Scarabaspis sternalis, Halliday, 2010

Halliday, R. B., 2010, Revision of the Australian Eviphididae (Acari: Mesostigmata) 2596, Zootaxa 2596 (1), pp. 1-60 : 22-29

Scarabaspis sternalis sp. nov.

( Figs 27–45 )

Material examined. Holotype. Female, New South Wales, Mount Warning, 11 December 1977, G. Williams coll., on Onthophagus neostenocerus (in ANIC). Paratypes. New South Wales. 2 females, 5 males, same data as holotype; 4 females, 6 miles east of Woodenbong, 8 December 1967, E. Matthews coll., on Onthophagus pugnax ; 1 female, 1 DN, 10 miles SW of Woodenbong, 7 December 1965, G. A. Yapp coll., on Onthophagus auritus ; 1 DN, same data except Onthophagus granulatus ; 3 females, Richmond Range, 13–14 February 1983, alt 600m, T. Weir and A. Calder coll., dung baited trap; 2 females, 3 DN, 5 December 1967, E. Matthews coll., on Onthophagus pugnax ; 8 females, 3 males, 3 DN, Dorrigo, 28 December 1976, G. Williams coll., on Onthophagus pugnax ; 2 females, 2 males, 1 DN, Doyles River, near Wauchope, 25 October 1978, G. Williams coll., on Onthophagus pronus ; 7 females, 2 DN, 1 male, Kirrawak State Forest, near Taree, 13 October 1979, G. Williams coll., on Onthophagus pugnax ; 4 females, Starrs Creek, Lansdowne, near Taree, 5 February 1981, G. Williams coll., on Onthophagus pugnax ; 3 females, 2 males, 1 DN, Harrington, 10 October 1976, G. Williams coll., on Onthophagus tabellifer ; 1 female, same data except 19 September 1976; 1 female, 1 male, 3 DN, same data except 30–31 December 1976; 3 females, 1 male, same data except 8 January 1978; 5 females, 2 males, Yarratt State Forest, near Wingham, 10 February 1981, G. Williams coll., on Onthophagus macrocephalus ; 6 females, 4 DN, Chichester State Forest, Allyn River, 31 October 1978, G. Williams coll., on Onthophagus capella ; 1 female, 1 male, Upper Allyn River, 11 February 1960, I. Common and M. Upton coll., on Onthophagus pugnax ; 4 females, 1 male, Terrys Creek, Putty Road, 1 October 1978, G. Williams coll., on Onthophagus pugnax ; 2 females, 2 males, 1 DN, Mount Wilson, 30 December 1979, G. Williams coll., on Onthophagus macrocephalus ; 3 females, 1 male, Barrengarry Mountain, near Kangaroo Valley, 29 January 1977, G. Williams coll., on Onthophagus pugnax ; 1 female, Kyogle, 14 December 1965, G. A. Yapp coll., on Onthophagus ouratita ; 1 DN, Marulan, 23 April 1964, G. F. Bornemissza coll., on Onthophagus nurubuan ; 2 females, Milton, 27 March 1978, J. Feehan coll., dung baited trap; 2 males, Royal National Park, 13 November 1979, G. Williams coll., on Onthophagus pugnax ; 2 DN, Mountain Lagoon, near Bilpin, 11 February 1978, G. Williams coll., on Onthophagus macrocephalus ; 1 male, Tooloom, 30 October 1961, I. F. B. Common and M. S. Upton coll., on Amphistomus pectoralis ; 1 male, Seal Rocks, 29 January 1981, G. Williams coll., on Onthophagus tabellifer ; 1 female, 31 miles S of Deniliquin, 14 December 1966; 1 female, Dingo Tops, NW of Wingham, 26 February 1981, G. Williams coll., on Onthophagus pugnax ; 1 female, Mount Irvine, 10 January 1908, G. Williams coll., on Onthophagus macrocephalus ; 1 DN, Wallingat State Forest, 30 September 1981, G. Williams coll., on Onthophagus pugnax ; 1 female, Somersby, 9 April 1964, G. F. Bornemissza coll., on Onthophagus macrocephalus ; 1 female, Acacia Plateau, date unknown, N. Davidson coll., on Onthophagus fuliginosus ; 1 female, Inverell, 6 December 1965, G. A. Yapp coll., on