Epidamaeus craigheadi ( Jacot, 1939 )

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 : 50-55

Epidamaeus craigheadi ( Jacot, 1939)

( Figs 25–32 )

Metabelba craigheadi Jacot, 1939 ; p. 324

Epidamaeus craigheadi ( Jacot, 1939) ; Marshall et al. 1987, p. 139

Damaeus (Epidamaeus) craigheadi ( Jacot, 1939) ; Subías (2004, p. 79)

Diagnosis

Epidamaeus species with total length of adult 365–426. Cerotegument excrescences ranging from granular to short, vermiform filaments; procuticle distinctly microtuberculate on much of body; without exuvial scalps or adherent debris. Propodolateral apophysis absent; postbothridial enantiophysis unbalanced: Ba prominent, Bp virtually absent, represented only by vague, ridge-like contour. Bothridial seta subflagellate, smooth, inclined posterolaterad. Notogaster with spina adnata straight, narrow to triangular, not quite reaching level of tubercle Ba; setae of c -, l - and h -series oriented longitudinally, thin, acuminate, strongly curved near base. Parastigmatic enantiophysis dimorphic, Sa horn-like, Sp short, blunt. Ventral enantiophyses E2 and M absent; V strongly developed; discidium in form of thick, slightly arched claw. Seta ad 3 close to anal plate. Leg IV 1.2–1.3 times body length; femur IV distinctly longer (1.5–1.8) than trochanter IV.

Adult

Dimensions. Total length and maximum width (n = 7 females, 7 males): 365–426 × 221–260; males usually slightly smaller (365–392) than females (387–426).

Integument. Body color of mature adults medium brown in life; preserved specimens medium to yellowish brown. Cerotegument excrescences forming conspicuous layer on legs and body; all excrescences pulverulent, coated with dusting of fine particles ( Fig. 26C ). Excrescences of prodorsum and notogaster mostly granular, columnar to short vermiform filaments ( Fig. 26B, C ); those of lateral regions and basal leg segments largely capitate-columnar, appearing globular viewed en face ( Fig. 27B, F ); setae bearing granular to capitate-columnar excrescences ( Fig. 26G ) or not ( Fig. 26F ). Procuticle conspicuously microtuberculate on prodorsum, subcapitulum, coxisternum, projecting tubercles and basal leg segments ( Figs 26D , 27A–D ), more weakly developed on genital and anal plates, latter as well as subcapitulum with regions of elongated microtubercles; microtubercles inconspicuous, but usually present on notogaster ( Fig. 26C ) and ventral plate. Without exuvial stack or noticeable adherent debris ( Fig. 26A, B ).

Prodorsum ( Figs 25A, B ; 26B, D ). Contour of body wall immediately anterior to acetabulum I oblique in dorsal view, nearly straight; contour anterior to acetabulum II broadly rounded (propodolateral apophysis absent). Without noticeable transverse contour anterior to bothridium. Postbothridial enantiophysis represented only by distally rounded tubercle Ba; Bp absent, but usually replaced by strong contour, appearing like short transverse ridge in dorsal view. Tubercle Da and laterosejugal enantiophysis absent. Bothridium with projecting part funnelshaped but relatively short, without noticeable vertical banding; mutual distance of pair slightly greater than that of tubercles Ba. Bothridial seta angled posterolaterad; long (182–196), smooth, subflagellate but usually only slightly curved or nearly straight in proximal two-thirds; without cerotegument. Setae ro (57–65) and le (65–73), both finely attenuate, curved anteromediad; ro usually smooth, le with few barbs at base, slightly thicker than ro; in (32–34) thin, acuminate, smooth, nearly straight, angled distinctly posterolaterad. Seta ex (~20) attenuate, thin, smooth; vestige exv present immediately posterior to and appearing to merge with ex alveolus ( Fig. 26E ).

