Epidamaeus michaeli (Ewing, 1909)

Norton, Roy A. & Ermilov, Sergey G., 2021, Redescriptions of North American Epidamaeus (Acari, Oribatida, Damaeidae) species proposed by N. Banks, H. E. Ewing, A. P. Jacot, and J. W. Wilson, Zootaxa 5021 (1), pp. 1-65 : 16-20

Epidamaeus michaeli (Ewing, 1909)

( Figs 6–11 )

Damaeus michaeli Ewing, 1909a, p. 129 ; Woolley (1957)

Belba michaeli (Ewing, 1909) ; Wilson (1936, p. 262; see R6)

Epidamaeus michaeli (Ewing, 1909) ; Marshall et al. (1987, p. 142; see R6)

Damaeus (Epidamaeus) michaeli (Ewing, 1909) ; Subías (2004, p. 79; see R6)

Oribata canadensis Banks, 1909, p. 139 (new synonymy; see R8)

Epidamaeus canadensis (Banks, 1909) ; Norton (1979a, p. 604)

Damaeus (Epidamaeus) canadensis (Banks, 1909) ; Subías (2004, p. 79)

Diagnosis

Epidamaeus species with total length of adult 448–563. Cerotegument mostly with thick loose layer of filamentous excrescences; exuvial scalps usually present on notogaster. Propodolateral apophyses absent; postbothridial enantiophysis dimorphic: Ba prominent, conical, Bp represented only by inconspicuous ridge. Bothridial setae bacilliform, with or without weakly lanceolate head. Notogaster with spina adnata straight, relatively thin, barely reaching level of tubercle Ba; setae of c -, l - and h -series acicular, radially directed. Parastigmatic enantiophysis with

1 Seniczak et al. (2016) identified a third seta on femur I as v 2 ’ but probably it is v 2 ʺ; if only one seta from this verticil exists, it is v 2 ʺ, which is the less regressive member of the pair ( Norton 1977).

Sa and Sp similar, horn-like, converging. Ventral enantiophyses E2 and V present, M absent; discidium thorn-like. Seta ad 3 close to anal plate. Leg IV 1.3–1.4 times body length; femur IV slightly longer (1.2–1.3) than trochanter IV; Nymphs with famulus minute, non-emergent from sunken pit.

Adult

Dimensions. Total length and maximum width (n = 5 females, 10 males) 448–563 × 265–332; males usually smaller (448–528) than females (520–563).

Integument. Color of preserved specimens yellowish to medium brown. Cerotegument conspicuous, mostly thick, loose mat of filamentous excrescences having dense external layer of spherical particles ( Figs 7E, F , 8D ); with variable amounts of entrapped small fungal spores and extraneous particles. Setae usually without intrinsic cerotegument (may have overlapping filaments from nearby cuticle); larger setae pigmented, greyish brown to light grey. Procuticle mostly smooth, but locally microtuberculate (e.g. grooves, enantiophyses, most of lateral prodorsum). Usually with full stack of juvenile exuvial scalps, usually lacking adherent fecal pellets, eggshells, or other large debris ( Fig. 7A ).

Prodorsum ( Fig. 6A, B ). Body wall anterior to acetabulum I nearly transverse in dorsal view; that of acetabulum II broadly rounded (propodolateral apophysis absent). Tubercles of postbothridial enantiophysis unequal (Ba strong, subconical, distally rounded; Bp represented only by short strong contour or thickened transverse ridge); tubercle Da and laterosejugal enantiophysis absent. Sigillar patches of cheliceral and subcapitular muscles conspicuous in transmitted light. Short but distinct transverse contour present anterior to each bothridium, appearing like ridge in dorsal view. Bothridium with projecting part funnel-shaped, with weak vertical banding; mutual distance of pair slightly greater than that of tubercles Ba. Bothridial setae long (150–218), bacilliform, distal two-thirds with inconspicuous minute barbs ( Fig. 7D ); distally acute or with weakly developed, lanceolate to spindle-shaped head ( Fig. 7C ). Setae ro (65–69) and le (77–93) finely attenuate, barbed in proximal half, curved anteromediad, le slightly thicker than ro; in (41–50) almost straight, acicular, barbed, usually directed posteromediad; ex (41–50) thin, attenuate, barbed; vestige exv minute, posterior to ex, separated from it approximately by diameter of ex alveolus ( Fig. 7B insert).