Onthophagus australis ; 1 male, 1 DN, 21 miles N of Tenterfield, 6 December 1965, G. A. Yapp coll., on Onthophagus australis ; 1 female, 1 DN, Donaldson State Forest, 12 April 1965, G. F. Bornemissza and G. A. Yapp coll., on Onthophagus nurubuan ; 3 females, 16 miles N of Mittagong, 4 April 1964, G. F. Bornemissza coll., on Onthophagus capella ; 6 females, 2 males, 1 DN, Swan Lake, near Nowra, 12 January 1977, G. Williams coll., on Onthophagus tenebrosus ; 4 females, 5 miles N of Batemans Bay, 10 October 1964, G. F. Bornemissza coll., on Onthophagus tabellifer ; 1 female, same data except Onthophagus bornemisszai ; 2 females, Durras Lake, near Batemans Bay, 11 November 1966, on beetles in kangaroo and pig dung; 2 females Durras Lake, 24 December 1964, G. Bornemissza coll., on Onthophagus nurubuan . Northern Territory. 2 females, 26 km N of Adelaide River, 12 February 1968, E. Matthews coll., on Temnoplectron involucre ; 3 females, same data except Onthophagus glabratus ; 1 female, 23 km S of Darwin, 29 January 1968, E. Matthews coll., on dung beetle; 1 female, Howard Springs, 27 January 1968, E. G. Matthews coll., on Onthophagus glabratus ; 1 male, Baroalba Creek, 19 km NE of Mount Cahill, 12°47'S 132°51'E, 16 November 1972, J. E. Feehan coll., rainforest, Berleseate ANIC 447. Queensland. 4 females, 1 male, Iron Range, 14 km NE of Mt Tozer, July 1986, T. Weir coll., trap baited with human faeces; 2 DN, Iron Range, 14 May 1971, T. G. Brooks coll., on Temnoplectron politulum ; 1 female, 1 male, 12 km SE of Daintree, 22 November 1981, J. Balderson coll., on dung beetle; 1 female, 22 km SE of Daintree, J. Balderson coll., on Diorygophyx simliciclunis; 1 female, 1 male, Gillies Highway, 30 March 1965, G. F. Bornemissza coll., on Onthophagus parallicornis ; 1 female, 21 km NE of Atherton, 18 November 1981, J. Balderson coll., on Diorygophyx tibialis ; 1 male, Gillies Highway, Heales Lookout, 7 May 1969, G. F. Bornemissza and P. Ferrar coll., on Onthophagus mundill ; 1 female, Hidden Valley, 15 miles W of Paluma, 30 May 1969, P. Ferrar and J. Huppatz coll., on Onthophagus desectus ; 1 female, Paluma, 24 April 1969, G. F. Bornemissza and P. Ferrar coll., on Onthophagus paluma ; 1 male, 5 miles W of Paluma, 24 April 1969, G. F. Bornemissza and P. Ferrar coll., on Onthophagus bornemisszai ; 13 females, 3 DN, Mount Lindesay Forest, 12 April 1965, G. Bornemissza and G. A. Yapp coll., on Onthophagus nurubuan ; 1 female, 3 DN, same data except Onthophagus auritus ; 1 female, same data except Onthophagus pugnax ; 9 females, 1 DN, Mount Lindesay Forest, 17 April 1965, Bornemissza coll., on Onthophagus auritita ; 2 females, Tamborine Mountain, 7 December 1967, E. Matthews coll., on Onthophagus neostenocerus ; 2 females, same data except Onthophagus pugnax ; 1 female, same data except Onthophagus mamillatus ; 1 female, Carnarvon Gorge, 9 April 1965, G. F. Bornemissza and G. A. Yapp coll., on Onthophagus semimetallicus ; 1 female, Mount Glorious, 8 April 1968, E. Matthews coll., on Onthophagus pugnax ; 1 DN, Conway Range, 28 March 1968, E. G. Matthews coll., on Onthophagus bunamin ; 1 DN, Ballengarra (= Ballengarry Homestead?), 15 December 1965, G. A. Yapp coll., on Onthophagus capella ; 1 female, Depot Beach, 22 April 1991, M. Manning and D. E. Walter coll., in kangaroo dung and soil; 1 female, Cardwell Range, 2 May 1964, G. F. Bornemissza coll., on Onthophagus jangga (all in ANIC).

