Teratothyas (s. str.) aucta, 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 : 51-52

Teratothyas (s. str.) aucta sp. nov.

Fig. 25 a–f

Type series: Holotype ♀, MNHN Ac 1373, MD 143, 10.11.2001 Andapa (Antsiranana), riparian springs at R Masiaposa (crossing R.N. 3b at km 5–6), 700 m, slide mounted together with paratype ♂ . Paratypes: same site and date, (0/1/0) slide mounted, Ac 1373 (with holotype); (1/2/0) in liquid, Ac 1447; MD 027, 15.08.2001 Ionilahy (Fianarantsoa), small stream crossing the railroad E from the village, 200 m, (0/1/0) slide mounted, Ac 1374; MD 084, 17.09.2001 F. Dauphin (Tulear), Pic St. Louis, stream exp. E, 70 m, (0/1/0) slide mounted, Ac 1375 .

Diagnosis: Membranous parts of integument with fine papillae. Genital field ( Fig. 25 b ) with short acetabula (L Ac-1-3, 30–48, 44–58, 33–41, relative L Ac-1, 19–28, Ac-2, 27–32 % genital flap); Ac-2/-3 distinctly separated from each other; medial genital flap margins in posterior 3/4 straight. An unpaired medial platelet between genital field and excretory plate ( Fig. 25 a ). Leg claws with rounded basal blade. Gnathosoma ( Fig. 25 e ) basal part extend- ed, proximodorsal apodeme barely developed. Palp ( Fig. 25 f ) short, P-4 very stout (L/H ratio 3.7–4.1), maximum H in distal part.

Description: Idiosoma rather slender. Membranous parts of integument with fine (occasionally barely visible) papillae. Pores of idiosoma sclerites rather large (<10 per transect on dorsocentralia), inner trabecular structures poorly developed, only in dorsolateral and posteroventral plates. Glandularia surrounded by a finely porose collar ( Fig. 25 c ). Legs relatively slender, claws with a projecting, rounded basal blade.

Unpaired sclerite between coxal margins slender, genital field not situated in a genital bay (Cx-IV with slightly convex posteromedial margin, medial projections weakly developed or absent); genital flaps with straight medial, and equally rounded lateral margins (secondary sclerite fringe narrow or absent), bearing about 13 pairs of medial, and 7 pairs of posterior setae. Ac-1 very small, in a short bay of concave genital flap margin (bordering setae here stronger than the posterior, pinnate), Ac-2 and -3 also short, away from each other. Plates embracing posterolateral genital field margin small, subtriangular, with concave anterior margin; between their posteromedial margins and the excretory pore plate an unpaired platelet.

Gnathosoma ( Fig. 25 e ) posterior to rostrum with a steeply S-shaped ventral margin, its proximal part elongated, with a prominent proximoventral apodeme, proximodorsal apodemes weakly developed as small, rounded projections. Chelicera ( Fig. 25 d ) relatively stout, L/H 5.6–7.5, basal segment/claw 0.9–1.1. Palp ( Fig. 25 f ) short and stout, P-1 with one pennate dorsal seta; P-2 and -3 distally expanding, P-2 bearing four fine dorsal and the two typical strong, pennate, distoventral setae, P-3 with three simple dorsal setae; P-4 short, with slightly undulating ventral and dorsal margins, maximum H in centre or distal part, bearing 4 fine, hair-like setae, one dorsally in the proximal half, three flanking P-5-insertion, distal margin forming an obtuse angle at the insertion of the pointed distolateral peg seta; P-5 not particularly slender, with little curved claws.

