Eutegaeus ptilosus, Colloff, 2023

Colloff, Matthew J., 2023, The oribatid mite superfamily Eutegaeoidea (Acari, Oribatida), with descriptions of new taxa from Australia and New Caledonia and a re-assessment of genera and families, Zootaxa 5365 (1), pp. 1-93 : 23-25

Eutegaeus ptilosus sp. nov.

( Figs. 8 , 9 )

Dimensions. Holotype length 1,074 μm, breadth 814 μm. Paratype females (n = 17): mean length 1,144 μm (range 1,101 –1,209 μm); mean breadth 844 μm (range 794–877 μm). Paratype males (n = 7): mean length 1016 μm (range 1,008 –1,023 μm); mean breadth 651 μm (range 605–690 μm). Paratype tritonymph length 893 μm, breadth 672 μm. Ratio of prodorsum to total length: 0.36 (holotype).

Description of adult. Prodorsum: rostrum acute; rostral setae (ro) on short tubercles, setiform, curved, smooth, visible in dorsal aspect. Lamellae broad, separated medially, parallel, with reticulate microsculpture, lateral margins strongly convex, incurved basally, with a complete translamella. Lamellar setae (le) smooth, curved, extending well beyond apices of rostral setae, emerging from shallow cup-shaped incisions of lamellar cusp, each flanked laterally by short sharp tooth and medially by blunted projection; cusps extending well beyond rostrum, their medial margins convex ( Fig. 8a ). Interlamellar setae (in) very long, almost as long as bothridial setae, but not reaching to translamella, positioned medially of bases of lamellae. Bothridia projecting laterally beyond median margins of humeral processes, marked invagination anteriorly at base of lamella; with stepped, peg-like anterior projection; posterior bothridial margin with V-shaped anterior condyle of enantiophysis H. Bothridial setae long, straight, bacilliform, smooth, pointed.

Notogaster: with thin cerotegument covering sinuous, interdigitate microsculpture; notogaster rounded, convex, ratio of length to breadth: 0.84. Humeral processes very broad, without dorsal keel, waisted at bases, expanded then becoming pointed apically, extending to point level with middle of lamella ( Fig. 8a ). Short, broad projection on notogaster posterolateral of humeral process; lyrifissure ia not visible. With eight pairs of notogastral setae: l series, h 2 and h 3 present, short (sub-equal in length to setae in), slightly curved, smooth; setae la in centrodorsal position, lm in sub-marginal position, lp, h 2 and h 3 and p series marginal ( Fig. 8a ); setae p 1 almost as long as h 2 and h 3, closely-spaced and originating on squat tubercles. Setae p 2 and p 3 visible only in ventral aspect, one third of length of p 1. Lyrifissures im not visible.

Ventral aspect: subcapitulum broad apically; mentum same breadth as length; subcapitular setae smooth, setae h close to anterior margin of mentum, longer than a and m ( Fig. 8b ). Tutorium not visible in ventral aspect. Median margins of epimeral plates not evident, plates sub-rectangular to circular, plates IV almost circular, very large; epimeral setation 3-1-2-2; setae 3a and 3b markedly longer than others. Pedotectum I (pd I) well-developed, sub-rectangular, with median notch; pd II curved, horn-shaped; discidium small, with sharp point. Ventral plate broader than long. Genital and anal plates separated by distance about same as length of genital plates; genital plates 113 µm long, with six pairs of setae, g 5 displaced laterally, g 6 longer than others; lyrifissure iad in para-anal position, some distance from margin of anal plate, same as distance of bases of setae ad 3. Anal plates lozenge-shaped, 237 µm long. Pre-anal organ (po) T-shaped.

Description of tritonymph and nymphal scalps. Tritonymph prodorsum: rostrum acute; rostral setae curved, smooth, long, emerging from tubercles; lamellar setae well-developed, with three or four long, pectinate spines, emerging from tubercle on lamellar cusp; cusp ovoid, rounded apically, lacking prominent tooth or teeth ( Fig. 9a ). Lamellae smooth, strongly incised laterally posterior of setae le and again anterior of bothridia, with thin, amorphous cerotegument. Central region strongly reticulate, bounded by curved ridges between bases of interlamellar setae and anterior incision of lamella; setae in short, peg-like, on squat tubercles. Bothridia short, no longer than broad, projecting laterally, with rounded posterior flange; bothridial seta long (125 µm), curved, bacilliform, with pointed tip.

