Decapauropus remyi Bagnall 1935

Decapauropus remyi (Bagnall, 1935)

Figures 1–10

Material examined. Norway, Rogaland, 17 km NW Egersund, Ognastranda, sandy foreshore, in Ammophila tufts, N58,51171o, E5,79613o, 1 ad. 9(Ψ), 4 subad. 8 (Ψ), 3 juv. 6, 2 juv 5, 13 October 2009, sample 9.325, leg. A. Fjellberg. 10 specimens.

Bagnall´s description is brief and incomplete. The material upon which the species was based has been searched for in vain in the Bagnall collections deposited in the Natural History Museum, London, the Oxford University Museum of Natural History, Oxford, and the Great North Museum, Hancock, Newcastle-upon- Tyne, all in Great Britain. The description is amended below and a neotype has been selected and deposited in the collections of the Zoological Museum, Lund, Sweden.

Redescription (by first author).

Neotype. Ad. 9(Ψ), chosen from the material reported above.

Length. 0.83 mm.

Head (Figure 1). Short broad; setae cylindrical pubescent-striate, inner tergal setae short blunt, lateral ones tapering, four transversal rows, relative lengths of setae, 1st row: a 1= a 2=10; 2nd row: a 1= a 3=35, a 2=75; 3rd row: a 1=10, a 2=15; 4th row: a 1=10, a 2=13, a 3=15, a 4 =50; lateral group setae, l 1=70, l 2=45, l 3=35. Ratio a 1/ a 1- a 1 in 1st row 0.4, 2nd and 4th rows 0.3, 3rd row 0.2. Temporal organs short, 0.8 of shortest interdistance, cuticle arched, pistil and pore not ascertained. Head cuticle glabrous.

FIGURES 1–9. Decapauropus remyi (Bagnall), neotype, ad.9 (Ψ). 1, head, median and right part, tergal view. 2, right antenna, tergal view. 3, collum segment, median and left part, sternal view. 4, tergites I–II. 5, T 3. 6, seta on coxa of leg 9. 7, tarsus of leg 9. 8, pygidium and posterior part of tergite VI, tergal view. 9, pygidium, posterior part, lateral view showing st and anal plate. Scale a:4; b: 1, 2, 3, 5, 6, 7, 8, 9.

Antennae (Figure 2). Setae cylindrical blunt, p annulate, r cylindrical, u rudimentary, their relative lengths: p =10, p' =?, u rudimentary, r= 15. Tergal seta p 0.8 of the length of tergal branch t, the latter short subcylindrical, 1.6 times as long as wide and 0.8 of the length of sternal branch s, that branch 1.3 times as long as its greatest diameter, anterodistal corner more truncate than posterodistal one. Setae q striate, 0.7 of the length of s. Relative lengths of flagella (basal segments included) and basal segments: F 1=100, bs 1=7; F 2=35, bs 2=5; F 3=83, bs 3=7. The F 1 6.8 times as long as t, F 2 and F 3 1.9 and 4.3 times as long as s respectively. Distal calyces flattened on F 1 and F 3, conical on F 2, distal part of flagella axes somewhat widened below calyces on F 1 and F 3, not at all on F 2. Globulus g spherical with thin stalk, 9 bracts, capsule spherical; width of g 1.2 times as long as the greatest diameter of t. Antennae glabrous.

Trunk (Figures 3, 10). Body cylindrical with very short legs. Setae of collum segment (Figure 3) short cylindrical blunt striate; appendages small, directed inward, caps low, sternite process small, all parts glabrous.

Tergites I and II (Figure 4) divided transversally into pro- and metatergite. Setae on anterior tergites as setae on median part of tergal side of head; 4+4 setae on tergite I, 6+6 on II–V, 4+2 on VI. Submedian posterior setae on VI short clavate, distinctly pubescent, length 0.2 of their interdistance. Tergites glabrous.

Bothriotricha (Figure 5). Their relative lengths: T 1=100, T 2=102, T 3=83, T 4=?, T 5=113. Axes simple, all but T 3 thin, the latter (Figure 5) with large clavate end-swelling, length 0.5 of the length of bothriotrix. Pubescence short erect on T 1 and T 2, oblique on proximal part of T 5, erect distally; proximal half of T 3 glabrous, swelling with short oblique hairs in irregular transversal rows.

Legs (Figures 6, 7). Legs 1 and 9 5-segmented, interposed pairs 6-segmented with short annulate metatarsi. Setae on coxa (Figure 6) and trochanter simple cylindrical annulate, distinctly pubescent. Tarsus of leg 9 (Figure 7) short tapering, 1.9 times as long as greatest diameter, proximal seta rudimentary, distal seta cylindrical blunt, with pubescence on upper side, underside glabrous, length of seta well 0.5 of the length of tarsus.

