Diphascon (Diphascon) ziliense, Lisi, Oscar, Sabella, Giorgio & Pilato, Giovanni, 2014

Lisi, Oscar, Sabella, Giorgio & Pilato, Giovanni, 2014, Mixibius parvus sp. nov. and Diphascon (Diphascon) ziliense sp. nov., two new species of Eutardigrada from Sicily, Zootaxa 3802 (4), pp. 459-468 : 462-465

Diphascon (Diphascon) ziliense sp. nov.

( Fig. 3 )

Type locality. Sicily, Caronia, by the side of Zilio Lake (37° 57′N, 14° 25′E; 1069 m a.s.l.).

Material examined. Caronia, by the side of Zilio Lake: holotype (slide No. 5500) and 1 paratype (slide No. 5499) in a moss sample collected by Mr. Angelo Zappalà, 29.5.1989.

Specific diagnosis. Cuticle with small tubercles but without gibbosities, eye spots absent; bucco-pharyngeal apparatus of the Diphascon type; pharyngeal bulb with two rod-shaped macroplacoids and a septulum; claws of the Hypsibius type, accessory points extremely thin, almost invisible; lunules present; a cuticular bar present near the internal claw on the first three pairs of legs; two short cuticular bars present on the hind legs (one near the base of the anterior claw and another between the anterior and the posterior claw).

Description of the holotype. Body length, 286 µm, colourless; eye spots absent; cuticle with small tubercles (<1.9 µm in diameter) more evident on the dorsal and lateral surface of the body ( Fig. 3A ), and also present, although less visible, on the legs. Bucco-pharyngeal apparatus of the Diphascon type: with a rigid buccal tube without ventral lamina, and a flexible pharyngeal tube with a spiral thickening; a drop shaped thickening is present between the buccal and the pharyngeal tube ( Fig. 3B ); mouth without peribuccal lamellae or papulae; very thin transverse ridges are visible in the buccal cavity, teeth are not visible but their absence needs to be confirmed. Buccal tube with dorsal and ventral apophyses for the insertion of the stylet muscles in the shape of hooks symmetrical with the respect to the frontal plane.

Mixibius parvus sp. nov. Mixibius tibetanus *

Slide No. 5336 Holotype Paratype

* According to Li & Li (2008) (paratype: Tibet 0706003).

Bucco-pharyngeal tube length, measured from the anterior margin of the stylet sheaths to the caudal end, excluding pharyngeal apophyses, 57.8 µm; buccal tube length, measured from the anterior margin of the stylet sheaths to the caudal end of the drop-shaped thickening, 26.6 µm; buccal tube length is 46% of the total length of the bucco-pharyngeal tube (pbf = 46); pharyngeal tube 31.2 µm long; external width of the buccal tube, 2.3 µm (ptd = 8.7). Stylet supports inserted on the buccal tube at 60.4% of its length (ptd = 60.4); pharyngeal bulb (34.1 µm x 30.9 µm) with apophyses, two rod-shaped macroplacoids and a septulum ( Fig. 3B ). First macroplacoid 7.3 µm long (ptd = 27.4); second macroplacoid 5.8 µm long (ptd = 21.8); septulum 2.9 µm long (ptd = 10.9); entire placoid + septulum row length 16.5 µm (ptd = 62.0); entire macroplacoid row length 13.4 µm (ptd = 50.4).

Claws of the Hypsibius type, well developed ( Fig. 3C, D, E ); with a short basal portion; in the external claws the basal portion is enlarged ( Fig. 3C, D ) and has a slightly indented margin; a very visible septum is present between the basal common portion and the branches ( Fig. 3D, E ). Legs I, external and internal claw lengths, 11.3 µm (ptd index = 42.5) and 8.8 µm (ptd = 33.1), respectively; legs II, external and internal claw lengths, 12.0 µm (ptd = 45.1) and 8.2 µm (ptd = 30.8), respectively; legs III, external and internal claw lengths, 12.1 µm (ptd = 45.5) and 8.5 µm (ptd = 32.0), respectively; legs IV, posterior and anterior claw lengths, 13.4 µm (ptd = 50.4) and 10.4 µm (ptd = 39.1), respectively. Main branches of all claws with extremely thin and short accessory points, which are very difficult to see; well developed, flexible lunules present ( Fig. 3C, D , arrow 1); a cuticular bar is visible near the internal claws of the first three pairs of legs ( Fig. 3C, D , arrow 2); two short cuticular bars present on the hind legs: one near the base of the anterior claw and the other between the anterior and the posterior claws ( Fig. 3E , arrows).

