Isohypsibius sabellai, Pilato & Binda & Napolitano & Moncada, 2004

Pilato, G., Binda, M. G., Napolitano, A. & Moncada, E., 2004, Remarks on some species of tardigrades from South America with the description of two new species, Journal of Natural History 38 (9), pp. 1081-1086 : 1082-1084

Isohypsibius sabellai n. sp.

(figure 1)

Material examined. Brazil: Iguazu falls : holotype and one paratype from an undetermined moss sample .

Description of the holotype. Body length 175 Mm (figure 1a), colourless, eyes present. Cuticle with about 20 undulations and reticular sculpture on the dorsal and lateral surfaces and on the legs. The posterior meshes have the largest size (maximum diameter about 2 Mm); the ridges delimiting the meshes are thicker where they cross (figure 1d). Ventral cuticle smooth.

Bucco-pharyngeal apparatus of Isohypsibius type (figure 1b): buccal tube rigid without ventral strengthening bar; apophyses for the insertion of the stylet muscles in shape of ridges symmetrical with respect to the frontal plane. Mouth ventral, without peribuccal lamellae and peribuccal papulae. Buccal tube, measured from the anterior margin of the stylet sheaths to the base of pharyngeal apophyses, 30.2 Mm long and 2.9 Mm wide (pt =9.6); stylet supports inserted on the buccal tube at 69.1% of its length (pt =69.1). The pharyngeal bulb (20 Mm×13 Mm) has welldeveloped apophyses and two rod-shaped macroplacoids both with a constriction (central in the first macroplacoid, more caudal in the second). Microplacoid and septulum absent. First macroplacoid 5.5 Mm long (pt =18.3), second 4.2 Mm (pt = 13.9), entire placoid row 10.2 Mm long (pt =33.9).

Claws of Isohypsibius type (figure 1c) well developed; short accessory points are present on the main branches; due to their flexibility, the orientation of the claws is unfavourable to measurements; in a paratype (207 Mm long, having the buccal tube 31.4 Mm long) we were able to measure the internal claws of the second pair of legs (9.6 Mm, pt =30.6), and the anterior claws of the hind legs (10 Mm, pt =31.8). Very flexible lunulae are present. A cuticular bar, wide and not very sclerotized, is present near the base of the internal claws on the first three pairs of legs. Eggs were not found.

The paratype is similar to the holotype.

Etymology. The species is named Isohypsibius sabellai in honour of Dr Giorgio Sabella (Dipartimento di Biologia Animale ‘Marcello La Greca’, Università di Catania) who kindly collected the samples.

Isohypsibius sabellai differs from Isohypsibius undulatus Thulin, 1928 in the following features: cuticular sculpture type (in I. undulatus the reticular sculpture is very regular and delicate; the ridges delimiting the meshes are not thickened where they cross); claw shape and size (in I. sabellai they are longer and more slender); accessory points less developed; stylet supports inserted on the buccal tube in a more caudal position (pt = 69.1–69.3 in I. sabellai , 66.8 in I. undulatus ).

The description of Isohypsibius pseudoundulatus (Da Cunha and Do Nascimiento Ribeiro, 1964) is very brief and not exhaustive. Isohypsibius sabellai differs from this species in the following features: more evident dorsal undulations; first and second placoid length not so different; narrower buccal tube. As regards the cuticular sculpture, Da Cunha and Do Nascimiento Ribeiro (1964) did not supply details; comparing I. pseudoundulatus with I. undulatus they only wrote that the undulations are less evident; they did not stress differences in the characters of the reticular sculpture and this statement may induce the consideration that I. pseudoundulatus has a sculpture similar to that of I. undulatus , and therefore different from that of I. sabellai ; but this interpretation should be confirmed.