Malaconothrus darwini, Colloff, Matthew J. & Cameron, Stephen L., 2013

Colloff, Matthew J. & Cameron, Stephen L., 2013, A phylogenetic analysis and taxonomic revision of the oribatid mite family Malaconothridae (Acari: Oribatida), with new species of Tyrphonothrus and Malaconothrus from Australia, Zootaxa 3681 (4), pp. 301-346 : 320-324

Malaconothrus darwini sp. nov.

( Figs. 12–14 )

Dimensions. Holotype female length 460 μm, breadth 205 μm. Paratype females mean length (n = 13) 477 μm (range 420–515 μm); mean breadth 223 μm (range 195–252 μm). Ratio of prodorsum to total length: 0.32 (holotype).

Female. Prodorsum. Rostrum acute, smooth, porose ( Fig. 12 a). Rostral seta (ro) smooth, slightly curved, setiform, 39 μm long, longer than distance between them, emerging from apex of prodorsal carina. Lamellar seta (le) smooth, setiform, 45 μm long, as long as mutual distance, extending as far as base of ro, emerging just medial of anterior convex region of lateral ridge. Interlamellar seta (in) smooth, setiform, 76 μm long, as long as distance between them. Exobothridial seta ex 1 smooth, 37 μm long. Prodorsum finely porose, with poorly-developed curved longitudinal ridges.

Notogaster. Dorsosejugal furrow slightly convex, cerotegument strongly reticulate laterally, becoming fainter medially ( Fig. 12 a). Humeral region rounded. Lyrifissure ia 21 μm long. With 15 pairs of smooth, setiform setae, plus f 1, represented by their alveoli. Setae c 1, d 1 and e 1 much longer than others. Seta c 1 65 μm long, longer than distance to d 1; c 2 45 μm, longer than distance to cp, closer to c 3 than to c 1; c 3 38 μm, longer than distance to cp; cp 56 μm, longer than distance to d 2; d 1 80 μm, longer than distance between them; d 2 63 μm, longer than distance to e 2; e 1 67 μm, longer than distance between them; e 2 43 μm long, shorter than distance to f 2; f 2 35 μm shorter than distance to h 2; h 1 51 μm, shorter than distance to p 1; h 2 45 μm, shorter than distance to p 1; h 3 28 μm, markedly shorter than h 2; p 1 43 μm, shorter than distance between them; p 1 positioned dorsally; p 3 48 μm long ( Fig. 3 b), longer than distance to p 2 (54 μm long). With concave ridges between h 1 and median caudal margin. Faint lateral longitudinal ridges extending from h 1 to c 2. With faint longitudinal ridges lateral of anal and genital plates. Notogastral margins more-or-less parallel, broadest between f 2 and e 2. Ratio of length to breadth 1.55. Caudal margin U-shaped, transverse or very slightly indented between setae p 1; well-developed indentation at level of h 2. Lyrifissurae ip acute.

Subcapitulum. Seta h on mentum 14 μm long ( Fig. 13 a). Gena with two setae: a (20 μm long) and m (13 μm long); coxal spine (e) present. Palp setal formula (solenidion in brackets) 0-1-3-9(1); palp tarsus short, rounded apically; eupathidial setae spiniform, pointed apically; solenidion ω curved, bacilliform. Seta d on tibia barbed. Cheliceral seta cha short, conical; Pb curved, barbed ( Fig. 13 b).

Coxisternum. Epimeral setal formula 3-1-3-3 ( Fig. 12 b). Epimeral setae smooth, setiform; 3b, 3c and 4c 26–35 μm long, much longer than others (5–18 μm); 1c in posteriolateral position, 3b in mediolateral position. Epimeral Anogenital Region. Genital setae four pairs, smooth, setiform ( Fig. 12 b); g 1-3 subequal in length (19–24 μm), closely spaced; g4 30 μm long, directed anteriorly; distance between bases of g 3 and g 4 2 × that between g 2 and g 3. Setae shorter than width of genital plate. Genital plate 93 μm long, 50 μm broad, sub-hexagonal; posterior margin transverse. Without reticulate or striated cerotegument between adanal plate and ventral margin of notogaster. One pair of anal setae 4 μm long, same width as that of anal plate. Each adanal plate 89 μm long, 37 μm broad; three pairs of long (43–54 μm) smooth, setiform adanal setae, longer than width of adanal plate; ad 1 not on median carina. Anterior margin of adanal plate acute, overlapped by posterior margin of genital plate, without thickened transverse ridge.

Lateral Aspect. Prodorsum smoothly curved from seta in to apex of rostrum ( Fig. 12 c). Seta le projecting as far as base of seta ro. Seta ex 1 projecting posteriolaterally; seta ex 2 represented by alveolar vestige. Pedotectum I welldeveloped, blunt, triangular. Interbothridial region slightly concave. Notaspis not strongly convex: ratio of height to length 0.49. Pleuraspis with well-developed humeral process.

