Weigmannia parki ( Jacot, 1937 ) Miko & Norton, 2010

Miko, L. & Norton, R. A., 2010, Weigmannia N. Gen. From Eastern North America, With Redescription Of The Type Species, Porobelba Parki Jacot, 1937 (Acari, Oribatida, Damaeidae), Acarologia 50 (3), pp. 343-356 : 344-352

Weigmannia parki ( Jacot, 1937) n. comb.

Diagnosis

With characters of Weigmannia as stated above. Prodorsum without distinct tubercles. Sensillus long, setiform, distally usually slightly thickened, lanceolate. Parastigmatic apophysis Sa very strong, distinct, pointed, slightly arched anteriad. Notogastral setae c 1 and c 2 pointing forward. Spinae adnatae acute, thorn-like, slightly diverging anteriad. Dorsal setae of all femora hypertrophied, strong, arched, roughened with distinct, scale-like barbs.

Redescription of adult

General characters. Maximum body length 305 - 380 µm (mean 347 µm; n = 4), ventral length 288-345 µm (mean 321 µm). Body covered by very thick layer of mostly filamentous (sejugal area, legs, ventral side etc.) but also glandular (notogaster, rostral part of prodorsum) cerotegument ( Figs. 1 ; 2A ; 4A ). Body colour brown to yellowish brown. Adults bear reticulate exuvial scalps on notogaster ( Figs. 1A ; 6B ; 8J ).

Prodorsum. Pentagonal to broadly triangular, with well developed propodolateral apophysis (P; Fig. 2A, C ). Rostrum broadly oval, with small longitudinal protuberance in central part between insertions of rostral setae ( Fig. 2A ). Bothridia quite distant from anterior notogastral margin (as in Porobelba ), funnel-like. Sensillus (ss; Fig. 2E ) relatively long (about 105-115 µm), setiform, distally usually broadened and lanceolate, with sparse, small and indistinct spines distally. Rostral (ro) and lamellar (le) setae of similar size (ro about 40 µm, le about 45-48 µm), bent, with attenuate tips; le longer and thicker than ro ( Fig. 3B ) and covered by cerotegument. Interlamellar seta (in; about 35 µm), shorter than ro and le, straight or slightly curved, about one third of sensillus length, also covered by cerotegument. Exobothridial seta (ex) shorter (about 20 µm) and finer than in, curved, hardly visible under cerotegument. No tubercles present on prodorsum, sejugal area strongly narrowed, best visible in slightly anterodorsal view. Anterior parastigmatic apophysis (S a) strong and well developed, directed almost perpendicular to body, slightly bent anteriad. Posterior parastigmatic apophysis (S p) much smaller, tubercular, oblique, sometimes hardly observable under thick layer of cerotegument.

Notogaster. Circular to slightly oval in outline, hemispherical in lateral view. Spinae adnatae thin, thorn-like, with tips slightly diverging anteriad (length about 30 µm). Notogastral setae mostly long and distinct, series c-l-h in pair of subparallel to slightly posteriorly converging longitudinal rows; setal row ps aligned along posterior border of notogaster, with row c-l-h perpendicular to it when seen from posterior ( Fig. 2D ). First two pairs of setae (c 1, c 2) longest (55-65 µm), directed anteriad, strongly bent close to insertion, then almost straight, close to notogastral surface ( Fig. 3A, B ).

Dorsolateral setae la-lp of similar shape, usually slightly shorter (45-50 µm) and thinner, directed posteriad. Setae h 1 -h 3 slightly diminishing in succession (55-50- 47 µm in one measured individual), with very indistinct, sparse spines unilaterally; less bent at base and more curved distally than c and l setae. Setae ps 1 - 3 diminishing in succession (23-18- 15 µm), strong, slightly bent. Lyrifissures and opening of opisthonotal gland with positions typical of Damaeidae .

