Atropacarus striculus (C. L. Koch)

Kamill, B. W. & Baker, A. S., 1980, The genus Atropacarus Ewing (Acari: Cryptostigmata), Bulletin of the British Museum of Natural History (Zoology series) 39, pp. 189-204 : 190-194

Atropacarus striculus (C. L. Koch)

(Figs 1-12; 27-32)

Hoplophora stricula Koch , 1836: Fasc. 2 t.10. [Type series lost.] NEOTYPE (here designated) (ZM Hamburg, reg. no. A91/79). [See under 'Material' below.]

Atropacarus striculus : Ewing, 1917: 131; Balogh, 1972: 137.

Steganacarus diaphanum Jacot, 1930: 236. 'Cotypes', Monroe, Connecticut (MCZ, Cambridge Mass., no. 261hl). [Examined.] Syn. nov.

Hoploderma striculum : Willmann, 1931: 190.

Steganacarus striculum : Grandjean, 1933: 314.

Steganacarus striculus : Jacot, 1936: 183; Feider & Suciu, 1957:33; Aoki, 1958: 174; Sellnick 1960: 128. [ Pérez-Iñigo, 1972: 190. Misidentification.]

Steganacarus senex Aoki , 1958: 172. Holotype, Utsukushigahara (NUY, Tokyo). [Synonymized by Fujikawa, 1972: 132.]

Steganacarus striculus insularis Weigmann, 1976:6. Holotype only, Azores (ITAZ, Berlin [Examined.] Syn. nov. [1976:7 (Material from Teneriffe described by Pérez-Iñigo, 1972: 190 Misidentification.]

Aspis (Figs 1-2; 28): 180-230 um long and with a greatest width of 141-163 µm. All the dorsal setae are moderately short, procumbent and serrated distally. The lamellar (la) and interlamellar setae (il) are located at the level of the bothridia. Setae (il) are at least twice the length of setae (la) and extend about one-third of the distance between the bases of setae (il) and (ro). The sensillus, 86-114 µm in length (but see striculus insularis below), is slender smooth and cranked near the base (Fig. 28); distally the sensillus is serrated and tapers to fine point. Three finger-like tracheoles are associated with each bothridium and there is Single pairof short exobothridial setae (ex). There is a rather low, broad, median keel in front ofthe il-la setae while posteriorly the integument is raised into a number of longitudinal ridges. The prodorsal integument is opalescent and distinctly pitted.

Notogaster (Figs 4-5; 27; 29-30): 375-475 µm in length and with a greatest depth of 225-300 µm. The notogaster carries 16 pairs of setae, all of which are stout, erect, serrated distally (Fig. 30) and shorter than the distance c1-d1 Setae c1 and c3 are inserted close to the posterior margin of the collar and seta c2 submarginally. In comparison with species oft the genus Steganacarus , A. striculus has an additional pair of setae in the posterior region of the notogaster between setae h1 and ps1 The vestiges of setae f1 and f2 are present, f1 being located just posterior to seta h1, and f2 between e2 and h2. The fissures ip and ips are absent. The integument is opalescent and generally distinctly pitted (Fig. 29).

Ano-genital region (Figs 3; 27): On each anal plate there are four pairs of marginal anal setae (an1-4) and a single pair of adanals (ad) located submarginally and rather far forward. Setae an1_4 are more or less equal in length and about twice as long as the adanal setae. Ventrally, each anal plate has a prominent anteromedian lobe, the left overlying the right ('right-fitting' arrangement, see van der Hammen, 1963). There are usually seven pairs of genital setae (g1_7) arranged in a pattern 4 + 3 along the paraxial margins of the genital plate setae g1_4 being approximately half the length of setae g5_7. A single aggenital seta ag located antiaxially in the genital furrow. The integument of the ano-genital region distinctly pitted with the exception of the setae-bearing areas which have no ornamentation. There are three pairs of genital papillae (g.p. 1_3), the anterior pair (g.p.1) being rather small.

Infracapitulum: Typically phthiracaroid in form (see, for example, Parry, 1979). There are three pairs of adoral setae, the anterior pair being brush-like distally and the posterior two pairs weakly serrated.

Pedipalps (Fig. 8): Three-segmented with the setal formula (2-2-7). Four of the tarsal setae (acm, ul', ul" and sul) are eupathidial, sul being the shortest.

Chelicerae (Figs 6-7): The movable digit has three distinct teeth and the fixed digit carries five. The latter are arranged in two rows, an inner one of three teeth and an outer one of two. The principal segment carries about six conical spines on the antiaxial surface and about 12 sharply pointed spines paraxially. Setae cha and chb are both serrated, cha being somewhat longer than chb.

