Eutegaeus nothofagi, 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 : 19-21

Eutegaeus nothofagi sp. nov.

( Figs. 5 , 6 )

Eutegaeus sp. nov. B: Colloff, 2022, p. 47.

Dimensions. Holotype: length 1,309 μm, breadth 980 μm; paratype females (n = 10): mean length 1,206 μm (range 1,106 –1,267 μm), mean breadth 874 μm (range 844–909 μm). Paratype males (n = 4): mean length 827 μm (range 792–901 μm), mean breadth 614 μm (range 614–620 μm). Tritonymph: mean length 995 μm, mean breadth 711 μm. Ratio of prodorsum to total length: 0.35 (holotype).

Description of adult. Prodorsum: rostrum acute; rostral setae (ro) flagelliform, reflexed, smooth, on short tubercles, visible in dorsal aspect.Lamellae broad, separated medially, parallel, lateral margins conspicuously convex, translamella absent. Lamellar setae (le) smooth, curved, extending well beyond apices of rostral setae, emerging from shallow cup-shaped incisions, each flanked by two short sharp teeth of equal size; cusps extending anteriorly well beyond rostrum ( Fig. 5a ). Interlamellar setae (in) shorter than setae le; anterior condyles of enantiophyses B present. Bothridia projecting laterally to inner margins of humeral processes, openings angled anteriorly, with anterior condyle of enantiophysis H in form of V-shaped posterior flange. Bothridial setae long, curved, bacilliform, smooth.

Notogaster: thin cerotegument with sinuous interdigitate microsculpture covering parts of notogaster ( Fig. 5c ); ratio of length to breadth: 0.84; notogaster rounded, convex. Humeral processes very broad, with dorsal keel, slightly waisted at their bases, expanded then becoming pointed apically, extending to point level with middle of lamella ( Fig. 5a ). Short, sharp lateral projection bearing lyrifissure ia on notogaster posterolateral of humeral process. With eight pairs of notogastral setae; l series, h 2 and h 3 present, relatively long, curved, smooth but with sparse covering of cerotegument basally; setae la and lm in sub-marginal position, lp, h 2 and h 3 and p series marginal ( Fig. 5a ); setae of p series very short, straight, smooth. Lyrifissures im present lateral of setae lm.

Ventral aspect: subcapitulum broad apically; mentum broader than long; subcapitular setae short, smooth, setae m twice as long as a and h ( Fig. 5b ). Tutorium short with blunt apex. Epimeral plates discrete, all broadly separated in midline, sub-rectangular to ovoid, plates IV shorter than others; epimeral setation 3-1-3-3; setae 3b at least twice as long as others. Pedotectum I (pd I) well-developed, sub-rectangular, margins angled obliquely; pd II small, pointed; discidium with rounded point. Ventral plate broader than long. Genital and anal plates separated by distance same as length of genital plate (164 µm), with six pairs of setae, g 5 displaced laterally, g 1 longer than others; lyrifissure iad in para-anal position, same distance from anal plate as seta ad 3. Anal plates lozenge-shaped, 291 µm long; with U-shaped ridge posterior of anal plates bearing setae ad 1 and ad 2. Pre-anal organ (po) T-shaped.

Description of tritonymph, nymphal and larval scalps. Tritonymph prodorsum: rostrum acute; rostral setae with fine spines, setae on short tubercles; lamellar setae with spinose ornamentation, emerging from shallow depression on lamellar cusp; cusp lacking prominent tooth or teeth ( Fig. 6a ). Lamellae with blocky, alveolate microsculpture, strongly incised laterally just posterior of setae le and again anterior of bothridia. Posteromedian prodorsum smooth, porose; setae in minute, linked by faint horizontal ridge Bothridia relatively short, no longer than broad; bothridial seta long (166 µm) bacilliform, with pointed tip.

Tritonymph gastronotum: U-shaped, broader (855 µm) than long (777 µm). Gastronotal setae emerging from elongate, cup-shaped or hemi-semicircular overlapping scales, each with a pointed tip anteriorly and posteriorly and ornamented with diagonal ribs extending from their base and with a median setal insertion canal ( Fig. 6a ). With 12 pairs of setae ornamented with few fine spines: full complement of c, l, h and p series present, c 2 on margin of scale bearing seta c 3; setae c 3, l and h series and p 1 straight, spiniform; seta h 1 and associated scale smaller than other h and l series and their scales; setae p 1 on single sub-rectangular scale; setae p 2 and p 3 small, setiform, smooth, positioned ventrally ( Fig. 6b ). Cuticle sparingly alveolate between setal scales, with cerotegument of blunt spines.

