Crotonia macfadyeni, Colloff, Matthew J., 2009

Colloff, Matthew J., 2009, Species-group concepts and biogeography of the genus Crotonia (Acari: Oribatida: Crotoniidae), with new species from South and Central America, Zootaxa 2081, pp. 1-30 : 3-8

Crotonia macfadyeni sp. nov.

( Figs. 1–3 )

Crotonia n. sp. Starý & Block, 1996, p. 525.

Dimensions: holotype female body length 1229, breadth 576; paratype females (n = 5) mean length 1263, mean breadth 554; paratype males (n = 3) mean length 1105, mean breadth 444; mean ratio of length of prodorsum to total length (both sexes): 0.3. In the following description of the female the measurements refer to the holotype.

Female. Prodorsum: rostrum very prominent, 36 long, 56 broad; rostral setae 24, straight, barbed ( Fig. 1 a). Lamellar setae recurved, 210, barbed. Lamellar apophyses extending anteriorly just beyond rostrum. Interlamellar apophyses twice as long as broad; interlamellar setae slender, flagelliform, smooth; extending anteriorly beyond apices of rostral setae. Shallow prodorsal ridges extending half the distance between interlamellar and lamellar apophyses. Posterior interbothridial ridge present, with median alveolar field. Prodorsal microsculpture tuberculate.

Notogaster: ratio of length to breadth 1.5; broadest at seta e 2 ( Fig. 1 a). Dorsosejugal suture simple, transverse. With 13 pairs of notogastral setae; all except h 2 with strongly barbed ornamentation. Notogastral shield discrete, porose, with marginal strip of diffuse tubercles; centrodorsal region smooth. Setae of c series long, barbed, flagelliform, subequal (265), on stout tubercles longer than broad; c 3 extending as far as interlamellar apophyses. Bases of c 3 positioned close to dorsosejugal suture; apophyses of setae c 1 slightly posterior of it; distance between tubercles c 3 and c 1 and both c 1 112 and 56 respectively. Lateral hyaline strip (suprapleural scissure) present bearing tubercles of setae cp, e 2 and f 2. Setae d 2 short, setiform, on alveoli. Apophyses of setae f 2 prominent, projecting beyond lateral margin, subequal to e 2; gla positioned slightly anterior of f 2. Apophyses of setae f 1 and h 1 adjacent, subequal, projecting posteriorlaterally, about half the length of well-developed apophyses of smooth, spiniform setae h 2. Caudal margin between apophyses of h 2 strongly concave; apophyses of h 3 ventral, between h 2 and h 1, subequal to apophyses h 1.

Ve n t e r: epimeral microsculpture porose, tuberculate marginally and in perigenital region ( Fig. 1 b); epimeral setae spiniform, formula 3-3-3-3; barbed or bifurcate apically, subequal ca. 20-25; supernumerary seta on left hand side of epimere 3 (arrow). Seta 3c situated close to anterior margin of epimere. Ventral margin of notogaster surrounding anal plates U-shaped; genital plates sub-circular. Each genital plate 265 long 133 broad with 9 spiniform setae. Aggenital setae subequal to epimeral setae. Anal plate 48 broad, 280 long; anal and adanal setae subequal, spiniform. Setae of p series on tubercles and barbed; p 2 and p 3 spiniform, short; p 1 setiform, barbed, considerably longer than others.

Protonymph. Dimensions: length 679, breadth 237.

Prodorsum: rostral setae small, blunt, straight, barbed, on squat tubercles as long as broad ( Fig. 2 a). Lamellar setae barbed, flagelliform. Lamellar apophyses diverging apically, extending as far as apices of rostral setae; about a third as long as distance between them. Interlamellar apophyses well-developed, about three times longer than broad; interlamellar setae smooth, flagelliform, long, extending well beyond apex of arch of lamellar setae. Prodorsal ridges straight, converging apically, extending just posterior to lamellar apophyses. Sensillus enclosed in bothridium; with veined microsculptural covering. Anterior prodorsal microsculpture porose, plicate laterally, tuberculate posterior of bothridia; with a median alveolar field but no interbothridial ridge.

