Davacarus reginaldi, Walter, 2004

Walter, David Evans, 2004, From the subantarctic to the subtropics: a revision of the Davacaridae Kethley, 1977 (Acari: Trigynaspida: Mesostigmata) with the description of a new genus and three new species, Journal of Natural History 38 (16), pp. 2033-2049 : 2045-2047

Davacarus reginaldi n. sp.

( figures 3B , 7 , 8 )

Material examined. HOLOTYPE: Tasmania: adult female, moss and leaf litter under Richea pandanus and Arthrotaxis, Pandani Grove (42‡41’S, 146‡36’E), 1050 m, Mt Field National Park, Tasmania, 16 January 1999, D. E. Walter. In UQIC. PARATYPES: Tasmania: two females, three males, two deutonymphs, six protonymphs same data as holotype; three females from moss and leaf litter in mature myrtle beech forest, Meander Forest Reserve (41‡44’S, 146‡32’E), 600 m, 21 January 1999, D. E. Walter. In UQIC.

Diagnosis. Brownish davacarid mites with elongate, mostly barbed-acuminate dorsal setae; podonotal shield reticulate throughout; mesonotal shields each with seven setae; pygidial shield with eight setae; fleshy, fimbriated process present behind coxa IV; sternal seta st1 and st4 of female in soft cuticle; internal malae barbed. Endogynium with oval, punctate regions flanked by boomerangshaped sclerites. Male tectum with median bifurcate process; genital valve setae present.

Adult female. Brown in life, body 600–620 M m long, primary shields ( figure 7 ) with colliculate-reticulate ornamentation and elongate, barbed setae, each far exceeding insertion of next seta in series; secondary sclerotization leathery and micropunctate. Podonotal shield ( figure 7A ) with 12 pairs of setae; mesonotal shields (150 across) each with seven setae; pygidial shield (220–225 across) bearing eight setae; marginal setae numerous, barbed, inserted on small plates or in leathery cuticle surrounding shields; lateral marginal setae (45–57) simple to barbed, posterolaterals longer (100–110) barbed, posteriors (58–60) barbed. Peritrematal shields broad, reticulate and truncate at level of coxae IV, uniting anteriorly, and bearing a pair of denticulate ridges and two pairs of setae (j1, z1); peritreme reaching to mid-coxa II. Sternal shield ( figure 8A ) bearing two pairs (st2, 3) of simple setae (24–35 long); st1 (40–45) strongly barbed, in soft cuticle; st4 (ca 35 long) lightly barbed, in soft cuticle. Tritosternum 75–90 long, base (33–35) with distal collar, laciniae fused basally, split distally. Ventrianal shield (245–250 M m across) reticulate, bearing seven pairs of simple to barbed setae (30–60 long); metapodal shields (95–97 on longest axis) reticulate. Opisthosomal gland openings supported by sclerotized rings (11–15 long, 9–12 wide), gld1 bracketed by large sclerotized pores. Mesogynial shield ( figure 8A ) bullet-shaped, with micropunctate ornamentation; latigynial region with two pairs of setae (st5, 6), anterior seta (28–33) in soft cuticle, posterior seta (28–36) on indistinct sclerite. Second cheliceral article (115–120 long) with fixed digit bearing gabelzahn and row of 11–13 teeth, the most basal enlarged; movable digit (40–47 long) with six to eight teeth; ventral excrescence (30–38 long) strongly fimbriate ( figure 8C ). Subcapitulum ( figure 8D ) with two pairs of rows of genal teeth, deutosternal gutter obsolete; corniculi (21–26) inserted dorsally; palpcoxal seta (22–25) and anterior hypostomal seta (26–31) barbed; external (28–33) and internal (38–43) setae attenuate; tectum rounded, denticulate ( figure 8B ). Leg I (460) longest, somewhat longer than leg IV (420). Coxae IV with acetabulum of seta pv retained; fleshy, fimbriated process in coxal acetabulum; pair of inguinal glands opening on postcoxal sclerite. Endogynium ( figure 3B ) with indistinct field supporting a pair of coarsely punctate regions (42–46 long) each with 9–19 oval punctae and flanked by a pair of boomerang-shaped sclerites (32–38).

Adult male. Chelicerae and body ( figure 8F ) similar to female except somewhat smaller (body 575–610 long); tectum ( figure 8E ) prolonged into bifurcate process; sternigenital region ( figure 7B ) with five pairs of sternal setae; genital valves at level of coxae III–IV, anterior valve (33–36) micropunctate, bearing two simple setae (15–21); posterior valve crescentic.

Etymology. This species is named in honour of Reg Williams who was instrumental in leading the author to the site where this mite was first discovered on Mt Field and in helping him to identify the plant association of the type locality.

Remarks. The specimens of D. reginaldi from Meander Reserve in northern Tasmania have fewer punctae on the vaginal sclerites than those from Mt Field (9–11 versus 15–18) in the extreme south of the island and tend to have fewer teeth on the cheliceral digits, but are otherwise indistinguishable. Both collections retain the insertion of a second seta (pv) on coxa IV, a plesiomorphy otherwise unknown in the family, and rare in the Trigynaspida.

Figures

FIG. 3. Endogynial complexes of (A) Davacarus gressetti Hunter; (B) Davacarus reginaldi, n. sp.; (C) Davacarus lindquisti, n. sp.

FIG. 7. Davacarus reginaldi, n. sp. (A) Dorsum of female; (B) venter of male. Scale bar: 100 Mm.

FIG. 8. Davacarus reginaldi, n. sp. (A–D) Female. (A) Sternogenital region; (B) tectum; (C) chelicera; (D) subcapitulum. (E, F) Male. (E) Tectum; (F) chelicera. Scale bars: 50 Mm.