Crotonia borbora Luxton 1987
Creators: name: Colloff, Matthew J.
Publisher: name: Zenodo
Year: 2010
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Sarcoptiformes
Crotoniidae
Crotonia
Crotonia borbora

description: Crotonia borbora Luxton, 1987
(Figs. 2, 18 b, 21)
Dimensions. Syntypes: males (n = 6), mean length 1192 (range 1153–1264), mean breadth 448 (range 427– 458); females (n = 8) mean length 1328 (range 1265–1438) mean breadth 478 (range 475–528. Ratio of length of prodorsum to total body length: 0.35 (male specimen labelled ‘holotype’).
Redescription of male. Prodorsum: ratio of length to breadth 1.33. Rostrum well-developed, with prominent naso, lateral edges slightly concave; rostral seta 47, straight, spiniform, smooth (Fig. 2 a). Lamellar seta 281, recurved, smooth, flagelliform. Lamellar apophyses 119, straight, thin, parallel, shorter than their mutual distance by a quarter; extending anteriorly as far as apices of rostral setae. Interlamellar apophysis twice as long as broad; interlamellar seta 375, flagelliform, smooth; extending anteriorly beyond apex of curve of lamellar setae. Prodorsal ridges very short, directed medially, extending anteriorly less than a fifth of the distance between bases of interlamellar and lamellar apophyses. Diameter of bothridium 34; auriculate ridge of bothridium in the form of a pair of short, blunt spurs (Fig. 18 b); hexagonal reticulations of operculum sparingly ornamented with well-developed ridges and with point of origin near lateral margin. one anteriolateral, one on posterior margin. Inter-bothridial ridge a faint, diffuse shallow curve of dense cuticular plaques; without a median invagination. Median field of muscle sigilla present. Prodorsal microsculpture smooth, porose with region of diffuse cuticular plaques posterior of inter-bothridial ridge. Prodorsum splaying posteriolaterally to form a ridge overlying cuticle dorsal of acetabulum III.
Notogaster: ratio of length of notogaster to breadth of notogastral shield 2.1; notogastral shield broadest at base of seta e 2 (Fig. 2 a); ratio of width of shield to entire notogastral width 0.65; lateral margins of notogastral shield lozenge-shaped, inflated. Dorsosejugal suture simple, diffuse medially; region posterior of apophysis of seta c 3 strongly concave, waisted. Lyrifissure ia located on anterior face of pronounced lateral ridge immediately posterior of concave region. With 14 pairs of smooth notogastral setae. Pre-notogastral shield separated from notogastral shield by narrow transverse hyaline strip bearing short (25), stout, apophysis of seta c 3 and compound apophysis of seta c 1 and c 2 (33 long, 28 broad) with bifurcating apices and single base; sub-apophysis of seta c 1 and c 2 subequal in length and breadth. Setae c 1-3 long, thin, flagelliform; c 1 410, c 2 505, c 3 495. Notogastral shield smooth, narrow, sides slightly convex, tapering to V-shape anterior of caudal apophyses; bordered laterally by two narrow strips of small, sparsely-distributed tubercles, extending to just posterior to seta f 2. Lateral hyaline strip (suprapleural scissure) well-developed, bearing sort, squat tubercles of setae cp, e 2 and f 2. Seta d 2 short (25), setiform; mutual distance sub-equal (81) to that between setae c 1-2; cp, e 2 and f 2 short, setiform, subequal in length (72–93). Opisthosomal gland opening gla positioned medial of seta f 2. Caudal apophyses on narrow, elongated stalk, with lateral folds, projecting posteriorly from caudal margin and slightly elevated dorsally. Caudal apophyses bi-lobed, those of h 2 slightly curved, diverging apically, 125 long. Apophysis of h 1 (50) emerging dorsolaterally from base of that of h 2, just posterior of that of f 1 (46). Flagelliform setae f 1 and h 1 subequal (95). Seta h 2 138, setiform, recurved. Seta h 3 positioned anteriorly and ventrally of f 1, just visible dorsally.
Ve n t e r: epimeral microsculpture smooth, porose (Fig. 2 b); epimeral setae smooth, spiniform, some with cerotegument, formula 3-1-3-3; ca. 20–30 long, 4a slightly longer (56) than others; seta 3c spiniform, on welldeveloped tubercle. With lcs narrow, straight, transverse, forming a 90° angle with pcs. Anteriolateral margin of adanal plate without an indentation. Genital plates sub-circular; posterior margin transverse. Perigenital region smooth. Each genital plate 163 long, 106 broad, with eight setiform setae, subequal in length (25); two pairs of aggenital setae, subequal in length to genital setae. Anal plate narrow (34 broad), 268 long with three short (31) setiform setae on central region of plate; three pairs of spiniform adanal setae, ad 2-3 slightly shorter and thinner than spiniform stout ad 1 (45). Ventral margin of notogaster surrounding anal plates V-shaped. Seta p 1 flagelliform (105), p 2-3 setiform, p 3 shorter (38) and thinner than p 2 (75).
