Scapheremaeus bulbosensillatus, Colloff, Matthew J., 2010

Colloff, Matthew J., 2010, The hyperdiverse oribatid mite genus Scapheremaeus (Acari: Oribatida: Cymbaeremaeidae) in Australia, with descriptions of new species and consideration of biogeographical affinities, Zootaxa 2475, pp. 1-38 : 11-14

Scapheremaeus bulbosensillatus sp. nov.

( Figs. 4 , 5, 6)

Dimensions. Holotype female: length 422, breadth 242; paratype females: length 460, 432, breadth 257, 265; paratype male: length 364, breadth 207. Ratio of length of prodorsum to total length (holotype): 0.3. Tritonymph length 460, breadth 278.

Adult: Prodorsum. With pattern of irregular short ridges (Fig. 5a). Rostrum blunt, rostral seta (ro) smooth, curved, ca. 23 long, positioned on short tubercle. Lateral carinae absent. Lamellar seta spiniform, 16, on short tubercle. Apical trans-costular ridge present. Costulae concave laterally, extending posteriorly as far as bothridia. Interlamellar seta absent. Sensillus with large, club-shaped, darkly-pigmented head, ca. 34 long, 26 broad, with elongate striations, emerging on short stalk from bothridium (diameter 19) almost abutting dorsosejugal suture. With irregular interbothridial ridge present.

Notogaster. Length 296. Circumdorsal scissure entire (Fig. 5a). Lenticulus elongate ovoid (27 x 18). Humeral process prominent, spine-shaped when viewed dorsally. Centrodorsal plate 233 long, 146 broad, oval, broadest at level midway between setae lm and lp, with reticulate microsculpture consisting of irregular ridges with nodes (Fig. 5d). Dorsal circumnotogastral plate plicate. With ten pairs of smooth, setiform notogastral setae (ca. 20–25), covered in cerotegument (Fig. 5c), positioned on short tubercles; two pairs on centrodorsal plate, five pairs on dorsal circumnotogastral plate; with three pairs of setae in p series positioned on ventral circumnotogastral plate (Fig. 5b). Opening of gla positioned anteriomedial of lyrifissure ih. With four pairs of lyrifissures visible dorsally. Posterior margin of distal circumnotogastral plate heavily crenellated, rounded.

Ventral region. Epimeral setae setiform, subequal in length, formula 3-1-2-2 (Fig. 5b). Microsculpture of ventral plate irregularly ridged. Sub-hexagonal genital plates slightly longer than broad, ornamented with irregular ridges, with six pairs of longitudinally-aligned genital setae (ca. 9–13) positioned close to, but not on, medial edges. Genital plates surrounded by thickened ridge. Anal setae spiniform, 7, positioned at least their length from median edge of anal plates, on posterior half of plates. Anal plates with irregular longitudinal ridges. With three pairs of short (9) spiniform adanal setae, positioned at least their length from anal plate. Ventral surface of circumnotogastral plate rounded posteriomedially.

FIGURE 5. Scapheremaeus bulbosensillatus sp. nov. a) dorsal; b) ventral; c) seta c 2; d) detail of microsculpture of Legs. Heterotridactylous; covered in thick cerotegument consisting of irregular plaques; porose areas on trochantera and femora. Seta l " on tibia I spiniform, curved, thick, strongly barbed ( Fig. 4 e). Solenidia φ1 and φ2 on tibia I emerging from common apophysis. Formula Leg I: 1-4-2(1)-4(2)-14(2); Leg II: 1-4-3(1)-3(1)- 12(1); Leg III: 1-2-2(1)-3(1)-11; Leg IV: 1-2-1(1)-3(1)-10.

Tritonymph: Prodorsum. With pattern of irregular short ridges ( Fig. 6 a). Rostrum blunt, rostral seta (ro) smooth, curved, ca. 27 long. Lateral carinae absent. Lamellar seta spiniform, 11. Apical, medial and posterior trans-costular ridges present. Costulae slightly concave laterally, extending posteriorly as far as bothridia. Interlamellar setae present, bacilliform, 10 long. Sensillus elongate, club-shaped, darkly-pigmented, head, ca. 33 long, 18 broad, with elongate striations. With longitudinal and transverse interbothridial ridge present.

