Scapheremaeus tumidus, Colloff, Matthew J., 2011

Colloff, Matthew J., 2011, A new genus of oribatid mite, Spineremaeus gen. nov. and three new species of Scapheremaeus (Acari: Oribatida: Cymbaeremaeidae) from Norfolk Island, South-west Pacific, and their biogeographical affinities, Zootaxa 2828, pp. 19-37 : 28-31

Scapheremaeus tumidus sp. nov.

( Figs. 5 , 6 )

Dimensions. Holotype female length 438 μm, breadth 271 μm. Paratype females (n = 8) mean length 431 μm (range 406–454 μm), breadth 250 μm (range 233–270 μm). Ratio of length of prodorsum to total length: 0.19 (holotype).

Female. Prodorsum: Rostrum rounded; rostral seta (ro) 23 μm long, setiform, curved medially and parallel with rostrum, barely visible in dorsal view, on squat tubercle ( Fig. 5 a). Lamellar apophyses 26 μm long, extending to point anterior of rostrum, slightly converging apically; lamellar seta (le) 16 μm long, incurved, with bacilliform cerotegument. Costulae slightly convex, with anterior trans-costular ridge connecting bases of lamellar apophyses. Narrow lateral carinae present, connecting with bases of costulae. Prodorsum smooth. Bothridium with broad rim; bothridial seta (bs) club-shaped, stalk 12 μm long, head 20 μm long 16 μm broad, smooth, darkly pigmented. Interbothridial region with complex series of transverse and longitudinal ridges.

Notogaster: Length 350 μm; ratio of length to breadth 1.32. Circumdorsal scissure entire, oval, with diagonal extensions into humeral region ( Fig. 5 a). Dorsosejugal suture more-or less transverse medially, with shallow lateral concave regions laterally, becoming rounded in humeral region. Lenticulus oval, 30 μm long, 41 μm broad, with discrete margin. Circumnotogastral plate with oval protuberance either side of lenticulus, each with discrete margin. Humeral processes present but not clearly visible in dorsal view (cf. lateral aspect, below). Centrodorsal region 252 μm long, 177 μm broad, rounded posteriorly, centrodorsal region raised, shallow concavities posteriolaterally; with polygonal pattern of ridges and alveoli; porose strip around margin of centrodorsal region. Ten pairs of smooth, short (8–12 μm long), spiniform notogastral setae on short tubercles; anterior setae with bacilliform cerotegument, setae lm, lp and h series with dark, club-shaped cerotegument. Two pairs of setae on centrodorsal plate: lm and lp positioned on lateral margin. Circumnotogastral plate plicate, bearing eight pairs of setae: c 2 posterior of lyrifissure ia, la some distance posteriolateral to c 2; h series positioned on dorsal circumnotogastral plate, setae of p series on ventral circumnotogastral plate - not visible from above (cf. ventral region, below).

Ventral region: Epimeral setae thin, setiform, subequal in length (9–13 μm); formula 3-1-2-2 ( Fig. 5 b). Genital plates sub-hexagonal, with faint irregular ridges; each plate 64 μm long, 34 μm broad, with six pairs of setae; g 1 longer (13 μm) than others (7 μm), aligned with setae g 2-6. Ventral plate with irregular ridges anteriorly and medially; alveolate posteriolaterally. Anal setae setiform, 6–9 μm long, positioned at least their length from median edge of alveolate anal plates. Adanal setae minute, subequal in length (6–9 μm); ad 1-2 positioned on ridge immediately posterior of anal plates; ad 3 positioned at distance twice their length from the lateral margin of anal plates; mutual distance between ad 1 3 × their length, distance between ad 1 and ad 2 and between ad 2 and ad 3 1.4–1.6 × that between ad 1. Circumgastric scissure entire medially. Ventral circumnotogastral plate (cnv) plicate, bearing three pairs of short (6–9 μm), spinose setae of p series; distance between bases of p 1 same as between those of setae ad 1; distance between p 1 and p 2 2.1 × that between bases of p 1 and between p 2 and p 3 and 1.5 × that between p 1. Setae of p series slightly shorter (6–8 μm long) than those of h series (12–15 μm long).