Notogaster: ratio of length to breadth: 2.1; lateral borders parallel as far as caudal apophyses; microsculpture transverse plicate, with diffuse lateral rows of shallow tubercles. Dorsosejugal suture not apparent; boundary between prodorsum and notogastral shield indicated by transverse plicate cuticle and apophyses of setae c 1 and c 3. With 13 pairs of long flagelliform notogastral setae barbed ( Fig. 2 a); apophyses of c 1 squat, twice as long as broad, those of c 3 long, well-developed, four times as long as broad; distance between apophyses c 3 and c 1 and both c 1 apophyses subequal; setae c 3, cp and e 3 and their apophyses subequal. Setae d 2 emerging from alveoli, positioned posteriomedially to apophyses of setae cp. Setae of the f and h series longer than other notogastral setae; their apophyses with bulbous bases. Apophyses of f 1 positioned just anteriodorsal of those of h 1; pointing posteriolaterally. Those of h 2 pointing posteriorly; setae h 2 stout, spiniform, slanted towards the medial line; apophyses of setae h 3 ventral, positioned between apophyses of setae h 1 and h 2. Caudal region tuberculate.

Ve n t e r: epimera smooth ( Fig. 2 b); bordered by longitudinally plicate cuticle medially. Epimeral setae short, stout, bifurcate and with cerotegument ( Fig. 2 d); formula 3-1-3-2. Genital plates oval, surrounded by circle of plicate cuticle, with one pair of bifurcate setae covered with cerotegument ( Fig. 2 c). Plications of cuticle between genital and anal plates transverse, becoming longitudinal around elongated, narrow anal plates. With no aggenital setae; p series relatively short, flagelliform, barbed; p 2 positioned just anteriolateral of p 1; p 3 positioned lateral of anal plates about midway along them.

Deutonymph. Dimensions: body lengths 716, 725; breadths 307, 331.

Prodorsum: as for protonymph but with posteriorly curved interbothridial margin between porose medial prodorsal plate and lateral, posterior transversely plicate cuticle ( Fig. 3 a).

Notogaster: as for protonymph, but ratio of length to breadth: 1.2; lateral borders convex, widest at level of setae cp ( Fig. 3 a). Notogastral microsculpture plicate with scattered tubercles. Apophyses of marginal setae elongate, bulbous at bases.

Ven t er: as for protonymph but epimeral microsculpture porose, tuberculate marginally ( Fig. 3 b); Epimeral setal formula 3-2-3-3. Genital plates oval, surrounded by circle of plicate cuticle. With four pairs of spiniform genital setae with cerotegument; one pair of aggenital setae, three pairs of short, straight adanal setae with spiniform ornamentation. No anal setae. Setae of p series well-developed, flagelliform, barbed; p 2 positioned midway between p 1 and p 3; apophyses of setae p 3 twice the length of the others.

Tritonymph. Dimensions: body length 883, breadth 397.

Prodorsum: as for deutonymph but with microsculpture of posterior region tightly plicate (Fig. 4a).

Notogaster: as for deutonymph, but ratio of length to breadth: 1.5, Notogastral microsculpture tight plicate reticulations. Specimen in Fig. 4a with a developmental abnormality in the form of doubled seta c 3 emerging from a bifurcate apophysis.

Ven t er: as for deutonymph but epimeral setal formula 3-2-3-3; epimeral seta 3c emerging from prominent tubercle on anterior margin of epimere; 7 pairs of genital setae, 2 pairs of aggenital setae and 3 pairs of anal setae. Reticulate, plicate microsculpture extending to region posterior of epimera 4 (Fig. 4b).