Notogaster ( Figs 25A–C ; 26A, F ). Nearly circular in outline, about 1.1 times longer than broad; hemispherical, uniformly curved in lateral view, with maximum height at or slightly posterior to middle ( Fig. 7A ). Spina adnata directed toward but not reaching tubercle Ba in dorsal view; of medium length (18–20), elongate-triangular to almost parallel-sided, straight to slightly curved laterad; relatively closely spaced, mutual distance of pair ~ 0.2 times maximum notogastral width. Setae of c -, l - and h -series oriented longitudinally, with c 1 directed anteriad, others posteriad; pairs inserted in nearly straight, closely parallel rows such that mutual distance of lyrifissures im almost twice that of pair lm in dorsal view; setae (53–61) with light greyish brown pigmentation, smooth, thinly acuminate, with strong bend in basal third ( Fig. 26F ). Setae of p -row finely attenuate, strongly bent in proximal third, smooth; relatively small, shorter than distance between alveoli; p 1 (36–41) slightly thicker than p 2, p 3 (32–36).

Coxisternum and lateral podosoma ( Figs 25B, D , 27A–D ). Tectum of podocephalic fossa normally developed, without lateral tooth-like projection. Distinct coxisternal pit absent from epimere I but inverted-Y-shaped depression in its place (Fig, 27A, arrow). Enantiophyses E2 and M absent, V strongly developed; tubercle Va triangular in ventral view, distally rounded; Vp of similar size but broadly rounded to subquadrate ( Fig. 27C ). Tubercles of parastigmatic enantiophysis dimorphic: Sa large, conspicuous, horn-like, Sp short, subconical, perpendicular to Sa (Fig, 27B). Epimeral setae finely attenuate, almost smooth, those of epimeres 1, 2 on small but distinct tubercles ( Fig. 27A ). Setation: 3–1–3–4; approximate lengths 1a, 1c, 2a, 3a (20), 1b, 3b, 4a (28–32) 3c, 4b, 4c, 4d (41–45). Seta 3b inserted near end of Vp, 4a inserted at base of Vp or slightly removed, 3c inserted between Sp and acetabulum III. Discidium usually sharply pointed, curved slightly posteriad like broad claw or thorn ( Fig. 27D ).

Anogenital region ( Fig. 25C, D ). Genital setae thin, attenuate, smooth or weakly barbed; setae ag similar to ad (~ 20), thin, attenuate, smooth; ad 3 inserted close to anal aperture, nearly aligned between ad 2 and ag. Lyrifissure ian obliquely oriented; located near anal plate at level of seta an 2; ian anterolateral to 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 ( Fig. 27 ). Subcapitulum longer than wide (98–102 × 73–82). Subcapitular setae (a, 18–20; m, h, 34–36) attenuate, barbed. Adoral setae (8–10) thin, slightly barbed. Palp (82–86) with typical setation: 0–2–1– 3–9(+ω). Solenidion baculiform, appressed to surface. Postpalpal seta (6) spiniform, smooth. Chelicera (90–94) typical of family; attenuate seta cha (28–30) barbed throughout, chb (18–20) barbed unilaterally in middle part.

Legs ( Figs 27E, F , 28 ). Relative lengths (I to IV) 1.0: 0.8: 1.0: 1.3–1.4; leg IV 1.2–1.3 times body length. Femur IV distinctly longer (1.5–1.8) than trochanter IV; approximate length of leg segments shown in Table 1. Proximal stalk of femur IV distinctly longer (1.4–1.5) than distal bulb. Claw of each leg smooth, without basal tooth. Formulas of leg setation and solenidia: I (1–7–4–4–20) [1–2–2], II (1–6–4–4–17) [1–1–2], III (2–5–3–3–17) [1–1–0], IV (1–4–3–3–14) [0–1–0]. Notably: all tarsi with proximal accessory pair (v) present, v 2 ʹ and v 2 ʺ; v 2 ʺ absent from femora I, II; seta vʺ present on femur III. Setae d (if uncoupled) and l barbed, acuminate to attenuate, d on femora larger, thicker than l; coupled setae d of genua I–III as long or slightly longer than respective solenidion. Solenidia φ 1 on tibia I flagellate, φ on tibia IV subflagellate; others tapered but blunt (‘ceratiform’), erect or slightly curved. Famulus of tarsus I acicular, erect.

