Scapheremaeus euthemellus, 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 : 14-16

Scapheremaeus euthemellus sp. nov.

( Fig. 7 )

Dimensions. Holotype female: length 460, breadth 273; paratype female: length 414, breadth 229. Ratio of length of prodorsum to total length (holotype): 0.4.

Prodorsum. With pattern of irregular ridges laterally ( Fig. 7 a). Rostrum blunt, rounded; rostral seta (ro) smooth, curved, ca. 30 long. Lateral carinae absent. Lamellar seta minute (7), spiniform, with dark, clubshaped cerotegument, on short tubercle. Apical trans-costular ridge present. Costulae straight, converging apically, extending posteriorly as far as bothridia, with strongly-developed interbothridial ridge. Inter-costular region with polygonal plaques. Interlamellar seta absent. Sensillus with large, smooth, club-shaped, darklypigmented head, ca. 28 long, 20 broad ( Fig. 7 e), emerging on short stalk from bothridium (diameter 17) positioned at least its own diameter from dorsosejugal suture. Region posterior of interbothridial ridge with irregular plaques.

Notogaster. Length 320. Circumdorsal scissure entire ( Fig. 7 a). Lenticulus ovoid, broader than long (25 long, 35 broad) with diffuse lateral and anterior margin and well-developed posterior ridge extending as far as setae c 2. Humeral process well-developed, broadly triangular when viewed dorsally. Centrodorsal plate 250 long, 165 broad, oval, broadest at level midway between setae lm and lp, with well-developed posterior centrodorsal ridge and lateral concavities ( Figs. 7 a,h). Dorsal circumnotogastral plate plicate. Centrodorsal microsculpture consisting of irregular transverse ridges and foveolae ( Fig. 7 a). With ten pairs of notogastral setae; those of c, l and h series bacilliform, short (ca. 20-25), smooth, covered in dark, club-shaped cerotegument ( Figs. 7 c,d), positioned on well-developed conical tubercles; two pairs of setae on centrodorsal plate, five pairs on dorsal circumnotogastral plate; with three pairs of setae in p series, spiniform, with or without cerotegument ( Figs. 7 f,g), positioned on ventral circumnotogastral plate. Opening of gla positioned anteriolateral of seta lp. With four pairs of lyrifissures visible dorsally. Posterior margin of dorsal circumnotogastral plate crenellated, rounded.

Ventral region. Epimeral setae setiform, setae 1b longer than others - almost twice the length of 1a, formula 3-1-2-2 ( Fig. 7 b). Microsculpture of ventral plate with irregular ridges and plaques. Sub-hexagonal striate genital plates slightly longer than broad, with six pairs of genital setae positioned close to, but not on, medial edges; g 1 positioned lateral of g 2-6; seta g 2 26 long, almost twice as long as other genital setae. Longitudinal ridges lateral of genital plates. Anal setae spiniform, 12, positioned almost their length from median edge of striate anal plates. With three pairs of spiniform adanal setae, ad 3 longer than others; ad 1 of holotype with club-shaped cerotegument. Posterior margin of ventral circumnotogastral plate incised.

Lateral aspect. Mid-line of rostrum vertical ( Fig. 7 h). Hysterosoma dorsoventrally flattened. Exobothridial seta absent. Humeral process a broad, triangular ridge.

Legs. Heterotridactylous; covered in thick cerotegument consisting of irregular plaques; porose areas on trochantera and femora. Seta l " on tibia I straight, thick, barbed, club-shaped; Solenidion φ2 on tibia I emerging from apophysis positioned on dorsal surface of apophysis of φ1. Solenidion ω on tarsus II with clubshaped tip.

Material Examined. Holotype and one paratype from a pyrethrin knock-down sample from mosses on a tree trunk, callidendrous rainforest dominated by Nothofagus cunninghami , coll. H. Mitchell and R. Coy, 25.xi.1989, on the slopes of Mount Victoria, within 100- 500 m. of the walking track, Mount Victoria Forest Reserve, Tasmania, 41°20´S, 147°50´E, ca. 900 m., mean annual rainfall 1600 mm.

Etymology. The specific name euthemellus is Latinised Greek for ‘pretty little thing’.

Remarks. Scapheremaeus euthemellus sp. nov. differs from other members of the genus by the following combination of characters: 1) lenticulus oval, broader than long; 2) setae lm, lp and the h series on welldeveloped conical tubercles; 3) minute lamellar setae with club-shaped, dark cerotegument; 4) setae g 1 about twice the length of the other genital setae and g 2 displaced laterally; 5) setae 1b about twice the length of the other epimeral setae; 6) the irregularly foveolate centrodorsal microsculpture with a well-developed posteriomedian ridge projecting onto the dorsal circumnotogastral plate, and with prominent posteriolateral depressions.

Scapheremaeus euthemellus sp. nov. is a member of the Petrosus species-group. It shares with S. truncatus sp. nov. (cf. below) the trapezoid shape formed by the costulae, interlamellar and interbothridial ridges, which contain large, irregular cuticular plaques, as well as the indented margin of the circumnotogastral plate in the humeral region. It differs in having a smooth sensillus (that of S. truncatus sp. nov. is tuberculate) and ridged (as opposed to striate) microsculpture on the ventral plate, as a well the prodorsum being rounded anteriorly, rather than truncate.

Figures

FIGURE 7. Scapheremaeus euthemellus sp. nov. a) dorsal; b) ventral; c) detail of setae lm; d) detail of seta lp; e) detail