Scapheremaeus pacificus, 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 : 25-28

Scapheremaeus pacificus sp. nov.

( Figs. 3 , 4 )

Dimensions. Holotype female length 410 μm, breadth 244 μm. Paratype females (n = 6) mean length 419 μm, (range 403–438 μm), mean breadth 248 μm (range 239–255 μm). Paratype male lengths 378, 391 μm, breadths 224, 240 μm. Ratio of length of prodorsum to total length: 0.25 (holotype).

Female. Prodorsum: Rostrum rounded; rostral seta (ro) 18 μm long, setiform, curved medially ( Fig. 3 a). Lamellar apophyses 20 μm long, incurved apically, broadening basally, mutual distance at base subequal to length; extending anteriorly not as far as rostrum; lamellar seta (le) 11 μm long, incurved, bacilliform, with club-shaped cerotegument. Costulae parallel, straight, with anterior trans-costular ridge connecting bases of lamellar apophyses; with posterior ridge demarcated anteriorly by row of tubercles and ridges, with strongly-developed tubercle at base of each costula. Well-developed lateral carinae connected posteriorly with bases of costulae, anteriorly by transverse ridge. Prodorsum ridged medially and laterally. Bothridium with broad rim; bothridial seta (bs) club-shaped, stalk 18 μm long, head 28 μm long 21 μm broad, with longitudinal striations, darkly pigmented. Interbothridial region with complex series of transverse and longitudinal ridges.

Notogaster: Length 310 μm; ratio of length to breadth 1.28. Circumdorsal scissure entire, oval, with diagonal extensions into humeral region; margin on centrodorsal plate side with series of shallow undulations ( Fig. 3 a). Dorsosejugal suture more-or-less convex, with blunted projection in humeral region. Humeral processes not visible from above. Lenticulus sub-rectangular, 26 μm long, 15 μm broad, with discrete margin, U-shaped posteriorly. Circumnotogastral plate with flat oval protuberance either side of lenticulus, each with discrete margin and digitate ridges anteriorly. Centrodorsal region 231 μm long, 172 μm broad, rounded posteriorly, with pattern of ridges and large, polygonate alveoli; circumference not so ornamented. Ten pairs of smooth, short, bacilliform notogastral setae on short tubercles; setae lm, lp and h series slightly longer (16–19 μm) than la and c 2 (11–13 μm) with dark, club-shaped cerotegument. Two pairs of setae on centrodorsal plate: lm and lp positioned on lateral margin. Dorsal 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, very short (5–8 μm); formula 3-1-2-2 ( Fig. 3 b). Genital plates sub-hexagonal, with faint irregular ridges; each plate 59 μm long, 28 μm broad, with six pairs of setae, sub-equal in length (13 μm), all in alignment. Ventral plate with irregular plaques anteriorly and polygonal alveoli and ridges posteriolaterally. Anal setae setiform, 6–9 μm long, positioned at least their length from median edge of alveolate anal plates. Adanal setae subequal in length (7–10 μm); ad 1-2 positioned almost 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 sub-equal to that between ad 1 and ad 2; distance between ad 2 and ad 3 2 × that between ad 1. Circumgastric scissure (cgs) entire medially, not indented. Ventral circumnotogastral plate (cnv) plicate, bearing three pairs of minute (6–9 μm), setiform 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 × that between bases of p 1; distance between p 2 and p 3 1.4 × that between p 1.

Lateral aspect: Mid-line of rostrum vertical, slightly concave; lamellar apophyses separated from prodorsum for their entire length ( Fig. 3 c). Lenticulus slightly flattened though projecting above dorsum. Humeral process reduced to minute triangular ridge ventral of seta c 2. Hysterosoma dorsoventrally flattened. Centrodorsal region of notogaster from posterior of lenticulus to caudal margin shallowly convex. Surfaces of dorsal and ventral circumnotogastral plate separated by well-developed circumferential scissure (cf) and wedge-shaped in caudal region.

Legs: Heterotridactylous, central claw barbed along dorsal surface; leg segments with ridged, polygonate cerotegument ( Fig. 4 ). Formulae: Leg I: 0-4-2(1)-2(2)-14(2); Leg II 0-3-2(1)-3(1)-14(2); Leg III 1-2 -1(1)-2(1)-13; Leg IV 1-2 -1(1)-2(1)-12. Lengths of leg segments (femur to tarsus): Leg I: 93, 19, 37, 23 μm; Leg II: 92, 15, 36, 33; Leg III: 76, 20, 54, 42 μm; Leg IV: 71, 18, 52, 44 μm. With pori on axial surface of femora I–IV and posterioventral surface of tarsi I–IV. Tarsus I squat, sub-triangular, only slightly longer than broad, with narrow, cylindrical apex. Solenidion φ2 on small tubercle emerging from base of apophysis of solenidion φ1 ( Fig. 4 a). Seta l " on tibia I and ft ' on tarsus IV stout, elongate, with clavate cerotegument apically ( Figs. 4 a, 4b).

