Hemigalichus Fain, 1970

Bochkov, Andre V. & Oconnor, Barry M., 2005, The life-cycle of Hemigalichus chrotogale sp. nov. (Acari: Listrophoridae), with comparative observations on listrophorid morphology, Journal of Natural History 39 (44), pp. 3811-3832 : 3813-3818

Genus Hemigalichus Fain, 1970

Hemigalichus Fain 1970, p 276 ; 1980, p 184; 1981, p 308.

Type species. Hemigalichus baramensis Fain, 1970 .

Diagnosis

Adults. Anterior margin of prescapular shield deeply notched in midline. Postscapular shield present, entire, well sclerotized. Small median spot distinctly visible in posterior third of this shield. Full set of idiosomal and leg setae present (see Discussion), except for tarsal setae d IV in males (in males of H. chrotogale sp. nov., setae g absent). Setae se filiform. Setae d of all tarsi not longer than this segment. Distinct longitudinal ridge connecting base of coxal apodemes II and prescapular shield present. Femur I with ventro-apical tooth.

Male. Hysteronotal shield present, entire, with at least some linear ornamentation, and occupying most of hysteronotum. Apodemes III fused to each other and forming distinct median crest. Progenital sclerites fused to each other and forming inverted Y-shape structure, bearing genital papillae remnants. Opisthosoma wide, not attenuate behind coxal fields IV, with pair of distinct posterior lobes. Opisthogastric sclerites present. Para-anal suckers well developed. Setae ps1–2 thickened. Setae h3 filiform. Tarsi and tibiae III and IV distinctly thickened, with dorsal crests. Tarsi IV without apical projections. Setae d IV absent. Female. Hysteronotal shield present, entire, with distinct linear ornamentation and occupying almost whole hysteronotum. Lateral parts of hysteronotal shield extending over ventral surface of opisthosoma leaving only a narrow median membranous area. Opisthosoma without scales or tubercles. Setae 4b situated behind level of genital papillae, slightly anterior to setae g. Setae h2 relatively short, not longer than f2. Basal cap of spermatheca globose, efferent sperm ducts straight.

Other species included

H. chrotogale sp. nov.

Hosts and distribution

Mites of the genus Hemigalichus are specific parasites of Asian viverrids of the subfamily Hemigalinae ( Carnivora : Viverridae ). Hemigalichus baramensis Fain, 1970 and H. chrotogale sp. nov. parasitize Hemigalus derbyanus (Gray, 1837) in Malaysia ( Fain 1970, 1980) and C. owstoni in Vietnam, respectively. The subfamily Hemigalinae includes four monotypic genera, and listrophorid mites are known from two of them, thus, we might expect two more species of the genus Hemigalichus to occur on the other potential hemigaline hosts, Diplogale hosei (Thomas, 1892) and Cynogale bennettii Gray, 1837 .

Description of developmental stages based on H. chrotogale sp. nov.

Larva ( Figure 1 ). Palps with large membranes and consisting of two podomeres. Basal podomere with two setae, d and v, apical podomere with one seta, d, and two solenidia (v). Fixed digit of chelicera with three teeth; teeth of movable digit indistinct. Paraxial hood of chelicerae triangular. Antiaxial apophysis, cheliceral spur, and seta-like apophysis present. Infracapitulum ventrally with pair of large lateral protrusions. Pair of subcapitular setae and supracoxal setae present. Idiosoma with prescapular shield, postscapular and hysteronotal shields absent. Coxal apodemes I and II fused medially and apodemes III fused in anterior part. Pair of large clasping flaps between coxal fields I present. Idiosomal setation: si, se, c1, c2, c3, cp, d1, d2, e1, e2, h1, h2, 1a, 3a. Setae h2 microsetae, situated ventrally. Prescapular shield extending lateroventrally between bases of legs I–II. Femur I with dorsal tooth situated medially. Leg sensilla: I trochanter 0, femur 1 (vF), genu 2 (cG, mG), tibia 2 (gT, w), tarsus 9 (wa, ra, la, s, d, e, f, E, v 1); II trochanter 0, femur 1 (vF), genu 2 (cG, mG), tibia 2 (gT, w), tarsus 8 (wa, ra, la, s, d, e, f, v 1); III trochanter 0, femur 0, genu 0, tibia 2 (kT, w), tarsus 5 (w, r, d, e, f).

