Miracarus hurkai Kunst 1959

Miko, Ladislav, Mourek, Jan, Meleg, Ioana N. & Moldovan, Oana T., 2013, Oribatid mite fossils from pre-Quaternary sediments in Slovenian caves II. Amiracarus pliocennatus n. gen., n. sp. (Microzetidae) from Pliocene, with comments on the other species of the genus, Zootaxa 3670 (4), pp. 557-578 : 559-561

Redescription of Miracarus hurkai Kunst 1959

Material examined. Single individual, holotype, from collection of M. Kunst, slightly damaged (see material and methods for more details).

Diagnosis. Microzetidae with characters of the genus: Body small (less than 250 µm), with round notogaster and elongated prodorsum. Pedotectum I large, reaching anteriorly beyond half of the prodorsum length. Tutorium curved, consisting of several tutorial carinae, with single tooth anteriorly. Lamella with broad and long cuspis, with two teeth distally—large adaxial and smaller abaxial tooth, with deep incision between them. Interlamellar seta inserted on prodorsum, between the lamellae. Sensillus elongate lanceolate, with long and densely barbed head. Pteromorph triangulate, with sharp distal angle. Notogastral seta h 3 inserted distant from notogastral lateromedial furrow, almost in one longitudinal row with seta e 2 and f 2.

Redescription of adult (immatures unknown)( Figs 1 , 5 D–F , 10 )

General characters. Body small, in comparison to other Microzetidae rather narrow, with almost round notogaster and elongated prodorsum. Body length 245 µm, notogaster length 154 µm, prodorsum length 91 µm, ratio prodorsum length:notogaster length about 1:1,7. Maximum notogaster width 148 µm, maximum prodorsum width (between convexities of pedotecta I) 113 µm. Body colour light brown. Body surface smooth, without visible layers of cerotegument or apparent microsculpture, except for fine striation on lamellae and pedotecta I.

Prodorsum. Rostrum appearing rounded or slightly angulated, with a broad, weakly defined rostral incision, hardly visible in dorsal view. Lamella long (about 87 µm), broad, with a long cuspis of about one third of its total length (33 µm). Lamellar cusps axially almost touching, parallel in entire length, each cuspis ending with a large distal adaxial tooth and smaller abaxial tooth. Length of abaxial tooth is about one third or one quarter of the length of adaxial tooth. Surface of lamella with fine longitudinal striation, best visible in basal part. Lamellar seta inserted in the incision between lamellar teeth, closer to smaller abaxial one. Distinct, straight line running from the insertion of lamellar seta posteriad, obliquely towards adaxial base of lamellar cuspis. Bothridium almost completely covered by posterior lamellar base. Another smaller lamellar structure (subbothridial lamella) present under the bothridium, running anteriad and upwards and fused with lamella anterior to bothridium. Tutorium appearing in dorsal view as long, arched rib, reaching rostral area approximately at the level of anterior end of lamellar cuspis. The complex structure of the tutorium, consisting of three parts (carinae), better visible in lateral or dorsolateral view ( Figs 1C , 5 E ): upper tutorial carina 1 present as distinct line, running parallel with lamellae. Tutorial carina 2 developed as strong and slightly arched rib, running below tutorial carina 1, ending anteriorly with a small, free tutorial tooth (cusp). The cusp is connected with the anterior end of tutorial carina 1 by a distinct line. Tutorial carina 3 splits into two lines running backwards, first, shorter line reaching border of camerostome and second, longer line developed as S-shaped line below tutorial carina 2, running towards base of pedotectum I. Three straight, rather short, well developed and almost parallel carinae present at the side of prodorsum below tutorial line 3, almost perpendicular to it. Pedotectum I well developed, large, in lateral view rather obliquely placed ( Figs 1C , 5 E ), thus in dorsal view reaching far anteriorly, beyond half of the length of the whole prodorsum (about to the level of adaxial base of free lamellar cuspis). This nevertheless depends on the position of the body during observation. Bothridium simple, cup-shaped, placed between the bases of lamella and subbothridial lamella. Sensillus ( Figs 1D , 5 F ) of characteristic shape, with short stalk and long lanceolate head with sharp tip. Entire head of sensillus covered by dense and quite long barbs, their maximum length as long as the width of sensillar head or even slightly longer. Prodorsal setae differently shaped, rostral seta short, simple setiform and smooth; lamellar seta of typical foliar appearance, with short barbs mostly on abaxial edge. Interlamellar seta simple, setiform, smooth and short, inserted on the prodorsum between lamellae, but close to their inner margins. Exobothridial seta very small, smooth, inserted below bothridia, visible only in lateral view (too minute to be shown on Fig. 1C ).

Notogaster. Almost circular in dorsal view, with well visible anterior margin. Pteromorph fully delimited by circumgastral line, triangular, distally ending by sharp angle. Lateromedial furrow (also called lateral slit, sl) present laterally on notogaster, slightly behind the level of insertion of seta h 3, not well visible in dorsal view. Notogastral setae fine and relatively short, smooth. Seta c 2 inserted slightly anteriad to the middle of pteromorph base, seta c p close to the posterior end of pteromorph or slightly behind. Seta e 2 inserted anteriorly, slightly behind level of c p. Setae h 1 and h 2 positioned at usual place along posterior end of notogaster, seta h 3 shifted anteriomediad, forming more or less one longitudinal line with setae e 2 and f 2. Notogastral lyrifissures at usual places. A pair of oval areas or spots present in the middle of notogaster between insertions of setae e 2 and h 3.

