Diphascon (D.) hydrophilum, Pilato & Binda & Bertolani & Lisi, 2005

Pilato, Giovanni, Binda, Maria Grazia, Bertolani, Roberto & Lisi, Oscar, 2005, Four new species of the Diphascon nobilei group (Eutardigrada, Hypsibiidae), Journal of Natural History 39 (14), pp. 1029-1041 : 1037-1039

Diphascon (D.) hydrophilum sp. n.

( Figure 5 ; Table I)

Material examined

Modena: Rocca Santa Maria: one specimen in sediments of the Torrente Fossa (holotype, slide N. 4927); Modena : Levizzano : three specimens in sediments of the Guerro stream; Trieste : Aurisina : seven specimens in sediments of the cave Grotta del Pettirosso .

Description of the holotype

Body length 307 M m, colourless, eyes absent, cuticle smooth without pearls. Buccopharyngeal apparatus is shown in Figure 5A . The bucco-pharyngeal tube is 49.4 M m long; the rigid buccal tube 23.3 M m long (pbf 547.2) and 2.2 M m wide (ptd 59.4). The stylet supports are inserted on the bucal tube at 63.1% of its length (ptd 563.1). The pharyngeal bulb (32.7 M m × 24 M m) has small apophyses, three rod-shaped macroplacoids and microplacoid, the septulum is absent. The first macroplacoid is 4.9 M m long (ptd 521.0), the second 4.6 M m (ptd 519.7), the third 5.8 M m (ptd 524.9), microplacoid 1.7 M m (ptd 57.3); the entire placoid row 18.1 M m long (ptd 577.7) including the microplacoid, 15.8 M m (ptd 567.8) excluding it.

The claws ( Figure 5B–E ) with accessory points on the main branches; the external claws are long and slender. The claws of the hind legs ( Figure 5E ) have the basal portion enlarged with the basal margin indented and prolonged in one medial and one lateral thickening. The external claws on the first three pairs of legs ( Figure 5C, D ) have an indented basal margin. They are 16.1 M m in length (ptd 569.1) on the second and third pair of legs; the internal claws are not measurable due their unfavourable orientation; we measured them in a specimen having the buccal tube 24.5 M m long where they are 9 M m long (ptd 536.7); on the hind legs the anterior claws are 10.4 M m in length (ptd 544.6) and the posterior claws 15.8 M m (ptd 567.8). A cuticular bar is present near the internal claws on the first three pairs of legs. Eggs not found.

The paratypes are similar to the holotype. In Table I the dimensions of some structures of the smallest and of the largest measured specimens are indicated.

Etymology

The name hydrophilum refers to the fact that the species was found in water.

Remarks

Diphascon hydrophilum sp. n. differs from D. nobilei in the following features: stylet supports inserted on the buccal tube in a more caudal position ( Table I); slightly higher value of the pbf index relative to the buccal tube length ( Table I); lower value of the ptd index relative to the placoid row length as a consequence of the shortness of the third macroplacoid ( Table I); longer and slender claws ( Figures 1 , 5 ; Table I); the internal claws on the first three pairs of legs without basal spines.

The new species differs from D. serratum in having a slightly higher value of the pbf index relative to the buccal tube length ( Table I); stylet supports inserted on the buccal tube in a more cephalic position ( Table I), shorter third macroplacoid, lower value of the ptd index relative to the placoid row length ( Table I), longer and more slender claws with longer secondary branches ( Figures 2 , 5 ).

The new species differs from D. nelsonae in having a slightly higher value of the pbf index relative to the buccal tube length ( Table I), lower value of the ptd index relative to the placoid row length as a consequence of the shortness of the third macroplacoid ( Table I), longer and more slender claws ( Figures 3 , 5 ; Table I).

The new species differs from D. platyungue in having a slightly shorter bucco-pharyngeal tube (both the buccal tube and the pharyngeal tube are shorter in relation to the body length) ( Table I), shorter third macroplacoid, claws very different in size and shape (the claws of D. hydrophilum are longer and more slender, and those of the fourth pair of legs have the basal portion less enlarged) ( Table I; Figures 4 , 5 ).

Figures

Figure 1. Diphascon (D.) nobilei Binda, 1969. (A) Bucco-pharyngeal apparatus; (B) claws of the third pair of legs; (C) claws of the fourth pair of legs. Scale bar: 10 Mm.

Figure 2. Diphascon (D.) serratum sp. n. (A) Bucco-pharyngeal apparatus; (B) claws of the third pair of legs; (C) claws of the fourth pair of legs. Scale bar: 10 Mm.

Figure 3. Diphascon (D.) nelsonae sp. n. (A) Bucco-pharyngeal apparatus; (B) claws of the second pair of legs; (C) claws of the fourth pair of legs. Scale bar: 10 Mm.

Figure 4. Diphascon (D.) platyungue sp. n. (A) Bucco-pharyngeal apparatus; (B) claws of the third pair of legs; (C) claws of the fourth pair of legs; (D) claws of the second pair of legs of a paratype. Scale bar: 10 Mm.

Figure 5. Diphascon (D.) hydrophilum sp. n. (A) Bucco-pharyngeal apparatus; (B) internal claw of the second pair of legs; (C) external claw of the second pair of legs; (D) claws of the second pair of legs of a paratype; (E) claws of the fourth pair of legs. Scale bar: 10 Mm.