Crotonia gorgonia, Colloff, Matthew J., 2010

Colloff, Matthew J., 2010, New species of Crotonia (Acari: Oribatida: Crotoniidae) from Lord Howe and Norfolk Islands: further evidence of long-distance dispersal events in the biogeography of a genus of Gondwanan relict oribatid mites, Zootaxa 2650, pp. 1-18 : 2-7

Crotonia gorgonia sp. nov.

( Figs. 1–3 , 8 a)

Dimensions: holotype female length 1122, breadth 561; paratype female length 1106, breadth 545; paratype males (n = 7): mean length 929 (range 758–1022), breadth 416 (range 363–474). Ratio of length of prodorsum to total length: 0.34 (holotype).

Female. Prodorsum: ratio of length to breadth 1.06. Rostrum well-developed, with prominent naso, lateral edges markedly incised, concave; rostral seta 42, straight, stout, spiniform, smooth ( Fig. 1 a). Lamellar seta 235, recurved, very sparsely barbed. Lamellar apophysis 117, curved medially, broadening basally, slightly longer than mutual apical distance, extending anteriorly as far as apices of rostral setae. Interlamellar apophysis twice as long as broad; interlamellar seta well-developed, 190, flagelliform, smooth; extending anteriorly as far as base of naso. Prodorsal ridges absent. Diameter of bothridium 53; lateral ridge of bothridium with blunt anterior spine and complex series of digitate projections; hexagonal reticulations of operculum sparingly ornamented with concentric ridges and with point of origin near lateral margin ( Fig. 8 a). Median field of muscle sigilla present. Inter-bothridial ridge broad, well-developed, curved, with slight median invagination and small indentations along posterior margin. Prodorsal microsculpture smooth, porose. Prodorsum splayed posteriolaterally, forming acute spur-shaped ridge overlying acetabulum III.

Notogaster: ratio of length to breadth 1.33; notogastral shield broadest at level between bases of setae cp and e 2 ( Fig 1 a); ratio of width of shield to entire notogastral width 0.85; lateral margins of opisthosoma oval, inflated, with well-developed diagonal ridge and indentation on pleuraspis lateral of seta e 2. Dorsosejugal suture simple, transverse. Notogaster with 14 pairs of setae. Pre-notogastral shield separated from notogastral shield by transverse hyaline strip bearing short, thin, smooth, setiform setae c 1 and c 2 (60–67). Apophysis of seta c 3 (30), 2–3 times longer than broad; seta c 3 245, flagelliform, extending anteriorly at least as far as apophysis of interlamellar seta. Lyrifissure ia immediately posterior of apophyses of setae c 3. Notogastral shield smooth, porose, sides convex, bordered laterally by narrow strips of small tubercles, ca. 1–2 tubercles wide, extending posteriorly as far as seta f 2. Lateral hyaline strip (suprapleural scissure) broad, welldeveloped, especially between setae cp and e 2. Setae cp and e 2 short (67–83), on tubercles as long as broad on lateral margin of notogastral shield; Seta d 2 very short (17), setiform, on small tubercle, mutual distance (195) slightly greater than that between setae c 2. Opisthosomal gland opening gla positioned anteriomedial of short (58), reflexed seta f 2. Tubercle of seta f 2 prominent, extending well beyond margin of notogastral shield. Caudal apophyses clustered, bi-lobed, arising from caudal margin; caudal stalk absent. Apophysis of seta f 1 (33) curving dorsolaterally; apophysis of h 1 (42), arising from dorsal surface of incurved, short apophysis of seta h 2 (58); those of h 3 (33) positioned ventrally between f 1 and h 1, projecting posteriolaterally. Median caudal margin between apophysis h 2 curved, sub-circular. Caudal setae covered in cerotegument, sparingly barbed, subequal in length (56–70). Caudal region densely tuberculate; tubercles extending onto pleuraspis.

