Neoeutegaeus melipsilon, 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 : 46-48

Neoeutegaeus melipsilon sp. nov.

( Figs. 22 , 23 )

Dimensions. Holotype female 300 μm, breadth 194 μm. Paratype females (n = 14): mean length 308 μm (range 300–318 μm); mean breadth 192 μm (range 183–202 μm). Paratype males (n = 4): mean length 281 μm (range 279–283 μm); mean breadth 172 μm (range 169–176 μm). Tritonymph length 317 μm, breadth 202 μm. Ratio of prodorsum to total length (holotype): 0.38.

Description of adult. Prodorsum: rostrum acute; rostral setae (ro) minute, smooth, not visible in dorsal aspect. Tutoria curved, projecting beyond margin of prodorsum. Lamellae broad, separated medially, lateral margins convex, covering prodorsum and extending well beyond rostrum ( Fig. 22a ). Lamellar seta (le) very short, curved, smooth, spiniform, emerging from slight concavity on apex of lamellar cusp between two small sharp teeth; medial margins of cusps parallel, with complete translamella basally. Interlamellar setae (in) well-developed, curved, smooth. Bothridia elongate, corniculate, not projecting as far as humeral processes, opening anterolaterally. Bothridial seta long, head expanded slightly then truncated, with few small spines.

Notogaster: cerotegument of small, scattered tubercles; ratio of length to breadth: 0.87; notogaster rounded, convex. Humeral processes long, straight, parallel, triangular, pointed, with dorsal keel, extending to point below middle of lamella, lateral margin expanded at anterolateral margin of notogaster forming slight conical projection ( Fig. 22a ). With eight pairs of notogastral setae, l series and h 2 and h 3 sub-marginal, smooth, setiform, curved, short, pointed, sub-equal in length; p series shorter, setiform, p 1 and p 2 visible in dorsal aspect.

Ventral aspect: subcapitulum acute; subcapitular setae short, smooth, setae h on anterior margin of mentum ( Fig. 22b ). Tutorium very broad, apex right-angled. Epimeral plates discrete, separated in midline, sub-rectangular, plates III and IV much shorter than I and II; with strip of triangular cuticle between epimeral plates I; epimeral setation 3-1-3-2; setae very short, sub-equal in length. Pair of shallow epimeral foveolae (ef) present between plates II and III. Pedotectum I (pd I) well-developed, rectangular, with anterior cusp and alveolate microsculpture; pd II very long, broad, lobe-like; discidium long, broad, rounded apically; perigenital carina and enantiophysis E4 present. Ventral plate ovoid, broader than long. Genital and anal plates separated by distance less than half length of genital plates; genital plates 38 µm long, with six pairs of short setae sub-equal in length, g 4 displaced laterally; two pairs of short adanal setae; lyrifissure iad in para-anal position, close to anal plate. Anal plates ovoid, 46 µm long. Pre-anal organ (po) oval.

Description of tritonymph, nymphal and larval scalps. Tritonymph prodorsum: with microsculpture of sub-hexagonal ridges on central prodorsum ( Fig. 23a ). Rostrum broad, rounded; rostral setae straight, smooth, short, on short tubercles; lamellar setae broad, ovoid, with small spines, straight, emerging from well-developed tubercles, joined by transverse ridge. Interlamellar setae very short, smooth, on squat tubercles. Bothridia cup-shaped, projecting laterally; bothridial seta long, curved, smooth, slightly expanded apically, pointed.

Tritonymph gastronotum: U-shaped, broader than long, smooth. Anterolateral margin with rounded, sub-rectangular humeral processes bearing setae c 3, indented posteriorly ( Fig. 23a ). 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, pointed; seta c 1 setiform, smooth; c 2 long, leaf, shaped, with fine spines.

Deutonymphal and protonymphal scalp: with eight pairs of setae: c 3 (c 1 and c 2 absent), l series, h series and p 1, all on short tubercles ( Fig. 23a ).

Larval scalp: with scattered alveolate microsculpture; seven pairs of leaf-like setae on short tubercles: la, lm, h 3 and p 1 and centrodorsal d series. Setae dp on long, pendulous tubercles ( Fig. 23a ).

Tritonymph ventral aspect: ventral plate with fine, widely-spaced ridges posteriorly ( Fig. 23b ); epimeral setal formula 3-1-3-2; with five pairs of minute genital setae, one pair of aggenital setae, two pairs of adanal setae.

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

Type designation, material examined and locality data. Holotype, ANIC accession no. 53-1060, wet moss, Cumberland Creek Valley, Marysville-Woods Point Road, near Cambarville , Yarra Ranges National Park , Victoria, 37º33’S 145º52’E, coll. R. E. Roughley, 12.iii.1996 . Paratypes: 22 females, seven males, one tritonymph, ANIC accession no. 53-1061, ANIC 297 , moss and litter, Nothofagus cunninghami rainforest, Cumberland Creek Valley, near Picnic Area [Cumberland Memorial Scenic Reserve], Yarra Ranges National Park , Victoria. 37°34’S 145°52’E, 920 m. Coll. R. W. Taylor and R. J. Bartell, 4.xi.1970 . Paratypes: 14 females, four males, ANIC accession no. 53- 1062, ANIC 592 , leaf litter and decaying log, Cement Creek, 5 km west of Warburton , Victoria, 37°3’3S 145°42’E, coll. J. Lawrence and T. Weir, 18.i.1977 .

Etymology. The prefix of the specific name is from the Latin mel (honey), referring to the colour of the cuticle. The suffix - ipsilon is an invented word, chosen for its Greek phonaesthetic.

Diagnosis. Neoeutegaeus melipsilon can be distinguished from other species in the genus by the following combination of characters: (1) the short, smooth, spiniform lamellar setae each emerging from between two teeth; (2) the relatively long, curved, stout interlamellar setae; (3) the bothridial setae with club-shaped heads, truncated apically and with a few spines; (4) the prominent median strip of triangular cuticle between epimeral plates I; (5) the large tutoria with blunt apices extending beyond the lateral margins of the lamellae; (6) the alveolate microsculpture on the lateral margin of pedotectum I; (7) the very large, lobe-shaped pedotectum II; (8) the pair of epimeral foveolae between epimeral plates II and II.

Remarks. Neoeutegaeus melipsilon shares with N. africanus the relatively long interlamellar setae, lamellar cusps each with two small apical teeth and the large discidia with rounded apices, but it lacks the anterior condyles of enantiophyses H. Also, in N. africanus the head of the bothridial seta is club-shaped with small spines, but is bilobed.

The association of the tritonymph with the adult is based on their presence in the same samples in 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, as for N. torsteini , there are no obvious morphological characteristics shared by the tritonymphs and adults.

Figures

FIGURE 22. Neoeutegaeus melipsilon sp. nov., adult (a) dorsal aspect; (b) ventral aspect; (c) detail of notogastral seta la. Scale bar = 100 μm.

FIGURE 23. Neoeutegaeus melipsilon sp. nov.: (a) tritonymph, dorsal aspect; (b) tritonymph, ventral aspect; (c) larval, protonymphal and deutonymphal scalps. Scale bar = 100 μm.