Ereca treses, Bauer, Christian & Prieto, Carlos E., 2009

Bauer, Christian & Prieto, Carlos E., 2009, Three new Assamiidae (Arachnida: Opiliones) from Cameroon, with a redescription of Chilon robustus and comments on related species, Zootaxa 2059, pp. 1-22 : 7-15

Ereca treses sp. nov.

Figs 3–4 , 15–21 , 48–51 , 69 , table 2

Types. 3 holotype (MRAC/148246), Kombetiko, Banbara, river Natadi ( Cameroon), 4º40’N, 14º35’E (UTM: 33NVF51), F. Puylaert leg., 4.02.1976. Paratypes: 1 Ƥ with the holotype (MRAC/148246bis). 1 3 & 2 Ƥ (MRAC/ 140752), Olounou ( Cameroon), 2º49’N, 12º08’E, F. Puylaert leg., 18.09.1971. 2 3 & 5 Ƥ (MHNG), Mt Eloumden ( Cameroon), 3º49’N, 11º26’E, 1100–1150m, J. L. Amiet leg., 12.04.1969. 2 3 & 1 Ƥ (MHNG), Mt Bikanga ( Cameroon), 3º54’N, 11º27’E, 800m, J. L. Amiet leg., 8.11.1968. 1 Ƥ (MRAC/148205), Mieri, Batouri ( Cameroon), 4º15’N, 13º58’E (UTM: 33 NUE 87), F. Puylaert leg., 5.02.1976. 4 3 & 1 Ƥ (ZUPV/ 2102); P. N. Altos de Nsork: Nsumu-2 ( Equatorial Guinea), 1º02’25”N, 11º08’08”E (UTM: 32NQG3714), J. M. Lafuente & C. Prieto leg., 23.07.2001.

Etymology. The species name is an invariable combination of letters referring to a series of the numeral „3” (in Spanish, the plural form of „three” is „ treses ”) and it refers to the form of the pigmentation of the opisthosomal part of scutum that looks like a series of the numeral “3” when the animal is oriented towards the left.

Diagnosis. An Ereca species characterized by an anterior carapace margin with a single row of small tubercles on each side and a central granulose region between them. Second free tergite with two median protuberances and third free tergite with three median protuberances. Anal operculum with two rows of six broad tubercles each; first coxa crested by a frontal row of 4–5 papilliform tubercles and ventrally by two divergent rows of tubercles and granules. Palpal tibia with four small teeth and one spine on the outer side, and with two teeth and two spines on the inner side. The pigmentation of the opisthosomal part of scutum shows a conspicuous pattern resembling a series of the numeral “3“.

Description. MALE (holotype): Total body length, 2.92; maximal width, 2.0 (at 2nd area of scutum). Scutum length, 2.3 (carapace/scutum ratio, 0.38).

Coloration ( Figs 3–4 ). Dorsal side: Light brown ground colour. Frontal region with darker lateral fields reaching ocularium, interrupted by light zones and broad lines along margins reaching posterior corners of scutum. Scutum areas I–IV with a dark pigmentation pattern resembling a series of the numeral “3” (when carapace facing to the right), each area with one central and two brown lateral patches connected by an anterior transversal stripe; central patches all fused together, lighter and broader than laterals, and all fading towards the back. Area V and first free tergites with a dark stripe in anterior half. Third free tergite dark in colour. Ventral side: Prosomal complex light yellow, darkening laterally. Coxa IV laterally with irregular darkish brown patches. Base of genital operculum with a brown spot. Posterior part of coxosternal plate with brown lateral patches and a brown line along posterior margin. Free sternites brown, except for yellow posterior part of the longer last sternite. Appendages: Basal segment of chelicerae whitish yellow. Pedipalp trochanter yellow; rest of segments light brown. Leg coxae and trochanters light yellow; remaining leg segments greenish brown.

Carapace ( Figs 3 , 15, 17 ). Frontal tubercle system with outer lateral tubercles curved slightly upwards, inner ones and central tubercle curved slightly downwards. Outer lateral tubercles two times longer than central tubercle and two-thirds of inner lateral tubercles. Anterior margin of carapace with a row of small tubercles on both sides and a central granulose region. Ocularium situated in first half of prosoma, its profile low, convex, carrying two rows of three granules each. Areas of sparse granules located laterally of ocularium. Lateral margin with an unordered row of small granules extending along lateral margin to posterior border of scutum. Posterior border of carapace appearing more sclerotised.

