Systematics of the Genus Sciurocheyla (Acari: Cheyletidae), Parasites of Tropical Squirrels (Rodentia: Sciuridae)

Abstract

Two genera of parasitic cheyletid mites, Smileycheles (monotypic) and Thryonomycheyla (two species), are synonymized with the genus Sciurocheyla . An emended diagnosis of the genus Sciurocheyla is provided. Sciurocheyla squamosa (Domrow & Baker, 1963), type species of the genus, and Sciurocheyla camerounensis (Fain, 1979), new combination, are redescribed. Females, males, teleo- and protonymphs of Sciurocheyla funisciurus, new species, collected from Funisciurus pyrrohopus F. Cuvier in tropical Africa are described and illustrated.

The rodent family Sciuridae is host to a morphologically diverse fauna of mites in the family Cheyletidae (Acari: Prostigmata). Six described species are placed in five genera and three tribes: HylopecheylaFain, 1972 (Cheyletini), Chelonotus Berlese, 1930, PromuricheylaFain, 1979, Thewkachela Ide & Kethley, 1977 (Chelonotini), and SciurocheylaVolgin, 1969 (Niheliini) (Gerson et al. 1999). All these genera are monotypic, associated exclusively with squirrels and known only from adult females, except for Hylopecheyla, which is known from females, males, and immature stages, and includes two species. One of these species parasitizes squirrels of the genus Hylopetes Thomas, and another is associated with the tree shrew, Tupaia glis (Diard) (Scandentia: Tupaiidae) (Fain and Bochkov 2001b).

Examination of mite specimens from faunal surveys in east Africa sponsored by the Field Museum of Natural History yielded new collections of cheyletid mites from sciurid hosts. The material collected includes females, males, and immature stages of a new species, Sciurocheyla funisciurus, from Funisciurus pyrrohopus F. Cuvier from Burundi, and Smileycheles camerounensisFain, 1979 from Heliosciurus undulatus (True) from Tanzania.

The genera Sciurocheyla and SmileychelesFain, 1979 were each described from a single damaged female specimen. The similarity of these genera had been noted in recent works (Bochkov and Fain 2001, Fain and Bochkov 2001a). However, Fain and Bochkov (2001a) stated that additional material would be necessary to clarify their status. The current study, which is based on both reinvestigation of all type material and large series of specimens of both the new species and S. camerounensis, including males and immature stages, allows us to confirm the synonymy of these genera.

Males and immature stages of the genus Sciurocheyla as well as other genera of the tribe Niheliini have not been described before. Surprisingly, the nymphal and male specimens of the Sciurocheyla species are similar to the two species of ThryonomycheylaFain, 1972, described from rodents of the genus Thryonomys (Thryonomyidae) in tropical Africa (Fain and Bochkov 2002). The genus Thryonomycheyla was considered as incertae sedis in the family Cheyletidae because the females are unknown and because of the morphological specialization of males and protonymphs (Bochkov and Fain 2001). The similarities of these stages to those of Sciurocheyla spp. allow us to place Thryonomycheyla as a junior synonym of this genus.

In the present article, we provide an emended diagnosis of the genus Sciurocheyla, redescribe S. squamosa (Domrow and Baker 1963) and S. camerounensis, new combination, and describe the new species.

Materials and Methods

Host specimens were collected in the field, individually bagged, wrapped in cheesecloth, and later examined for parasites in the laboratory by one of us (B.M.O.). Parasites removed were cleared in lactophenol and mounted in Hoyer's medium. Drawings were made with a phase contrast Zeiss microscope with a camera lucida. Host specimens are deposited in the Field Museum of Natural History, Chicago (FMNH). Holotypes of S. camerounensis, Thryonomycheyla congolensisFain, 1972, and T. angolensisFain & Bochkov, 2002 were studied by A.V.B. at the Musée Royal de l'Afrique Centrale, Tervuren, Belgium (MRAC). The type of S. squamosa (Domrow & Baker, 1963) was loaned from the U.S. National Museum of Natural History, Washington, DC (USNM).