Legs (Figs 9-12; 31-32): The solenidial formulae for the legs are I (2-1-3); II (1-1-2); III (0-1-1) and IV (0-1-0). All the solenidia are rather long, usually with a single coil distally. Solenidion omega2 on tarsus I is coupled with a small distal seta (Fig. 31). The latter was first observed in S. striculus by Griffiths and Sheals (1971) who described the seta as being sabre shaped. On all legs the tibial solenidion phi is coupled with a reduced dorsal seta (Fig. 32) while on genu I solenidion sigma1, is coupled with a reduced posterolateral seta (l"). The formulas for the leg setae are I (1-4-2-5-16-1); II (1-3-2-3-12-1); III (2-2-1-2-10-1) and IV (2-1-1-2-10-1). On tarsus I six of the setae (s, (it), (p) and a') are eupathidial. The famulus

is rugose and closely associated with omega1. Seta a" is short (approximately half as long as the famulus), smooth and located on a level with the solenidion omega1. Setae (tc) and (u) on tarsus I and (tc), (u), (p) and s on tarsi II to IV are ribbon-like, hooked distally and covered with whorls of spicules in the middle third. Seta d on femur I is rather short, hooked distally and apparently smooth, while the anteroventral seta v' on this segment is comparatively short and stout. On all segments the ventral setae (v) bear two or three rows of distinct serration while the lateral setae (l) carry only a few weakly-developed serrations. All the tarsi terminate in a single claw bearing two ventral teeth.

Material: Material was examined from the following unnamed and unsorted collections of the British Museum (Natural History): beech litter, Box Hill, Surrey, August, 1973 (K. H. Hyatt); beech litter, Chalfont St. Giles, Buckinghamshire, 8.xi.64 (J. G. Sheals); hedgerow litter, Peterborough, Cambridge, 23.i.78 (P. N. Lawrence & B. R. Pitkin); Sphagnum litter Hartland Moor, Dorset, 8.xi.63 (P. N. & K. Lawrence); yew humus, Manor Wood Rothamsted Experimental Station, Hertfordshire, 22.viii.61 (P. N. Lawrence); deciduous humus, Roudsea Woods, Grange-over-Sands, Lancashire, 24.ix.62 (P. N. Lawrence); alder litter, Westwood Marshes, Suffolk, 8.iii.64 (P. N. & K. Lawrence); mixed hawthorn and sallow litter, Woodwalton Fen, Huntingdonshire, 18.ix.63 (P. N. & K. Lawrence); soil in cracked rock, Inchiquin Lough, Co. Clare, 9.vii.60 (P. N. Lawrence); sycamore humus Newtown Castle, Co. Clare, 5.vii.60 (P. N. Lawrence); rhododendron humus, Milke Danda East Nepal, 2.xii.61 (J. G. Sheals); forest litter, Kronasen, Sweden, 23.V.64 (P. N. Lawrence Material was also examined from: moss on branches of Juniperus brevifolia , Faial, Azores 19.vi.69 (P. Ohm) (ITAZ, Berlin); moss, Donaustaufer Forest, Regensburg, West Germany 14.viii.59 (M. Sellnick) (ZM, Hamburg) (one of these specimens, now dissected and mounted in Berlese's fluid, is hereby designated as the neotype); litter and humus under Fagus crenata , Kuromatsunai, Japan, 25.xi.68 (T. Fujikawa) (NSM, Tokyo).

Remarks: Hoplophora stricula was described by Koch from marshy places near Regensburg West Germany. Although Koch's original specimens are presumed to be lost, his figures and description permit reidentification.

Material collected at Regensburg by Dr Max Sellnick has been compared with specimen from the British Isles, Japan and Nepal. With the exception of the British material, the general form of the aspis and notogaster and their setal arrangements appear to be identical However, amongst the British population, a number of'variants' were observed in which femur I carried four setae and genu IV carried no setae. Moreover, the 'femur I-4, genu IV-0' condition (see also, Parry, 1979) was invariably associated with the presence of one or two additional pairs of setae on the genital plates (total 8 or 9 pairs respectively) while on the notogaster the setae were always rather short and weakly serrated. By contrast, the notogastral setae of the Nepalese specimens (see also, Sheals, 1965) were very much stout and more strongly serrated than those of the other populations. Again, amongst the British 'variants', the aspal carina was only weakly developed while the lamellar setae were considerably less than half the length of the interlamellars. The sensilli appear to be identical in all four populations.

The single specimen of striculus insularis collected on the Azores has also been compared with the Regensburg material and the following differences noted: aspal crest somewhat lower than in typical A. striculus ; lamellar setae considerably shorter than half the interlamellar length; sensilli about 65 um long and slightly thickened; notogastral setae relatively shorter and more slender than in typical A. striculus ; notogastral integument punctate as in species of the genus Phthiracarus ; nine pairs of genital setae (Weigmann figures only eight pairs) arranged in a pattern of 5 + 4 along the paraxial margins of the genital plates; genu IV-0. Bearing in mind the degree of variation observed in the populations studied above, it seems inadvisable at the present time to warrant the single specimen from the Azores with subspecific ranking.

Steganacarus spinosus , recorded by Sellnick (1920) from humus in the woods around Lötzen, West Germany, closely resembles A. striculus , and it seems likely that in the past the identities of these two species have been confused. Two specimens, determined by Sellnick from Patscherkofel, Nordtirol, Austria have been examined and although they have been found to fall within the size range given above for striculus (notogastral length 375-475 µm), the notogaster bears only 15 pairs of setae while the solenidion on tibia IV is free.