Protonymph ( Figure 2 ). Setae f2, h3, ps1–3, and g added. One pair of distinct genital papillae present between coxal fields IV. Coxal apodemes III fused medially. Leg setation with setae d, r, and w of tarsus IV added.

Teleonymph ( Figure 3 ). Setae 4a and 4b added on idiosoma, setae kT and solenidion w added on tibia IV, and setae e, f added on tarsus IV. Two pairs of distinct genital papillae between coxal fields IV. Setae 4b microsetae, situated immediately behind 3a. Fused coxal apodemes III form short median crest.

Remarks

We did not detect any qualitative distinctions that would allow recognition of male and female proto- and teleonymphs. However, we did discern two size classes among protonymphs that differed significantly from each other (t test, P,0.05). The ‘‘large protonymphs’’ ranged from 270 to 310 in 10 specimens, while the ‘‘small protonymphs’’ ranged from 200 to 230 in 10 specimens. These two size classes also exist in teleonymphs. Based on observations of pharate specimens, the ‘‘large teleonymphs’’ (body length 350–370 in 10 specimens) moult into the heteromorphic males, and the ‘‘small teleonymph’’ (body length 280–300 in 10 specimens) include both the homeomorphic male and female lines.

Precopulatory mate-guarding behaviour

We observed numerous males attached to teleonymphs. This phenomenon is widely observed among parasitic Astigmata and has been termed pre-copulatory mate-guarding behaviour ( Witalinski et al. 1992). This is the first record of such behaviour in the Listrophoridae and probably represents an isolated instance of this behaviour. In many parasitic Astigmata exhibiting precopulatory mate guarding (e.g. Chirodiscidae , some Psoroptidae , Proctophyllodidae , etc.), teleonymphs have specialized projections on the posterior idiosoma or modified setae that interact with the male para-anal suckers. In most cases of precopulatory mate guarding, the male is positioned above the posterior part of the teleonymphal idiosoma, and the long axes of the bodies of the partners are orientated in opposite directions. In H. chrotogale , however, the male is positioned above the anterior part of the teleonymphal idiosoma, and the body axes of the partners are orientated in the same direction. The heteromorphic male clutches the teleonymph’s idiosoma with modified legs III–IV; the femora and genua III–IV in these mites are ventrally concave and armed with strongly sclerotized crests, but the para-anal suckers do not participate in the attachment. Teleonymphs have no idiosomal protrusions or other special attaching structures. This positioning and modification of the posterior legs are similar to those of certain Atopomelidae (e.g. Chirodiscoides Hirst, 1917 ). Among the possible functions of precopulatory mate guarding, sperm competition and shortening of the receptivity of the newly moulted female have been suggested ( Witalinski et al. 1992; Fashing 2001). In parasitic Astigmata , the latter reason could be especially important for dispersal to new hosts at the time of host social or sexual contacts. In this case, the timely meeting of the sexual partners is assured even in conditions of low mite population density on the new host.

Figures

Figure 1. Hemigalichus chrotogale sp. nov., larva. (A) Lateral view; (B–D) legs I–III in ventral view, respectively. Abbreviations: c.f., clasping flap, l.i., lateral incision, l.t., lateral tooth, o.g., opening of oil gland, p.c., podocephalic canal, s.g., opening of supracoxal gland. Scale bars: 25 mm (A); 50 mm (B–D).

Figure 2. Hemigalichus chrotogale sp. nov., protonymph. (A) Dorsal view; (B) ventral view; (C) leg IV in ventral view. Scale bars: 25 mm (A, B); 50 mm (C).

Figure 3. Hemigalichus chrotogale sp. nov., teleonymph. (A) Ventral view; (B) coxa of leg II; (C) leg IV in ventral view. Abbreviations: fe, femur; ge, genu; ta, tarsus; ti, tibia; tr, trochanter. Scale bars: 100 mm (A); 50 mm (B, C).