Hypsibius microps Thulin, 1928

(Figs.1–3, 7–9, 13, 15–17)

Redescription. Adult (measurements in Table 1): Body white/transparent (Fig. 13). Large eyes present.

Cuticle smooth, without pores. Bucco-pharyngeal apparatus of the Hypsibius type (Figs.7, 15). Mouth anteroventral, without lamellae or papulae.

Oral cavity armature absent or not detectable under DIC. Buccal tube rigid and with one bend in posterior part (visible in lateral view). Ventral buccal lamina absent. Pharyngeal bulb almost spherical with distinct triangular apophyses, two macroplacoids and without the microplacoid. Macroplacoids in the shape of small granules (almost as wide as long), without constrictions. The first microplacoid only slightly longer than the second (Figs.7, 15).

Claws of the Hypsibius - type, small and stout (Figs.8–9, 16–17). Internal claws much smaller and in a different shape than the external ones.

External claws with slender primary branches connected with the rest of the claw by a thinner, lightrefracting part. Secondary branches equal or longer than base claws (i.e., primary branches seem to be attached low, near the claw base), secondary branches relative lengths vary between 50.0% and 62.9% (mean ± SD: 57.3 ± 3.2%, calculated from all measurable claws, n=20).

Internal claws smaller and more robust with primary branches connected to the rest of the claw without a thinner, light-refracting part (Fig. 9). Primary branches of external and internal claws with distinct accessory points. Lunules and other cuticular structures on legs absent.

Eggs: White/transparent, smooth, oval, deposited in exuvium (1–4 per exuvium).

Remarks: Measurements and pt values of selected morphological structures for 5 specimens are provided in Table 1. Among 5 analysed specimens, three had eyes (60%).

Material examined: Holotype and 8 paratypes (see Material and Methods for details).