FIGURE 4. Crotonia macfadyeni sp. nov. tritonymph a) dorsal; b) ventral, with supernumerary seta on apophysis of c 3 (arrowed)

Material examined and locality data. Type material: holotype female and paratypes (five females, three males, one protonymph, two deutonymphs, two tritonymphs) from under tussocks of whitegrass, Cortaderia pilosa, Gun Hill, Christmas Harbour , West Falkland, Falkland Islands; coll. A. Macfadyen, November- December 1989. Holotype, three paratype females, three paratype males and all nymphal paratypes deposited in Australian National Insect Collection, CSIRO Entomology, Canberra. Two paratype females deposited in the Natural History Museum, London

Other material: one female, grassland, soil and rhizosphere sample of grass, near The Canache, Rookery Bay, Port Stanley, East Falkland, Falkland Islands, coll. W. C. Block, 8th November1971, field sample no. 65- 7-f(3)FLI-39. One protonymph, two deutonymphs, sample of Blechnum penna-marina , on outcrop of rocks, west of Port Stanley, East Falkland, Falkland Islands, coll. W. C. Block, 5th November 1971, field sample no. 64-6-a(1)FLI-18.

Etymology. This species in named in honour of Professor Amyan Macfadyen as a tribute to his contribution to the ecology of soil arthropods and his commitment to environmental conservation.

Remarks. Crotonia macfadyeni sp. nov. is closest morphologically to C. cophinaria ( Michael, 1908) and thus shows clear affinities with the Cophinaria species-group ( Wallwork 1977 ; Luxton, 1982; Lee, 1985). It shares with C. cophinaria the complex anterior margin of the notogastral shield and dorsosejugal suture, and the shield with a marginal strip of diffuse tubercles and smooth centrodorsal region. Crotonia macfadyeni sp. nov., C. cophinaria and C. obtecta ( Pickard-Cambridge, 1875) are the only members of the genus that have notogastral setae other than the caudal cluster barbed (barbed caudal setae are present in members of the Caudalis and Unguifera groups), but for C. cophinaria it is only the c series that are ornamented whereas for C. macfadyeni sp. nov. and for C. obtecta it is all of them.

Crotonia macfadyeni sp. nov. can be distinguished from all other members of the genus by the following combination of characters: 1) lamellar, rostral and all notogastral setae except h 2 barbed; 2) epimeral setae bifurcate or barbed; 3) setae c 1 and c 3 subequal, long, flagelliform, as long as interlamellar setae; 4) three pairs of setae on epimere 2. Neotrichy of epimere 2 is rare. Two members of the Capistrata group, C. tasmaniana Colloff, 2009 and C. ecphyla Colloff, 1990 have two pairs of setae on epimere 2, as does C. tuberculata Luxton, 1982 ( Caudalis group), but no other species has three.

The association of the immatures with the species is based on the following characters: 1) the flagelliform marginal and notogastral setae barbed; 2) the neotrichous development of the epimeral setal formula; with three pairs of setae on epimere 3 in the protonymph compared with two pairs for every other described protonymph of Crotonia ; with two pairs of setae on epimere 2 of the deutonymph (compared with one pair for other Crotonia spp.), and with three pairs of setae on epimere 2 in the tritonymph and adult; 3) the caudal cluster of spiniform; smooth setae h 2 and the shape of their apophyses, together with the barbedly-ornamented setae f 1 and h 1; 4) the shape, size and ornamentation of the rostral setae; the shape and size of the lamellar setae and their apophyses; 5) epimeral microsculpture of deutonymph, tritonymph and adult porose medially and tuberculate marginally. Immatures and adults were found in the same samples and no other Crotonia spp. were present. There were no discernible morphological differences between males and females other than the smaller size of the males.

Figures

FIGURE 1. Crotonia macfadyeni sp. nov. adult female a) dorsal b) ventral, with supernumerary seta on epimere 3 (arrowed)

FIGURE 2. Crotonia macfadyeni sp. nov. protonymph a) dorsal; b) ventral; c) genital plates; d) detail of sternal region and setae 1 a.

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