Ventral characters ( Fig. 2B ). Venter covered by layer of cerotegument. Discidium (dis) short, tubercular, but distinct, directed slightly forwards or perpendicular to body. Epimeral setation 3-1-3-4; setae relatively short, setiform, thin, lateral ones longer than others, seta 1c longest. Epimeral setae insertions of first two epimeres on more or less distinct papillar protuberances, setae 4c and 4d inserted close together. With six genital, one aggenital, two anal and three adanal pairs of setae present, as usual in Damaeidae ; all similar in shape and size. Genital aperture well separated and quite distant from anal opening; longer and broader than anal.

Gnathosoma (Characters were studied only on non-dissected individuals, and therefore are not described in full detail). Type and form of subcapitulum typical of Damaeidae . Palps relatively long, with elongated tarsus; setation (tarsal solenidion not included) 0-2-1-3-8, three distal setae on tarsus eupathidial ( Fig. 3C ). Setae of rutella and mentum similar in shape to other ventral setae. Chelicerae without unusual characters.

Legs. Moniliform ( Figs. 4 , 1A ), covered by thick layer of mostly filamentous and columnar cerotegument, making setation difficult to study. Setal formula of legs as follows (famulus included, solenidia not included): I, 1-7-4-4-20; II, 1-6-4-4-17; III, 2-4-3-3-16; IV, 1-4-3-4-13. Solenidia quite short, except φ 1 long, flagellate, tactile. Solenidia of tibiae II-IV coupled with seta d; latter about as long as, or longer than, respective solenidion ( Fig. 4C,D,F ). Solenidia of tarsus II inserted as if paired ( Fig. 4C ), parallel, straight and relatively long. Famulus emergent, shorter than other setae, simple, setiform ( Fig. 4B ). Dorsal setae of all femora of very characteristic shape ( Figs. 3B , 4 ), hypertrophied (55- 68 µm), with distinct, thorn- and scale-like spines. Anomalous doubling of lateral seta on tarsus II observed on one specimen ( Fig. 4C ).

Ontogeny: ( Figs. 5-8 )

Facies and Dimensions (all from slide-mounted specimens, complemented by measurements of one tritonymph used for drawings — Figs. 5-7 ). General characters of larva and eupheredermous nymphs typical of family ( Grandjean, 1954) ( Figs. 5A,B ; 6A ); exuvial scalps strongly reticulate ( Figs. 6B ; 8J ). Total length of: larva (La, n = 2) 192-201 (mean 197) µm; protonymph (Pn; n = 3) 225-245 (mean 235) µm; deutonymph (Dn; n = 4) 255-294 (mean 278) µm; tritonymph (Tn; n = 2) 320-334 (mean 327) µm. Measurements of structural details (below) approximate, taken from average-sized specimen of respective instar (separate structures not measurable in single slide-mounted Tn).

Integument, setae. Cuticle colorless, covered with cerotegument in all instars, except under exuvial scalps of nymphs. Excrescences of cerotegument densely packed, touching or nearly so; those on body, legs and setae columnar to bottle-shaped ( Fig. 8K ), ≈ 1 µm diameter or less, smallest distally on leg tarsi; those on solenidia minute, very fine, making solenidia appear fuzzy ( Fig. 8K ). Setae of dorsum and legs light to dark brown, except for hyaline birefringent base ( Figs. 6 ; 8F,G ); pigmentation increasing with seta size, ventral setae with little or no pigment. Most setae flagellate when intact; flexible, undulating, threadlike distal region can comprise 1/3 setal length, which when broken makes measurements highly variable and imprecise.

Prodorsum. Setae le, ro ≈ 30 µm in La, anteriorly directed, curved in basal third, with 1-2 conspicuous barbs; 35-40 in Dn, with several inconspicuous barbs; pairs ro and le arranged in shallow arch; mutual distance of ro 1/4 (La) to 1/3 (nymphs) that of le. Seta ex relatively straight, smooth (≈ 20 µm in La, 25-30 in Dn and Tn). Seta in subflagellate (≈ 45 µm), with 1-2 barbs in La ( Fig. 8C ; short in nymphs (≈ 15 µm in Dn and Tn), posterodorsally directed, only slightly tapered to tip with terminal brush of small spines ( Figs. 5E ; 8D,E ). Sensillus (≈ 70 µm in La, 130 in Dn; 98-110 µm in drawn Tn), with similar form in all immatures: smooth or with sparse small barbs, flagellate; proximal 3/4 stiff, nearly straight and tapered, distal 1/4 threadlike, flexible, strongly undulating; cerotegument thickness and size of excrescences increase along length ( Fig. 8A,B ).

