Geophilus arenarius Meinert, 1870

Bonato, Lucio & Minelli, Alessandro, 2011, Geophilus arenarius, a long-misunderstood species in the still unresolved carpophagus species-complex (Chilopoda: Geophilidae), Zootaxa 3114, pp. 40-49 : 41-44

Geophilus arenarius Meinert, 1870

Full list of citations. Meinert 1870: 78 (original description, and in key). Tömösváry 1880: 618. Daday 1889: 24, 28, 30, 33, 37, 85 (in key), 86 (description, and new records). Verhoeff 1896: 88 (in key). Attems 1903: 169, 221 (in key), 228. Depoli 1907: 25, 85, 86, 89. Brolemann 1921: 103. Attems 1929a: 182 (description). Attems 1929b: 287, 296. Brolemann 1932: 43 (in key). Szabó 1932: 48 (new record). Matic et al. 1970: 98. Matic 1972: 107 (in key), 118 (description). Kos 1992: 354. Stoev 1997: 102.

Type locality. “Østen for Bona ” [= east of Annaba ( Algeria)]( Meinert 1870).

Type material. Syntypes: a total of 36 specimens, including 16 females and 20 males, according to the original description ( Meinert 1870); however, a total of 34 specimens, including 13 females, 20 males and another incomplete specimen of unknown sex, are currently preserved in the Zoological Museum, Natural History Museum of Denmark, University of Copenhagen, and confidently recognised as the original series examined by F. Meinert.

Synonyms. None.

Differential diagnosis. With respect to the most similar species ( Table 1 , Figs 1–11 ), G. arenarius differs from both G. carpophagus and G. easoni in lacking the transverse suture on the head and the so-called carpophagusstructures on the trunk, and having relatively stouter antennae and forcipular coxosternite (see also below, under Discussion). Additionally, G. arenarius differs from G. carpophagus in the distinctly smaller size at full growth, the usually blunt and more sclerotised tubercles lining the intermediate part of the labrum, and the presence of a minute denticle at the basis of the forcipular tarsungula. Geophilus arenarius differs from G. easoni in the fewer bristles lining the lateral parts of the labrum, in the greyish colour of the trunk, and the higher number of legs.

Description of an adult female (one of the syntypes, 34 mm long, with 57 pairs of legs; Figs 1–5 ).

General features. Body only slightly narrowing forward, more attenuated towards the posterior tip. Colour (preserved in 70% ethanol) almost uniform, pale brownish grey.

Cephalic capsule. Cephalic plate ( Fig. 1 ) sub-trapezoid, as long as wide; anterior margin slightly angulated, lateral margins evidently convex and convergent forward, posterior margin slightly concave; no transverse suture. Clypeus ( Fig. 2 ) uniformly areolate, without finely areolate clypeal areas and without plagulae; lateral margins complete; 10 pairs of setae, including a paramedian pair close to the anterior margin, most setae arranged in a transverse row in the anterior part of the clypeus, and two paramedian pairs posterior to the latter. Labrum ( Fig. 2 ): intermediate part continuous with the clypeus, bearing 4 sclerotised stout tubercles; each lateral part separated from the clypeus by a complete margin, bearing ca. 8 bristles branching into fine short filaments close to the tip. Pleurites uniformly areolate, with 3 anterior setae.

Antennae ( Fig. 1 ). Each antenna ca. 2.2 times as long as the head; intermediate articles about as long as wide; article XIV ca. 1.6 times as long as wide. Setae of various size on the most basal articles, gradually denser and shorter from the basal articles to the distal ones. Apical sensilla ca. 14 μm long, spear-like, slender, slightly narrowing towards the tip. Club-like sensilla only on article XIV, grouped on the distal parts of both the internal and external sides. Three longitudinal rows of propioceptive spine-like sensilla at the bases of the articles; rows lacking on articles VI, X and XIV, where only a single, dorsal sensillum is present. Groups of 1–6 sensilla, similar to the apical ones but shorter, on both the ventro-internal and the dorso-external sides of the distal part of articles II, V, IX and XIII.

Mandible. A single pectinate lamella.

Maxillary complex ( Fig. 3 ). First maxillae: coxosternite entire, with short lappets; coxal projections sub-triangular, longer than wide; telopodites longer than the coxal projections, composed of two articles, with elongate lappets; coxal projections and the distal article of the telopodites bearing setae on the basal part, spine-like sensilla close to the tip, and minute scales on the tip. Second maxillae: coxosternite entire, uniformly areolate, the anterior margin widely concave, with setae close to the anterior margin; metameric pores featuring as transverse slits; telopodites composed of three articles, gradually narrowing towards the tip; claw simple, sub-conic, gradually tapering, slightly bent, with 1–2 short sensilla on the ventral side.

Forcipular segment ( Fig. 4 ). Forcipules, when closed, just reaching the anterior margin of the head. Tergite subtrapezoid, ca. 4.4 times as wide as long, lateral margins evidently converging forward; no pretergite exposed. Pleurites without a distinct dorsal ridge. Coxosternite: two paramedian groups of 4–5 small setae on the dorsal side, close to the anterior margin; no denticles; ventrally exposed part ca. 1.76 times as wide as long; coxopleural sutures entirely ventral, strongly converging backward; chitin-lines incomplete, diverging lateral from the condyles. Trochanteroprefemur ca. 1.1 times as wide as long, the external side ca. 2.0 times as long as the internal side. Tarsungulum abruptly narrowing near the base, the distal part curved and tapering uniformly, the internal margin entire. A tiny denticle at the basis of tarsungulum; no denticles on the other forcipular articles. Poison calyx relatively long, asymmetric, lodged in the distal part of the trochanteroprefemur.