Juveniles ( Figs 30–32 )

Dimensions. Larva unknown except as exuvial scalp. Total length of PN (n = 3) 245–255, DN (n = 3) 269–308, TN (n = 4) 343–377. Maximum width of hysterosoma about half body length. Setal lengths given below only for one average TN: proportional in other nymphs unless noted.

Integument. Excrescences of cerotegument, short, strongly pulverulent; dense, adjacent or slightly separated on most of body and legs; mostly bottle-shaped to capitate-columnar, but appearing granular (diameter 2–3) seen faceon ( Figs 31B, C , 32D ). Setae of untreated specimens usually with cerotegument; excrescences smaller, shaped like those of body surface or minute (1) spheres.

Prodorsum. About half length of gastronotum; rostrum broadly rounded. Setae ro (54 in TN) and le (62 in TN) attenuate, barbed, curved anteromediad ( Fig. 31B ); ex (37 in TN) attenuate, weakly barbed ( Fig. 31E ); seta in (20 in TN) spiniform—smooth, straight, with several minute terminal teeth ( Fig. 31D ). Bothridial seta (189 in TN) subflagellate, smooth, usually covered in cerotegument over whole length ( Fig. 30D , 31A ).

Gastronotic region. Larval scalp with strong topography of broad transverse grooves ( Fig. 30A, B ); attachment induration (ind; Fig 30B , insert) conspicuously darkened in transmitted light ( Fig. 30C , insert). Setal ontogeny normal. Except as noted, setae pigmented, directed dorsad and curved slightly posteriad, barbed on outer curvature; finely attenuated to threadlike hyaline tip, inserted on distinct tubercles (measurements for TN only): seta h 1 (220 –245) subflagellate, pair nearly straight, diverging from nearly adjacent insertions on pygidial process; pair c 1 (170– 183) nearly adjacent on single weak sclerite, posterior bend strongest near base; c 2, la, lm, lp similar (147–170), h 3 (110 –135) and h 2 (98–110) slightly smaller; seta c 3 (50) smallest; p 2 (61–74) and p 3 (50–60) relatively close together, p 1 (61–78) more distant, inserted lateral to h 1 on weak sclerite of pygidial process. Attachment cornicle k of nymphs positioned between setal pair lp ( Fig. 30E ); relatively short (~ 35 in TN), mostly straight, with slight bend in distal third; in PN, distal third inserted in sleeve-like induration on ventral surface of larval scalp ( Fig. 30B ).

Venter. Epimeral setae acuminate to attenuate, smooth or weakly barbed, 1b longest (TN 28; others mostly 17–20); genitals and aggenital (15 –20) similar in form; anals (20–25) and adanals (30–50, ad 1 longest) extended in threadlike tip when intact.

Gnathosoma . Subcapitulum length and width about equal. Setae of mentum (h ~20) and gena (a ~20, m ~25) attenuate, nearly smooth.

Legs. Formulas of leg setation and solenidia counts: 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 (1–2–2–3–12) [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]. Ontogeny of setae and solenidia in nymphs as in E. michaeli (Table 4) except as follows: seta vʹ of trochanter IV deutonymphal; seta v ʹ of genu IV tritonymphal.

Setal pair (p) appears eupathidial on tarsus I of all observed instars, seta s normal in juveniles (becoming eupathidial in adult). Famulus ( Fig. 32D ) acicular, emergent in all nymphs (8 in TN); without sunken cup but base internalized as short ‘root’ (2) at least in TN (no opportunity to study in PN or DN; see R23). Solenidion ω 1 of tarsus I ceratiform, distinctly curved laterad, slightly S-shaped or with third weak bend distally ( Fig. 32D, E ); ω 2 smaller, piliform. Coupled solenidia of genua ( Fig. 32A, B ) almost isodiametric, about 1/2 length of seta d on genua; those of tibiae II–III similar or ceratiform but longer, about 3/4 length of d, that of tibiae I (φ 1) and IV flagellate or subflagellate (‘tactile’; Fig. 32B, C ), much longer than d.