The idiosomal chaetotaxy follows Fain et al. (1997). All measurements are in micrometers. Host nomenclature follows Wilson and Reader (1993).

Genus SciurocheylaVolgin, 1969

Hemicheyletus (Sciurocheyla) Volgin, 1969: 384

Sciurocheyla, Fain & Lukoschus, 1985: 264

SmileychelesFain, 1979a: 627, new syn.

ThryonomycheylaFain, 1972: 37, 1979b: 416, new syn.

Type Species Nihelia squamosaDomrow & Baker, 1963

Revised Diagnosis. Female

Gnathosomal apex with several hair-like median protuberances. Peritremes arched. Palpal tarsi strongly reduced, bearing 1–2 setae. Palpal tibia with three filiform setae. Palpal claw curved ventrally, without teeth. Palpal genu devoid of setae, shortened and completely covered dorsally by tibia. Palpal femur with five setae and with a strong retrorse ventro-lateral process. Idiosoma rhomboid in outline. Eyes absent. Propodosomal and hysterosomal shields present. Idiosomal setation: vi, ve, sci, sce, h, l1-l5, d1-d5, ic1, ic3, ic4, pg1-pg3, g1, g2, and a1-a3; 1–2 pairs of neotrichial setae presented on the propodosomal shield. All legs well developed, tarsi with claws and empodium. Apical tarsal knobs and claws angles absent. Outer seta of coxae III filiform. Guard seta of solenidion on tarsus I lacking. Solenidion of genu I asterisk-like, solenidion of tarsus II situated ventrally. Leg setation: tarsus 8 (+ solenidion ω) - 7 (+ solenidion ω) - 7–7, tibia 5 (+ solenidion ϕ) - 4–4 - 4, genu 2 (+ solenidion υ) - 2–2 - 2, femur 2–2 - 2–1, trochanter 1–1 - 2–1, coxa 2–1 - 2–2.

Male

Peritremes arched. Palps not modified. Palpal tarsus with four setae, without solenidion. Palpal tibia with three setae. Palpal claw finely striated longitudinally, without basal teeth. Palpal genu not shortened, bearing two setae. Palpal femur variable in length, sometimes hypertrophied, bearing three setae. Idiosoma rhomboid in outline. Eyes absent. Propodosomal and hysterosomal shields present. Idiosomal setation: vi, ve, sci, sce, h, l1-l5, d1-d5, ic1, ic3, ic4, pg1, p g2, and g1, g2; one pair of neotrichial setae present. Legs setation as in female, but solenidion υ of genu I very short and straight.

Species Included

S. squamosa (Domrow & Baker, 1963), S. funisciurus new sp., S. camerounensis (Fain 1979) new comb. from Smileycheles, S. congolensis (Fain 1979) new comb., and S. angolensis (Fain & Bochkov, 2002) new comb. from Thryonomycheyla.

Remarks

The monotypic subgenus Sciurocheyla was created by Volgin (1969) for the species Nihelia squamosaDomrow & Baker, 1963 within the genus Hemicheyletus Lawrence, 1954 (now considered as Nihelia Domrow & Baker, 1960). This species was described from a single female found on Menetes berdmorei (Blyth) (Sciuridae) in Thailand (Domrow and Baker 1963). Later on, the subgenus Sciurocheyla was elevated to generic rank by Fain and Lukoschus (1985). These authors considered Sciurocheyla and Smileycheles as closely allied but separate genera. Two main distinctions between them were the presence of palpal tarsi and scale-like setae on the dorsal shields of the idiosoma in Sciurocheyla, whereas in Smileycheles, the palpal tarsi were described as completely lost and all idiosomal setae as setiform. However, both these distinctions are the result of incorrect observations. Reexamination of the holotype of Sm. camerounensis and additional specimens from Heliosciurus undulatus showed that this species does retain, albeit strongly reduced, palpal tarsi bearing a microchaeta, which are similar to those of S. squamosa. The other character separating the genera, the shape of the dorsal idiosomal setae was also incorrectly described. Actually, in S. camerounensis, setae d1-d3 are represented by small, transparent, scale-like setae. Because there are no generic distinctions between Sm. camerounensis and S. squamosa, we consider the genus Smileycheles as a junior synonym of the genus Sciurocheyla.

