Teratothyasides (Hansvietsia) ravenala, 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 : 60-63

Teratothyasides (Hansvietsia) ravenala sp. nov.

Fig. 28 a–d

Type series: Holotype ♂, MNHN Ac 1457, MD 063a, 07.09.2001 Andohahela ( Tulear ), Isaka , stream exp. W 1 km N from the village, 250 m, riffle, in liquid . Paratypes: same site and date, (1/2/0) in liquid, Ac 1458; MD 063c, 07.09.2001 Andohahela (Tulear), Isaka, stream exp. W 1 km N from the village, 250 m, spring, (0/1/0) in liquid, Ac 1459; MD 022, 12.08 . 2001 Ionilahy (Fianarantsoa), spring stream in area Marosaro (S from R Ionilahy), 300 m, (1/0/0) in liquid, Ac 1460; MD 027, 15.08 . 2001 Ionilahy (Fianarantsoa), small stream crossing the railroad E from the village, 200 m, (2/0/0) in liquid, Ac 1461; MD 028, 15.08 . 2001 Ionilahy (Fianarantsoa), small stream crossing the railroad between the village and MD 027, 200 m, (0/2/0) slide mounted, Ac 1399-1400; MD 029, 15.08 . 2001 Ionilahy (Fianarantsoa), R Avatamboka ca. 1 km NW from the village, 210 m, (0/1/0) in liquid, Ac 1462; MD 065, 08.09 . 2001 Andohahela (Tulear), Fenoevo, right affluent of the turbid water stream (MD 064) at N margin of forest (clear water), 330 m, (0/0/1) slide mounted, Ac 1401; MD 070a, 09.09 . 2001 Andohahela (Tulear), Isaka, E stream at the S National Park border (W RIP 118), 200 m, riffle, (3/0/0) in liquid, Ac 1463; MD 074a, 11.09 . 2001 Andohahela (Tulear), Isaka, stream crossing RIP 118 at km 32, 360 m, riffle, (1/1/0) in liquid, Ac 1464; MD 074b , same site and date, pool, (0/1/0) in liquid, Ac 1465; MD 175, Joffreville (M. d’Ambre, Antsiranana) , Voie 100 arbres, outflow of temporary lake MD 174, 1048 m, S 12°31’13’’, E 049°10’31’’, 21.03.2011, (0/2/0) slide mounted, Ac 1402; MD 187, Joffreville (M. d’Ambre, Antsiranana) , first right affl. below Grande Cascade, linear spring area, 966 m, S 12°30’18.0’’, E 049°10’35.4’’, 26.03.2011, (0/1/0) slide mounted, Ac 1403; MD 188, Joffreville (M. d’Ambre, Antsiranana) , Maison Rousettes, river with small cascade and pool near house of guardian, 1044 m, S 12°31’37.0’’, E 049°10’19.9’’, 28.03.2011 (1/0/0) slide mounted, Ac 1404; MD 210, Andringitra National Park (Fianarantsoa) , small stream ca. 400 m W Cascade du Roi , 1725 m, S 22°08’15.3’’, E 046°53’07.6’’, 14.04.2011, (1/0/0) slide mounted, Ac 1405; MD 234, Ranomena (Fianarantsoa) , spring area of the stream NW from the 1.07 km-railway- tunnel (same site: MD 043, right affluent of MD 034), 1017 m, S 21°29’45.9’’, E 047°24’07.5’’, 26.04.2011 (1/2/0) slide mounted, Ac 1406-1408.

Material examined for comparison: Teratothyasides scutulatus Smit & Pešić, 2009 , ♂; det. H. Smit, Natu- ralis Biodiversity Center Leiden, RMNH. ACA. 3070, Mayotte, Comoros, Bouyouni upstream, 12°45’39.1986’’S, 45°08’46.4467’’ E, 23.VII.2016, leg Nathalie Mary .

Diagnosis: Genital field ( Fig. 28 a ) relatively small (L ♂ 138–180, ♀ 160–200), with about 12 (9–17) pairs of rather small acetabula (diameter Ac-1, ♂ 23–30, ♀ 21–25), not arranged closely in touch with each other. Mouth parts ( Fig. 28 b–d) comparatively small (gnathosoma L 175–215, chelicera total L 300–437, palp total L 338–388), segments not particularly elongated (L/H P-2, 1.3–1.7, P-3, 1.5–1.7; P-4, 4.0–4.8).