Notogaster ( Fig. 6A–C ). Nearly circular in outline, about 1.1 times longer than broad; uniformly curved, hemispherical with maximum height in middle ( Fig. 7A ). Spina adnata elongate (36–45), usually barely reaching level of prodorsal tubercle Ba; relatively narrow, straight; mutual distance of pair greater than that of setae in. Setae of c -, l - and h -series directed radially, inserted in shallow curve, such that mutual distance of lyrifissure im almost twice that of lm in dorsal view; acicular (61–70), grayish brown, weakly bowed with minute barbs on outer face of curvature ( Fig. 7E ). Setae of p -row of finely attenuate, barbed proximally; p 1 (69–73) slightly thicker than p 2 (69–73), p 3 (57–65) thinnest. Lyrifissures ia, im, ip, ih, ips, opisthonotal gland opening (gla), and circumgastric sigillar band all distinct in transmitted light.

Coxisternum and lateral podosoma ( Figs 6B, D , 8C ). Tectum of podocephalic fossa normally developed, without lateral tooth-like projection. Inconspicuous medial coxisternal pit present on epimere I, shallow, with vaguely defined margins (cp; Figs 6D , 8A ). Enantiophyses E2 and V present across epimeral groove 2 and ventrosejugal groove, respectively ( Fig. 8C ): tubercles of E2 weakly developed; Va, Vp both larger, subconical; strong contour immediately lateral to E2p and Va giving appearance of connecting ridge in ventral view. Tubercles of parastigmatic enantiophysis converging and of similar form: horn-like, slightly bowed. Mediosejugal enantiophysis absent. Epimeral setae attenuate, barbed, most on small tubercles (e.g. Fig. 8C ; 1b ), setation: 3–1–3–4; approximate lengths 1a, 1c, 2a, 3a (20–24), 1b, 4a, 4b (30–32), 3b, 3c, 4c, 4d (41–45). Seta 3b inserted on Vp, 4a almost adjacent, inserted at tubercle base; 3c slightly removed mediad from Sp and acetabulum III. Discidium of medium size, conical to tooth-like, directed laterad to posterolaterad.

Anogenital region ( Fig. 6C, D ). Genital, aggenital, anal, and adanal setae attenuate, barbed, similar in length (30–32). Adanal seta ad 3 inserted close to anal aperture, nearly aligned between ad 2 and ag. Lyrifissure iad oriented diagonally; ian anterolateral to seta an 2, minute, length about equal to setal alveolus diameter. Medial edge of anal plate with usual narrow longitudinal band, sharply demarcated by carina.

Gnathosoma . Subcapitulum longer than wide (110–114 × 82–90). Subcapitular setae attenuate, barbed (a, 20–24; m, h, 36–41). Adoral setae (12) thin, slightly barbed. Palp (90–94) with typical setation: 0–2–1–3–9(+ω); ω baculiform, appressed to surface. Postpalpal seta (6) spiniform, smooth. Chelicera (110–114) typical of family; attenuate seta cha (32–36) barbed throughout, chb (20–24) barbed unilaterally in middle part.