Males and nymphs of the genera Thryonomycheyla (female unknown) and Sciurocheyla, respectively, show strong similarity in habitus. There are no significant differences in the setation of the idiosoma and legs. Moreover, representatives of these two genera share several unique synapomorphies. In males of both genera, the palpal claws are striated longitudinally, and there are sclerotized ingrowths of characteristic shape on the dorsal shields. In protonymphs, the palps are shorter than subcapitulum, consisting of two segments, which are not clearly separated from each other, each palpal segment bears one serrate dorsal seta and one nude ventral seta, and the palpal thumb-claw complex is absent. Taking into consideration the above mentioned observations, we consider the genus Thryonomycheyla as a junior synonym of the genus Sciurocheyla.

Sciurocheyla squamosa (Domrow & Baker, 1963) (Figs. 1–6)

Nihelia squamosaDomrow and Baker, 1963: 227, Figs. 1–2; Summers and Price, 1970: 75

Hemicheyletus (Sciurocheyla) squamosus, Volgin, 1969: 384, Figs. 484-485

Sciurocheyla squamosus, Fain and Lukoschus, 1985: 264

Diagnosis

In female, palpal tarsus with two setae; setae d5, l5 and a1-a3 densely barbed, other idiosomal setae nude; there are two pairs of neotrichial setae; setae d1-d3, N1, and N2 scale like; idiosomal shields devoid of ornamentation; idiosomal cuticle striated.

Female (holotype)

Body, including gnathosoma, 320 long, maximum width 250 (Figs. 1 and 5). Gnathosoma 65 long. Peritremes arched, with 10 pairs of segments. Gnathosomal apex with 5–6 pairs of hair-like median protuberances. Gnathosomal setae rd, ra, and rp nude. Palpal femur bearing dorsally two densely barbed setae, one lateral barbed seta and two ventral nude setae. Palpal tibia elongated, bearing three nude setae. Palpal tarsus bearing two nude seta (Figs. 3–4). Idiosoma 255 long. Dorsal shields covering most of dorsal idiosomal surface, devoid of ornamentation. Propodosomal shield 100 long in midline and 170 wide, bearing seven pairs of setae, four pairs of slightly thickened, nude setae, vi, ve, sci, and sce, and three pairs of scale-like setae, d1 and neotrichial setae N1, N2 18–20 wide. Neotrichial setae situated at the same level behind setae d1. Humeral setae h situated on small separate plates. Hysterosomal shield 100 long in midline and 175 wide, bearing seven pairs of setae, five pairs of setiform, nude setae, d4, l1-l4 and two pairs of scale-like setae, d2 and d3, similar in size with scale-like setae on the propodosoma. Setae l2 situated close to middle part of the shield. Setae d4 and l4 distinctly shorter than other setae of the hysterosomal shield. Setae d5 and l5 situated off the hysterosomal shield, barbed, and subequal in length. Anal setae and second pair of genital setae barbed, other anal-genital setae nude (Fig. 6). Setal lengths: vi 50, ve 30, sci and sce ≈50, h 40, d4 and l4 ≈20, d5 and l5 ≈16, l1 and l2 ≈45, l3 40. Coxae finely striated. Coxae I with small retrorse protrusion.

Male and Immature Stages

Unknown.

Material Examined

HOLOTYPE female (n 2854), ex Menetes sp. (Rodentia: Sciuridae) (B 17719), Thailand, Nan Prov., Pang Nam NU, a village in the Bun Yun district, seven km. east of the Phrae-nan border, between Ban Rong Kwang and Ban Klang Wiang, 1-I-53, H.G. Deignan. Holotype in USNM.

Sciurocheyla funisciurus Bochkov & OConnor, new species (Figs. 7–28)

Diagnosis

In female, all idiosomal setae setiform; there is a single pair of neotrichial setae; dorsal shields without ornamentation; setae d5, l5, a1-a3, and g1-g2 densely barbed. In male, palpal tarsi bearing a strongly flattened seta; setae d1 and N situated at the same level; setae l1 situated on the hysterosomal shield, setae l5 nude and subequal in the length to other hysteronotal setae.