Pygidium (Figures 8, 9). Tergum. Posterior margin evenly rounded. Relative lengths of setae: a 1=10, a 2=2, a 3=8, st =5; a 1 thickest in proximal half, tapering, somewhat S-shaped, with distinct but sparse oblique pubescence, a 2 straight short cylindrical blunt, distinctly pubescent, a 3 as a 2 but longer and with indistinct pubescence; st clavate, shortly pubescent, curved downward and somewhat inward. Distance a 1 -a 1 as long as a 1; distance a 1 -a 2 ≈3 times longer than distance a 2 -a 3; distance st-st twice longer than st and almost as long as distance a 1 -a 1. Cuticle glabrous.

Sternum. Posterior margin indented. Relative lengths of setae (pygidial a 1=10): b 1=18, b 2=7. Setae thin cylindrical blunt, shortly pubescent; b 1 1.5 times as long as interdistance, b 2 0.7 of distance b 1- b 2.

Anal plate (Figures 8, 9) faintly pubescent, directed obliquely upward, linguiform, narrowest anteriorly, 1.6 times as long as broad, posterior margin evenly rounded. Sternal side may have two very short appendages marked as black spot in figure 9.

Distribution. The species was discovered by Bagnall in 1934, in the Forth area in Scotland, at Dalmeny Estate, near Cramond (Bagnall 1935a), and the following year also collected at South Queensferry (Bagnall 1935b). It was briefly described under the name Thalassophilus remyi (1935a). In the paper about the Queensferry material (1935b) Bagnall also mentioned that Remy had found the species at a French locality in Roussillon, Banyuls-sur-mer, later confirmed by Remy (1938) who also moved it to the genus Decapauropus. Remy described incompletely (1954) a juvenile Algerian specimen too, from between Bou Zadjar and Cape Falcon, under the name of A. cf. remyi.

Taxonomical remarks. The specimens collected from Scotland and Roussillon seem to be conspecific but there are reasons to suspect that the Algerian material belongs to another species because at least its pygidial setae and the pubescence of the anal plate are different.

Habitat. The specimens reported above from a beach were collected in the upper 10 cm of sandy soil in Ammophila tufts. Bagnall´s sites were probably similar because he says that D. remyi was halophilous (1935a) and that it occurred “under stones well embedded in sand at from just below to considerably below high-water mark” (1935b). In the later paper, some accompanying microarthropods were mentioned: Allopauropus littoralis Bagnall (incompletely described) and the collembolans Anuridella submarina Bagnall and Onychiurus spp. In tidal refuse at high-water mark it was accompanied by Allopauropus danicus Hansen and A. littoralis.

FIGURE 10. Decapauropus remyi (Bagnall), neotype, ad. 9 (Ψ, 0.83 mm), fully extended animal, ventral view (somewhat simplified, trunk slightly compressed).

About a tenth of Pauropoda species have been collected in the soils of sandy beaches, some in the upper strata, others close to the ground water surface. Most of them have wide distributions in other biotopes and do not show special adaptations for living in unstable soils, but in two cases the colonization of sand beaches seems to have led to the development of anatomical and functional adaptations. One is the species reported above, Decapauropus remyi, and the other is Amphipauropus rhenanus (Hüther, 1971). Like D. remyi the latter species seems to have a wide distribution, but it has rarely been collected and up to now is known only from Germany, Denmark, Norway, Sweden and Iceland (Andersson et al 2008, Hűther 1971, Scheller 1998, Scheller 2005, Scheller et al. 2006), and maybe also from France (?Brachypauropoides moselleus (Remy, 1960)).

Decapauropus remyi and Amphipauropus rhenanus are alike with worm-like, cylindrical, not fusiform, bodies, which are also weakly sclerotized, and with shortened antennal branches, bothriotricha and legs. According to observations on live specimens made by the second author, A. remyi moves very slowly. In general pauropods are swift runners adapted for life in soils with a stable system of pores and canals, and are rarely collected in sandy soils. These two species, however, seem to have developed adaptations for life in looser soils such as those on sandy shores, including cylindrical bodies and shortened trunk appendages. Amphipauropus has been reported from three continents in the northern hemisphere, in Europe (see above), in North America from Canada (Scheller, 1984) and in Asia from Japan (Hagino 2002, 2003). The wide distribution of Decapauropus remyi and Amphipauropus may point to the occurrence of a fauna of miniaturized specialized pauropods adapted to the structures and dimensions of sandy soil. This fauna probably has reduced potential for dispersal, maybe also for speciation. Unfortunately it has been neglected in most studies of the shore fauna.