Notogaster. Length 305, with pattern of transverse irregular plications. With eleven pairs of notogastral setae of which eight are visible in dorsal view: two in c series, three in l series and three in h series, with three in p series positioned ventrally ( Fig. 6 a) Dorsal setae (ca. 20–25), setiform to spinose, covered in club-shaped dark cerotegument, positioned on short tubercles.

Ventral region. Epimeral setae setiform, subequal in length, formula 3-1-2-2 ( Fig. 6 b). Ventral plate plicate, epimeral plates porose. With five pairs of longitudinally-aligned minute genital setae (ca. 8), one pair of aggenital setae, two pairs of anal setae, three pairs of adanal setae. Setae of p series short, spiniform.

Material Examined. Holotype female, co-occurring with white wax scale Ceroplastes destructor ( Hemiptera : Coccidae ), on Large-leaf Hop-bush, Dodonaea triquetra J.C. Wendl., Sydney , New South Wales, 3.ix.1928. Paratype female and paratype male, under bark of mistletoe, Sydney, New South Wales, coll. S.L. Allman, 16.viii.1934 (ex. Biological and Chemical Research Institute, New South Wales Department of Agriculture, Rydalmere, New South Wales). One paratype female, on bark of eucalypt, Sydney, New South Wales, 16.viii.1934 [coll. S.L. Allman]. Other material: one tritonymph, on bark of eucalypt, Sydney, New South Wales, 16.viii.1934 [coll. S.L. Allman]. Holotype and paratypes in the Agricultural Scientific Collection, New South Wales Department of Primary Industries, Orange.

Etymology. The specific name of this species refers to its exceptionally large, rounded sensillus.

Remarks. Scapheremaeus bulbosensillatus sp. nov. differs from other members of the genus by the following combination of characters: 1) the large, inflated oval, smooth sensillus with longitudinal striae; 2) the strongly crenellated posterior margin of the dorsal circumnotogastral plate; 3) the reticulate, ridged microsculpture of the centrodorsal region, with prominent nodes; 4) the well-developed humeral processes, projecting laterally and clearly visible from above.

The tritonymph is associated with the adult on the basis of the morphology of the sensillus with characteristic longitudinal striae and its co-occurrence in a sample from Eucalyptus bark. Setae in and c 1, present in the tritonymph, are absent in the adult. In S. argentinensis Travé & Fernandez, 1986 and S. tillandsiae Fernandez & Cleva, 1997 the deutonymph has fifteen pairs of notogastral setae, the tritonymphs and adults have ten pairs. The exobothridial and interlamellar setae are lost in the tritonymphal-adult moult in both species.

Scapheremaeus bulbosensillatus sp. nov. is a member of the Petrosus species-group. It is morphologically most similar to S. minjambuta sp. nov. (cf. below) with which it shares well-developed humeral processes, similar centrodorsal microsculpture, and rostral and lamellar setae of similar shape and size, but it differs in the shape and dimensions of the sensillus, the well-defined costulae and the vertical alignment of the genital setae. In S. minjambuta sp. nov. seta g 1 is displaced laterally and the costulae are represented by a diffuse series of ridges.

Figures

FIGURE 6. Scapheremaeus bulbosensillatus sp. nov. tritonymph a) dorsal; b) ventral.

FIGURE 4. a) Scapheremaeus baylyi sp. nov., circumnotogastral plates, viewed ventrally (centrodorsal plate removed); b – e) tibiae I (right, antiaxial); b) Scapheremaeus allmani sp. nov., showing cerotegument; c) Scapheremaeus tuberculosus sp. nov.; d) Scapheremaeus alisonae sp. nov.; e) Scapheremaeus bulbosensillatus sp. nov.