Female (Holotype)

Body, including gnathosoma, 310 long (295–320 in 10 paratypes), maximum width 220 (205–230) (Figs. 7 and 11). Gnathosoma 58 long (50–58) (Figs. 10 and 14) Peritremes with 8–9 pairs of segments. Gnathosomal apex with 5–6 median protuberances. Palpal setation as in previous species, but palpal tarsus bearing a single nude seta. Idiosoma 250 long (245–265). Dorsal shields covering most of dorsal idiosomal surface, devoid of ornamentation. Propodosomal shield 100 long (90–100) in midline, maximum width 175 (165–185), bearing five pairs of slightly thickened, nude setae, four pairs of them (vi, sci, sce, d1 and one pair of neotrichial setae N) subequal in length, setae ve slightly shorter than these setae. Setae d1 and N situated at the same level. Humeral setae h situated on small separate plates. Hysterosomal shield 180 long (165–180) in midline, maximum width 120 (120–125), bearing seven pairs of nude setae similar in shape to those on the propodosomal shield (d2-d4, l1-l4). Setae l2 situated close to middle part of the shield. Setae d4 and l4 distinctly shorter than other setae of the hysterosomal shield. Setae d5 and l5 situated off the hysterosomal shield, densely barbed and subequal in length, in most specimens, setae l5 situated ventrally. Setal lengths: vi 48 (45–55), ve 33 (30–35), sci 46 (45–50), sce 45 (40–50), h 28 (25–35), d1 and N 45–50, d2 40 (40–45), d3 33 (30–40), d4 20 (15–20), d5 and l5 15–18, l1 37 (35–45), l2 40 (35–45), l3 33 (30–35) and l4 19 (18–20). All anal and genital setae densely barbed (Fig. 15); paragenital setae nude. Coxae striated. Shape of leg setae as in Figs. 8 and 9, 12, 13.

Heteromorphic Male (Five Paratypes)

Body, including gnathosoma, 320–350 long and 235–260 wide (Figs. 16 and 17). Gnathosoma 145–155 long. Rostral shield (=tegmen) laterally with a pair of strong triangular projections directed anteriorly. Peritremes each with 10–11 segments. Protegmen with a pair of triangular projections smaller that those on tegmen. Gnathosomal setae rp serrate, rd and ra nude. Palpal femur 65–90 long and 50–55 maximum wide, bearing three serrate setae, one dorsally and two ventrally. Palpal genu with two serrate dorsal setae. Palpal tibia with three nude setae, one strong lanceolate, situated dorsally and two ventral filiform. Palpal claws not bifurcate. Palpal tarsus bearing one slightly serrate seta, two nude setae and one strongly flattened seta (Figs. 18 and 19). Idiosoma 225–235 long. All idiosomal setae nude. Dorsal shields almost completely covered dorsal idiosomal surface, devoid of ornamentation. Propodosomal shield 100–130 long in midline, and 165–175 wide. Hysterosomal shield 90–100 long in midline and 120–140 wide. Setation of idiosomal dorsum very similar to that in female, except for setae d5 situated on the hysterosomal shield. Penis tube-like 70–77 long. Genital orifice situated in posterior part of hysterosomal shield. Setal lengths: vi 30–35, ve 14–15, sci 25–35, sce 20–25, h 25–27, d1 30–37, d2 20–26, d3 17–20, d4 6–9, d5 15–17, l1 20–25, l2 20–25, l3 17–20, l4 6–8 and l5 12–15. Tibiae I with small paraxial spur.

Homeomorphic Male (Four Paratypes)

Body, including gnathosoma, 245–265 long and 175–200 wide. Gnathosoma 75–85 long (Fig. 20). Lateral projections of tegmen very short, projections of protegmen not developed. Dorsal seta of palpal tibia lanceolate and slightly serrate. Length and width of palpal femur subequal, length 30–40 and maximum width 30–35. Idiosoma 175–210 long. Propodosomal shield 85–100 long in midline and 125–135 wide. Hysterosomal shield 85–90 long in midline and 95–105 wide. Setal length: vi 33–35, ve 13–15, sci and sce 33–37, h 23–25, d1 33–40, d2 26–30, d3 22, d4 6–9, d5 14–15, l1 24–28, l2 22–25, l3 17–22, l4 6–8 and l5 12–14.