Tritonymph gastronotum: U-shaped, broader (712 µm) than long (634 µm). Gastronotal setae emerging from elongate, overlapping scales with long, horn-shaped lateral projections; scales smooth with median setal insertion canal ( Fig. 9a ). With 12 pairs of smooth setae: c, l, h and p series present, c 1 and c 2 shorter than l and h series, c 1 positioned medially on dorsosejugal scissure, c 2 emerging from tubercle on margin of scale bearing seta c 3; c 3, l and h series and p 1 long, straight, setiform, with rounded apex and three sharp tines ( Fig. 9c ); seta h 1 and associated scale smaller than other h and l series and their scales; both setae p 1 on single scale; setae p 2 and p 3 thin, setiform, smooth, positioned ventrally, posterolateral of anal plate, but not on scales ( Fig. 9b ). Cuticle with spines of cerotegument between scales.

Deutonymphal scalp: with eight pairs of setae: c 1 and c 3 (c 2 absent), l series and h 2, h 3 and p 1; c 3 thin, smooth, flagellate, emerging from short tubercles posterior of bothridium, tubercles with median apical spine; l series and h 2, h 3 and p 1 same morphology as tritonymphal setae but shorter; setae p 1 each on separate sub-rectangular scale ( Fig. 9a ). Cuticle with strongly reticulate microsculpture.

Protonymphal scalp: with six pairs of setae: l series, h 2, h 3 and p 1; setae of the c series and h 1 (and scale) absent. Cuticle with strongly reticulate microsculpture ( Fig. 9a ).

Tritonymph ventral aspect: ventral plate with fine striae with small tubercles of cerotegument; epimeral setal formula 3-1-2-2; four pairs of genital setae, one pair of aggenital setae, two pairs of anal setae and three pairs of adanal setae ( Fig. 9b ).

Ontogenetic formula of gastronotic setae (including two protonymphal and deutonymphal setae not present on scalps):?-(8,10,12)-8.

Type designation, material examined and locality data. Holotype female, ANIC accession no. 53-1039 ; paratypes: 12 females, one tritonymph, ANIC accession no. 53-1040, ANIC 754, Nothofagus moorei and Sassafras ( Atherosperma moschatum ) litter, rainforest, Cobark Forest Park, Barrington Tops, New South Wales, 31°59’S, 151°49’E, coll. T. Weir and A. Calder, 15.xi.1981. Paratypes: seven males, five females, ANIC accession no. 53-1041, ANIC 749, litter, closed Eucalyptus forest, Barrington Tops National Park, Gloucester Road, 30°04’S, 151°41’E, coll. T. Weir and A. Calder, 12–14.ix.1981.

Etymology. The specific name is derived from the Greek, πτῐ́λον (ptilon), meaning a feather, referring to the feather-like lamellar setae of the tritonymph.

Diagnosis. Eutegaeus ptilosus can be distinguished from other species in the genus by the following combination of characters: (1) the lamellar cusp with a lateral tooth and a blunt medial projection; (2) the complete translamella; (3) the elongated interlamellar setae; (4) the peg-like projection on the anterior of the bothridium; (5) the presence of the anterior condyle of enantiophysis H; (6) the pointed lateral projections posterior of the humeral processes; (7) the notogastral setae la in the centrodorsal position, lm in the sub-marginal position and the others in the marginal position; (8) setae p 1 about three times the length of p 2 and p 3, closely-spaced and on squat tubercles; (9) pedoctectum pd II curved, horn-shaped; (10) the large, sub-circular epimeral plates IV.

Remarks. Eutegaeus ptilosus shares with E. nothofagi , E. bidhawal , E. soror , E. curviseta and E. membraniger the lateral projections posterior of the humeral processes. The latter two species have setae p 1 on squat tubercles, but setae p 1 of E. ptilosus are considerably longer. The squat tubercles, complete translamella, anterior condyle of enantiophysis H, notogastral setae la in the centrodorsal position and lm in the sub-marginal position place E. ptilosus as morphologically closest to E. curviseta . However, E. curviseta has two teeth on the lamellar cusp, lamellar setae with spinose ornamentation and only five pairs of genital setae.

The epimeral setal formula of 3-1-2- 2 in the tritonymph and adult of E. ptilosus is unusual. Seta 4b is absent as well as 3c.

Figures

FIGURE 8. Eutegaeus ptilosus sp. nov., adult (a) dorsal aspect; (b) ventral aspect. Scale bar = 200 μm.

FIGURE 9. Eutegaeus ptilosus sp. nov., tritonymph (a) dorsal aspect with larval, protonymphal and deutonymphal scalps; (b) ventral aspect; (c) detail of apex of seta lm. Scale bar = 200 μm.