Scapheremaeus nivalis, 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 : 18-20

Scapheremaeus nivalis sp. nov.

( Fig. 9 )

Dimensions. Holotype female: length 480, breadth 207; paratype females: length 469, 439, 381; breadth 248, 223, 211; paratype males 356, 363; breadth 167, 182. Ratio of length of prodorsum to total length (holotype): 0.24.

Prodorsum. Rostrum broad, with sparse tubercles. Rostral seta short (10), slightly curved, setiform ( Fig. 9 a). Lamellar seta 11, bacilliform, covered in club-shaped dark cerotegument, emerging from squat tubercle positioned at apex of costula and attenuated, lateral carina, converging with costula. Apical trans-costular ridge absent, medial ridge present. Costulae more or less parallel, extending posteriorly to point anterior of bothridia. Lateral margins of prodorsum with irregular ridges. Interbothridial ridge and interlamellar seta absent. Inter-costular region with polygonal plaques. Sensillus with large, tuberculate, club-shaped, darklypigmented head, ca. 26 long, 14 broad, emerging on short stalk from bothridium (diameter 17), almost abutting dorsosejugal suture. Interbothridial region with irregular plaques.

Notogaster. Length 365. Circumdorsal scissure entire, with diagonal humeral extensions ( Fig. 9 a). Lenticulus sub-rectangular (28 long, 26 broad) with discrete margin. Humeral process not visible dorsally. Centrodorsal plate 280 long, 170 broad, oval, broadest at level midway between setae lm and lp. Without welldeveloped posterior centrodorsal ridge or posteriolateral concavities. Dorsal circumnotogastral plate plicate. Centrodorsal microsculpture consisting of irregular transverse ridges and foveolae; ridges bearing small tubercles ( Fig. 9 d). With nine pairs of notogastral setae; those of c, l and h series bacilliform or spiniform, short (ca. 12-15), smooth, covered in dark, club-shaped cerotegument, positioned on short tubercles; two pairs of setae on centrodorsal plate, five pairs on dorsal circumnotogastral plate; with two pairs of setae in p series, positioned on ventral circumnotogastral plate. Opening of gla not visible. With five pairs of lyrifissures visible dorsally; ia positioned on dorsal circumnotogastral plate, anterior of seta c 2. Posterior margin of dorsal circumnotogastral plate rounded.

Ventral region. Epimeral setae setiform, subequal in length; formula 3-1-2-2 ( Fig. 9 b). Microsculpture of ventral plate with irregular ridges and plaques. Sub-hexagonal genital plates, with irregular ridges, slightly longer than broad, with six pairs of longitudinally-aligned genital setae positioned close to, but not on, medial edges of plates. Well-developed shallow arcuate ridge anterior of genital plates, with setae 4a at either end. Minute aggenital setae (5) positioned laterally of setae g 6. Anal setae spiniform, 10, positioned on posterior halves of anal plates, almost their length from the median edge. Anal plates with longitudinal ridges. With only two pairs of spiniform adanal setae Posterior margin of circumgastric scissure produced into a pointed ridge.

Lateral aspect. Mid-line of rostrum vertical ( Fig. 9 c). Hysterosoma dorsoventrally flattened. Exobothridial seta absent. Humeral process a broad, triangular ridge.

Legs. Heterotridactylous; covered in thick cerotegument consisting of irregular ridges; porose areas on trochantera and femora. Seta l " on tibia I spiniform, straight, thick, barbed. Formula Leg I: 1-4-3(1)-4(2)- 14(2); Leg II: 1-4-3(1)-3(1)-12(1).

Material Examined. Holotype female, two paratype females and two paratype males, ex. lichen ( Usnea sp.) on Melaleuca sp., Snowy River, 1 km south of Willis (36°56´S, 148°25´E), New South Wales, coll. M.J. Colloff, 18.iii.1996. One paratype female, litter from tree fern, in riparian zone, coastal Angophora and Eucalyptus forest, Quarry Beach, Mallacoota (37°35'S 149°44'E), Croajingolong National Park, Victoria, coll. J. Błoszyk & S. Konwerski, 3.viii.2007 (CRO-010).

Etymology. The specific name nivalis is Latin for ‘snowy’ and is a reference to the high-altitude, cold climate conditions of its type locality on the Snowy River.

Remarks. Scapheremaeus nivalis sp. nov. differs from other members of the genus by the following combination of characters: 1) translamella absent; 2) lenticulus sub-rectangular; 3) sensillus tuberculate; 4) circumgastric scissure with a pointed ridge posterior of the anal plate; 5) nine pairs of notogastral setae (p 3 absent); 6) two pairs of adanal setae (ad 3 absent).

Scapheremaeus nivalis sp. nov. is a member of the Carinatus species-group, with clear, well-developed humeral extensions of the circumnotogastral scissure and short but well-developed lateral carinae extending on either side of the lamellar setae, as mentioned above in the remarks section of S. alisonae sp. nov., to which S. nivalis sp. nov. is morphologically most similar. They share the reduced number of setae in the p and ad series and a similar arrangement of short lateral carinae, a transbothridial ridge and a lack of an interlamellar ridge. They differ in that the costulae of S. alisonae are disconnected from the tubercles of the lamellar setae and in their centrodorsal microsculpture: that of S. nivalis sp. nov. being ridges and foveolae, that of S. alisonae sp. nov. being tessellated tubercles.

Figures

FIGURE 9. Scapheremaeus nivalis sp. nov. a) dorsal; b) ventral; c) lateral; d) detail of centrodorsal microsculpture.