Archegozetes, Grandjean, 1931

Norton, Roy A. & Ermilov, Sergey G., 2024, Evaluation of morphological traits in Trhypochthoniidae with focus on Allonothrus, and morphology-molecule conflict in classification and phylogeny of Nothrina (Acari: Oribatida), Zootaxa 5556 (1), pp. 144-199 : 166

Leg setation in Archegozetes

Archegozetes longisetosus , originally collected from Thailand ( Aoki 1965), is a widespread tropical-subtropical species ( Subías et al. 2012). Adult legs were illustrated by Beck (1967; his Figs 6–9 ), but no ontogenetic data were presented. Most setae were not labelled, but several errors can be corrected. (1) The three solenidial notations on tarsus I (Beck’s Fig. 6 ) are incorrect, based on our observations and on ontogenetic studies of tarsus I in the similar A. magnus by van der Hammen (1955b): using the standard ontogenetic sequencing, Beckʹs ω 1 should instead be ω 3; his ω 2 should be ω 1; and his ω 3 should be ω 2. 4 (2) On tibia I (his Fig. 6 ), the seta labelled vʺ is actually larval seta cʺ (vʺ does not form).

Appendix 2 presents the ontogeny of setiform organs based on specimens from Costa Rica, complemented by observations from cultured Puerto Rican specimens (see Heetoff et al. 2013). Notable traits include: the presence of four larval setae (including cʺ) on tibia I, with a final complement of five; the absence of cʺ from larval tibia II, with a final complement of four; the absence of several fundamental tarsal setae, including the primilateral pair (pl) from tarsus I, primiventral setae (pv) from tarsi II and III, and fastigial seta ftʹ from tarsus III 5. Seta d is coupled with the respective solenidion on genua and tibiae I, II, but on tibiae III, IV and genu III they are noticeably separated. Both antelateral setae (a) are formed on tarsus IV. Regarding accessory setae, the iteral pair (it) are absent and the adult forms proximal setae on tarsi I–III and sometimes IV. The number of proximal accessory setae is variable and we did not study the statistics. But at least one lateral (l) pair forms on tarsi I and II, in addition to one or more ventral pairs (v); tarsus III seems to form only ventral setae; tarsus IV forms only vʹ or none. The tarsal variation in adults reported by Beck (1967) is certainly related to these setae.

Figures

FIGURE 6. Allonothrus tuxtlasensis (adult female, light micrographs): a—subcapitulum, ventral view (palps removed); b— postpalpal seta; c—ovipositor, lateral view (anterior to top); d—three coronal setae (k) of ovipositor; e—seta τ1 and unidentified strongly bent τ-seta on anterior lobe of ovipositor; f—genu I, dorsal view; g—same, different specimen; h—as in g, but deeper focus to show canal of minute solenidion σ m; i—genu and tibia II, dorsal view; j—genu III, dorsal view. Scale bars 10 µm (a–c), 5 µm (d–j).

FIGURE 7. Allonothrus tuxtlasensis (adult female, scanning electron micrographs): a—anteromedial part of notogaster, showing encrusting cerotegument with variably-developed surface granules (black arrows), broken parts exposing exocuticular foveolae (white arrows); b—posterior notogastral setae (lateral view); c—rostrum and left leg I, lateral view; d—partial ventral view, black arrow to ventrosejugal articulation (* = fibrous artefact); e—dorsal region of genu I; f—closeup of solenidion σm. Scale bars 100 µm (d), 20 µm (c), 10 µm (a, b), 5 µm (e), 1 µm (f).

FIGURE 8. Gnathosomal region of several Trhypochthoniidae (adult females, scanning electron micrographs): a—Allonothrus tuxtlasensis, near-ventral view showing distal half of subcapitulum; b—same, anteroventral view showing almost entire subcapitulum; c—Allonothrus sinicus, ventral aspect showing entire subcapitulum, slightly distorted (laterally compressed); d—Afronothrus incisivus, anteroventral view of gnathosomal region (insert = nearer to anterior view of rutellum). Scale bar 10 µm. Some setae damaged during scanning process.

FIGURE 9. Trhypochthoniidae, adults of various species (light micrographs): a—Afronothrus incisivus, dorsal view of right bothridium, external (upper) and internal (lower) focus; b—Allonothrus sinicus bothridium, external (upper) and internal (lower) focus; c—Archegozetes magnus bothridium, external (upper) and internal (lower) focus; d—Mainothrus badius bothridium, internal focus; e—Trhypochthonius tepoztecus bothridium, internal focus; f—Afronothrus incisivus genu I (upper) and genu III (lower); g—Allonothrus sinicus genu I (upper) and genu II (lower); h—Allonothrus russeolus genu I (upper) and genu II (lower); i—Archegozetes magnus genu III; j—Trhypochthonius tectorum genu II; k—Mainothrus badius genu I (upper) and genu II (lower); l—Allonothrus sinicus, posteromedial region of notogaster. Scale bar (lower right): 20 µm (all to same scale). * = insertion of bothridial seta at base of bothridium; white arrows in a–e indicate respiratory pouches or brachytracheae.