Eutegaeus Berlese, 1916

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 : 13-15

Eutegaeus Berlese, 1916

Eutegaeus Berlese, 1916, p. 62 .

Type species: Oribata bostocki Michael, 1908, p. 136 .

Birotegaeus Luxton, 1988a, p. 82 , syn. nov.

Type species: Eutegaeus biroi J. Balogh, 1970, p. 296 .

Pareutegaeus Woolley, 1965, p. 384 , syn. nov.

Type species: Eutegaeus similis Trägårdh, 1931, p. 575 .

Diagnosis. The following diagnosis is modified from that of Luxton (1988a) and Ermilov (2020b) and includes a character state for immatures. Adults: large oribatid mites (>800 μm); rostrum rounded; lamellar cusp about one-third length of lamella, projecting beyond rostrum, separated medially and joined by complete or partial translamella or translamella absent; lamellar setae inserted in notch on anterodorsal edge of lamellae, each seta flanked by one or two teeth or teeth absent. Bothridia often with anterior condyle of enantiophysis H on posterior margin but posterior condyle absent from anterior notogaster; with or without two ovoid structures posterior of interlamellar setae representing anterior condyles of enantiophysis B. Bothridial seta long and bacilliform or setiform, rarely short and club-shaped. Humeral process ovoid, pointed, waisted basally, projecting from anterior edge of notogaster, reaching beyond bothridia anteriorly but not extending posteriorly beyond anterior margin of notogaster nor broad basally. Notogaster with eight (rarely nine) pairs of setae; l series in centrodorsal position, the rest marginal or sub-marginal. Pedotectum I (pd I) sub-rectangular in ventral view, pd II and discidium triangular, pointed. Six pairs of genital setae with penultimate pair displaced laterally; three pairs of adanal setae; perigenital carina absent. Chelicerae chelate-dentate, of normal proportions. Pre-anal organ T-shaped. Nymphs: all gastronotal setae except c 1 and c

2 emerging from scales.

Remarks. Subías (2004) listed Eutegaeus curviseta Hammer, 1966 as a junior synonym of E. bostocki ( Michael, 1908) although Luxton (1985) recognized them as distinct species. Both have short setae p 1 on squat tubercles and lamellar cusps with well-developed teeth and a pair of condyles on the prodorsum posterior of the interlamellar setae. This character state is also present in E. biovatus Hammer, 1972 from Tahiti, E. fueginus Arcidiacono, 1993 and E. lagrecai Arcidiacono, 1993 from Tierra del Fuego, E. nothofagi sp. nov. from Australia (cf. below) and E. papuensis Aoki, 1964 from Papua New Guinea. However, the two species differ in that the bothridial setae of E. bostocki are expanded apically and each has a sharp tip, described by Michael (1908, p. 136, Plate 17, Fig. 3 ) as ‘slightly fusiform heads upon thin peduncles’, whereas those of E. curviseta are longer, slightly expanded apically but blunt. Also, the interlamellar setae and notogastral setae of the l and h series of E. bostocki are much shorter than those of E. curviseta and the l and h series are in the sub-marginal position, whereas in E. curviseta setae la and lm are centrodorsal (cf. Fig. 13a for definition of locations of centrodorsal, sub-marginal and marginal notogastral setae). The lateral tooth of the lamellar cusp is larger than the medial one in E. bostocki and the lamellar seta emerges from a deep cup-shaped cleft between them, whereas in E. curviseta the medial tooth is larger and the lamellar seta emerges from a slight indentation of the apex of the lamellar cusp. Accordingly, I also consider E. bostocki and E. curviseta to be distinct species.