Figures

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

FIGURE 25. Epidamaeus craigheadi (Jacot 1939), adult: A—dorsal view (legs except right trochanters I–III not shown); B—anterior half of body, right lateral view (gnathosoma and legs not shown); C—posterior part of body, right lateral view; D—ventral view (legs represented only by trochanters). Scale bar 100 μm.

FIGURE 26. Epidamaeus craigheadi (Jacot 1939), light and SEM photographs of adult: A—habitus, lateral view; B (SEM)— anterior half, dorsal view; C (SEM)—cuticle of notogaster, near sejugal furrow, showing weak procuticular microtubercles (short arrows) and two forms of overlying cerotegument excrescences, vermiform and granular (long arrows), all pulverulent (covered with minute, dust-like particles); D—microtuberculate procuticle of rostrum in vicinity of right setae le, ro (cotype); E—alveolus of seta ex, with arrow to vestige exv (anterior to right); F—partial notogaster, lateral view (upper left insert = enlarged spina adnata, dorsal view); G—seta lʹ of genu IV. Scale bars 2 μm (C, E), 10 μm (D, G), 20 μm (F), 50 μm (A, B).

FIGURE 27. Epidamaeus craigheadi (Jacot 1939), light photographs of adult: A—central epimere I and base of subcapitular mentum; B—right ventrosejugal region with insert (upper right) at higher focus on trochanter III, showing cerotegument (seta lʹ labeled for orientation); C—ventrosejugal enantiophysis, ventrolateral view (anterior to right); D—region of left discidium, ventral view (cotype); E—legs I–IV; F—partial femur IV, with inserts showing enlargements of cerotegument excrescences on dorsal (lower left) and ventral (lower right) section of stalk. Scale bars 5 μm (C, D), 10 μm (A, B, F), 50 μm (E).

FIGURE 28. Epidamaeus craigheadi (Jacot 1939), adult: A—subcapitulum, ventral view; B—palp, right, abaxial view; C— chelicera, left, adaxial view (seta chb on opposite side, not labeled). Scale bars 20 μm.

FIGURE 29. Epidamaeus craigheadi (Jacot 1939), adult:A—right leg I, except trochanter, abaxial view (femur slightly twisted, cf Fig. 27E); B—femur, genu and tibia of right leg II, abaxial view; C—femur, genu and tibia of left leg III, abaxial view; D— left leg IV, except trochanter, abaxial view. Scale bar 50 μm.

FIGURE 30. Epidamaeus craigheadi (Jacot 1939), light photographs of nymphs: A—protonymph, lateral view; B—same, posterior region of gastronotum (left insert = enlargement of attachment cornicle k inserting in induration (ind) on underside of larval scalp; C—protonymph, dorsal view of hysterosoma with larval scalp intact (white labels on scalp setae; insert = larval scalp removed from different specimen, arrow to attachment induration); D—tritonymph, dorsal view (scalps removed; several setae broken; body artificially swollen by clearing); E—tritonymph, lateral view (scalps removed; lower left insert = enlargement of attachment cornicle k). Scale bars 20 μm (B, C), 50 μm (A, D, E).

FIGURE 31. Epidamaeus craigheadi (Jacot 1939), light photographs of protonymph (A), tritonymph (B–G):A—lateral view of

FIGURE 32. Epidamaeus craigheadi (Jacot 1939), light photographs of deutonymph (A), tritonymph (B–E):A—middle portion of leg II, abaxial view; B—middle portion of right leg I, dorsoadaxial view; C—portion of tibia I from different specimen, abaxial view (arrow to coupled seta d); D—bulb of left tarsus I, dorsoabaxial view, showing ‘tarsal cluster’ (lower right insert = isolated famulus, arrow to basal ‘root’); E—isolated solenidion ω1 and cerotegument excrescences. Scale bars 5 μm (D, E), 10 μm (A–C).