Description: Membranous integument with densely arranged, long papillae. Sclerite plates with relatively few, large, rounded pores (6–10 along an imaginary transect crossing dorsocentral plates). Genital field ( Fig. 28 a ) with 9–17 pairs of acetabula, at lateral genital plate margin arranged in a single or double line; Ac-1 separated by a distinct gap from the remaining, posteriormost Ac slightly enlarged. Strong asymmetry in Ac numbers is possible (in one case, 11/17, with triplication of posterior Ac and multiplication of lateral ones. Each genital plate with about 15 (9–11 medial, 5–8 posterior) setae. Leg claws proximoventrally with a poorly prominent, obtuse projection. Gnathosoma ( Fig. 28 c ) short and robust, in lateral view with an S-shaped ventral margin. Chelicera ( Fig. 28 b ) strong, claw generally longer than, or at least as long as, basal segment. Palp ( Fig. 28 c–d) slender; P-1 with a dorsal seta in distal third; P-2 distoventrally elevated near insertion of the two strong setae, dorsally with four setae; P-3 with a lateral seta in proximal half and three dorsal setae, P-4 basally narrowed and curved, maximum H in distal third, one dorsal seta in proximal quarter, near distal margin with three hair-like setae ventrally, dorsally and medially, mediodistal seta fine and pointed, not on a projection; P-5 with three setae (proximal, dorsodistal, ventrodistal: one word) and three long, slender claws.

Measurements: Males: Idiosoma L/W 720–1050/460–800; coxal field L/W 470–550/490/600; Cx-I+II L/W 230– 275/160–200; Cx-III+IV L/W 240–250/200–220; genital field L/W 160–180/160–190, Ac n 10–14 pairs; maximum diameter Ac-1/posterior Ac 23–30/24–30; medial/posterior genital setae n 9–13/7; gnathosoma L 175–190; chelicera total L 300–400, basal segment maximum L 240–290; basal segment/claw ratio 0.9–1.0, L/H ratio 5.45–7.60; palp total L 338–348; L, L/H ratio, relative L [% total L] palp segments: P-1, 50–55, 1.43–1.57, 14–16; P-2, 58–65, 1.63–1.86, 17–19; P-3, 55–60, 1.64–1.69, 16–17; P-4, 125–133, 4.42–4.73, 37–38; P-5, 40–44, 2.83–3.52, 12–13; L ratio P-2/-3, 0.96–1.18, P-2/-4, 0.44–0.52, P-3/-4, 0.44–0.46. Leg segments L, L/H ratio: I-L-2, 85–90, 1.55– 1.57; I-L-3, 90–100, 1.64–1.82; I-L-4, 130–140, 2.60–2.80; I-L-5, 140–160, 3.00–3.76; I-L-6, 145–148, 3.22–3.47, claw 35–43. II-L-2, 90–117, 1.71–2.03; II-L-3, 93–118, 1.85–2.04; II-L-4, 145–183, 3.05–3.65; II-L-5, 165–190, 3.88–4.47; II-L-6, 148–180, 3.42–3.69; claw 40–43. III-L-2, 85–105, 1.68–1.91; III-L-3, 90–105, 1.80–2.10; III- L-4, 145–185, 2.90–3.67; III-L-5, 160–180, 3.43–3.78; III-L-6, 163–180, 3.67–3.82; claw 40-50. IV-L-2, 108-120, 1.79-2.09; IV-L-3, 115-135, 2.19-2.45; IV-L-4, 205-235, 4.10-4.70; IV-L-5, 210-225, 4.94–5.29; IV–L–6, 185–200, 4.11–4.28; claw 40–50. Total L segments 2–6: I-L 593–635, II-L 740–787; III-L 643–743, IV-L 833–915.