Lateral view: Caudal margin almost perpendicular to notogastral shield, curving ventrally (Fig. 2 c); dorsal and ventral surfaces more or less parallel, distance between them ca. 350. Apophyses of setae f 1 and h 1 pointing posteriodorsally, those of h 2 prominent, curved, more-or-less horizontal, pointing posteriorly; those of h 3 positioned anterioventral of f 1, pointing posteriolaterally. Caudal cluster significantly more elevated than level of notogastral shield. Apophyses of seta p 1 on caudal margin midway between underside of caudal stalk and ventral surface; p series equidistantly spaced. Pleuraspis sparsely tuberculate.
Material examined. Syntypes: male (labelled ‘holotype’), QM S40778, ferny vine on tree trunks, rainforest, Summit TV Station, Bellenden Ker Range, Queensland, 17°16'S 145°51'E, 1560 m., coll. Earthwatch/QLD. Museum, Nov. 1–7, 1981 (QM Berlesate No. 345). Female (labelled ‘paratype’), QM S40772, stick brushings, rainforest, Cableway Base Station, Bellenden Ker Range, Queensland, 17°16'S 145°51'E, 100 m., coll. 17–24.x.1981. Female (labelled ‘paratype’), QM S40773, stick brushings, rainforest, Summit TV Station, Bellenden Ker Range, Queensland, 17°16'S 145°51'E, 1560 m., coll. 1–7.xi.1981. Two males, QM S40731, stick/moss brushings, rainforest, Summit TV Station, Bellenden Ker Range, Queensland, 17°16'S 145°51'E, 1560 m., coll. Earthwatch/QLD. Museum, 1–7.xi.1981 (QM Berlesate No. 370). One female (‘variant’) QM S40733, stick brushings, rainforest, 1 km S. of Cable Tower 6, Bellenden Ker Range, Queensland, 17°16'S 145°51'E, 500 m., coll. Earthwatch/QLD. Museum, 17–24.x.1981 (QM Berlesate No. 310). One female (‘variant’) QM S40737 coll. Russel R. Moss, 18.x–xi.1981 [Bellenden Ker Range, Queensland]. One female (‘variant’) QM S40738, Cable Tower 3, Bellenden Ker Range, Queensland, 17°16'S 145°51'E, 1054 m., coll. Earthwatch/QLD. Museum, 25–31.x 1981 (QM Berlesate No. 325). One male, QM S40739, ferny vine on tree trunks, rainforest, Summit TV Station, Bellenden Ker Range, Queensland, 17°16'S 145°51'E, 1560 m., coll. 25–31.x.1981. Four females, two males, QM S40771, pitfall traps and litter, rainforest, Summit TV Station, Bellenden Ker Range, Queensland, 17°16'S 145°51'E, 1560 m., coll. 25– 31.x.1981.
Remarks. Luxton (1987) did not publish a holotype designation, so all the material mentioned by him constitutes a syntype series (Article 73.2, International Commission on Zoological Nomenclature, 1999). The male specimen from sample QM S40778 is labelled ‘holotype’ and this is hereby designated the lectotype. All other members of Luxton’s series therefore become paralectotypes.
The redescription of Crotonia borbora above differs in some significant respects from the original description. The illustration of the compound, bifurcate apophyses of setae c 1-2 by Luxton (1987) is unclear (in part because their bases are obscured by the right seta c 3), but they appear to be separate, though contiguous. Also the caudal stalk is longer and thinner than originally illustrated, and the caudal setae are flagelliform and smooth, not barbed and spiniform. Luxton (1987) mentioned a variant that had ‘round areas with a dark central spot’ covering the notogastral shield. Two females (from samples S40733 and S40737) with this character were examined as part of the present study and found to be identical with Crotonia borbora. The round areas with the central dark spot appear to be cerotegument secreted from cuticular pores. The structures were not part of the cuticle itself.
Crotonia borbora differs from all other Crotonia spp. by the following combination of characters: 1) all caudal setae are borne on apophyses extending from the caudal stalk; 2) the presence of compound, bifurcate apophyses bearing setae c 1 and c 2 on a single basal stalk; 3) the apophyses of setae f 1 are adjacent to those of setae h 1; 4) the narrow notogastral shield with parallel margins; 5) setae cp short, subequal in length to e 2 and f 2; 6) lateral margins of notogastral shield tuberculate; 7) prodorsum with extensive network of plaques.
Crotonia borbora is morphologically most similar to Crotonia sterigma (cf. remarks section on C. sterigma above for similarities and differences).
description: Published as part of Colloff, Matthew J., 2010, The Gondwanan relict oribatid genus Crotonia (Acari: Oribatida: Crotoniidae) from rainforests in Queensland and Northern New South Wales: new species show a mixed pattern of short-range and long-range endemism, pp. 1-51 in Zootaxa 2649 on pages 6-9, DOI: 10.5281/zenodo.198744