Neoeutegaeus torsteini Colloff 2023, sp. nov.

Neoeutegaeus torsteini sp. nov.

(Figs. 20, 21)

Neoeutegaeus sp.: Colloff, 2019, p. 306, Figs. 10c, 10d; 11f; 12f; 13f; 14f.

Dimensions. Holotype female length 301 μm, breadth 208 μm. Paratype males (n = 8): length 274 μm (range 261– 295 μm), breadth 182 μm (range 163–191 μm). Paratype females (n = 17): mean length 293 μm (range 287–308 μm); mean breadth 195 μm (range 188–209 μm). Ratio of prodorsum to total length: 0.48 (holotype). Tritonymphs (n = 5) mean length 317 μm (range 298–316 μm), mean breadth 202 μm (range 189–218 μm).

Description of adult. Prodorsum: rostrum acute, rostral setae (ro) short, curved, smooth, not visible in dorsal aspect. Lamellae broad, separated medially, lateral margins convex, extending beyond lateral margin of prodorsum and anteriorly beyond rostrum (Fig. 20a). Lamellar setae (le) with spinose ornamentation, curved medially, apices overlapping, emerging from apices of free, sub-triangular lamellar cusps; medial margins of cusps forming V-shape; with complete translamella. Interlamellar setae (in) minute, curved. Bothridia as broad as long, projecting beyond inner margins of humeral processes, openings angled anterolaterally, posterior margin lacking anterior condyle of enantiophysis H. Bothridial setae long, curved, bacilliform, head slightly expanded with small spines.

Notogaster: ratio of length to breadth: 0.81; notogaster rounded, convex with cerotegument of small, scattered tubercles. Humeral processes very long, straight, parallel, triangular, pointed, lacking dorsal keel, extending to point level with middle of lamella, lateral margin expanded where process joins margin of notogaster, then incurved (Fig. 20a). Lyrifissure ia long, positioned at base of humeral process lateral of posterior condyle of enantiophysis H. With eight pairs of notogastral setae, l series and h 2 and h 3 sub-marginal, smooth, thin, curved, covered in cerotegument thus appearing thickened (Fig. 20c); p series extremely short, setiform, not visible in dorsal aspect.

Ventral aspect: subcapitulum broad; subcapitular setae minute, smooth, setae h on anterior margin of mentum (Fig. 20b). Tutorium very broad, pointed. Epimeral plates discrete, separated in midline, sub-rectangular, plates III and IV shorter than I and II, with median strip of cuticle between plates I; epimeral setation 3-1-3-2; setae minute, sub-equal in length. Pedotectum I (pd I) well-developed, rectangular, with short lateral cusp; pd II long, broad, rounded apically; discidium lobe-like; perigenital carina and enantiophysis E4 present. Ventral plate ovoid, much broader than long. Genital and anal plates separated by distance of just over half length of genital plates; genital plates 39 µm long, with six pairs of short setae sub-equal in length, g 4 displaced laterally; two pairs of minute adanal setae; lyrifissure iad in para-anal position, close to margin of anal plate, less than length of iad. Anal plates ovoid, 42 µm long. Pre-anal organ (po) oval.

Description of tritonymph, nymphal and larval scalps. Tritonymph prodorsum: with cerotegument of scattered tubercles; centrodorsal microsculpture tessellated, bounded by slight ridges (Fig. 21a). Rostrum broad, rounded; rostral setae straight, smooth, on short tubercles; lamellar seta broad, ovoid, with small spines, straight, emerging from short tubercle, joined by transverse ridge. Interlamellar seta very short, smooth, on squat tubercle. Bothridia cup-shaped, slightly constricted basally, with exobothridial seta (ex) on posterior margin; bothridial seta long (103 µm), curved, smooth, slightly expanded apically, pointed.

Tritonymph gastronotum: U-shaped, longer (229 µm) than broad (202 µm), with cerotegument of scattered tubercles. Anterolateral margin with rounded, squat humeral process bearing seta c 3 (Fig. 21a). With 12 pairs of gastronotal setae: full complement of c, l, h (h 1 present) and p series; c 3, l and h series and p 1 broad, ovoid, with fine spines; seta c 1 setiform, smooth; c 2 long, leaf, shaped, with fine spines.

Deutonymphal and protonymphal scalp: deutonymphal scalp with seven pairs of setae: c 3 (c 1 and c 2 absent), l series, h 2, h 3 and p 1, all on short tubercles; protonymphal scalp with six pairs of setae c 3 (c 1 and c 2 absent), l series, h 3 (h 2 absent) and p 1 (Fig. 21a).

Larval scalp: with scattered alveolate microsculpture; nine pairs of leaf-like setae on short tubercles: c 1 and c 3, la and lm, h 3 and p 1 and the centrodorsal d series. Setae dp on very long, pendulous tubercles (Fig. 21a).

Tritonymph ventral aspect: microsculpture of ventral surface with fine, widely-spaced striations (Fig. 21b); epimeral setal formula 2-1-2-2; with five pairs of genital setae, two pairs of adanal setae.

Ontogenetic formula of gastronotic setae (including one larval and two protonymphal and deutonymphal setae not present on scalps): 10-(8,9,12)-8.

Type designation, material examined and locality data. Holotype female; ANIC accession no. 53-1058, paratypes: 27 females, 12 males, five tritonymphs, ANIC accession no. 53-1059, moss on Sassafras (Atherosperma moschatum), rainforest, Errinundra Saddle, Errinundra National Park, Victoria, 37°19’S 148°51’E, 1,030 m., coll. M.J. Colloff, 29.ix.2009.

Etymology. This species is named in honour of my friend and colleague, the late Associate Professor Thorstein Solhøy, formerly of the Department of Biology, University of Bergen, in recognition of his contribution to the taxonomy and ecology of oribatid mites.

Diagnosis. Neoeutegaeus torsteini can be distinguished from other species in the genus by the following combination of characters: (1) the sub-triangular apices of the lamellar cusps, without teeth; (2) the well-developed, overlapping lamellar setae with spinose ornamentation; (3) the posterior condyles of enantiophyses H; (4) the minute, stout interlamellar setae; (5) the very broad tutoria; (6) the very long lyrifissures ia; (7) the long bothridial setae with an expanded head bearing small spines.

Remarks. Neoeutegaeus torsteini shares with N. melipsilon sp. nov. (cf. below) the broad, rounded pedotecta II and short, thick, blunt notogastral setae, but the latter species has nine pairs of notogastral setae, two teeth on the lamellar cusp and much shorter lamellar setae.

The association of the tritonymph with the adult is based, in part, on their presence in the same samples, and the absence of other Neoeutegaeus spp., but also the size range of the tritonymphs fits with that of the adults, being slightly shorter and narrower. However, there are no obvious morphological characteristics shared by the tritonymphs and the adults.