Deutonymphal scalp: with eight pairs of setae: c 1 and c 2 (c 3 absent), l series and h 2, h 3 and p 1; c 2 on short tubercles posterior of bothridium, smooth, setiform; scale of seta h 1 present but seta absent; setae p 1 both on single rectangular scale ( Fig. 6a ).

Protonymphal scalp: with eight pairs of setae, same complement as deutonymphal scalp, scale of seta h 1 absent ( Fig. 6a ).

Larval scalp: microsculpture tuberculate; scales absent, eight pairs of setae on short tubercles: c 1, the l series, h 3 and centrodorsal series d. Setae dp on small sclerite ( Fig. 6a ).

Tritonymph ventral aspect: ventral plate with fine corrugations and tubercles; anal plate with fine tubercles; epimeral setal formula 3-1-3-3; with four pairs of genital setae, one pair of aggenital setae, two pairs of anal setae and three pairs of adanal setae ( Fig. 6b ).

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

Type designation, material examined and locality data. Holotype female, ANIC accession no. 53-1033; paratypes: ten females, four males, one tritonymph, ANIC accession no. 53-1034, litter, Nothofagus cunninghami rainforest, Triplet Falls, Great Otway National Park , Victoria, 38°40’S, 143°30’E, coll. M.J. Colloff, 19.vii.2011 . Paratypes: ten females, one tritonymph, ANIC accession no. 53-1035, moss, Nothofagus cunninghami rainforest, rainforest walk, Maits Rest, Great Otway National Park , Victoria, 38°45’S, 143°33’E, coll. M.J. Colloff, 19.vii.2011 .

Etymology. This species is named for the Myrtle Beech forest ( Nothofagus cunninghami ) in which it was found.

Diagnosis. Eutegaeus nothofagi can be distinguished from other species in the genus by the following combination of characters: (1) the very broad lamellar cusps with apical teeth pointing laterally; (2) the absence of a translamella; (3) the presence of anterior condyles of enantiophyses B; (4) the broad, sharply pointed humeral processes with a pronounced dorsal keel; (5) the bothridium with the anterior condyle of enantiophysis H; (6) the prominent, sharp projection posterolateral of the humeral process; (7) the prominent, sub-rectangular pedotecta I with their lateral margins angled obliquely; (8) the U-shaped ridge posterior of the anal plates bearing setae ad 1 and ad 2.

Remarks. The absence of a translamella in this species is shared with E. bidhawal sp. nov., E. parapapuensis , E. paralagrecai and E. pulcher J. Balogh & Csiszár, 1963 . The latter species also has broad, sharply pointed humeral processes and the anterior condyle of enantiophysis H on the posterior margin of the bothridium but differs in the shape of the lamellar cusps and the reticulate microsculpture on them, the barbed lamellar setae and very short interlamellar setae. The notogaster of E. nothofagi is also much broader than long, whereas in E. pulcher the notogaster is almost as long as broad.

The association of the immatures with the adult is based, in part, on their presence in the same samples. At Triplet Falls in the Otway National Park, adults of E. woiwurrung were also present and the rationale for matching this species with its immatures is given above. In the material of from Maits Rest there were no adult eutegaeoid individuals present other than E. nothofagi . The tritonymph, at 1,011 μm long, more closely matches the adult of this species, at 1,309 μm long, than that of E. woiwurrung , at an average length of 1,009 μm for females and 976 μm for males. Also, the small paired teeth on the lamellar cusp of the tritonymph of E. nothofagi matches the cusp of the adult.

Figures

FIGURE 5. Eutegaeus nothofagii sp. nov., adult (a) dorsal aspect; (b) ventral aspect; (c) detail of cerotegument on notogaster. Scale bars: (a, b) = 200 μm; (c) = 20 μm.

FIGURE 6. Eutegaeus nothofagii sp. nov. tritonymph (a) dorsal aspect with larval, protonymphal and deutonymphal scalps; (b) ventral aspect. Arrow indicates the scale associated with seta h1, but the seta itself is absent. Scale bar = 200 μm.