Measurements: Male: Idiosoma L/W 640/430; coxal field L/W 420/380; Cx-I+II L/W 220/180; Cx-III+IV L/W 295/170; genital field L/W 145/140; maximum diameter Ac-1, 35, Ac-2, 45, Ac-3, 41; ejaculatory complex L/W 155/50; gnathosoma L/W 160/85; chelicera total L 298, basal segment/claw 1.06, L/H 7,5; Palp partly damaged; L, L/H ratio, palp segments: P-3, 43, 1.55; P-4, 93, 4.1; P-5, 35, 3.1; L ratio P-3/-4, 0.46. Leg segments L/H, L/H ratio: I-L-2, 65, 1.63; I-L-3, 63, 1.56; I-L-4, 83, 2.36; I-L-5, 85, 2.43; I-L-6, 98, 2.67; claw L 30. II-L-2, 80, 2.13; II-L-3, 70, 1.87; II-L-4, 105, 2.80; II-L-5, 105, 3.50; II-L-6, 113, 3.08; claw L 30. III-L-2, 63, 1.79; III-L-3, 60, 1.60; III-L- 4, 100, 2.86; III-L-5, 103, 3.73; III-L-6, 113, 3.75; claw L 33. IV-L-2, 80, 2.13; IV-L-3, 90, 2.40; IV-L-4, 150, 4.00; IV-L-5, 145, 4.46; IV-L-6, 125, 4.17; claw L 43. Total L segments 2–6: I-L, 393; II-L, 473; III-L, 438; IV-L, 590.

Female: Idiosoma L/W 840–1050/530–650; coxal field L/W 470–580/420–560; Cx-I+II L/W 250–340/165– 210; Cx-III+IV L/W 330–390/210–280; genital field L/W 160–180/160–190; maximum diameter Ac-1, 30–48, Ac-2, 44–58, Ac-3, 33–40; gnathosoma L 190–230; chelicera total L 300–350, basal segment/claw 0.89–1.06, L/H 5.56–7,50; Palp total L 264–303; L, L/H ratio, relative L [% total L] palp segments: P-1, 33–50, 1.00–1.46, 12–17; P-2, 53–68, 1.62–2.13, 20–22; P-3, 48–50, 1.43–1.73, 17–18; P-4, 93–100, 3.33–3.95, 32–37; P-5, 33–36, 2.60– 2.90, 12–13; L ratio P-2/-3, 1.11–1.36; P-2/-4, 0.53–0.68; P-3/-4, 0.48–0.54. Leg segments L/H, L/H ratio: I-L-2, 95, 1.90; I-L-3, 85, 1.79; I-L-4, 110, 2.44; I-L-5, 118, 2.94; I-L-6, 120, 2.82; claw L 35. II-L-2, 105, 1.91; II-L-3, 90, 1.80; II-L-4, 150, 3.16; II-L-5, 150, 3.75; II-L-6, 140, 2.50; claw L 43. III-L-2, 90, 2.00; III-L-3, 75, 1.67; III-L-4, 135, 3.00; III-L-5, 140, 3.84; III-L-6, 130, 2.74; claw L 40. IV-L-2, 113, 2.25; IV-L-3, 115, 2.30; IV-L-4, 200, 4.44; IV-L-5, 175, 4.12; IV-L-6, 190, 4.22; claw L 45. Total L segments 2-6: I-L, 528; II-L, 635; III-L, 570; IV-L, 793.

Derivatio nominis: augere (Latin): to increase, with reference to additional ventral platelet.

Remarks: Teratothyas aucta differs from all other species of the genus in the shape of the genital field with rather small acetabula notably separate from each other, and the presence of an unpaired postgenital platelet. If some kind of a small unpaired postgenital platelet is occasionally found in individuals of other species (in our material two specimens of T. planipapillata ), this sclerite is always asymmetric, obviously a result of an individual aberration. From all other species of the subgenus, it differs furthermore in the fine papillosity of the membranous integument and the elongated basal part of the gnathosoma, and from all other Madagascan species in the stout P-4. Teratothyas (Teratothyasides) clathratus , described from East Africa, another species with a stout P-4 (but distinctly shorter, L/H <3.0) differs from T. aucta among others in acetabula which are absolutely and relatively far larger in size (90- 100,> 35 % genital flap L) and all fused with the genital plates, as typical for the subgenus. Considerable differences in palp proportions are observed between the females from the three well separated collecting sites. More material is necessary in order to ascertain if T. aucta represents a species complex.

Habitat: Low and middle order streams in the northern, central and southern parts of eastern forests.

Distribution: Madagascar, endemic, only known from three localities on the lower Eastern slopes of the island.

Figures

FIGURE 25. Family Teratothyadidae, Teratothyas (s. str.) aucta (MD 084), female. a. idiosoma, venter; b. genital field; c. dorsocentral sclerite 2; d. chelicera; e. gnathosoma lateral; f. palp.