Synaptia, Bader, 1988

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 : 457-459

‘ SYNAPTIA ’-LIKE SPECIES

New species from Costa Rica: T. amalgamada . Differential diagnosis of the group: Antero-medial and antero-lateral dorsal platelets completely fused with dorsal plate.

TORRENTICOLA AMALGAMADA SP. NOV.

( FIG. 10A–D; TABLE 1)

Type series: Holotype female, CR 201, Puntarenas, Peninsula de Osa, above Los Angeles de Drake , Los

Migueles, rheopsammocrene, 150 m asl, 23.iii.1996, mounted.

Habitat: Slow flowing rheopsammocrene at 150 m asl; akal; temperature 24.9 °C; conductivity 194 µS cm −1.

Distribution: Costa Rica (Peninsula de Osa, only known from type locality).

Derivatio nominis: amalgamar (Spanish = to fuse); referring to the antero-dorsal platelets completely fused with the dorsal plate.

Diagnosis (only 1 female): As for the ‘ Synaptia ’-like species. Coxal field very short and blunt, anterior coxae (Cx-I/II) merely surpassing idiosoma, anterolaterally sharply graded; capitulum with short rostrum, separated from basal part of capitulum by sharp ventral and lateral bends; palp very characteristic, compact, especially P4 very short; P2/3 without ventral projections.

Description – Male: Unknown.

Female (N = 1): Idiosoma compact oval-shaped; dorsal plate reddish, antero-medial and antero-lateral platelets fused with dorsal plate; Dgl-4, lateral to Dgl-5 ( Fig. 10B ); coxal field very short, blunt, merely protruding anterior margin of idiosoma; Cx-I/II and Cx-II/ III laterally sharply graded, antero-lateral corners of Cx-II and Cx-III pointing to anterior; Cxgl-4 far posterior, at margin of Cx-I and Cx-II, capitular bay wide U-shaped; posterior margin of Cx-IV far behind genital field; genital field large (gf L/Id L 0.25), broadrhombic, anteriorly rounded, laterally nearly straight, posteriorly tapering; excretory pore slightly posterior Vgl-2, pore and glands partly under caudal margin of primary sclerotization ( Fig. 10A ); capitulum high, ventral margin with sharp bend towards short rostrum, separated by a sharp lateral ridge; palp very compact, especially P4 very short (L/H 1.18, P2/P4 2.00, P3/P4 1.15), P2/3 without ventral projections, ventral setae at P4 subterminal ( Fig. 10C ); chelicera relatively stout ( Fig. 10D ).

Discussion: Torrenticola amalgamada is separated from all other species of the genus so far known, in the completely fused anterior platelets. This character is also found in several species of Monatractides : M. gorda Cook, 1980 and M. golfitensis Cook, 1980 , both described from Costa Rica, as well as in the old world species M. synapta (Viets, 1935) , M. synapta luchtae Lundblad, 1971 , M. amabilis ( Lundblad, 1941) , M. magnipharynx ( Lundblad, 1941) and M. magnipharynx rostrata Lundblad, 1971 from Java, M. uniscutata (Viets, 1925) from Cameroon and M. maryellenae Cook, 1966 from Liberia. Bader (1988) proposed the subgenus ‘ Synaptia ’ for these species, which has been refused by Wiles (1997a) based on phylogenetic analysis (see above). The finding of T. amalgamada also bearing this feature demonstrates that this character may have developed convergently also in the sister genus Monatractides and does not support the separation of an independent subgenus. Nevertheless, the species group is named according to Bader’s suggestion. Apart from the very obvious feature of a completely fused dorsal shield, the structure of the gnathosoma is very characteristic, especially the extremely short P4 and the sharply graded (ventrally and laterally) capitulum. Furthermore, the position of the Cxgl-4 far posterior of the ‘normal’ position at the tip of Cx-I is remarkable. This species probably represents a separate phylogenetic entity. However, as only one species (in one specimen) is yet known, no phylogenetic group is defined at the present state of knowledge. With regard to the very short coxal field and the shape of the capitulum, T. amalgamada is similar to T. brevicoxalis (see below).

Figures

Figure 10. Torrenticola amalgamada. A–D, holotype female (CR 201). A, idiosoma, ventral view; B, idiosoma, dorsal view; C, capitulum with right palp, lateral view; D, chelicera, lateral view. Scale bars = 100 µm.