Material examined. Holotype female, paratype female, 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. One paratype female, one paratype male, ANIC 3505, trough of flight intercept trap, Filmy Fern Gully, Norfolk Island National Park, 29°01'S, 167°57'E, ca. 180 m., coll M. Christian, 17.iv.1985. One paratype female, ANIC 3506, 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. 1.ii.1985. One paratype female, ANIC 3508, same data as 3506, but coll. 1.iv.1985. Two paratype females, one paratype male, ANIC 3511, same data as 3509 but coll. M. Christian, 17.iv.1985. Holotype and paratypes deposited in the Australian National Insect Collection, CSIRO Ecosystem Sciences, Canberra.

Etymology. This species is named for the Pacific Ocean.

Remarks. Scapheremaeus pacificus differs from other members of the genus by the following combination of characters: 1) the flat oval protuberance either side of the lenticulus, each with anterior digitate ridges; 2) the incurved lamellar apophyses with an anterior trans-costular ridge and parallel costulae; 3) the bothridia with longitudinal striae; 4) the polygonate, ridged centrodorsal region; 5) the large lateral tubercles at the junction between the base of each costula and the posterior trans-costular ridge; 6) the U-shaped ridge posterior of the sub-rectangular lenticulus; 7) the undulating margin of the centrodorsal plate; 8) with setae p shorter than those of the h series and positioned on the ventral circumnotogastral plate; 9) the reticulate, ridged, rectangular region between the costulae and the anterior and posterior transcostular ridges; 10) the tuberculate posterior trans-costular ridge; 11) the lateral carinae and the well-developed transverse ridge between them.

Scapheremaeus pacificus is a member of the Carinatus species-group ( Colloff, 2009), based on the presence of lateral carinae, an anterior transcostular ridge and the humeral extensions of the circumnotogastral scissure. It belongs to a sub-group which have elongated lamellar apophyses and which includes Sc. allmani Colloff, 2010a ( Australia) ; Sc. balazsi Mahunka, 1983 ( Surinam) ; Sc. bicornutus Hammer, 1971 ( Fiji) ; Sc. chaac Rios & Palacios- Vargas, 1998 ( Mexico); Sc. fisheri Aoki, 1966 (Hawaii) ; Sc. insularis Hammer, 1966 ( New Zealand); Sc. semiconvexus Hammer, 1982 (Bali) ; Sc. tuberculosus Colloff, 2010a ( Australia) , Sc. tumidus sp. nov. ( Norfolk Island, cf. below) and Sc. uncinatus Wang, 1998 ( China) .

Scapheremaeus pacificus shares with Sc. tumidus the general shape of the costulae, carinae and lamellar apophyses, the presence of anterior and posterior transverse prodorsal ridges, the small setae of the p series positioned ventrally but differs in having much reduced humeral processes, a smaller elongate lenticulus, larger polygonate alveoli on the centrodorsal region, longitudinally striate bothridial setae, an alveolate epimeral region, with lyrifissurae im and ih located more anteriorly and the convex curve of the centrodorsal region extends further posteriorly in lateral view. Scapheremaeus pacificus is closest morphologically to Sc. insularis with which it shares the polygonate pattern of the centrodorsal shield, very similar morphology of the lamellar apophyses and the flat oval protuberance either side of the lenticulus, each with anterior digitate ridges. The two species appear to differ in the positions of the notogastral setae. But the pair of setae on the dorsal circumnotogastral plate anteriolateral of h 1 illustrated by Hammer (1966, her Fig. 53) are most probably lyrifissurae ip which are normally in this position. The position of the setae on the anterior margin of the centrodorsal plate of Sc. insularis requires confirmation. No other species of Scapheremaeus has setae in this position.

Figures

FIGURE 3. Scapheremaeus pacificus sp. nov., holotype female; a) dorsal; b) ventral; c) lateral.

FIGURE 4. Scapheremaeus pacificus sp. nov., paratype female; a) left leg I, anti-axial; b) right leg IV, axial. Pori are on axial surfaces.