratothyasides (s. str.) heptaplax, Gerecke, 2020

Gerecke, Reinhard, 2020, The early derivative water mites (Acari: Hydrachnidia, superfamilies Eylaoidea, Hydrachnoidea and Hydryphantoidea) of Madagascar, Zootaxa 4727 (1), pp. 1-77 : 59-60

Teratothyasides (s. str.) heptaplax sp. nov.

Fig. 28 e–i

Type series: Holotype ♀, MNHN Ac 1396, MD 165a, 21.11.2001 Joffreville (M. d’Ambre, Antsiranana), R Antomboka downstr. large cascade, 850 m, riffle, slide mounted . Paratypes: MD 154b, 17.11.2001 Joffreville (M. d’Ambre, Antsiranana), R de Manques in Reserve Fontenay, 550 m, roots (1/2/0) slide mounted, Ac 1397-1398 .

Diagnosis: Dorsum with Dc-2 fused to an unpaired medial plate ( Fig. 28 e ). Genital field with roundish, rather short Ac-1 (L 30–48, 23–27 % flap L) and rather large Ac-2 (L 75–90, 40–50 % flap L–see Fig. 28 f ). Mouth parts ( Fig. 28 g–i) stout (L/H chelicera 5.1–5.6; P-3, 1.0–1.2, P-4, 2.7–3.0).

Description: Membranous integument with rounded papillae. Sclerite plates with relatively few, large, angular pores (6–10 along an imaginary transect crossing dorsocentral plates–see Fig. 28 e ). Genital field with three pairs of acetabula, basal sclerite of Ac-1 fused to medial genital flap margin, but posteriorly with an indentation indicating area of fusion ( Fig. 28 f ). Each genital plate with 20–25 (10–15 medial, about 10 posterior) setae, the posterior setae rather strong and stiff. Leg claws proximoventrally with a very flat projection. Gnathosoma ( Fig. 28 g ) short and robust, in lateral view rostrum distinctly set off from base. Chelicera ( Fig. 28 h ) stout and relatively short, claw strong, as long as, in one specimen distinctly longer than, basal segment. Palp ( Fig. 28 g, i ) stout; P-1 with a dorsal seta in distal third; P-2 ventral margin slightly concave, the two strong setae shifted to mediodistal margin, dorsally with four setae; P-3 and -4 shortened, P-3 with a lateral seta in proximal half and two dorsal setae, P-4 maximum H in centre, distally strongly narrowed, ventral margin bowed, one dorsal seta in proximal quarter, near distal margin with three hair-like setae ventrally, dorsally and medially, mediodistal seta fine and pointed, on a prominent projection; P-5 long and slender (14–16 % total L), with three setae (proximal, dorsodistal, ventro distal) and three long, slender claws.

Measurements: Male: Idiosoma L/W 1070/750; coxal field L/W 580/650; Cx-I+II L/W 335/240; Cx-III+IV L/W 380/310; genital field L/W 180/210, maximum diameter Ac-1–3, 45, 75, 50; medial/posterior genital setae n 14/10; gnathosoma L 195; chelicera total L 285, basal segment maximum L 190; basal segment/claw ratio 1.0, L/H ratio 5.18; palp total L 295; L, L/H ratio, relative L [% total L] palp segments: P-1, 40, 0.89, 14; P-2, 67, 1.60, 23; P-3, 44, 1.10, 15; P-4, 98, 2.80, 33; P-5, 46, 3.07, 16; L ratio P-2/-3, 1.52, P-2/-4, 0.68, P-3/-4, 0.45. Leg segments L/H, L/H ratio, segments 2-6: I-L-2, 105, 1.62; I-L-3, 100, 1.48; I-L-4, 150, 2.31; I-L-5, 148, 2.81; I-L-6, 145, 2.76, claw 55. II-L-2, 130, 1.86; II-L-3, 115, 1.70; II-L-4, 195, 3.00; II-L-5, 190, 3.45; II-L-6, 175, 2.80; claw 30. III-L-2, 115, 1.77; III-L-3, 100, 1.60; III-L-4, 180, 3.00; III-L-5, 180, 3.43; III-L-6, 170, 3.09; claw 55. IV-L-2, 135, 1.86; IV-L-3, 135, 2.00; IV-L-4, 245, 4.08; IV-L-5, 230, 4.00; IV-L-6, 195, 3.39; claw 43. Total L segments 2-6: I-L 648, II-L 805; III-L 745, IV-L 940.