Legs ( Figs 8E , 9A –D ). Relative lengths (I to IV) 1.0: 0.8–0.9: 1.0: 1.2; leg IV 1.3–1.4 times body length. Femur IV slightly longer (1.2–1.3) than trochanter IV; approximate length of leg segments shown in Table 1. Proximal stalk of femur IV slightly longer (~ 1.4) than distal bulb. Claw of each leg smooth, without basal tooth. Formulas of leg setation and solenidia: I (1–7–4–4–21) [1–2–2], II (1–6–4–4–17) [1–1–2], III (2–4–3–3–17) [1–1–0], IV (1–4–3– 3–14) [0–1–0]; homologies of setae and solenidia indicated in Table 4. Notably: all tarsi with proximal accessory pair (v) present, v 2 ʹ and v 2 ʺ absent; v 2 ʺ present on femur I, absent from II; seta vʺ absent from femur III. Setae d (if uncoupled) and l barbed, acuminate to attenuate; coupled seta d of genua I–III ~1.5–2 times longer than respective coupled solenidia. Solenidion φ 1 on tibiae I flagellate (‘tactile’), φ on tibia IV attenuate (‘piliform’), others tapered but blunt (‘ceratiform’), erect or slightly curved. Famulus of tarsus I acicular, erect. Shapes and relative sizes of other setae shown in Fig. 9 .

Juveniles ( Figs 10 , 11 ; see R11)

Dimensions. Total length of LA (n = 2) 242–252, PN (n = 4) 291–310, DN (n = 3) 349–388, TN (n = 4) 431–485. Maximum width of smallest TN (intact specimen) 215; detailed measurements (below) also from smallest TN.

Integument. Cerotegument with excrescences dense in most areas of body, more spaced on parts of prodorsum, absent on nymphal gastronotum under scalps. Excrescences granular, conical, columnar, or bottle-shaped ( Fig. 11D ), with minute dust-like surface particles. Cerotegument usually absent from setae (except bothridial seta), but present on solenidia with small granular excrescences ( Fig. 11F ). Soft cuticle colorless, medium to large setae darkly pigmented; body sclerites and large tubercles finely porose, pale yellow in older nymphs.

Prodorsum. About 1/2 length of gastronotic region in nymphs, slightly more in larva. Rostrum broadly rounded. Rostral (45 in TN), lamellar (57 in TN) and exobothridial (45 in TN) setae attenuate, barbed. Interlamellar seta ontogeny typical of family: attenuate in larva (45), but short, nearly isodiametric in nymphs (16 in TN), smooth except for terminal denticles ( Fig. 11B ). Bothridial seta (~ 200 in TN) partially barbed, finely attenuate, flagellate, with strong S-shaped bend near tip; distal half covered in dense cerotegument ( Fig. 11A ).

Gastronotic region. Setae barbed, all but smallest flagellate, with hyaline (isotropic) threadlike extension approximately as long as pigmented part of seta ( Fig. 11E ). Setae inserted on small tubercle or (mostly) strong apophysis with basal sclerite, proportionate to setal size; measurable lengths in intact TN ( Fig. 10 ): c 1, c 2, la, lm, lp (196–205); h 1 (315); h 2, p 1 (110); h 3 (155); c 3, p 2, p 3 (57). 2 Pair c 1 adjacent on common sclerite, pairs h 1 and p 1 inserted collectively on common terminal sclerite. Ontogeny of hysterosomal cupules normal; ia, im and ip present but inconspicuous due to cerotegument; ih distinct in all instars, ips distinct in all nymphs. Seta h 3 small but wellformed in larva. Cornicle k of nymphs ( Fig. 11C ) vermiform, narrow, consistently with strong middle bend and often weaker distal undulation; located between insertions of setal pair lp.

Venter. Development of epimeral setation normal; setae attenuate, weakly barbed; lengths (in TN) 1a, 2a, 3a (16); 1c, 4a, 4b (20); 1b, 3b, 3c, 4c (28–32). Anogenital region with genital (16 in TN), aggenital (16–20), anal (16) and adanal (20–24) setae attenuate, weakly barbed; respective ontogeny normal. Cupule iad appearing fully formed in DN; ian appearing in TN but minute.