Lateral aspect: Mid-line of rostrum vertical or slightly bowed posterioventrally; lamellar apophyses separated from prodorsum for their entire length ( Fig. 5 c). Lenticulus slightly flattened though projecting above dorsum. Humeral process broad, short, triangular, not extending ventrally as far as dorsal facies of acetabulum III. Centrodorsal region of notogaster from posterior of lenticulus to position anterior of setae h 3 domed, prominent. Lateral region shelf-like posterior of setae h 3 and p 3; surfaces of dorsal and ventral circumnotogastral plate wedge-shaped in caudal region.

Legs: Heterotridactylous; leg segments with ridged, linear cerotegument ( Fig. 6 ). Formulae: Legs I: 0-4-3(1)- 4(2)-15(2); Legs II 0-4-3(1)-3(1)-14(1); Legs III 0-3-1(1)-3(1)-14; Legs IV 0-3-2(1)-4(1)-14. Lengths of leg segments (femur to tarsus): Leg I: 104, 18, 42, 32 μm; Leg IV: 69, 10, 48, 34 μm. With pori on axial surface of femora I–IV and posteriodorsal surface of tarsi I–IV. Tarsus I squat, sub-triangular, as broad as long, with narrow, cylindrical apex. Proximal third of femur I narrow, cylindrical. Seta l " on tibia I stout, clavate and barbed apically; solenidion φ2 on small tubercle emerging from base of apophysis of solenidion φ1 ( Fig. 6 a); seta ft ' on tarsus IV long, stout, with clavate cerotegument apically ( Fig. 6 b).

Material examined. Holotype female, one paratype female, ANIC 3507, trough of flight intercept trap, Maurge Jowett’s [garden] (Red Road), Norfolk Island, 29° 0'38"S, 167°56'44"E, ca. 250 m., coll. M. Christian & M. Sexton, 8.iii.1985. Paratype female, ANIC 3506, same data as 3507 but coll. 1.ii.1985. Two paratype females, ANIC 3508, same data as 3507 but coll. 1.iv.1985. Four paratype females, two paratype males, ANIC 3509, trough of flight intercept trap, Red Road Track, Norfolk Island National Park, 29° 01'S, 167°57'E, coll. M. Christian & C. Baker, 8.ii.1985. Holotype and paratypes deposited in the Australian National Insect Collection, CSIRO Ecosystem Sciences, Canberra.

Etymology. The specific name, tumidus , is Latin, meaning ‘swollen’, referring to the pair of protuberances either side of the lenticulus.

Remarks. Scapheremaeus tumidus sp. nov. differs from other members of the genus by the following combination of characters: 1) the strongly medially-curved rostral setae running parallel to the outline of the rostrum, only clearly visible in ventral aspect; 2) the prominent lamellar apophyses with an anterior trans-costular ridge; 3) the complex series of transverse and longitudinal ridges on the interbothridial region; 4) the smooth head of the bothridial seta; 5) the lenticulus broader than long; 6) the oval protuberance either side of the lenticulus; 7) the porose strip around the margin of the centrodorsal region of the notogaster; 8) setae p shorter than h series and positioned on the ventral circumnotogastral plate.

Scapheremaeus tumidus is morphologically most similar to Sc. pacificus sp. nov. (cf. above) and, to a lesser extent, Sc. insularis Hammer, 1966 with which it shares the general shape of the costulae, carinae, lamellar setae and apophyses, the presence of anterior and posterior transverse prodorsal ridges, the broad oval lenticulus, and the smooth bothridial seta. Scapheremaeus tumidus differs from Sc. insularis in having smaller polygonate alveoli on the centrodorsal region, the absence of setae on the anterior margin of the centrodorsal plate, and the porose lateral strip around the centrodorsal plate.

Figures

FIGURE 5. Scapheremaeus tumidus sp. nov., holotype female; a) dorsal; b) ventral; c) lateral.

FIGURE 6. Scapheremaeus tumidus sp. nov., paratype female; a) right leg I, axial; b) right leg IV, axial.