Females: Idiosoma L/W 1100–1200/700–800; coxal field L/W 580–610/620–640; Cx-I+II L/W 330–370/240– 250; Cx-III+IV L/W 390–430/300–320; genital field L/W 180–200/170–230, maximum diameter Ac-1-3, 45–50, 75–90, 60–65; medial/posterior genital setae n 10–12/10; egg maximum nr, 10, diameter 160–170; gnathosoma L 200–230; chelicera total L 305–310, basal segment/claw 0.63–1.07, L/H 5.08–5.64; Palp total L 284–306; L, L/H ratio, relative L [% total L] palp segments: P-1, 40–43, 0.89–1.05, 14; P-2, 65–70, 1.51–1.91, 22–23; P-3, 40–48, 1.00–1.20, 14–16; P-4, 95–100, 2.71–3.03, 33–34; P-5, 40–45, 2.67–3.14, 14–15; L ratio P-2/-3, 1.44–1.63, P-2/- 4, 0.65–0.70, P-3/-4, 0.42–0.48. Leg segments L/H, L/H ratio: I-L-2, 105–125, 1.80–1.93; I-L-3, 100, 1.33–1.43; I-L-4, 70–75, 3.23; I-L-5–6 and claw not measured. II-L-2, 135–145, 1.80–1.93; II-L-3, 115–120, 1.64–1.71; II-L- 4, 188–210, 3.00–3.23; II-L-5, 175–200, 3.18–3.64; II-L-6, 160–175, 2.78–2.92; claw L 50–53. III-L-2, 95–115, 1.46–1.64; III-L-3, 95–105, 1.52–1.62; III-L-4, 185–200, 3.22–3.33; III-L-5, 170–185, 3.40–3.52; III-L-6, 160–180, 3.05–3.13; claw L 55–63. IV-L-2, 128–148, 2.03–2.04; IV-L-3, 118–135, 1.93–1.96; IV-L-4, 215–255, 3.91–3.92; IV-L-5, 160–235, 4.00–4.27; IV-L-6, 130–200, 3.33–3.47; claw L 35–68. Total L segments 2–6: I-L, not measured, II-L, 773–850; III-L, 705–785; IV-L, 750–973.

Derivatio nominis: ἕπτα (Greek: seven) & πλάξ (Greek: plate), with reference to the seven (not, as typical, eight) dorsocentral plates.

Remarks: Teratothyasides heptaplax differs from all other species of the genus in the medial fusion of Dc-2. It is furthermore highly characteristic in proportions of the palp, combining a rather inflated and stout P-4 with a slender P-5, and the shortened and elevated chelicera. Remarkable differences are found between two females from MD 154 in proportions of segments 5–6 and claws of the fourth leg. For clearing the question of whether this is due to individual variation, the study of more material is required.

Habitat: Low and middle order streams and their riparian springs.

Distribution: Madagascar, endemic. Only found far north on the Montagne d’Ambre, at 550–850 m a.s.l..

Figures

FIGURE 28. Family Teratothyadidae. a.–d., Teratothyasides ravenala, female; a. genital field and surrounding sclerites (MD 175); b. chelicera (MD 028); c. gnathosoma with palp and chelicera (MD 175); d. palp medial (MD 187); e.–i., Teratothyasides heptaplax; e.–f. male (MD 154); e. dorsum, f. genital field, partial view; g.–i. female; g. gnathosoma with right palp, lateral (MD 154); h. chelicera (MD 165); i. left palp lateral (MD 154, P-1 lacking).