Females: Idiosoma L/W 950–1200/630–920; coxal field L/W 550–600/590–680; Cx-I+II L/W 240–350/170– 220; Cx-III+IV L/W 250–320/200–260; genital field L/W 160–200/180–230; Ac n right/left 9–17/ 9–14; egg maximum diameter 340; gnathosoma L 175–210; chelicera total L 370–450, basal segment/claw 0.81–1.06, L/H 5.8–8.6; Palp total L 353–388; L, L/H ratio, relative L [% total L] palp segments: P-1, 50–65, 1.25–1.77, 14–17; P-2, 60–68, 1.40–1.69, 17–19; P-3, 60–70, 1.50–1.73, 17–18; P-4, 130–143, 4.04–4.75, 36–38; P-5, 40–45, 2.67–3.60, 11–13; L ratio P-2/-3, 0.92–1.08, P-2/-4, 0.44–0.52, P-3/-4, 0.44–0.50. Leg segments L, L/H ratio: I-L-2, 90–105, 1.38–1.64; I-L-3, 95–120, 1.65–1.73; I-L-4, 138–170, 2.50–2.76; I-L-5, 145–180, 3.42–3.60; I-L-6, 145–160, 2.70–3.33; claw L 35–50. II-L-2, 100–140, 1.52–2.17; II-L-3, 110–140, 1.69–2.00; II-L-4, 160–225, 3.05–3.65; II-L-5, 170–230, 3.78–4.56; II-L-6, 163–195, 2.88–4.53; claw L 35–55. III-L-2, 83–120, 1.50–1.91; III-L-3, 90–125, 1.68–1.89; III-L-4, 145–213, 2.90–3.81; III-L-5, 170–225, 4.00–4.31; III-L-6, 165–180, 3.58–4.25; claw L 48–50. IV-L-2, 103–155, 1.78–1.94; IV-L-3, 125–173, 2.16–2.43; IV-L-4, 218–295, 4.14–4.77; IV-L-5, 205–270, 4.56–5.44; IV-L- 6, 190–220, 3.52–4.75; claw L 40–63. Total L segments 2–6: I-L, 613–725; II-L, 718–923; III-L, 660–785; IV-L, 860–1113.

Derivatio nominis: The “traveller’s tree” Ravenala ( Strelitziaceae ) is the heraldic plant of the state of Madagascar and, like T. ravenala , distributed all over the island. The name is a noun in apposition.

Remarks: Teratothyasides ravenala agrees with the type species of the subgenus, T. sempiternus K. Viets, 1951 (only known from the ♀ sex), in general dimensions of idiosoma and appendages (K. Viets 1951). It differs from the latter in proportions of the palp, with a relatively and absolutely shorter P-2 (L 60–68, 17–19 %, T. sempiternus 70, 20 % total L), longer P-3 (L 60–70, 17–18 % total L, T. sempiternus 54, 16 % total L) and longer P-4 (L 130–134, 36–38 %, T. sempiternus 125, 36 %). These differences are more clearly expressed as segment L ratios ( T. sempiternus in parentheses): P-2/-3, 0.92–1.08 (1.30); P-2/-4, 0.44–0.52 (0.56); P-3/-4, 0.44–0.50 (0.43), with the P-2/-3 ratio as the most distinct diagnostic difference. Furthermore, the P-3 is more stout (L/H 1.38) in T. sempiternus , and the cheliceral claw longer (L 272).

At this point, data published by Schoonbee (1959) merit a brief discussion, concerning two Teratothyasides species found coexisting in a spring in South Africa. The proposal of K.O. Viets & Böttger (1974) to synonymize T. reticulatus ( Schoonbee, 1959) with T. sempiternus , must be rejected in view of differences in palp morphology (total L 239, T. sempiternus 347; L/H P-4, 5.8, T. sempiternus 4.3). Also the South African specimen attributed by Schoonbee to T. sempiternus differs from that species in a distinctly shorter palp. Furthermore, it differs from both T. reticulatus and T. sempiternus in a very stout P-4 (L/H 3.4).

Teratothyasides congoensis K.O. Viets & Böttger, 1974 , introduced as type species of the very distinct subgenus Rhynchohansvietsia , differs from T. ravenala in the combination of an extremely elongate and slender gnathosoma (L> 270) located at the end of protrusible membranous tube, bearing rather short palps (total L <300) with a relatively short P-3 (12–14 % total L, P-2/-4 ratio 0.62), and an extremely slender chelicera (L/H> 10.0). Another species differing from T. ravenala in having an elongated gnathosoma (L 330–370, only ♂♂ known) is T. sagariphorus Cook, 1966 from Liberia. This species is similar in palp dimensions, but differs in an extremely elongated chelicera (L 786–873) with an absolutely and relatively very long claw (L 489–584, basal segment/claw ratio 0.5–0.6). A further species described from Liberia, T. undulatus Cook, 1966 , is rather similar to T. ravenala in most measurements and proportions, except for the central palp segments (P-2 distinctly longer than P-3, L ratio 1.2–1.3) and the chelicera (claw relatively shortened, basal segment/claw ratio 1.2–1.3). Furthermore, acetabula are equally distributed over the whole length of the genital plates, without an extended gap between Ac-1 and the remainder.

