Hypsibius pallidus, Thulin, 1911

Kaczmarek, Łukasz & Michalczyk, Łukasz, 2009, Redescription of Hypsibius microps Thulin, 1928 and H. pallidus Thulin, 1911 (Eutardigrada: Hypsibiidae) based on the type material from the Thulin collection, Zootaxa 2275, pp. 60-68 : 62-64

H. pallidus Thulin, 1911

( Figs.4–6 , 10–12 , 14 , 18–20 )

Redescription. Adult (measurements in Table 2 ): Body white/transparent. Large eyes present. Cuticle smooth, without pores. Bucco-pharyngeal apparatus of the Hypsibius type ( Figs.10 , 18 ). Mouth anteroventral, without lamellae or papulae.

Mouth cavity armature absent or not detectable under DIC. Buccal tube rigid and with one bend in posterior part. Ventral buccal lamina absent. Pharyngeal bulb oval with distinct, triangular apophyses, two macroplacoids and without the microplacoid. Macroplacoids in the shape of elongated granules, without constrictions. The first microplacoid clearly longer then the second.

Claws of the Hypsibius - type, small and stout ( Figs.11–12 , 19–20 ). 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 the thinner, light refracting part. Secondary branches of a similar length or shorter than the basal claws (i.e., primary branches seem to be attached high above the claw base), secondary branches relative lengths vary between 43.1% and 51.5% (mean ± SD: 47.8 ± 2.1%, calculated from all measurable claws, n=19).

Internal claws smaller and more robust. Primary branch connected to the rest of the claw without the thinner, light-refracting part.

Primary branches of external and internal claws with distinct accessory points. Claws with evidently enlarged bases, but lunules and other cuticular structures on legs absent.

Eggs: White/transparent, oval (53.0–60.0 in diameter), deposited in exuvium (2–5 per exuvium).

Remarks: Measurements and pt values of selected morphological structures for 3 specimens are provided in Table 2 . All examined specimens had eyes.

Material examined: Holotype and 2 paratypes (see Material and Methods).

CHARACTER Paratype 2 Paratype 4 Paratype 3 Paratype 1 Holotype

µm pt µm pt µm pt µm pt µm pt Body length 149.8 666.5 185.3 708.3 190.3 827.4 211.6 730.3 230.2 810.8 Claw 4 - sb/(bc+sb) (ext=ant) [%]? –? – 56.5 – 61.7 – 55.7 –

Claw 4 - bc (int=post) length?? 3.6 13.8?? 4.0 13.7??

Claw 4 - pb (int=post) length 9.1 40.6 10.5 40.1 9.1 39.7 10.7 36.9 11.5 40.5 Claw 4 - sb (int=post) length 5.5 24.5 4.4 16.7 4.2 18.3 6.0 20.6 4.8 17.0 Claw 4 - sb/(bc+sb) (int=ext) [%]? – 54.8 –? – 60.1 –? – CHARACTER Paratype 1 Holotype Paratype 2

µm pt µm pt µm pt

Body length 239.8 922.1 251.1 1109.2 309.0 1069.6

Figures

FIGURES 1 – 6. The type material of Hypsibius microps and Hypsibius pallidus from the Thulin collection: 1 – 3, H. microps; 4 – 6, H. pallidus.

FIGURES 7 – 12. Thulin’s original drawings of H. microps and H. pallidus: 7 – 9, H. microps (7, buccal apparatus; 8, external claw III; 9, claws IV); 10 – 12, H. pallidus (10, buccal apparatus; 11, external claw III; 12, claws IV). (7 – 11 from Thulin 1928, 12 from Thulin 1911, not scaled)

FIGURES 13 – 14. The type material of Hypsibius microps and Hypsibius pallidus from the Thulin collection: 13, H. microps, habitus (holotype); 14, H. pallidus, habitus (paratype). (scale on 14 same as on 13)

FIGURES 15 – 20. The type material of Hypsibius microps and Hypsibius pallidus from the Thulin collection: 15 – 17, H. microps (15, buccal apparatus (holotype); 16, claws III (holotype); 17, claws IV (holotype )); 18 – 20, H. pallidus (18, buccal apparatus (paratype); 19, claws III (holotype); 20, claws IV (paratype )). (scale on 18 same as on 15, and on 17, 19 - 20 same as on 16)