Megapalpis, Halbert, 1944

Goldschmidt, Tom, 2007, Studies on Latin American water mites of the genus Torrenticola Piersig, 1896 (Torrenticolidae, Hydrachnidia, Acari), Zoological Journal of the Linnean Society 150 (3), pp. 443-678 : 491-493

‘ MEGAPALPIS ’-LIKE SPECIES

New species from Costa Rica: T. flexirostris .

Differential diagnosis of the group: Idiosoma oval; Cx-I/II broad, apically triangular with pointed tips; genital field large; capitulum basal relatively high, bend towards elongated, up-curved rostrum; palps without (with very small) ventral projections at P2 and P3; cheliceral claws straightened, elongated.

Discussion: The ‘ Megapalpis ’-like species group is named after the subgenus Megapalpis Halbert, 1944 until now only known from Europe and Asia ( Di Sabatino et al., 2003b). At the present state of knowledge, with only one species of this group known from Central America, it cannot be decided if this species group could be regarded as a phylogenetic entity. Besides some striking similarities between the new species from Costa Rica and the species of the subgenus Megapalpis from the Old World, there are also some differences (see below). Therefore, at the present state of knowledge, the new species should not be placed within that subgenus.

TORRENTICOLA FLEXIROSTRIS SP. NOV.

( FIG. 25A–D; TABLE 11)

Type series: Holotype female, CR 288, Guanacaste, 1 km south-west Dos Ríos, Quebrada La Gato, right affluent Río Cucaracho , small stream, 520 m asl, 03.ii.1997, mounted; paratypes: same locality and date as holotype, 0/2/0 unmounted.

Habitat: Fast flowing small mountain stream at 520 m asl; mesolithal, leaf packages; temperature 22.0 °C; conductivity 92 µS cm −1.

Distribution: Costa Rica (only known from type locality, Cordillera de Guanacaste).

Derivatio nominis: flexus (Latin = curve), rostrum (Latin = snout, rostrum); referring to the clearly up-

curved rostrum, typical for the species (and species group).

Diagnosis (only one female): Characters of the ‘ Megapalpis ’-like species; idiosoma oval-drop shaped, small; dorsal plate reddish, anterior pointed; lateral margin of Cx-I/II straight, anterior part of Cx-I/II triangular; genital field large, broad-rhombic; ventral margin of capitulum basely rounded, rostrum ventrally +/– straight, curved upwards; cheliceral claws straightened, long (bs/claw L 3.3); P2/P3 only with very small ventral projections.

Description – Male: Unknown.

Female (N = 1): Idiosoma small (L 510 µm, L/ W 1.46); dorsal plate pale reddish, anterior elongated, anterolateral margins nearly straight, apically pointed; antero-medial platelets medially convex, widened, laterally straight to convex, oblique; antero-lateral platelets longer, anterior margins straight to convex, posterior tapering, rounded; Dgl-4 lateral to Dgl-5 ( Fig. 25B ); coxal field (especially anterior part) broad, Cx-I/II antero-laterally straight, apically pointed, Cxgl-4 postero-lateral of Cx-I tips, lateral margin of Cx-II/III hardly graded; capitular bay wide, U- to slightly V-shaped; medial margin of Cx-II/III very short ( Table 11, Fig. 25A ); posterior margin of Cx-IV far postero-lateral of caudal end of genital field; genital field large compared with coxal shield (gf L/dist cb-gf 1.18), broad-rhombic, anterior truncated, anterolateral and lateral margins straight, posterior rounded; excretory pore posterior Vgl-2, glands and pore posterior to caudal margin of primary sclerotization ( Fig. 25A ); capitulum basely curved, with clear bend towards rostrum, rostrum basely very high, ventral margin only slightly concave, nearly straight, distally curved upwards, pointed; chelicera basely short, claw slightly straightened, long; ventral projections on P2 and especially P3 very small, P2 and P4 of similar length (P2/P4 1.07), P4 relatively thin, ventral setae on flat hump, slightly distally ( Fig. 25C, D ).

Discussion: Torrenticola flexirostris from Costa Rica differs from the European and Asian species of the subgenus Megapalpis in the clearly shorter palps and rostrum, and therefore it should not be assigned to this subgenus. However, the characteristic shape of the rostrum, cheliceral claw and Cx- I/II, as well as – to a certain extent – of the palps, strongly suggests the classification of T. flexirostris in a separate group. The new species differs from all other species known from Central and South America in this combination of characters.

Figures

Figure 25. Torrenticola flexirostris. A–D, holotype female (CR 288). A, idiosoma, ventral view; B, idiosoma, dorsal view; C, capitulum with right palp, lateral view; D, left palp, medial view. Scale bars = 100 µm.