Woolley (1965) established Pareutegaeus for Eutegaeus similis Trägårdh, 1931 from the Juan Fernández Islands based on the rounded lamellar cusps and lamellar setae emerging from near their tips, reticulate lamellar microsculpture, long interlamellar setae and with a pair of small tubercles on the posterior margin of the notogaster. Luxton (1988a), who redescribed E. similis based on the lectotype, found the lamellar cusp has a slight excavation and the lamellar seta emerges apically from the cusp in a shallow invagination between two short, blunt teeth. This character state is found in several Eutegaeus spp. ( E. fueginus , E. lagrecai and E. papuensis ). Likewise, the reticulate lamellar microsculpture is common in Eutegaeus ( E. curviseta , E. lagrecai , E. paralagrecai , E. parapapuensis , E. pinnatus , E. radiatus Hammer, 1966 , E. soror , E. stylesi Hammer, 1966 and E. woiwurrung sp. nov.) and in Atalotegaeus mensarosi. This pattern of microsculpture is part of the lamellae themselves, as illustrated in the scanning electron micrograph of E. lagrecai by Arcidiacono (1993, Fig. 2 and 3 therein) and is not due to any overlying cerotegument as assumed by Ermilov (2020b, pp. 332, 340). The presence of long interlamellar setae, almost as long as the lamellae or longer, is also common in Eutegaeus ( E. bidhawal sp. nov., E. curviseta , E. paralagrecai , E. pinnatus and E. soror ). Luxton (1988a) found no small tubercles on the posterior notogaster of E. similis . He considered Pareutegaeus a valid genus and differentiated it from Eutegaeus based on the absence of prominent teeth on the lamellar cusps, but this character state also occurs in Eutegaeus , as discussed above, as do the other character states in the diagnosis of Pareutegaeus by Luxton (1988a). Accordingly, I do not consider Pareutegaeus Woolley, 1965 is a valid genus and hereby designate it a junior synonym of Eutegaeus Berlese, 1916 .

Luxton (1988a, p. 82) established Birotegaeus for Eutegaeus biroi J. Balogh, 1970 from Papua New Guinea and differentiated it from Eutegaeus on the basis that it has nine pairs of notogastral setae rather than eight pairs, with la in the centrodorsal position, and a mound on the posterior notogaster. In other respects, the character states that Luxton (1988a) used in his diagnosis of Birotegaeus do not differ from those of Eutegaeus , including the shape of the lamellae and lamellar cusps, the humeral processes, the absence of condyles of enantiophyses H, B and E4 and the number and disposition of the notogastral setae. Eutegaeus papuensis also has nine pairs of notogastral setae (with h 1 present) and several species have setae la (and le) displaced medially to the centrodorsal position, including E. bostocki , E. curviseta , E. pinnatus Hammer, 1966 , E. membraniger Hammer, 1966 , E. woiwurrung sp. nov., E. nothofagi sp. nov. and E. bidhawal sp. nov. A slight posterior notogastral mound is also present in E. parapapuensis Ermilov, 2020 and E. paralagrecai Ermilov, 2020 and several species have setae p 1 emerging from a pair of short, closely-adjacent tubercles on the posterior notogaster ( E. biovatus , E. bostocki , E. curviseta , E. membraniger , E. papuensis , E. pinnatus , E. radiatus and E. stylesi ). In the remaining species of Eutegaeus , setae p 1 emerge from an alveolus. Accordingly, I do not consider the character states of Luxton (1988a) sufficient to differentiate Birotegaeus from Eutegaeus and hereby designate Birotegaeus Luxton, 1988a as a junior synonym of Eutegaeus Berlese, 1916 .

In his revised definition of the genus, Ermilov (2020b) included the morphology of the bothridial seta as clavate, lanceolate, setiform or bacilliform in his revised diagnosis of Eutegaeus . The four species that have short, club-shaped bothridial setae ( E. fueginus , E. lagrecai , E. parapapuensis and E. similis ) are all from the southern Neotropical region.

Ermilov (2020b, p. 350) stated that Eutegaeus has “eight pairs of notogastral setae (la, lm, lp, h 1, h 2, p 1, p 2, p 3)…rarely with nine pairs of setae (if h 3 present).” I consider that in Eutegaeus it is not h 3 that is labile and subject to loss in the adult, but h 1, based on the occurrence in the deutonymph of E. woiwurrung and E. nothofagii of a scale corresponding with h 1 but the absence of a seta (arrowed in Figs. 3a , 6a ). Neither the scale or seta h 1 is present in the deutonymph of E. ptilosus sp. nov. ( Fig. 9a ).

Figures

FIGURE 2. Eutegaeus woiwurrung sp. nov., adult (a) dorsal aspect; (b) ventral aspect; (c) detail of left notogastral seta lm. Scale bar = 200 μm.

FIGURE 3. Eutegaeus woiwurrung sp. nov., immatures (a) tritonymph (Tn), dorsal aspect, bearing larval (La), protonymphal (Pn) and deutonymphal (Dn) scalps. Arrow indicates the scale associated with seta h1, but the seta itself is absent. Scale bar = 200 μm; (b) tritonymph, bothridium. Scale bar = 40 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.

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.

FIGURE 13.Atalotegaeus crobylus sp. nov., adult (a) dorsal aspect showing notogastral setae in the centrodorsal position (cd), sub-marginal (sm) and marginal (m) positions; (b) ventral aspect. Scale bar = 200 μm.