Nilotonia (Dartiella) onilahy, Goldschmidt, 2008

Goldschmidt, Tom, 2008, Taxonomical, ecological and zoogeographical studies on anisitsiellid water mites (Acari: Hydrachnidia: Anisitsiellidae Koenike, 1910) from Madagascar, Zootaxa 1954 (1), pp. 1-120 : 14-21

Nilotonia (Dartiella) onilahy sp. nov.

( Figs 11–27 , Table 2)

Type series: Holotype male, MD 91 , Ambohimahavelona (Tulear), rheocrenes west school complex (left border of MD 90 ), 50 m asl, 25.6 °C, 1240 µS/cm, 23.09.2001; paratypes, same locality and date, 5/7/1 mounted, 28/11/0 unmounted.

Habitat: Spring at 50 m asl.

Distribution: Madagascar (Onilahy valley, SW Madagascar (Tulear)).

Derivatio nominis: Onilahy — referring to the region of the type (and only known) locality of the species.

Diagnosis: Dorsum typical for the genus; integument lined (mainly laterally, medially granular); venter with small areas of secondary sclerotization; Cx-I and Cx-II medial not fused, suture between Cx-III and Cx- IV incomplete; Cx-III medially with slight secondary sclerotization; Cx-IV with caudal secondary sclerotization; genital bay apically narrow; genital field in males relatively small, oval acetabula mid-sized, slender, posterior genital sclerite in males latero-caudally extended; legs bearing strong setae; claws on leg-I to leg-III with one ventral and one dorsal clawlet, leg-IV distally with one long sub-terminal seta, no sexual dimorphism in the legs; palp relatively slender.

Description, male (n = 6): Idiosoma small (L/W 559 (466–559)/392 (334–402)) ( Fig. 11 ); integument dorso-laterally lined, dorso-medially and ventrally rather granular; posterior dorsal plate large (L/W 179 (174–191)/145 (123–167)), rounded rectangular-oval, posteriorly wider ( Fig. 12 ), anterior dorsal platelets oval (L/W 49 (39–50)/39 (29–42)), one pair of small knob-shaped sclerites anterior to Dgl–3; glandularia extended; lateral eyes, separated on both sides, lying free under the integument, very close lateral to Dgl–2 ( Fig. 12 ); Cx-I medially closely approached, but separated ( Fig. 11 ), postero-lateral margin of Cx-II overlapping Cx-III; medial margin of Cx-III extended by fine secondary sclerotization, medial margin of Cx-IV curved to latero-caudally, with small, knob-shaped caudal corner ( Fig. 11 ), caudally extended by secondary sclerotization ( Fig. 11 ); Cxgl-2 fused with Cx-III, Cxgl-4 closely approached to the anterior margin of Cx-III ( Fig. 11 ); genital field small, rectangular-oval, genital flaps, anteriorly slightly tapering ( Fig.11 ); acetabula mid-sized, slender (L/W 29–37 (32–37)/10–11 (7–11)) oval, slightly distant from each other, Ac1 and Ac3 distant from anterior and caudal margin of genital flaps respectively ( Fig. 11 ); anterior genital sclerite small with medial bump ( Fig. 11 ), posterior genital sclerite large, broader than genital field ( Fig. 11 ); excretory pore without sclerotization; Vgl extended by secondary sclerotization, four small, irregular platelets on a curved line parallel the caudal margin of idiosoma ( Fig. 11 ); genital skeleton compact, relatively broad, brachia distalia and proximalia strong, directed to caudo-lateral, carina anterior distinct, proximal sclerite elongated, cella proximalis distinct ( Fig. 13 ); legs bearing several large setae (several pinnate, distally mostly flatly broadened); leg-I to leg-III terminate in well developed claws with one small dorsal and one larger ventral clawlet ( Fig. 14 ), leg-IV-6 distally tapering with one larger terminal seta ( Fig. 15 ); capitulum compact, ventrally relatively straight, no distinct rostrum ( Fig. 16 ), palps typical ( Figs 16, 17 ), P1 with one fine dorsal seta, P2 with one relatively short latero-ventral seta and five to six dorsal setae, ventral margin straight, P3 with two laterodorsal and two latero-medial setae, ventral margin curved, P4 relatively straight, ventro-distally slightly curved, ventral setae slightly distal on weak protrusions ( Figs 16, 17 ), chelicera with strong, pointed claw ( Fig. 16 ).

Female (n = 7): Idiosoma larger than in males (L/W 598–697/412–491) ( Fig. 18 ); posterior dorsal plate irregular oval (L/W 149–181/115–149) ( Fig. 19 ); medial margin of Cx-IV concave ( Fig. 18 ); genital field larger than in males (L/W 154–169/118–127); posterior genital sclerite smaller, not protruding genital field ( Fig. 18 ); legs and gnathosoma as in male.