Gastronotic region. Body elliptical to almost rectangular in larva, oval in nymphs. Exuvial attachment cornicle k of nymphs (15 µm in Pn, 20 in Dn; ≈ 33 µm in Tn) straight, smooth and tubular in basal half, slightly constricted, flame-shaped in distal half with thinner walls and irregular longitudinal wrinkles ( Figs. 5D ; 6D ; 8H,I ). Opisthonotal gland and all normal cupules in positions typical of family. Gastronotic setae inserted on prominent, sclerotized, conical to cylindrical tubercles; tubercles independent, except as noted below. Larva with great range of setal size and form: darkest and most heavily barbed include c 1 (30 µm), c 2 (90 µm), da (100 µm), dm (100 µm), dp (75 µm), and lp (100 µm); thinner, less pigmented and less strongly barbed setae include c 3 (30 µm), la and lm (50 µm), and h 3 (90 µm); h 2 (25 µm) and h 3 (15 µm) with little pigment, 1-2 minute barbs. Setal pair dp on common medial sclerite; c 1 directed anterodorsally ( Fig. 8F ), c 2 dorsolaterally, about equidistant from c 1 and c 3.

Nymphal setae well pigmented except as noted, also with wide range of size (measured in deutonymph but proportionally similar in other nymphs); coarseness and density of barbs greatest in anterior setae, gradually decreasing in more posterior setae. Seta c 1 (100 µm; Fig. 8G ) strongly curved posterodorsad; c 2, la, lm, lp, h 3 (all ca 130 µm) weakly curved posterolaterally; h 1 (ca 130 µm) thinner, almost straight, posteriorly directed, with few, minute barbs; ventrally positioned h 2 (40 µm) and ps 1 - 3 (40, 35, 20 µm respectively) smooth, lightly pigmented. Setal pairs c 1 and h 1 each on shared microtuberculate median sclerite. Length of setae on tritonymph as follows ( Fig. 6 ): c 1 205 µm, la 210 µm, h 1 240 µm, h 2 80 µm, h 3 165 µm, ps 1 72 µm. Seta c 3 absent unilaterally from one observed tritonymph.

Ventral region. Setation typical for family. Setal formulae for epimeres (I-IV): La 3-1-2, Pn 3-1-2-1, Dn 3-1-2-2 (Tn not studied). Seta 3c (included in formula) of larva with typical scale-form, closely covering Claparède’s organ. Genital setation (Pn-Tn): 1-3-5. Aggenital seta first appearing in Dn.

Gnathosoma. Typical of family. Second palpfemur seta formed in Pn ( Fig. 5C ).

Legs ( Figs. 7 , 8 K-L). Overall form typical of family. Ontogeny of setae and solenidia given in Table 1; no variation observed. Most setae with several small barbs. Seta d of all tibiae and all genua (except IV which lacks solenidion) closely coupled with respective thin, isodiametric solenidion. In most cases, d 1.5 to 2 times longer than respective solenidion, with following exceptions. Seta d on larval genua regressed, much shorter (≈2, 4, 5 µm on I-III, respectively) than solenidion; latter curves ventrodistad around posterior face of segment (both becoming normal in nymphs). Also, tibia I seta d in all immature instars about half length of flagellate (tactile) φ 1 (but, seta d absent on both tibia I of observed tritonymph, Fig. 7 E,F ); φ 2 similar to other tibial solenidia but slightly thinner. Tarsal solenidion ω 1 of leg I ceratiform ( Fig. 8K ), 2- 3 times as thick and half-again as long as ω 2; both solenidia of tarsus II thin, similar to ω 2 of tarsus I. Famulus minute, sunk in deep sclerotized cup in all immature instars, not noticeably projecting beyond edge; with straight or slightly curved root-like internal extension from cup, about equal to cup in length ( Figs. 8L ; 7D ). Proral setae (p) of tarsus I appear eupathidial in all instars; subunginal seta of tarsus I normal and proximal to antelateral setae (a) in immatures, becoming eupathidial and distal to pair (a) only in adult; no other setae eupathidial.