Gnathosoma ( Fig. 3 b ). Subcapitulum little longer than wide (90 × 86 in TN). Subcapitular setae (h and m, 20; a, 12 in TN) setiform, slightly barbed. Adoral setae (6 in TN) setiform, thin, indistinctly barbed. Palp (73 in TN) with setation as in adult. Postpalpal seta (4 in TN) spiniform, smooth. Chelicerae (90 in TN) with seta cha (32 in TN) longer than chb (20), both attenuate, barbed.

Legs. Formulas of leg setation and solenidia counts: LA, I (0–2–3–3–16) [1–1–1], II (0–2–3–3–13) [1–1–1], III (0–2–2–3–13) [1–1–0]; PN, I (0–2–3–3–16) [1–1–2], II (0–2–3–3–13) [1–1–1], III (1–2–2–3–13) [1–1–0], IV (0–0–0–0–7) [0–0–0]; DN, I (1–4–4–5–16) [1–2–2], II (1–4–4–4–13) [1–1–2], III (2–3–3–4–13) [1–1–0], IV (0–2– 3–3–12) [0–1–0]; TN, I (1–5–4–5–18) [1–2–2], II (1–4–4–5–15) [1–1–2], III (2–3–3–4–15) [1–1–0], IV (1–3–3–4– 12) [0–1–0]. Homologies of setae and solenidia indicated in Table 4. Notably: seta v ʹ of all genua formed in DN; lʺ and vʺ of tibia II formed in DN and TN, respectively; vʺ of tibia IV formed in TN. Setal pair (p) appears eupathidial on tarsus I in all instars, seta s normal in all juvenile instars (becoming eupathidial in adult). Famulus (2–3 in TN) sunken in cup ( Fig. 11G ), non-emergent, with distinct internal ‘root’ of similar length. Coupled solenidia about 1/3 length of seta d on genua, 3/4 length of d on tibiae II –IV ( Fig. 11F ).

Figures

FIGURE 1. Epidamaeus puritanicus (Banks, 1906), adult:A—dorsal view (legs not shown except trochanters I, II); B—anterior half of body, right lateral view (gnathosoma and legs not shown); C—posterior region of body, right lateral view; D—ventral view (legs represented only by trochanters). Scale bar 100 μm.

FIGURE 3. Epidamaeus puritanicus (Banks, 1906), light photographs of adult (A–F) and tritonymph (G): A—notogaster,

FIGURE 6. Epidamaeus michaeli (Ewing, 1909), adult: A—dorsal view (legs not shown except trochanters I, II); B—anterior half of body, right lateral view (gnathosoma and legs not shown); C—posterior region of body, right lateral view; D—ventral view (legs represented only by trochanters). Scale bar 100 μm.

FIGURE 7. Epidamaeus michaeli (Ewing, 1909), light and SEM photographs of adult:A—habitus, lateral view; B—bothridial

FIGURE 8. Epidamaeus michaeli (Ewing, 1909), light photographs of adult: A—coxisternum, ventral view, surface focus; B—same, deeper focus; C—same, lateral view, optical section in plane of enantiophyses E2, V; D—bulb of femur II, showing cerotegument and captured spores; E—legs I–IV from dissected specimen. Scale bars 20 μm (A–D), 50um (E).

FIGURE 9. Epidamaeus michaeli (Ewing, 1909), adult: A— right leg I, without trochanter, abaxial view; B—femur, genu and tibia of right leg II, abaxial view; C—femur, genu and tibia of left leg III, abaxial view (femur lower proximally, out of plane with other segments); D—left leg IV, without trochanter, abaxial view. Scale bar 50 μm.

FIGURE 10. Epidamaeus michaeli (Ewing, 1909), tritonymph (legs not shown, exuvial scalps removed): A—dorsal view; B—ventral view. Scale bar 50 μm.

FIGURE 11. Epidamaeus michaeli (Ewing, 1909), slide-mounted juveniles from culture, light photographs: A—protonymph,