Larva

Unknown.

Protonymph (Two Paratypes)

Body, including gnathosoma, 205–235 long and 150–175 wide (Figs. 21 and 22). Gnathosoma 33–35 long, bearing nude setae rd, ra and rp. Peritremes arched, with nine pairs of segments. Tegmen with a pair of short retrorse projections situated dorsally in its basal part. Palps shorter than subcapitulum, with two segments not clearly separated each from other, thumb-claw complex absent. Palpal segments each bearing one serrate dorsal seta and one nude ventral seta. Idiosoma 165–200 long. Posterior end of idiosoma with a small median incision. Propodosomal shield 60–70 long in midline and ≈80 wide, bearing four pairs of nude thickened setae, vi, ve, sci and d1. Setae sce situated off the shield, on small sclerotized plates like other dorsal idiosomal setae. Hysterosomal shield not developed, however, there is a pair of relatively large plates bearing setae l2. Setae d4, d5 and l4 absent. Ventrally with three pairs of nude intercoxal setae and anal setae, respectively. Setal lengths: vi 23–25, ve 13–15, sci 11–12, sce and h 15–17, d1 15–16, d2 11–13, d5 8–9, l1 15–17, l2 12–13, l3 10–11 - all nude and l5 6–7 serrate. Guard seta of solenidion ω on tarsi I present. Solenidion of genua asterisk-like. Coxal fields striate. Setal length: tarsus 8 (+ solenidionω) - 7 (+ solenidion ω) - 7–5, tibia 4 (+ solenidion ϕ) - 4–4 - 4, genu 2 (+ solenidion υ) - 2–1 - 0, femur 2–2 - 1–1, trochanter 0–0 - 1–0, coxa 2–1 - 2–0.

Teleonymph (Six Paratypes)

Body, including gnathosoma, 245–295 long and 185–200 wide (Fig. 23). Gnathosoma 45–55 long (Figs. 24 and 25). Gnathosomal apex with hair-like median protuberances. Palps shorter than subcapitulum. Palpal femur with four setae, one dorsal strongly barbed and three nude ventral. Palpal genu with one dorsal strongly barbed seta. Palpal femur and genu completely fused ventrally. Palpal tibia with three nude setae and strong claw curved ventrally. Palpal tarsus strongly reduced with a single short seta. Idiosoma 215–250 long. Posterior end of idiosoma with small median incision. Propodosomal shield 75–77 long in midline and 135–140 wide. Hysterosomal shield 63–65 long in midline and 80–90 wide. Dorsal setation as in the female, except for l4 situated off hysterosomal shield and setae d4 absent. three pairs of paragenital setae added. Setal length: vi 38–40, ve 19–20, sci 30–42, sce 28–32, h 20–22, d1 30–34, d2 22–30, d3 16–18, l1 22–25, l2 20–26, l3 16–20 - all nude, d5 6–8, l4 and l5 6–9 - all serrate. Leg chaetotaxy: tarsus 9 (+ solenidion ω) - 7 (+ solenidion ω) - 7–7, tibia 5 (+ solenidion ϕ) - 4–4 - 4, genu 2 (+ solenidion υ) - 2–2 - 2, femur 2–2 - 2–2, trochanter 1–1 - 2–1, coxa 2–1 - 2–2.

Type Series

HOLOTYPE female (BMOC 92–0605-069, 1), ex Funisciurus pyrrohopus (FMNH 149000), Burundi, Cibitoke Prov., Kibira National Park, Ndora Zone, 1.1 km N, 0.8 km E Kirumura, 2100 m., 2-VIII-91, J.C. Kerbis (JCK 2638). PARATYPES: 26 females, nine males, two protonymphs, and six teleonymphs, same data.

The holotype and half of paratypes are deposited in FMNH, one female paratype in MRAC and Zoological Institute RAS, St. Petersburg, Russia, other paratypes in the University of Michigan, Museum of Zoology.

