Itaquascon pisoniae, Pilato, Giovanni & Lisi, Oscar, 2009

Pilato, Giovanni & Lisi, Oscar, 2009, Description of three new species of Tardigrada from the Seychelles, Zootaxa 2005, pp. 24-34 : 30-33

Itaquascon pisoniae sp. n.

Fig. 4

Material examined: Silhouette ( Pisonia forest): holotype and 1 paratype from a soil sample (collected 07.08.2000) sent by Justin Gerlach.

Type repository. The holotype (slide N. 5099) and paratype are deposited in the collection of Binda & Pilato (Museo del Dipartimento di Biologia Animale “Marcello La Greca”, Università di Catania).

Species diagnosis. Cuticle smooth without pores, eye spots absent; pbf index relative to the buccal tube higher than 50 (about 55); pharyngeal apophyses and placoids absent; stylet furcae very small; base of claws slightly enlarged but without well-developed lateral processes; lunules absent; a very faint cuticular bar near the internal claws on the first three pairs of legs; no cuticular thickening present on the hind legs.

Description of the holotype. Body elongate, slender, tapering anteriorly, 270 μm long; colorless; eye spots absent; cuticle smooth without pores. Bucco-pharyngeal apparatus of Itaquascon type ( Fig. 4 A), i.e., with a rigid buccal tube, without ventral lamina, dorsal and ventral apophyses for the insertion of the stylet muscles in the shape of flat ridges; flexible pharyngeal tube with a spiral thickening; peribuccal lamellae and papulae absent; stylet supports present, but very difficult to see, inserted between the buccal and the pharyngeal tube. Bucco-pharyngeal tube 41 μm long; buccal tube 22.7 μm (pbf = 55.4) long and 2.1 μm wide externally (pt = 9.2). Pharyngeal bulb oval (18 μm long and 10.5 μm wide), without apophyses or placoids. Stylets 16 μm long; stylet supports inserted at the end of the buccal tube (pt = 100); stylet furcae small triangular in shape, with two short tapering caudal processes ( Fig. 4 A).

Claws of Hypsibius type ( Fig. 4 B–D); external and internal claws differing in shape and size; main branches with accessory points. The base is slightly enlarged but without well-developed lateral processes ( Fig. 4 D). On the first pair of legs the external claw length is 11.8 μm (pt = 52.0) and internal claw length 6.9 μm (pt = 30.4); the claws on both second and third pair of legs are: external 14.2 μm (pt = 62.6) and internal 8.6 μm (pt = 37.9); and on the hind legs the posterior claw is 14.5 μm (pt = 63.9) and anterior claw 9.0 μm long (pt = 39.6). For additional measurements see Table 3 . Lunules are absent; a faint cuticular bar is present near the internal claws on the first three pairs of legs, but sometimes these structures are very difficult to see and may appear absent.

Eggs not found.

The paratype is similar to the holotype in both qualitative and metric characters ( Table 3 ).

I. pisoniae sp. n. holotype I. pisoniae sp. n. paratype I. placophorum Etymology. The name pisoniae refers to the generic name of the plant forming the Pisonia forest where the new species has been found.

Remarks. Six species within the genus Itaquascon have buccal tube shorter than half of the total length of the bucco-pharyngeal tube (pbf <50). These are: I. umbellinae , I. globuliferum Abe & Ito, 1994 , I. unguiculum , I. cambewarrense , I. biserovi and I. pawlowski Weglarska, 1973 ). Only three species (I.

placophorum , I. mongolicum Kaczmarek, Michalczyk & Weglarska, 2002 and I. pisoniae sp. n.) have pbf index higher than 50.

Itaquascon pisoniae sp. n. differs from I. placophorum by having smooth cuticle, shorter claws ( Table 3 ), by the absence of placoids and by the absence of a cuticular bar between the claws of the hind legs.

It differs from I. mongolicum by the absence of lunules and by the presence of a cuticular bar (sometimes very difficult to see) near the internal claws of the first three pair of legs.

Figures

FIGURE 4. Itaquascon pisoniae sp. n. A, bucco-pharyngeal apparatus of the paratype. B, claws of the third pair of legs of the paratype. C, claws of the first and second pairs of legs of the holotype; arrow indicates the faint cuticular bar near the base of the internal claw. D, claws of the fourth pair of legs of the paratype. (Scale bar 10 = µm)

Tables

TABLE 3. Measurements (in μm), and values of the pt index, of some structures of holotype and paratype of Itaquascon pisoniae sp. n. and of one specimen of Itaquascon placophorum.

Body length 270	310	?
Bucco-pharyngeal tube 41	45.5	45.6
Buccal tube length 22.7	24.9	24.9
pbf 55.4	54.7	54.6
Buccal tube external width 2.1	2.0	2.9
pt 9.2	8.0	11.7
Stylet supports 22.7	24.9	23.9
pt 100	100	96.0
External claw I 11.8	?	18.2
pt 52.0	?	73.1
Ext. claw I main branch 8.4	?	?
%/tot 71.2	?	?
Internal claw I 7,0	?	?
pt 30.8	?	?
Int. claw I main branch 4.4	?	?
%/tot 62.0	?	?
Int/ext % 59.3	?	?
External claw III 14.0	14.5	22.8
pt 61.7	58.2	91.6
Ext. claw III main branch 9.6	10.0	?
% tot. 68.6	69.0	?
Internal claw III 8.2	9.2	13.7
pt 36.1	36.9	55.0
Int. claw III main branch 4.8	5.1	?
%/tot 58.5	55.4	?
Int./ext. % 58.6	63.4	60.1
Posterior claw IV 14.5	15.4	?
pt 63.9	61.8	?
Post. claw IV main branch 10.0	10.9	?
% tot 69.0	70.8	?
Anterior claw IV 8.9	?	?
pt 39.2	?	?
Ant. claw IV main branch 5.2	?	?
% tot 58.4	?	?
Ant/post % 61.4	?	?