Ve n te r: epimeral microsculpture smooth, porose ( Fig. 2 a); epimeral setae smooth, spiniform, short (11– 22), formula 3-1-3-3; 3c on well-developed tubercle. Lateroventral circumgastric scissure (lcs) narrow, straight, sloping diagonally, forming a strongly obtuse angle (ca. 140°) with narrow perianal circumgastric scissure (pcs). Anteriolateral margin of adanal plate at junction of lcs and pcs indented. Genital plates subcircular, with transverse band of less sclerotised cuticle; posterior margin transverse; posteriolateral margins straight, diverging. Perigenital region sparsely tuberculate. Each genital plate 209 long 111 broad with nine spiniform setae, subequal in length (22–36); two pairs of aggenital setae, subequal in length to genital setae. Anal plate 56 broad, 267 long, with three short (17) setiform setae; distance between a 2 and a 3 slightly more than half that between a 1 and a 2; anal setae distributed along most of length of plate; three pairs of spiniform adanal setae, ad 2-3 shorter (16) and thinner than spiniform stout ad 1 (33). Distance between ad 2 and ad 3 half as long again as that between ad 2 and ad 1. Ventral margin of notogaster surrounding anal plates broadly Vshaped. Setae p 1 long, flagelliform (139) on short tubercles, adjacent; p 2 and p 3 setiform, subequal in length (64–67).

Male. As for female except for the following characters. Prodorsum: ratio of length to breadth 0.95. Lamellar seta smooth, lamellar apophysis long (140), flattened, extending anteriorly well beyond apices of rostral setae ( Fig. 1 b). Prodorsal ridges curved, extending two thirds of the distance between bases of interlamellar and lamellar apophyses. Inter-bothridial ridge straight, angled anteriolaterally at margins. Notogaster: ratio of length to breadth 1.45; ratio of width of shield to entire notogastral width 0.93; lateral margin of notogaster oval ( Fig. 1 b). Apophysis of seta c 3 short (14), only slightly longer than broad. Apophysis of seta h 1 (50) as long as those of h 2. Ve nt e r: epimeral setae smooth ( Fig. 2 b), relatively long (25– 40). Each genital plate 160 long 84 broad with nine spiniform setae, subequal in length (20–25). Anal setae distributed along posterior half of plate. Distance between ad 2 and ad 3 half that between ad 2 and ad 1.

Deutonymph. Prodorsum: rostrum with prominent naso, lateral edges incurved; rostral seta (ro) 54, reflexed, smooth ( Fig. 3 a). Lamellar seta (le) 210, recurved, smooth. Lamellar apophyses 73, their mutual distance half as long again as length, extending anteriorly beyond curve of rostral setae. Interlamellar seta (in) 230, flagelliform, smooth; extending anteriorly beyond apices of lamellar apophyses. Prodorsal ridges extending half the distance between interlamellar and lamellar apophyses. Lateral ridge of bothridium with blunt anterior spine and complex series of digitate projections. With curved inter-bothridial ridge. Median field of muscle sigilla present. Prodorsum porose; region posterior of interbothridial ridge with striate unsclerotised cuticle interspersed with small tubercles.

Gastronotic region: ratio of length to breadth 1.58; broadest at level of base of apophyses of setae c 3 ( Fig. 3 a). Dorsosejugal suture marked by line of tubercles. With 14 pairs of smooth notogastral setae. Seta c 1 29, situated at medial end of oval porose sclerite; seta c 2 42, at lateral end of sclerite. Seta d 2 31, mutual distance (38) subequal to that between setae c 1-2. Apophyses of lateral setae prominent tubular extensions (54–63 long) of ovoid porose sclerites. Lateral setae flagelliform: c 3 167, cp 254, e 2 258, f 2 295, f 1 290, h 1 263. Seta h 2 stout, short (83). Caudal apophyses elongated, tubular, subequal in length to lateral apophyses; that of h 1 the longest (77), directed posteriorly; caudal margin between apophyses of h 1 a blunt V-shape. Apophysis of h 2 (54) emerging medially from basal part of that of h 1, converging apically. Notogaster with series of longitudinal lines of tubercles interspersed by striate unsclerotised cuticle.

Ve nt e r: epimeres porose ( Fig. 3 b), with median unsclerotised longitudinally striate integument, diverging laterally in perigenital region, and becoming transverse posterior of genital plates. Epimeral setae smooth, spiniform, some with bacilliform cerotegument, formula 3-1-3-3; seta 3c longer than others, on welldeveloped tubercle. Genital plates elongate, ovoid; each plate 71 long, 17 broad with four spiniform setae; one pair of aggenital setae, subequal in length to genital setae. Anal plate 150 long, 40 broad; three pairs of spiniform adanal setae subequal in length. Setae of p series flagelliform, on sclerotised apophyses; p 1 133, p 2, 113, p 3 94; mutual distance between apophyses of p 1 more than twice their length.