Etymology

The name funisciurus is derived from the generic name of the host, a noun in apposition.

Remarks

This new species is clearly distinguished from S. squamosa and S. camerounensis by the following characters. In females of S. funisciurus, all idiosomal setae are setiform; in males, the palpal claw has a single apex, the palpal tarsus bears a strongly flattened seta, setae d1 and N are situated at the same level, setae l5 are nude and subequal to the other hysteronotal setae in length. In females of S. squamosa and S. camerounensis, setae d1-d3 and N are scale-like; in males of S. camerounensis (males unknown in S. squamosa), the palpal claws are bifid, all setae of the palpal tarsi are setiform or sickle-like, setae d1 are situated above N, setae l5 are serrate and are 2–3 times longer than the other hysteronotal setae. Males of the new species differ from S. congolensis and S. angolensis by the same characters as from S. camerounensis.

Sciurocheyla camerounensis (Fain, 1979) new comb. (Figs. 29–30)

Smileycheles camerounensisFain 1979: 627, Figs. 7–12

Diagnosis

In female, all idiosomal setae nude; a single pair of neotrichial setae present; setae d1-d3 and N scale like; idiosomal shields ornamented; idiosomal cuticle verrucose. In male, setae N situated behind setae d1, setae l1 situated on the hysterosomal shield.

Redescription Based on Specimens from H. undulatus

Female (10 specimens)

Body, including gnathosoma, 450–470 long and 310–330 wide. Gnathosoma 75–85 long. Peritremes arched, with 10–12 pairs of segments. Gnathosomal apex with 5–6 hair-like median protuberances. Palpal setation as in other species, but all setae nude and one seta of palpal tarsi represented by a microchaeta (Fig. 30). Idiosoma rhomboid in outline, 380–400 long (Fig. 29), cuticle striated and verrucose. All idiosomal setae nude. Dorsal shields occupy most of dorsal idiosomal surface, covered with reticulate ornamentation. Propodosomal shield 135–165 long in midline and 220–235 wide, bearing six pairs of setae, four pairs of slightly thickened setiform setae, vi, ve, sci, and sce, and two pairs of transparent and very small scale like setae, d1, and neotrichial setae N, situated at the same level. Humeral setae h situated off striated cuticle. Hysterosomal shield 180–200 long in midline and 180–190 wide, bearing seven pairs of setae, five pairs of setiform setae, d4, l1-l4 and two pairs of scale-like setae. Setae l2 situated close to middle part of the shield. Setae d4 and l4 distinctly shorter than other hysterosomal setae. Setae d5 ≈3 times longer than l5, both situated off hysterosomal shield. Setal lengths: vi, sci and sce ≈55–60, ve 35–40, h 28 55–65, d4 and l4 20–25, d5 65–75, l1 and l2 50–55, l3 30–35, and l5 20–25. Coxae striated.

Male (Two Specimens)

Body, including gnathosoma, 400–465 long and 330–350 wide (Fig. 31). Gnathosoma 115–120 long. Peritremes with nine segments. Gnathosomal setae rp, rd, and ra nude. Palpal femur 75–85 long and 45 maximum wide, bearing one dorsal slightly widened and serrate seta, one ventro-lateral and one ventral nude setae. Palpal genu with two nude dorsal setae. Palpal tibia with three nude filiform setae. Palpal claws bifid. Palpal tarsus bearing two sickle-like setae and two filiform setae (Fig. 32). Idiosoma 315–365 long. All setae of idiosoma nude. Dorsal shields almost completely cover dorsal idiosomal surface. Propodosomal shield 120–145 long in midline and 225–240 wide bearing setae vi, ve, sci, sce, d1, and N and a small sclerotized ingrowth situated in its posterior half. Setae d1 situated above N. Hysterosomal shield 120–135 long in midline and 120–165 maximum wide, bearing setae d2-d5, and l1-l5, and a pair of small sclerotized ingrowth situated in its anterior half. Setae l5 serrate, 2–3 times longer the other hysteronotal setae. Penis tube-like 155–165 long. Genital orifice situated near to posterior margin of hysterosomal shield. Setal length: vi 35–40, ve 28–33, sci 45–47, sce 44–45, h 130–145, d1-d5 ≈15–17, l1 35–37, l2, l3 and l4 ≈25 and l5 85–95. Coxae densely granulated.