The original description of Teratothyasides scutulatus Smit & Pešić, 2009 , from a single male from the Co- moros, is incomplete, and partly erroneous. In the undissected holotype, obviously due to poor visibility, the starshaped trabecular structures on inner plate surfaces were misinterpreted as plate margins. In fact, the idiosoma plates of a specimen taken in comparison are not rhomboid on the dorsum (no unpaired dorsocentral plates exist), and not “irregularly shaped, and partly obliterated” on the venter. Instead, a pattern is found typical for the genus (see Fig. 29 e ). In the holotype of T. scutulatus (MNHN), edges of dorsal plates are not clearly visible due to a layer of precipitation, but the internal lines that were drawn as continuous in the original publication actually show breaks where the borders of the plates should be (M. Judson, pers. comm.). The investigated male has the following measurements (data from the original description in parentheses, for P-2–4 calculated from figure): Idiosoma L/W 1060/720 (1025/689); coxal field 580/600; Cx-I+II, 330/230; Cx-III+IV, 280/290; genital field L/W 175/210 (168/190), 16–17 pairs of Ac (8–11, differences between diagnosis, description and figure, but possibly 12–the posteromedial pair probably overlooked, as suggested by Fig. 4 of the original description); maximum diameter Ac- 1/posterior Ac 45/50; medial/posterior genital setae n 12/?; gnathosoma L 215 (215); chelicera total L 445 (437), basal segment maximum L 290; basal segment/claw ratio 0.8–0.9, L/H ratio 6.9; palp total L 360 (346); L, L/H ratio, relative L [% total L] palp segments: P-1, 50 (53), 1. 50, 14 (15); P-2, 68 (64), 1.93 (2.00), 18–19; P-3, 58 (60), 1.60 (1.64), 17 (17); P-4, 135 (132), 5.4 (5.1), 38 (38); P-5, 42 (45), 3.27, 13 (12); L ratio P-2/-3, 1.13 (1.10), P-2/-4, 0.50 (0.48), P-3/-4, 0.44 (0.44). Leg segments L, L/H ratio: I-L-2, 95, 1.73; I-L-3, 90, 1.64; I-L-4, 130, 2.48; I-L-5, 150, 3.00; I-L-6, 145, 2,52, claw 38; IV-L-2, 117 (2.02); IV-L-3, 135 (2.45); IV-L-4, 235 (4.27); IV-L-5, 230, 4.84; IV- L-6, 200; claw 45. Total L segments 2–6: I-L 610, IV-L 917. These data reveal that T. scutulatus is similar to T. ravenala (and differs from T. vanilla sp. nov., see below) in comparably low dimensions of idiosoma, coxal plates and genital field (with Ac number <20 pairs). A particular feature of T. scutulatus is the rather large size of anterior and posterior Ac (both> 40 in L,> 25 % genital plate L, in the Madagascan species 23–40, 13–17 % genital plate L). In chelicera and gnathosoma L, T. scutulatus is intermediate between the two Madagascan species, palp segments are similar in length to T. ravenala , but P-2 and P-4 agree in their slender shape with T. vanilla . The gnathosoma of T. scutulatus (not treated in the original description) is more slender than in T. ravenala , but of the typical shape of the subgenus Teratothyasides s. str., with a well developed rostrum and prominent proximodorsal apodemes. No particular features are found in leg segment proportions and shape of claws.

Habitat: Turbulent forest streams and springs with cascades.

Distribution: Madagascar, endemic. Found in many different parts of the island, at 200–1725 m a.s.l., from the northern Montagne d’Ambre to the southern Andohahela reserve.

Figures

FIGURE 4. Family Limnocharidae, Limnochares connexa female. a. coxae and genital field, partial view; b. frontal shield; c. palp; d. gnathosoma.

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).

FIGURE 29. Family Teratothyadidae, Teratothyasides vanilla (MD 040). a.–c. female; a. chelicera; b. palp; c. genital field; d.–e. male; d. venter; e. dorsum.