Description. Female. Dorsal idiosoma ( Figs 30 , 37–42 ). Dorsal shield covering entire idiosoma, length 457–515 µm, width 288–325 µm (n=10), surface ornamentation variable, from almost completely smooth, with weak lines of punctate ornamentation parallel to antero-lateral margins of shield ( Figs 37, 38 ), to strongly ornamented with overall punctate pattern and strongly developed longitudinal ridges ( Figs 40–42 ). Shield with 30 pairs of setae and ca. 15 pairs of pores, all setae subequal in length, ca. 20 µm; j 1 and r 3 thick, spinelike, erect, all others fine, smooth, pointed.

Ventral idiosoma ( Fig. 31 ). Tritosternum with short square base and robust finely pilose laciniae. Pre-sternal area smooth or with indistinct granular transverse lines of ornamentation. Sternal shield with straight to slightly undulating anterior margin, lateral and antero-lateral projections short and blunt, posterior margin with two shallow indentations; surface smooth except for a few weak anterior and lateral lines. Sternal setae st 1- st 3 fine, short, smooth; first pair of lyrifissures oblique, second pair smaller, almost transverse; metasternal pores minute, circular, on posterior edge of shield. Metasternal setae slightly longer than sternal setae, inserted in soft skin, endopodal plates represented only by very narrow fragments adjacent to coxae III. Anterior section of epigynal shield parallel-sided, widening abruptly to an oval-shaped posterior section; surface smooth except for a pair of weak longitudinal lines, epigynal setae in soft skin adjacent to shield. Anal shield sub-circular, anus centrally placed, surface with faint concentric markings, para-anal and post-anal setae very short, cribrum conspicuous. Unsclerotised opisthogastric skin with a pair of short setae adjacent to posterior margin of epigynal shield, and seven pairs of short setae surrounding anal shield; metapodal plates narrow, oriented obliquely. Stigmata located at a level between coxae III and IV, peritremes extending anterior to coxae I. Peritrematal shields narrow, their anterior ends fused and fused to dorsal shield, post-stigmatal section very short, irregular, variable, with two small post-stigmatal pores; exopodal plates absent.

Gnathosoma . Palp coxal seta short, fine (10 µm), internal posterior seta h 3 and external posterior seta h 2 longer (20 µm), h3 twice as thick as h 2, rostral seta fine, long enough to reach tip of corniculus ( Fig. 32 ). Deutosternal groove with six transverse rows of denticles, ca. 8 denticles per row; anterior row indistinct, curved; teeth in posterior row rounded; corniculi short, thick, blunt, inner margins concave; internal malae smooth, broad. Palp chaetotaxy: trochanter 0 0/1 0/1 0, femur 1 1/0 2/0 1, genu 2 1/0 2/0 1, tibia 14, tarsus 15. Palp trochanter seta av (25 µm) longer and thicker than pv (20 µm). Seta al on palp femur thick and spine-like; al 1 on palp genu short, thick, blunt, al 2 longer and finer. Outer edge of each palp tarsus with two long parallel sinuous setae with rounded slightly spatulate tips; palp tarsal claw with two spatulate tines. Epistome with a single long pointed process, margins strongly serrated ( Fig. 33 ). Fixed digit of chelicera with a low blunt proximal ridge, a large robust triangular median tooth, and a small distal tooth, pilus dentilis fine and short, dorsal seta not seen, apparently minute; movable digit with a single very large robust triangular tooth, arthrodial membrane represented by a rounded flap ( Fig. 34 ).

