Scapheremaeus

Norton, Roy A. & Franklin, Elizabeth, 2010, Scapheremaeus rodickae n. sp. (Acari: Oribatida: Cymbaeremaeidae) associated with temporary rock pools in Georgia, with key to Scapheremaeus species in eastern USA and Canada, Zootaxa 2393, pp. 1-16 : 12

Key to described species of Scapheremaeus known from eastern USA and Canada

1. All leg pretarsi tridactylous, with strong empodial claw and thin lateral claws. Rostrum broadly and evenly rounded; costulae and connecting ridges form small trapezoid, narrowest anteriorly. Microsculpture of central region of notogaster mostly of large, irregular transverse ridges. 460–540 μm ................................ S. marginalis (Banks) , Fig. 6 B.

- All leg pretarsi monodactylous. Rostrum tapered anteriorly, parabolic in outline; costulae strongly or weakly defined, connecting ridges present or absent, but central area not in form of small trapezoid. Microsculpture of central notogaster usually alveolate-reticulate; if with irregular ridges, patterns appear more longitudinal than transverse ..................................................................................................................................................................................... 2

2. Circumdorsal scissure with inverted U-shape, centrodorsal region of notogaster not separated from lateral regions posteriorly. Notogastral microsculpture uniformly and densely areolate, with thick separating ridges almost as wide as small areoles. Bothridial seta with flattened, fan-shaped head, brown in transmitted light, longitudinal ridges clearly visible. 410–450 μm ............................................................................................... S. rodickae n. sp., Fig. 6 A.

- Circumdorsal scissure elliptical, completely isolating centrodorsal region of notogaster as separate plate. Notogastral microsculpture with larger or more poorly defined areoles. Bothridial seta clavate to subcapitate, with thicker, more massive head; head black, longitudinal ridges (if present) inconspicuous in transmitted light .......................... 3

3. Posterior margin of notogaster evenly convex in dorsoventral aspect. Distal setae of leg tarsi with tips conspicuously expanded to twice width of seta immediately proximal to tip (“tenet hairs”). 300 μm (single known specimen) ........ ................................................................................................................................................... S. pulchellus (Berlese)

- Posterior margin of notogaster medially concave in dorsoventral aspect. Distal setae of leg tarsi finely attenuate ( S. parvulus ) or very slightly expanded at tip ( S. palustris ) ............................................................................................. 4

4. Prodorsum without transverse ridge connecting costulae anteriorly; with narrow, sharply defined proximal ridges forming flattened “X”. Bothridial setae clavate, with head much longer than wide. Notogaster with pair of longitudinal ridges bearing setae lm and lp, and short extension of circumdorsal scissure toward humeral region on each side; alveolae of microsculpture all completely circumscribed by pattern of relatively reticulate ridges; each notogastral setae emerging through center of large alveola. 355–425 μm ....................................... S. parvulus (Banks) , Fig. 6 D.

- Prodorsum with costulae connected anteriorly by transverse ridge; with single irregular transverse proximal ridge (if with “X” then anterior arms very short). Bothridial seta subcapitate; head little longer than wide. Notogaster without longitudinal ridges or extensions of circumdorsal scissure; alveolae often irregular, incompletely formed or merged due to absence of separating reticulation; notogastral setae not emerging through conspicuous alveolae. 440–480 μm ...................................................................................................................................... S. palustris (Sellnick) , Fig. 6 C.

Figures

FIGURE 6. Scapheremaeus species from eastern USA and Canada, dorsal aspect: A) S. rodickae n. sp.; B) S. marginalis (Banks); C) S. palustris (Sellnick); D) S. parvulus (Banks). Differential interference contrast illumination, layered from 6 – 8 sequentially focused images. Scale bars 50 μm.