Gretacarus occidentalis, Smit, Harry, 2016

Smit, Harry, 2016, The water mite genus Gretacarus K. O. Viets, 1978 from Australia (Acari: Hydrachnidia, Mideopsidae: Gretacarinae), with the description of three new species, Zootaxa 4121 (2), pp. 159-166 : 161

Gretacarus occidentalis n. sp.

( Figs. 2A–F )

Material examined. Holotype male, Helena River, pool downstream of crossing with Yarra Road, Western Australia, Australia, 31º 56.421 S 116º 25.237 E, alt. 200 m a.s.l., 30-iv-2008 ( WAM). Paratype: one female, same data as holotype ( WAM).

Diagnosis. IV-leg-2 with very long setae, IV-leg-4 with a large bowed seta; genital field with two rows of one acetabulum in width, genital field with rows of radiating minute setae; P4 ventrally with a truncated seta.

Description. Male: Idiosoma yellowish, dorsally 535 long and 429 wide, ventrally 486 long. Dorsal shield with three pairs of glandularia, 482 long and 397 wide. Anterior coxae not extending to anterior idiosoma margin. Without a ridge extending posteromedially of fourth leg sockets. Fourth coxae with a distinct posterior margin, which hides vgl-4. Genital field with two rows of one acetabulum in width. Genital field 90 long and 104 wide, with several rows of radiating minute setae. Length of P1-5: 22, 45, 32, 40, 22. P4 stocky, ventrally with a truncated seta on a large hump. Length of I-leg-4–6: 60, 66, 90. Length of IV-leg-4–6: 106, 102, 80. IV-leg-2 with approximately ten very long setae (not all of these illustrated) and three shorter long setae, the long setae extending to IV-leg-6. IV-leg-4 with a large bowed seta, dorsal margin with one heavy seta. IV-leg-5 with three long swimming setae.

Female: Idiosoma yellowish, dorsally 624 long and 543 wide, ventrally 567 long. Dorsal shield with three pairs of glandularia, 567 long and 486 wide. Anterior coxae not extending to anterior idiosoma margin. Posterior margin of fourth coxae less distinct than in male. Gonopore 110 long and 140 wide; genital plates with few acetabula more or less in one row. Length of P1-5: 22, 50, 38, 52, 26; palp as in male. Length of I-leg-4–6: 62, 70, 96. Length of IV-leg-4–6: 96, 128, 122. Third and fourth leg with numerous swimming setae.

Etymology. The name refers to its western (Australian) origin.

Remarks. Gretacarus ravenscroftae Wiles, 1997 from New Guinea has two smaller patches of setae laterally of the gonopore. Moreover, the latter species has the gonopore with acetabula rows more than one acetabulum in width, while the new species has less swimming setae on IV-leg-2, IV-leg-4 and IV-leg-5 ( Wiles 1997). The female has less distinctive characters, but the low number of acetabula lying in one row might be diagnostic. This is the first Gretacarus species from SW Australia.

Figures

FIGURES 2 A – F. Gretacarus occidentalis n. sp., A – E holotype male, F paratype female. A = dorsum; B = venter; C = genital field; D = palp; E = IV-leg- 4 – 6; F = venter. Scale bars: A – B, F = 200 µm, C – E = 50 µm.