Legs. Chaetotaxy: Leg I. Coxa 0 0/1 0/1 0, trochanter 1 0/1 1/2 1, femur 2 3/1 2/2 2, genu 1 3/2 2/1 2, tibia 1 3/2 2/1 2. Leg II. Coxa 0/1 0/1 0, trochanter 1 0/1 0/2 1, femur 2 3/1 2/2 1, genu 2 3/1 2/1 2, tibia 2 2/1 2/1 2, tarsus 3 3/2 3/2 3 + mv, md. Leg III. Coxa 0 0/1 0/1 0, trochanter 1 0/1 0/2 1, femur 1 2/1 1/0 1, genu 1 2/1 2/1 1, tibia 1 1/1 2/1 1, tarsus 3 3/2 3/2 3 + mv, md. Leg IV. Coxa 0 0/0 0/1 0, trochanter 1 0/1 0/2 1, femur 1 2/1 1/ 0 1, genu 1 2/1 2/0 1, tibia 1 1/1 2/1 1, tarsus 3 3/2 3/2 3 + mv, md. Both setae on coxa I and pv on coxa II modified to flat oval-shaped disks, other leg setae smooth and pointed, most dorsal setae thicker than ventral and lateral setae. Tarsi I–IV each with a well-developed pair of claws and a rounded pulvillus, claws on tarsus I smaller and less robust than those on tarsi II–IV.

Genital structures. Sperm induction pores apparently on posterior margin of coxa III, insemination ducts unfused, opening into sacculus through circular pores ( Fig. 35 ), sacculus not visible in available specimens, apparently unsclerotised.

Male. Dorsal idiosoma. Dorsal shield length 371–397 µm, width 187–250 µm (n=5), structure and chaetotaxy as for female, variation in ornamentation similar to that of female.

Ventral idiosoma ( Fig. 27 ). Pre-sternal area without platelets, with a few very indistinct transverse lines of ornamentation. Sternal and epigynal shield fused to form a sterno-genital shield, with five pairs of smooth pointed setae and three pairs of minute circular pores; antero-lateral and lateral corners of shield bluntly pointed. Surface of shield smooth except for a weak sub-marginal line and a pair of transverse anterior lines, other features of ventral idiosoma as for female.

Gnathosoma . Fixed digit of chelicera with a very large rounded medial tooth and a small triangular distal tooth; pilus dentilis and dorsal seta obscure; movable digit with a very large rounded medial tooth and a low blunt proximal tooth; spermatodactyl short, robust, sinuous, projecting beyond end of movable digit, distally expanded ( Fig. 28 ). Other features of gnathosoma as for female.

Legs. Legs II slightly thicker than those of female, seta av on femur II modified to a thick rounded spur ( Fig. 29 ); legs otherwise as for female.

Etymology. The name of this species refers to the unusual placement of the metasternal pores on the posterior margin of the sternal shield.

Notes. Females of S. sternalis can be distinguished from most other members of the genus by the fact that the third pair of sternal pores is on the posterior edge of the sternal shield in almost every female specimen. In one specimen, one of these pores is on the shield and the other is in the soft skin just behind the shield, and in one other specimen, both pores are off the shield. In other species of Scarabaspis these pores are in the soft skin between the anterior margin of the epigynal shield and the posterior margin of the sternal shield, near the metasternal setae. This is true in S. concavus Gu & Fan , S. goulouensis Liu et al. , S. inexpectatus (Oudemans) , S. orientalis (Berlese) , S. punctatus Evans , and S. spinosus Ishikawa. The position of the metasternal pores in the female of S. altaicus Sklyar is unknown because this species was described only from the deutonymph. However, it would appear that this is not a species of Scarabaspis , because its deutonymph lacks the modified disk-like setae on coxae I and II that are characteristic of both females and deutonymphs in the genus. The position of the metasternal pores in S. africanus Ryke & Meyer was not described, but S. sternalis differs from S. africanus in having the humeral seta on the dorsal shield (r3) short, spinose, and erect, while it is unmodified in S. africanus . The only other species that has both the metasternal pores on the sternal shield, and seta r3 spinose, is S. rykei Shoemake & Krantz. Shoemake & Krantz (1966) drew attention to the fact that the sternal shield of S. rykei is elongate. This may be quantified as the distance st 1- st 3 (length of shield) at least 1.5 times the distance st 2- st 2 (width of shield). In S. sternalis st 1- st 3 is approximately equal to st 2- st 2, as it is in most other species in the genus.