Leg-bearing segments. Tergite 1 wider than metatergite 2, lateral margins slightly converging backward; no distinct pretergite 1. Metasternites without carpophagus pits on the anterior margin, only a small projection on the posterior margin of those of the anterior segments (resembling the peg usually facing the pit in a typical carpophagus-structure; Fig. 11 ). Ventral pore-fields from segment 1 to the penultimate: a transverse posterior band, which is entire on the most anterior segments, medially interrupted on the remaining segments; anterior segments with additional small pores-fields close to the anterior corners of the metasternite and on procoxae and metacoxae. Legs 1 smaller than the other legs. Claws with two accessory spines, the anterior one distinctly longer than the posterior one.

Ultimate leg-bearing segment ( Fig. 5 ). Pleuropretergite entire, without sutures. Metatergite ca. 1.8 times as wide as long, lateral margins convex and converging backward, posterior margin truncate. Metasternite sub-trapezoid, ca. 2.0 times as wide as long, lateral margins convex, posterior margin almost straight; setae uniformly scattered. Coxopleura moderately swollen, reaching forward the posterior margin of the presternite; setae uniformly scattered. Coxal organs opening through distinct pores, all on the ventral side along the lateral margins of the metasternite, 10 on one side and 9 on the other side. Ultimate telopodites ca. 1.1 times as long as, and as wide as, the penultimate; setae uniformly scattered on both dorsal and ventral sides; claws similar to those of precedent legs, only slightly smaller than those, the accessory spines distinctly shorter.

Postpedal segments ( Fig. 5 ). First genital pleurosternite entire, without distinct pleurites. Gonopodal lamina distinctly bilobed. A pair of distinct anal organs and pores.

Differences in an adult male (one of the syntypes, 27 mm long, with 55 pairs of legs; Fig. 6 ).

Ultimate leg-bearing segment ( Fig. 6 ). Distinctly denser, shorter setae on the posterior part of the metasternite, the postero-mesal parts of coxopleura, and the ventral side of all articles of the telopodites. Ultimate telopodites moderately swollen, ca. 1.3 times as wide as the penultimate. First genital sternite separated from pleurites by distinct sutures. Gonopods bi-articulate, with conical penis in between.

Geographical distribution. G. arenarius is known only from the type locality, near Annaba, Algeria. Our direct examination of other specimens of the carpophagus species-complex collected throughout north-western Africa (from Morocco to Tunisia, including coastal and mountainous sites; listed under Material and methods) failed to detect other specimens of G. a re n a r i u s. Instead, these specimens confirm that north-western Africa is inhabited by at least two species in the carpophagus complex, one of which is G. arenarius .

Records of G. arenarius from different localities in Croatia, Hungary and Romania have been listed synthetically by Tömösváry (1880) and in more detail by Daday (1889). These have been repeatedly mentioned acritically by subsequent authors, and an additional record from Hungary has been given by Szabó (1932) under the misspelled name arenius. However, all these old records have not been confirmed by modern authors ( Matic 1972; Kos 1992; L. Danyi, pers. comm.), or by our preliminary examination of Geophilus specimens from throughout Europe. Matic (1972) suspected explicitly that the records from Romania should actually be referred to G. carpophagus . Taking into account the information given by Daday (1889), the specimens examined by him depart obviously from the syntypes of G. arenarius in major morphological features (complete chitin-lines, higher number of trunk segments, distinct carpophagus structure), so that they are obviously misidentified specimens of another species, possibly not in the carpophagus species-complex, more probably G. e l e c t r i c u s Linnaeus. Even the record by Szabó (1932) is most probably to be referred to G. carpophagus , based on investigations on surrounding localities (L. Danyi, pers. comm.).

Figures

FIGURES 1 – 6. Geophilus arenarius; line-drawings from a syntype Ƥ, 34 mm long, with 57 pairs of legs (Figs 1 – 5), and a syntype 3, 27 mm long, with 55 pairs of legs (Fig. 6). 1 — head, without right antenna, setae omitted, dorsal view; 2 — anterior part of head, without antennae, mandibles and maxillae, ventral view; 3 — maxillary complex, left half, ventral view; 4 — forcipular segment, setae omitted, ventral view; 5 — ultimate leg-bearing segment and postpedal segments in the female, setae omitted, ventral view; 6 — ultimate leg-bearing segment and postpedal segments in the male, setae omitted, ventral view.

FIGURES 7 – 9. Geophilus arenarius; photos taken from a syntype 3, 27 mm long, with 55 pairs of legs. 7 — anterior part of body, dorsal view; 8 — head and forcipular segment, ventral view; 9 — part of trunk at ca. 20 % of the series of leg-bearing segments (segments 9 – 12 out of a total of 55), ventral view.

FIGURES 10 – 11. Comparison between G. carpophagus, G. e a s o n i, and G. arenarius; line-drawings from adult specimens, setae omitted. 10 — forcipular segment, ventral view; 11 — a trunk segment at about 20 % of the sequence of leg-bearing segments, ventral view.