Thoracophoracarus, K. Viets, 1914

Gerecke, Reinhard, 2009, Revisional studies on Thoracophoracarus K. Viets, 1914 (Arachnida, Acari, Hydrachnidia, Arrenuridae), Zoosystema 31 (1), pp. 127-145 : 129-131

Thoracophoracarus (s.s.) arrhenuroides K. Viets, 1914

( Fig. 2 )

Thoracophoracarus arrhenuroides K. Viets, 1914: 354 , fig. 43a-e.

TYPE MATERIAL. — Holotype: Cameroon, southern border of bay of Duala , fishermen village Manoka, larger permanent stream east of the village (water support place of the village during dry season), 1.I.1912, Damköhler leg., 1384, ♂ ( SMF 47455).

Paratype: same area as holotype, temporary stream, 11.XI.1911, Damköhler leg., 1265, ♀ ( SMF 47431).

MATERIAL EXAMINED. — Cameroon. Catchment of River Ebo (Dibamba), small affluent at Miap cascade, from stones, 4.XI.1913, Damköhler leg., 1831, ♀ ( SMF 47458).

DESCRIPTION

Idiosoma egg-shaped, posterior margin concave ( Fig. 2A, B, D ). Body colour probably deep blue (traces of colour visible in the slide-mounted specimens). Anterior and posterior idiosoma margins with elevated humps – the anterior ones associated with the antenniformia (dorsoglandularia 1), the posterior ones flanking a bay with the excretory pore. Legs with numerous swimming setae, arranged in longitudinal lines on the anterior surface, in transverse lines at the distal margin on the posterior surface. Distal margins of segments 3-5 of all legs anteriorly and posteriorly projecting, with pointed tips. Genital field about halfway between posterior margin of Cx-4 and posterior idiosoma margin, with slender, laterally narrowed acetabular fields, extending to the dorsolateral idiosoma. Acetabula number c. 40 + 40. Palp setation ( Fig. 2C ): P-1 without setae; P-2, 5 (2 on the mediodistal surface, 3 dorsally); P-3, 2 (1 fine medially, 1 stronger laterodistally); P-4, 1 stronger mediodistal seta, 4 or 5 fine hair-like setae dorsodistally and at the ventrodistal extension. P-4 relatively long, with subparallel dorsal and ventral margins. Sexual dimorphism little developed, mostly apparent in the shape of the genital field.

Male ( Fig. 2A, B ): anterior idiosoma humps strongly developed, with a pointed, triangular tip directed medially, setae inserting dorsally. Lateral idiosoma margin slightly bulging where the acetabular field reaches the flanks, more distinctly bulging between the acetabular fields and caudal humps, and forming an obtuse-angled caudal bay. In posterior part of dorsum a small, caudally directed finger-shaped extension, located posterior to a pair of glands lying on an inversely V-shaped transverse bar. Gonopore directed ventrocaudally, located at posterior edge of acetabular fields. Ventrodistal extension of P-4 with a rounded tip. Measurements: idiosoma L/W 570/400, Cx-4 W 420; acetabular field L/W 35/160; palp L/H P-1 23/20, P-2 50/38, P-3 33/36, P-4 58/31, P-5 -/- (measurement impossible).

Female ( Fig. 2C, D ): similar to male, but 1) idiosoma slightly larger; 2) anterior and posterior humps more rounded and caudal indentation less developed; 3) gonopore large, opening directed ventrally, with its anterior edge at the level of the acetabular field; and 4) ventrodistal extension of P-4 sharply pointed. Measurements: idiosoma L/W 570/520, Cx-4 W 500; acetabular field L/W 20/200; palp L/H P-1 18-25/20-25, P-2 48-61/33-40, P-3 33-39/33-38, P-4 55-65/28-33, P-5 25-28/9-10.

REMARKS

This species differs from all other members of the genus in the presence of an obtuse-angled caudal indentation (in both sexes bearing the anal pore) and the finger-like projection on the posterior dorsum in males. Further important characters, partly found also in other species of the genus, are the plesiotypical ventral position of the gonopore, acetabular fields extending to the dorsum and P-2 bearing only two mediodistal setae.

Figures

FIG. 2. — Thoracophoracarus arrhenuroides K. Viets, 1914: A, B, holotype ♂ (SMF 47455), idiosoma in ventral (A) and dorsal (B) views; C, ♀ (SMF 47458), palp; D, paratype ♀ (SMF 47431), idiosoma in ventral view. Scale bars: 100 μm.