Immature Stages

Unknown.

Material Examined

HOLOTYPE female (MRAC no. 150915), ex Zenkerella insignis Matschie, 1898 (Rodentia: Anomaluridae) (MRAC no. 28806), Cameroon, Foulassi, (no date). Mite removed by A. Fain.

Additional Material Examined

Eleven females and two males (BMOC 93–1250-108), ex H. undulatus (True, 1892) (FMNH 151467), TANZANIA: Kilamanjaro Prov., Kilamanjaro Distr., S. Pare Mts., Chome Forest Reserve, 7 km S. Bombo, near Kanza village, 1100 m. 4° 19′S, 38° 00′E, 25-VII-93, W.T. Stanley (WTS 1276).

Remarks

This species had been originally described from a single female specimen found on Z. insignis in Cameroon (Fain 1979a) and has not been recorded since the original description. The holotype of S. camerounensis (female) is slightly damaged and some its dorsal setae are broken. Therefore, the original description of Fain (1979a) contains some inaccuracies. The small transparent scale-like setae d1-d3 and N were mistakenly interpreted as the bases of broken setiform setae. There are some disagreements in numbers of leg setae on the figures (Fain 1979a: Figs. 9–12, p. 628) and in the description (Fain 1979a: 629). The bases of broken setae d4 and the rudimentary palpal tarsi bearing a microchaeta were overlooked.

Discussion

Mites of the genus Sciurocheyla are strongly specialized, permanent parasites of rodents. The host associations of these species seem very unusual because their hosts, squirrels and thrynomyid rodents, are ecologically and phylogenetically distant. Two species parasitize squirrels, one species is known from both squirrels and an anomalurid rodent and two species, are described from rodents of the family Thryonomyidae. After finding numerous specimens of S. camerounensis on the squirrel H. undulatus, it seems likely that this species is the principal host of S. camerounensis. Previously, S. camerounensis was known from a single female collected from an ethanol preserved specimen of Z. insignis. This finding could be the result of accidental contamination in the field or later in the museum. However, it is also possible that Z. insignis is a natural host of this species because these rodents are also arboreal like squirrels and, therefore, the horizontal transfer of their ectoparasites is highly possible.

However, parasitism of Sciurocheyla species on squirrels and thryonomyid rodents is difficult to explain. The family Thryonomyidae is not closely allied to squirrels, and these two host families differ in their ecology. It should be noted that both species associated with thryonomyid rodents are poorly represented in museum collections: S. congolensis is known from a single male specimen and S. angolensis from one male and a protonymphal exuvium only. Repeated, verifiable collections of Sciurocheyla spp. (=Thryonomycheyla) from these hosts have not been reported. Moreover, the senior author's attempt to collect additional material on rodents of the genus Thryonomys deposited in MRAC yielded no further specimens. Therefore, there is some probability that the associations of these mites with rodents of the genus Thryonomys were accidental. However, additional investigations are necessary for a better understanding of host associations of Sciurocheyla species.

Acknowledgements

Host specimens were collected and made available by Julian Kerbis-Peterhans and William Stanley, Division of Mammals, Field Museum of Natural History, Chicago, IL. We thank Alex Fain (Institut royal des Sciences naturelles de Belgique, Brussels, Belgium) and Henri André (Musée royal de l'Afrique Centrale, Tervuren, Belgium) for access to type specimens. We thank Ronald Ochoa (USDA, Systematic Entomology Laboratory, Beltsville, MD) for loaning the holotype of S. squamosa. We express our appreciation to Pavel Klimov (University of Michigan, Ann Arbor, MI) and Sergei Mironov (Zoological Institute, St. Petersburg, Russia) for comments on the manuscript. This research was supported by a grant from the U.S. National Science Foundation DEB-0118766 (PEET) to B.M.O.

References Cited