Legs. Pre-tarsi heterotridactylous; lateral claws sparingly barbed on dorsal edge ( Fig. 14 ). Legs short and broad: Leg I 183 μm long; tarsi sub-conical. Ratio of length to breadth of Tarsi: I 1.94; II 2.38; III 2.5; IV 3.3. Setal formula: Leg I 1-5 -4(1)-4(1)-11(3); Leg II 1-7 -3(1)-3(1)-10(1); Leg III 2-3 -2-2(1)-10; Leg IV 0- 2 -2-2-10. All setae on all segments smooth. Tarsus I with proral setae (p) short, broad basally, flagelliform apically ( Fig. 14 a): short, blunt and broad on other tarsi; unguinal setae (u) short, blunt and broad: peg-like; solenidia (ω1-3) clustered; famulus (ε) thin, relatively long (12 μm); fastigial setae (ft) homeomorphic: short, blunt and broad. Tarsus II and III with ft ” short, blunt and broad and ft ’ longer, broad basally, tapering and pointed apically ( Figs 14 b,c). Tarsus IV with ft ” long (43 μm), curved, pointed; seta s same shape and length as primiventral setae (pv) ( Fig. 14 d).

Material examined. Holotype female and paratype female, soaking moss, Overcliff Walk, west of Weeping Rock, Wentworth Falls, Blue Mountains, New South Wales, 33°43'36"S 150°22'14"E, 830 m., coll. M.J. Colloff, 14.i.2011. Five paratype females, wet Cladonia sp. on rocks and soil, Tarpeian Rock, nr. Leura, Blue Mountains, New South Wales, 33°43'26"S 150°19'31"E, 910 m, coll. M.J. Colloff, 13.i.2011. Paratype female, wet moss on tree trunk, between Elysian Rock and Gordon Falls Lookout, Price Henry Walk, Leura, Blue Mountains, New South Wales, 33°43'35"S 150°19'53"E, 835 m, coll. M.J. Colloff, 14.. i.2011. Paratype female, ANIC 430, rainforest, Eacham National Park, Queensland. 17°17'24"S 145°37'38"E, 760 m., coll. R.W. Taylor, 1–7.iv.1973.

Three paratype females, ANIC 771, litter, Nothofagus moorei, Wiangaree State Forest, New South Wales, 28°22'S 153°05'E, 1050 m., coll. T. Weir & A. Calder, 10–12.ii.1983. Three paratype females, ANIC 773, same data as previous sample. Twenty eight paratype females, ANIC 4016, moss on trunk of Sassafras ( Atherosperma moschatum ), cool temperate rainforest, 1077 m., Errinundra Saddle, Errinundra National Park, Victoria, 37°19'18"S 148°51'11"E, 1030 m., coll. M.J. Colloff, 30.v.2009. Holotype and paratypes deposited in the Australian National Insect Collection, CSIRO Ecosystem Sciences, Canberra.

Etymology. This species was collected from its type locality near Wentworth Falls, by chance three days prior to the 175th anniversary of the visit by Charles Darwin to the same locality on 17th January, 1836 (Darwin, 1845; Nicholas & Nicholas, 2008, p. 48 et seq.) and is named in Darwin’s honour.

Remarks. Malaconothrus darwini sp. nov. differs from other members of the genus by the following combination of characters: 1) rostral and lamellar setae are subequal in length; 2) the reticulate cerotegument; 3) the concave ridges between h 1 and the caudal margin; 4) the four pairs of relatively long genital setae, with g 4 separated from the others and pointing anteriorly; 5) the median setae c 1, d 1 and e 1 are longer than the other notogastral setae and overlapping; 6) epimeral setae 4b are on prominent posteriorly-directed, lateral spines; 7) the very long adanal setae.

Malaconothrus darwini sp. nov. is one of a group of species characterised by a reticulate cerotegument and the most posterior pair of genital setae separated from the anterior, posteriolaterally-pointing cluster of three or four setae, and pointed anteriorly. This group contains M. angustirostrum ( Hammer, 1966) , M. opisthoseta ( Hammer, 1966) ; M. oxyrhinus ( Hammer, 1962) ; M. platyrhinus Hammer, 1962 ; M. prahuensis Hammer, 1979 ; M. repetitus Subías, 2004 (= T. reticulatus Yamamoto, 1977 ) and M. talaitae sp. nov. Malaconothrus repetitus has very long, thick body setae and genital setae g 3-4 much longer than g 1-2; M. prahuensis , M. oxyrhinus and M. platyrhinus have much shorter median notogastral setae and the genital setae vary markedly in length. Both M. angustirostrum and M. opisthoseta have notogastral setae that more closely match the relative lengths of those of M. darwini but have broader, more arched apodemata IV and much shorter genital setae. Malaconothrus darwini is morphologically most similar to M. talaitae sp. nov. (cf. below). They share similar configuration and proportions of the notogastral ridges and setae as well as the overall shape of the notogaster. They differ in that the prodorsum of M. talaitae is broader and has an inter-rostral ridge; setae ro are reflexed, setae in are only 1.5 × the length of setae ex 1; epimeral plates IV have only two setae, plates II are separated in the midline; plates III and IV are fused and the anal setae are long and flagelliform.

Figures

FIGURE 3. Tyrphonothrus gnammaensis sp. nov., holotype female; a) dorsal; b) ventral.

FIGURE 12. Malaconothrus darwini sp. nov., holotype female; a) dorsal; b) ventral; c) lateral.

FIGURE 13. Malaconothrus darwini sp. nov., paratype female; a) subcapitulum; b) chelicera; Malaconothrus gundungurra sp. nov. paratype female; c) palp; d) chelicera.

FIGURE 14. Malaconothrus darwini sp. nov., left legs, antiaxial view; a) Leg I; b) Leg II; c) Leg III; d) Leg IV.