Pycnonoticae and poronoticae with wrinkled nymphs
An example of Circumdehiscentiae with wrinkled nymphs, Scapheremaeus argentinensis TRAVÉ & FERNÁND. (Cymbaeremaeidae) protonymph, in dorsal view, with the legs omitted.
– Comments. The cuticle is strongly plicate, mainly on the dorsal and ventral sides of the opisthosoma. In the dorsal side of the opisthosoma (in yellow), the ridges are transverse except anterolaterally where they are clearly longitudinal, and anteriorly where the cuticle is embossed.
The anterior region of the prodorsum (or rostrum) is substantially tilted downwards. Consequently, from the dorsal orientation, this part of the body is only partly seen and a convex line of apparent outline is shown above the rostral setae ro. The rostrum is a large-sized cuticular fold (a border tectum sensu Grandjean, 1934b, called ‘rostral tectum’ or ‘rostral hood’) which protects the chelicerae at rest (‘stegasimous’ oribatid mite). Above the rostral border and in front of the rostral setae, the rostral surface is occupied in its mid part by a kind of pad (not shown).
The chaetotaxy of the prodorsum is normal for a circumdehiscent oribatid mite. In addition to the rostral setae ro, the following pairs of setae are detected: the lamellar setae le; the interlamellar setae in; the sensilli; and, the exobothridic setae (not shown). It should be noted that the existence of only one pair of exobothridic setae corresponds to the state Ex1 in the numerical regression which affects these setae over the whole field of the Oribatida (cf. Grandjean, 1953a, p. 426).
The sensilli bo (or bothridic or pseudostigmatic setae) have a short stalk and are apparently club-shaped. In fact, their head consists of ten to a dozen leaf-like elements arising from a central axis where they are more or less completely fused. The cavities into the bottom of which the sensilli are inserted (or bothridia; in green) are widely open and slightly prominent.
The dorsal surface of the prodorsum bears nine carinae as follows:
(a) a pair of longitudinal ridges (in blue) between the bothridia and lamellar setae le.
(b) an unpaired, transverse carina.
(c) three pairs of small ridges in the vicinity of the interlamellar setae in.
The dorsosejugal furrow dsj (or das) is relatively deep and slightly convex anteriorly.
As in the other Circumdehiscentiae, the ecdysial cleavage line δ runs posteriorly and laterally on the opisthosoma (i.e. ‘circumopisthosomatic dehiscence’). Yet the line δ is ‘abnormal’ in the protonymph insofar as it passes on both sides above the pseudanal seta p1 instead of, as usual, between the two pseudanal setae p1 and p2. In contrast, the dehiscence is normal in the deutonymph and tritonymph (cf. Grandjean, 1947b, and Norton & Kethley, 1994). It should be noted that, as usual, the line δ runs above the notogasteral setae c3 and the cupule-shaped lyrifissures ia (strain detectors; cf. Barth, 1981),
The notogasteral chaetotaxy is of ‘unidificient’ type (group N4 in Grandjean, 1949a, pp. 214, 216) as normally found in many Circumdehiscentiae with naked nymphs (data in Grandjean, 1953a, pp. 435-440). The pair of setae f1 of the opisthosomatic segment F (i.e. the setae close to the plane of symmetry of the body) are missing and the centrodorsal setae (labelled da, dm and dp or d1, d2 and e1) are present. Consequently, there is a total of 30 notogasteral setae. Posterior setae lp (also labelled f2) and h1-3 are inserted on relatively wide tubercles. They are also a bit longer than the other notogasteral setae.
The exocrine, latero-abdominal glands gla (or ‘lateral opisthosomal glands’ or ‘opisthonotal glands’ or ‘oil glands’) are small. Their opening is on the ventral side of the opisthosoma. Consequently, in accordance with the rule, the glands come out beneath the line of dehiscence δ. As usual, there are five pairs of opisthosomatic, cupule-shaped lyrifissures (not shown).
– Abbreviations. c, row of notogasteral setae. la, lm, laterodorsal, anterior and median notogasteral setae, respectively. (after Travé & Fernández, 1986).