Material examined. Holotype female, pyrethrum knock-down, subtropical rainforest, North-east summit, Mt. Gower, Lord Howe Is., 31°34'58"S 159°05'01"E, ca. 850 m, coll. G.B. Monteith, 9.xi.1979 (QM S26076 ). Paratype female, litter, south side of Erskine Valley, Lord Howe Is., 31°33'S 159°05'E, coll. G.B. Monteith, 24.xi.1979 (QM S26048 ). Paratype male, vegetation debris under Ficus macrophylla , broad sclerophyll forest, Lord Howe Is., 31°13'S 159°03'E, 0–50 m, coll. 15.xii.1991 ( ANIC bulk sample no. 3758). Six paratype males, one paratype deutonymph, leaf litter, low forest, base of cliff, Malabar Hill, Lord Howe Is., 31°30'53.09"S 159° 3'38.43"E, 120 m., coll. S. & J. Peck, 20.v.1980 (Field Museum Berlesate no. 80–367). Holotype, and paratype from Erskine Valley, deposited in Queensland Museum, Brisbane. Paratype from under Ficus macrophylla deposited in Australian National Insect Collection, CSIRO Ecosystem Sciences, Canberra. Paratypes from Malabar Hill in Field Museum of Natural History, Chicago.

Etymology. The specific name gorgonia is Latin, derived from the mythical Gorgo (also called Medusa ) who had snakes for hair; a reference to the shape of the sinuous caudal apophyseal cluster and their flagelliform setae.

Remarks. Crotonia gorgonia differs from all other Crotonia spp. by the following combination of characters: 1) the clustered, sinuous shape of the caudal apophyses and setae, with apophyses of setae h 2 incurved apically and either subequal with those of h 1 (male) or only slightly longer (female); 2) the long, broad lamellar apophyses; 3) the full complement of setae in the c series; 4) the short lateral notogastral setae; 5) nine pairs of genital setae; 6) the lateral ridge of the bothridium with a blunt anterior spine and digitate projections; 7) the long, flagelliform setae p 1 with their apophyses adjacent; 8) seta h 2 are flagelliform apically and reflexed; 9) the caudal setae are sparingly barbed.

The association of the male and the female of Crotonia gorgonia is based on the following shared characters: the morphology of the caudal apophyseal cluster and its barbed, apically flagelliform setae; the long, smooth flagelliform setae p 1; the concordant dimensions of the non-caudal notogastral setae (c 1-3, cp, e 2, d 2 and f 2); the prominent tubercles of setae c 3; the morphology of the lateral ridge of the bothridium and the position and dimensions of the apophyses of setae h 3. As well as being smaller, the male differs from the female in having a narrower notogastral shield, the presence of prodorsal ridges, the smooth lamellar setae, the absence of a less sclerotised transverse band on the genital plates and relatively longer epimeral setae.

The association of the deutonymph with the adults is based upon their co-occurrence in samples from Malabar Hill, as well as the convergent apophyses of setae h 2, 14 pairs of notogastral setae, the dimensions of the setae of the c series and the morphology of the lateral ridge of the bothridium with digitate projections. Crotonia gorgonia is a member of the Capistrata species group. It is closest morphologically to C. weiri Colloff, 2010 from south east Queensland in the morphology of the caudal apophyseal cluster which is characterised by the short apophyses of setae h 2 directed medially, only slightly longer than those of setae f 1 and h 1. Crotonia weiri differs in being considerably larger, with a more strongly inflated, rotund opisthosoma, with shorter setae c 1, c 2 and p 1 and lacking the tuberculate microsculpture of the caudal region.

Figures

FIGURE 1. Crotonia gorgonia sp. nov. dorsal a) holotype female; b) paratype male.

FIGURE 2. Crotonia gorgonia sp. nov. ventral a) holotype female; b) paratype male.

FIGURE 3. Crotonia gorgonia sp. nov. paratype deutonymph a) dorsal; b) ventral.

FIGURE 8. Bothridia a) Crotonia gorgonia sp. nov.; b) Crotonia norfolkensis sp. nov.; c) Crotonia utricularia sp. nov.