Opisthosomal part of scutum ( Figs 3 , 15, 17 ) dorsally bulged in profile. Areas I–III with some tubercles concentrated in central part, some of them enlarged; areas II and III with larger central tubercle pair. Area IV with a short central row of few tubercles; area V with a closed row of small tubercles along posterior border of scutum.

Free tergites ( Figs 15, 17 ). First and second free tergites with a uniform row of tubercles; second with pair of larger central tubercles. Third free tergite longer than others; anterior row with some isolated tubercles; posterior row on hind margin, including three enlarged central tubercles. Anal operculum with two rows of six broad tubercles each.

Ve n te r ( Figs 4 , 16, 18 ). Surface of prosomal complex fully covered with dense granulation. First coxa crested by a row of 4–6 papilliform tubercles on its anterior edge; ventrally two divergent rows of tubercles and granules running from coxapophysis to outer margin, each ending near the corresponding corner. Anterior row procurved and ending in a group of papilliform tubercles; the second following posterior margin and ending in a broad tubercle; some small granules between them. Coxae II and III with tubercle rows along both anterior and posterior margins. Coxa II with two large tubercles posterolaterally, beyond the end of coxa III. Coxa IV dorsally and laterally with dense setaceous tuberculation. Tubercles merging ventrally into densely granulated area covering whole ventral part of coxosternal complex. Granule row on posterior margin of coxosternal plate transforming into dense tubercles towards the spiracle. Spiracle groove entering under rear of coxa IV. Opisthosomal sternites IV–VII bearing rows of granules, the lateral ones largest; VIII with fine, loose granulation.

Chelicerae ( Fig. 19 ). Basal segment with granular bulla inflated and inclined towards carapace, lying in front of tips of anterior tubercle system. Second segment with dorsal granules and a few setae on dorso-apical surface.

Trochanter Femur Patella Tibia Metatarsus Tarsus Total Pedipalps ( Fig. 20 ). Trochanter with two ventral denticles and two small tubercles on ectal side. Femur with a ventral row of 6–8 unequal denticles, each of them with an anterior notch housing a seta; large spine at distomesal end; granulaes on dorsal and dorsoectal surface. Patella, tibia and tarsus dorsally granular, and with a few small setae. Patella with three small denticles on ventro-mesal edge and with two granules on ectal edge. Tibia with iIiI on mesal and iiIii on ectal edges. Tarsus with iiiiiII on mesal and iiiII on ectal edges.

Legs ( Table 2 ). Fully covered by short setae and small granules. Femur basally slightly curved mediad; patella drop-shaped, with a median bend in the patella-tibia articulation. Trochanter, femur, patella and tibia of leg IV thickened in males. Calcaneus I 12 % of metatarsus length. Tarsal formula: 4 (2) / 7–8 (2) / 5 / 6.

Penis ( Figs 48–51 ). Total length, 1.1. Penial head broad, diamond-shaped, with a round apex in ventral view and spoon-shaped in lateral view. Two pairs of setae on lateroventral surface, apical pair much shorter than proximal one, with one pair of microsetae between them. Lateral surface with nine setae on each side, one apical behind glans and two on the distolateral borders, all similar in shape and size, with acute tips. Other six on broadest part of penial head, curved downwards and with blunt tips, arranged in two rows, each one with three setae. Glans free in its apical part, proximally encompassed by a basal collar-like structure of the trunk with a median slit. In lateral view apical crest bent, with a dorsal concavity. “Stacheltrichter” (according to Martens, 1986) beginning basally between the most basal setae.

FEMALE (MRAC/ 140752) ( Fig. 21 ): Total body length, 2.7; maximal width, 1.8 (at 5th area of scutum). Scutum length, 2.13 (carapace/scutum ratio, 0.40). Lateral bulge of opisthosomal part of scutum less wide than posterior border of scutum, giving the body a guitar shape. Scutum with two more regular rows of tubercles on each area and more tubercles in each row; lacking larger tubercles. Coxae and other leg segments weaker. Spiracle groove partially covered by a process of the posteromedian region of coxa IV reaching the sternal plate. Measurements of pedipalp and legs, see table 2.