Ventral characters. Camerostome relatively broad, ovoid, anteriorly with well visible rostral incision, at the base with well developed, wide mentotectum. Gnathosoma broad, rutellum normally developed ( Fig. 1 B ). Setae h, m and a fine, short and smooth. Chelicera slightly elongated (width:length ratio = 0,36), setae cha and chb long and distinctly barbed. Palp with elongated tarsus and usual setation (0-2-1-3-9, solenidion not included in formula), dorsal seta of pedipalp tibia (d) long, rather strong and barbed. Solenidion recumbent, difficult to observe.

Circumpedal line well developed, running from carina ku on pedotectum I, slightly undulated but nearly parallel to each other in central part and ending laterally behind coxa IV, about at the level of aggenital seta insertion. Epimeral plates with net-like structure of muscular sigillae, epimeres II and III separated by broad and well visible ventrosejugal band, similar band developed posteriorly between epimeres IV and anogenital shield. Epimeral setation 3-1-3-3, epimeral setae fine, medium long, smooth. Epimeral setae 3c and 4c inserted laterally, beyond circumpedal line, seta 3c on pedotectum II, seta 4c not on discidium, but slightly more axially, close to discidium base.

Lateral part of podosoma developed similarly to other Microzetidae . Pedotectum I large, massive, with distinct carina ku. Pedotectum II also well developed, protruding laterally as a blunt tip. Discidium and acetabular protrusion R of leg III strongly developed, tubercular, reaching far laterally, distance between R-R as long as between tips of both discidia, and clearly longer than between tips of pedotecta II. Trochanteral seta II well visible in ventral view, smooth and fine, similar to epimeral setae. Anogenital plate broader than its length, but still relatively long, distance between genital and anal openings almost equal to length of genital opening, anal opening slightly longer. Standard numbers of 6 genital, 1 aggenital, 2 anal and 3 adanal setae present, all setae short to medium long, fine and smooth. Lyrifissure iad paraanal, long, at certain distance from anal opening.

Legs. As there is only a single specimen of M. hurkai available, legs were not specifically studied in order to avoid further damaging. Legs appearing similar to other microzetid species, trochanters and femora III–IV with ventral carinae extended distally into angular, blunt projection, yet not developed as a sharp spur. Femora III and IV shorter, almost cylindrical in ventral view and not extended distally, while femora I and II are longer, distally extending (see also Fig. 10 ).

Remarks. M. hurkai described above differ in several important characters from all other species placed until now within the genus. The most remarkable and easily visible is the sharp angle at distal end of pteromorphs, but differences were constantly found also in tutorium development, form of camerostome, development of mouthparts, positions of prodorsal, notogastral and ventral setae. As M. hurkai is the type species of the genus, and all other known species, including the new fossil species described here, differ consistently in several characters, they are not any more considered to be congeners, and for all other species except M. Hurkai a new genus, related to Miracarus , is proposed. In the light of this, and based on the study of the holotype, a revised diagnosis of the genus Miracarus is given here.

Figures

FIGURE 1. Miracarus hurkai Kunst, 1959 (holotype). A—dorsal view (without legs); B—ventral view (legs only partly depicted); C—dorsolateral view of prodorsum (notogaster and ventral structures only partly sketched); D—detailed view of sensillus. Bar indicating 100 µm (A, B, C). Abbreviations: an—anal plate, cgl—circumgastric line, cpl—circumpedal line, dis—discidium, g—genital plate, lam—lamella, mt—mentotectum, pd1—pedotectum I, pd2—pedotectum II, pt— pteromorph, R—acetabular protrusion of leg III, ro—rostrum, sl—notogastral lateromedial furrow, ss—sensillus, TrIII— trochanter III, Tr IV—trochanter IV, tsII—trochanteral seta II, tu—tutorium, tu1—tutorial carina 1, tu2—tutorial carina 2, tu3—tutorial carina 3. Rest represents names of setae or setal insertions and lyrifissures.

FIGURE 5. Main differences between genera Amiracarus Miko n. gen. (A–C) and Miracarus Kunst 1959 (D–F), based on the type species (Amiracarus senensis—left, Miracarus hurkai—right, reconstructed from holotype figure, see Fig. 1). Dorsal view of whole body (A and D): proportion between length of prodorsum and length of notogaster (grey arrows); proportion of width of prodorsum and width of notogaster (black arrows); position of interlamellar setae; form of pteromorphs; position of seta e2—in relation to setae in row c2–cp–e2–f2; position of the seta h3—in relation to the seta in row h –h2–h3. Lateral view of anterior part of the body (B and E): form of pteromorph; development of tutoria and tutorial cusps; size and form of pedotectum I. Development of the sensilus (C and F).

FIGURE 10. Miracarus hurkai Kunst 1959, holotype (Kunst Coll.). A—dorsal view, B—ventral view, C—lateral view, D—detail of pteromorph and bothridial area, E—detail of interlamellar region. Bars indicating 50 µm. Abbreviations: abn—anterior border of notogaster, bo—bothridium, cgl—circumgastric line, lam—lamella, pd1—pedotectum I, pt— pteromorph, sbl—subbothridial lamella, ss—sensillus, tu2—tutorial carina 2. Rest represents names of setae or setal insertions.