Deutonymph (n = 1): Idiosoma rounded-oval (L/W 353/294) ( Fig. 20 ); integument granular, also coarsely lined dorsally, ventrally only indistinct lines visible; posterior dorsal plate small, irregularly rounded (L/W 40/44), anterior dorsal platelets irregularly oval (L/W 27/20), small knob-shaped sclerite antero-medial to Dgl-3; glandularia on slightly extended platelets, setae of Dgl-3, -4 and -5 long ( Fig. 21 ); coxal field more compact, less elongated than in adults (especially Cx-III/IV), without secondary sclerotization, coxal groups farther distant from each other (slightly broken in preparation); Cx-I medially approached (anterior overlapping) but separated, Cx-II postero-laterally overlapping Cx-III, Cx-I/II and Cx-III/IV medially diverging; medial margin of Cx-III/IV convex, caudally nearly oblique; glandularia Cxgl-2 lying on Cx-III, Cxgl-4 slightly approached to the anterior margin of Cx-III ( Fig. 20 ); provisional genital field clearly caudal Cx-IV, on irregular oblique rectangular plate ( Fig. 20 ), two pairs of acetabula, flanked by three pairs of setae; Vgl on small platelets; legs similar to adults, bearing less heavy setae ( Fig. 22 ); leg-IV with one large (32) sub-termi- nal seta ( Fig. 23 ); gnathosoma similar to adults ( Figs 24–27 ), palps bear less setae, P2 slightly more slender, without ventral seta ( Figs 24, 25 ).

Remarks: According to Panesar (2004), the subgenus Dartiella comprises 14 species from Africa, Asia and Europe. Nilotonia (Dartiella) ivelany sp. nov. and Nilotonia (Dartiella) onilahy sp. nov. from Madagascar are separate from most of these in bearing simple ventral and dorsal clawlets on leg-I to leg-III; N. (Dartiella) longipora , micropora, navina, pontifica, pyrenaica, rackae, robusta and thermophila – beside other differences – bear serrate ventral clawlets. In N. (Dartiella) catarrhacta and ortali the suture between Cx-III and Cx-IV is complete – medially incomplete in N. (Dartiella) ivelany and onilahy . N. (Dartiella) fundamentalis is characterised by a large ventral plate formed by the secondarily enlarged postgenital sclerite; in N. (Dartiella) hanniae the genital field is very small and completely lying in the genital bay and in N. (Dartiella) parva and gallica the ventral surface of P2 bears small denticles – these specific characters also separate the species from the two new species from Madagascar. Nilotonia (Dartiella) ivelany and Nilotonia (Dartiella) onilahy share the character state of an incomplete suture between Cx-III and Cx-IV and claws on leg-I to -III with simple ventral clawlets with two further African species: N. (Manotonia) violacea ( Lundblad, 1951) and N. (Manotonia) gracilipalpis ( Lundblad, 1942) , described from East African mountains and Ethiopia, respectively. Both continental African species bear smaller genital fields that are closely bordered by the genital bay formed by the less divergent Cx-IV. Within this species group, N. (Manotonia) violacea is separated by the extended secondary sclerotization (especially the posterior genital sclerite, caudal margin of Cx-IV, Vgl-2 and postero-ventral platelets). Furthermore, in N. (Manotonia) violacea , no terminal seta is present on leg-IV-6 and the posterior dorsal plate is nearly circular. Nilotonia (Manotonia) gracilipalpis is mainly characterised (and separated from the other species of this group) by very large Cx-IV forming a narrow genital bay; furthermore, the palps are very slender and in the elongated P4, the ventral setae are inserted far distally.

The new species from Madagascar are very similar. However, in N. (Dartiella) ivelany , the genital field is longer and more slender, the palps are slightly more slender, the acetabula are larger (especially wider) and the sub-terminal seta on leg-IV-6 is much shorter. Furthermore, N. (Dartiella) onilahy has only been found (in a large population) in a single lowland spring with high conductivity, in South-western Madagascar (Onilahy valley, 50 m asl, MD 91), whereas N. (Dartiella) ivelany has been found in very low conductivity springs and a stream in the central highlands (mainly the Ankaratra mountains, 1800–2300 m asl).

Figures

FIGURES 11–17. Nilotonia (Dartiella) onilahy sp. nov., male holotype (MD 91): 11, idiosoma, ventral view; 12, idiosoma, dorsal view; 13, genital skeleton, anterior view; 14, leg-II-2 to -6; 15, leg-IV; 16, capitulum with left palp, lateral view; 17, right palp, medial view. Scale bar = 100 µm.

FIGURES 18–19. Nilotonia (Dartiella) onilahy sp. nov., female paratype (MD 91): 18, idiosoma, ventral view; 19, idiosoma, dorsal view. Scale bar = 100 µm.

FIGURES 20–27. Nilotonia (Dartiella) onilahy sp. nov., deutonymph (MD 91): 20, idiosoma, ventral view; 21, idiosoma, dorsal view; 22, leg-II; 23, leg-IV (ventral seta at first segment completed (only socket visible)); 24, capitulum with left palp, lateral view; 25, right palp, medial view; 26, left chelicera, lateral view; 27, right chelicera, medial view. Scale bars = 100 µm.