Scapheremaeus walteri, 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 : 28-30

Scapheremaeus walteri sp. nov.

( Fig. 14 )

Scapheremaeus sp. s.: Walter et al., 1994, p. 224; Walter, 1995, p. 51; 1999, p. 75.

Dimensions. Holotype male: length 343, breadth 173; paratype male: length 339, breadth 170. Ratio of length of prodorsum to total length (holotype): 0.3.

Prodorsum. Anterior region smooth. Rostrum broad, U-shaped. Rostral seta (ro) smooth, curved ventromedially, ca. 25 long, their points overlapping ( Fig. 14 a). Lateral carinae present in the form of longitudinal ridges anterior of bothridia. Lamellar seta minute, on broad, squat tubercle, connected by slight, irregular ridge. Costulae irregular, with prominent pointed apices lateral of lamellar setae, connecting posteriorly with bases of carinae. Intercostular region a series of irregular ridges. Interbothridial ridge welldeveloped, not connecting with carinae or costulae. Sensillus with large, smooth, club-shaped, darklypigmented head, ca. 26 long, 17 broad, emerging on short stalk from bothridium (diameter 12) positioned adjacent to dorsosejugal suture. Region directly anterior of interbothridial ridge smooth.

Notogaster. Length 238. Circumdorsal scissure absent: circumnotogastral plate fused with centrodorsal plate ( Fig. 14 a). Lenticulus oval, broader than long (16 long, 25 broad), surrounded by thick rim of cuticle. Dorsosejugal suture transverse, slightly convex; outline of notogaster relatively narrow, U-shaped, broadest at level of setae lm; margins almost parallel. With posteriolateral concavities. Centrodorsal microsculpture consisting of large ovoid foveolae. With seven pairs of short notogastral setae, similar in size and shape, covered in dark, club-shaped cerotegument; lm and lp positioned on centrodorsal region, the others more laterally, on well-developed cylindrical tubercles. Setae of p series absent. With four pairs of lyrifissures visible dorsally, ventrally and caudally ( Figs. 14 a-c). Posterior margin of dorsal circumnotogastral plate rounded.

Ventral region. Epimeral setae setiform, thick, subequal in length, formula 3-1-2-2 ( Fig. 14 b). Microsculpture of ventral plate a series of large scattered foveolae. Genital plates sub-hexagonal, slightly longer than broad, surrounded by ridges of cuticle, with five pairs of longitudinally-aligned genital setae positioned close to, but not on, medial edges; setae same size and shape as epimeral setae. Anal setae setiform, 8, an 1 positioned near anterior margin of anal plate, an 2 near posterior margin. With one pair of adanal setae, ad 1, with dark, club-shaped cerotegument, on small tubercles. Ventral plate V-shaped.

Caudal aspect. Notogaster with lateral and central regions demarcated by slight furrow, indicating vestige of circumdorsal scissure ( Fig. 14 c). With well-developed circumferential scissure, apparent as double lines, ventral of setae of h series, indicating vestige of dorsal and ventral circumnotogastral plates.

Lateral aspect. Mid-line of rostrum vertical ( Fig. 14 d). Carinae evident. Hysterosoma not strongly dorsoventrally flattened. Seta ex absent. Humeral process consisting of shallow triangular ridge. Centrodorsal region markedly curved.

Legs. Heterotridactylous.

Material Examined. Holotype and paratype, ex. roots of Asplenium sp. on fallen Ficus sp., O’Reilly’s, Lamington National Park (28°19´S, 153°05´E), Queensland, coll. M.J. Colloff and D.E. Walter, 18.x.1994.

Etymology. Scapheremaeus walteri sp. nov. is named in honour of Dr David Evans Walter in recognition of his pioneering contribution to the ecology and systematics of mites in Australian forest canopies.

Remarks. Scapheremaeus walteri sp. nov. differs from other members of the genus by the following combination of characters: 1) the absence of the circumnotogastral scissure; 2) with only one pair of adanal setae; 3) the absence of setae of the p series, leaving seven pairs of notogastral setae; 4) five pairs of genital setae; 5) costulae with acute apices lateral of tubercles of lamellar setae, 6) lenticulus broader than long; 7) the almost parallel margins of the notogaster; 8) the V-shaped ventral plate; 9) microsculpture of notogaster and ventral plate consisting of large ovoid foveolae.

Scapheremaeus walteri sp. nov. is a member of the Emarginatus species-group. The other members, S. emarginatus Hammer, 1966 ; S. striatomarginatus Hammer, 1979 and S. morenoi ( Balogh & Mahunka, 1974) all lack the circumnotogastric scissure, have a sub-rectangular or U-shaped notogaster with foveolate or polygonate microsculpture. The prodorsum has a diffuse, complex series of ridges, including costulae, lateral carinae and a translamellar ridge with short lamellar setae and their tubercles. Scapheremaeus walteri sp. nov. is the only one that definitively lacks setae of the p series.

Figures

FIGURE 14. Scapheremaeus walteri sp. nov. a) dorsal; b) ventral; c) caudal; d) lateral.