The distribution of S. sternalis is very extensive, from Iron Range in far north Queensland to Batemans Bay in southern New South Wales, and in the Northern Territory ( Fig. 36 ), covering a north-south range of 2,500 km. Across that range, the degree of ornamentation of its dorsal shield is extraordinarily variable, from almost completely smooth with only indistinct punctate lines parallel to the lateral margins of the shield ( Fig. 37 ), to highly ornate, with a general punctate polygonal pattern, especially laterally, a strong medial longitudinal ridge, and two pairs of very distinct sigillae in the dorsal hexagon j 5/ z 5/ j 6 ( Fig. 42 ) (photographed in differential interference contrast illumination, focal level of the bases of setae j 5/ z 5/ j 6). This kind of variation arouses suspicion that more than one species may be present. I therefore examined the pattern of variation in this ornamentation, at both intra- and inter-population levels.

I chose a series of localities from which at least two specimens were available, and examined the degree of ornamentation of the dorsal shields of specimens from these localities. I scored each female on an arbitrary scale from 1 to 5, in which a score of 1 represents a specimen whose dorsal shield is almost completely smooth ( Fig. 37 ), a score of 5 is assigned to a specimen whose dorsal shield is very highly ornate ( Fig. 42 ), and scores of 2–4 represent intermediate levels of ornamentation ( Figs 38–41 ). The results are presented in Table 1. This scoring system is arbitrary and subjective, and probably subject to artefacts of specimen preparation and illumination. Any interpretations drawn from the data must therefore be only of a very general kind. However, the following observations can be made: (1) there is a concentration of very ornate specimens near the middle of the geographic range of the species (populations 5 and 6, Mount Lindesay/Tamborine Mountain, ornamentation level 3.2–3.9); (2) very smooth specimens occur at the northern end of the species’ range (populations 1 and 2, Iron Range/Daintree, ornamentation level 1–1.5); (3) smooth specimens also occur at the southern end of its range (populations 20, Batemans Bay/Durras, ornamentation range 1.1–2.0); (4) there is sometimes a wide range of variation in the degree of ornamentation within a population (e.g. population 14, Taree/Lansdowne, ornamentation range 1–5).

Therefore, in the absence of any discontinuous morphological differences among both male and female specimens, in view of the fact that the variation in degree of ornamentation does not follow any particular geographic pattern, and because the variation in ornamentation within a population can be as large as that for the species as a whole, I conclude that all the specimens listed above belong to a single variable species.

In most adult female specimens of S. sternalis the two setae on coxae I are modified into flat oval-shaped discs, as is normal for the genus Scarabaspis ( Fig. 43 ). In a few specimens, the proximal seta is not completely flattened, but can be seen as dome-shaped or hemispherical ( Fig. 44 ). In the deutonymph, this seta is not always flattened, but may be slightly domed, hemispherical, higher than hemispherical, or in a few specimens, takes the form of a short thick seta with a bluntly rounded tip ( Fig. 45 ). This suggests that the developmental modification of this seta, from setiform to disc-shaped, takes place during the transition from protonymph to deutonymph, and is not always complete.

Figures

FIGURE 36. Distribution records of Scarabaspis sternalis. 1–21 = populations in which dorsal shield ornamentation was studied. Details in Table 1. Other localities as mentioned in text.

FIGURES 24–29. Scarabaspis spp., males. 24, S. masani, ventral idiosoma; 25, S. masani, chelicera; 26, S. masani, femur and genu II; 27, S. sternalis, ventral idiosoma; 28, S. sternalis, chelicera; 29, S. sternalis, femur and genu II. Scale bar = 100 µm for 24, 27; 50 µm for 25, 26, 28, 29.

FIGURES 30–35. Scarabaspis sternalis, female. 30, dorsal shield; 31, ventral idiosoma; 32, hypostome; 33, epistome; 34, chelicera; 35, insemination ducts and coxae III. Scale bar = 100 µm for 30, 31; 50 µm for 32, 33, 34, 35.

FIGURES 37–42. Scarabaspis sternalis, female. Variation in level of ornamentation of dorsal shield in six different specimens. 37, ornamentation level 1; 38, ornamentation level 2; 39, ornamentation level 3; 40, ornamentation level 3 (different specimen); 41, ornamentation level 4; 42, ornamentation level 5. Scale bar = 100 µm.

FIGURES 43–46. Scarabaspis spp., coxa I. 43, S, sternalis, female; 44, S. sternalis, female, different specimen; 45, S. sternalis, deutonymph; 46, S. victoriensis, female. Proximal seta pv arrowed. Scale bar = 50 µm.