Figures

FIGURE 1: Weigmannia parki (Jacot,1937), habitus of adult: A – lateral view, with nymphal scalps (ventral setae and setae of legs only partly depicted); B – dorsal view (legs and their setation only partly depicted). Bar indicates 100 µm.

FIGURE 2: Weigmannia parki (Jacot, 1937), adult: A – dorsal view without legs (slightly anterodorsal aspect showing dorsosejugal area); B – ventral view without legs, gnathosoma only partly depicted; C – right region of sejugal furrow, dorsal view; D – pygidial region of notogaster, posterior view; E – right bothridial area and sensillus, lateral view. Bars indicating 100 µm (A+B), 50 µm (C+D), and 50 µm (E). Explanations in text and in Appendix 1.

FIGURE 4: Weigmannia parki (Jacot, 1937), legs of adult (antiaxial views): A – leg I; B – tarsus I in detail; C – leg II (arrow indicates anomalous doubling of lateral seta l”); D – leg III, E – trochanter and femur IV; F – genu, tibia and tarsus IV. Bar indicating 100 µm (A,C-F). Light, irregular lines around A, E, F indicate extent of cerotegument covering. Designations of leg setae according to Grandjean, as reviewed by Norton (1977).

FIGURE 6: Weigmannia parki (Jacot, 1937), tritonymph: A – lateral view (black distal parts of setae c1, c2, la and lm reconstructed on basis of nymphal scalp); B – detail of net-like structure of nymphal scalps; C – notogastral setae from tritonymphal scalp in detail; D – notogastral cornicle in lateral view. Bars indicating 100 µm (A) and 50 µm (B+C+D). Explanations in text and in Appendix 1.

FIGURE 8: Weigmannia parki (Jacot, 1937) immatures: A – sensillus of deutonymph; B – same, enlargement of distal half; C – interlamellar seta of larva; D – bothridial area of protonymph; E – interlamellar seta of deutonymph; F – setae c1 of larva; G – setae c1 of deutonymph; H – cornicle k from protonymph; I – same, from protonymphal scalp on deutonymph; J – portion of exuvial scalp from larva; K – deutonymphal tibia I, focused on seta ft" and solenidion ω1; L – same, focused on sunken famulus, arrow on "root". All photomicrographs, from slide-mounted, slightly flattened specimens; all except J-L layered from 2-4 images.

FIGURE 3: Weigmannia parki (Jacot, 1937), adult: A – lateral view, ventral setae and legs not fully depicted; B – detailed views of prodorsal setae, notogastral setae and dorsal setae of femora I and IV; C – palp in lateral (antiaxial) view. Bars indicating 200 µm (A), 50 µm (B) and 50 µm (C). Explanation in text and in Appendix 1.

FIGURE 5: Weigmannia parki (Jacot, 1937), tritonymph: A – dorsal view; B – ventral view; C – palp; D – cornicle k, dorsal view; E – bothridial area and sensillus. Legs and gnathosoma only partly depicted. Bars indicating 100 µm (A+B) and 50 µm (C+D+E). Explanations in text and in Appendix 1.

FIGURE 7: Weigmannia parki (Jacot, 1937), tritonymph: A – leg I, antiaxial view; B – leg II, antiaxial view; C – leg IV, antiaxial view; D – tarsus I, antiaxial view; E – tibia I, paraxial view; F – genu and tibia I, antiaxial view. Bar indicating 100 µm (A,B,C) and 50 µm (D,E,F). Designations of leg setae accordingly to Grandjean, as reviewed by Norton (1977).