Ovipositor ( Fig. 69 ). Bilobed; inner surface smooth and convex; medially, near opening, with a denticle on each lobe. Each lobe with five setae, two ventral and three dorsal; setal tips with ramus; ramus and axial tip of equal length.

Remarks. The genus Ereca Sørensen, 1910 (type species: Ereca undulata Sørensen, 1910 ) was erected for some East African species with a four-segmented tarsus I and two-segmented distitarsus II. Subsequent contributions ( Roewer, 1961; Lawrence, 1962; Kauri, 1985) increased the number to 24 species. All these are from East Africa, with the exception of Ereca robusta Kauri, 1985 and Ereca silvatica Kauri, 1985 , both described from the Feshi Territory ( Kwango, Bandungu state, Democratic Republic of Congo), which is more than 1000 km south-east of the known localities of E. treses sp. nov.

The tarsal formula, the scutum without a clear partition of the first area, the denticulation along the two basal thirds of the pedipalp femur, the enlarged leg IV in males, and the shape of the head of the penis indicate that E. treses sp. nov. belongs to Ereca . Following the key of Kauri (1985), E. treses sp. nov. shows a close affinity to Ereca robusta and Ereca loekenae Kauri, 1985 . These two species differ from E. treses sp. nov. in their much shorter appendages, relatively longer calcaneus I, uniform dorsal armature of scutum and free tergites (more concentrated in E. robusta and looser in E. loekenae ), and by a dorsal colour pattern with transversal dark brown bars on the opisthosomal part of scutum in E. robusta and a serrated foliate pattern in E. loekenae . All described penises of Ereca species are very similar to each other, but the penial head (ventral plate) of E. loekenae has a more concave frontolateral margin, and that of E. robusta is wider than long.

Figures

FIGURES 1 – 8. Dorsal (left) and ventral (right) views of males. 1 – 2, Chilon robustus Sørensen, 1896. 3 – 4, Ereca treses sp. nov. 5 – 6, Bueana vitteli sp. nov. 7 – 8. Rhabdopygus puylaerti sp. nov.

FIGURES 15 – 21. External morphology of Ereca treses sp. nov. (15 – 20, male holotype; 21, female paratype). 15, body, dorsal view. 16, body, ventral view. 17, body, lateral view. 18, body, posterior view. 19, right chelicera, ectal view. 20, right pedipalp, mesal view, and detail of its trochanter, ectal view. 21, outline of female scutum, dorsal view. Scale bars: 1 mm.

FIGURES 48 – 55. Ereca treses sp. nov. and Bueana vitteli sp. nov., penis head in ventral (48, 52), lateral (49, 53) and dorsal view (50, 54), and total penis in dorsal view (51, 55). 48 – 51, Ereca treses sp. nov. (paratype from Mt Eloumden). 52 – 55. Bueana vitteli sp. nov. (paratype from Kounden, MRAC / 148384). Scale bars: Left 0.1 mm, right 1 mm.

FIGURES 68 – 70. Ovipositors (with detail of their hair tips). 68. Chilon robustus Sørensen, 1896. 69. Ereca treses sp.

Tables

TABLE 2. Measurements of pedipalp and legs of male holotype / female paratype (MRAC / 140752) of Ereca treses sp. nov.

Pedipalp	0.45	0.85	0.65	0.5	–	0.45	2.9
Leg I	0.35 / 0.3	1.15 / 1.1	0.55 / 0.55	0.85 / 0.9	1.5 / 1.25	0.75 / 0.8	5.15 / 4.9
Leg II Leg III	0.35 / 0.35 0.35 / 0.35	1.8 / 1.55 1.35 / 1.15	0.7 / 0.6 0.55 / 0.55	1.45 / 1.3 1.0 / 0.9	2.1 / 1.7 1.6 / 1.55	1.6 / 1.45 0.65 / 0.85	8.0 / 6.95 5.5 / 5.55
Leg IV	0.45 / 0.3	2.15 / 1.85	0.75 / 0.6	1.35 / 1.1	2.55 / 2.3	1.1 / 0.95	8.35 / 7.1