Eggs not found.

Remarks. The paratypes are similar to the holotype in both qualitative and metric characters ( Table 2 ).

Dihascon (D.) ziliense sp. nov D. (D.) procerum D. (D.) ramazzottii Etymology. The name ziliense refers to the locus typicus; the species was found in mosses growing by the side of Zilio Lake.

Differential diagnosis. Few species of the sub-genus Diphascon (Diphascon) have a cuticle with tubercles (or granulation) and a pharyngeal bulb with two macroplacoids and a septulum: D. (D.) oculatum Murray, 1906 ; D. (D.) nodulosum ( Ramazzotti, 1957) ; D. (D.) ramazzottii ( Robotti, 1970) , D. (D.) granifer Greven, 1972 ; D. (D.) opistoglyptum Maucci, 1987 ; D. (D.) burti Nelson, 1991 and D. (D.) procerum Pilato, Sabella & Lisi, 2014 .

The new species differs from D. (D.) oculatum , D. (D.) nodulosum , D. opistoglyptum and D. (D.) burti in lacking eye spots and in having lunules and a cuticular bar on the legs. In addition, it also differs from: D. (D.) oculatum in having cuticular tubercles present in the central and anterior portion of the body, in having a clearly shorter pharyngeal tube and longer placoids; from D. (D.) nodulosum in having caudal tubercles less developed, a shorter pharyngeal tube and longer macroplacoids; from D. (D.) opistoglyptum in having cuticular ornamentation not limited to the posterior portion of the body and in lacking a microplacoid; from D (D.) burti in lacking a pseudoseptulum (i.e. the cuticular thickening situated posterior to the septulum in the pharyngeal lumen, as described by Nelson (1991) in D. (D.) burti ).

Diphascon (D.) ziliense sp. nov. differs from D. (D.) granife r in having lunules and in having a cuticular bar on the first three pairs of legs and two bars on the hind legs.

It differs from D. (D.) ramazzottii in lacking eye spots, in having a more evident cuticular ornamentation and the presence of lunules. In addition, it has longer claws in proportion to the body size and the buccal tube length ( Table 2 ), and the main branch of the internal claws is less developed in relation to the total claw length ( Table 2 ; Figs 4A and 4 C).

The new species is very similar to D. (D.) procerum but differs in having a more visible cuticular ornamentation. In addition, a very obvious difference is the stouter claws, with a wider common portion and the main branches shorter in proportion to the total length of the respective claws (but they are of comparable length in both species in proportion to the buccal tube length) ( Table 2 ; Fig. 4A, B and D).

Figures

FIGURE 3 A – E, Diphascon ziliense sp. nov. A, cuticular ornamentation (paratype No. 5499) (Scale bar = 10 µm). B, Buccopharyngeal apparatus (holotype). C, Claws of the first pair of legs (holotype); the lunule under the external claw (arrow 1) and a cuticular bar near the base of the internal claw (arrow 2) are visible. D, Claws of the third pair of legs (holotype). Arrows indicate the wide base of the external claw (arrow 1) and the cuticular bar near the base of the internal claw (arrow 2). E, Claws of the hind legs (holotype). The cuticular bars near the base of each claw are visible (arrows). (Scale bar = 10 µm).

FIGURE 4 A, B, Diphascon ziliense sp. nov. (holotype). A, Claws of the second pair of legs. B, Claws of the hind legs. C, Diphascon (D.) ramazzottii (slide No. 1464). Claws of the second pair of legs (paratype). D, Diphascon (D.) procerum (slide No 3253). Claws of the hind legs (paratype). Scale bar = 10 µm.

Tables

TABLE 2. Measurements (in µm) and pt values (in brackets) of selected structures of two specimens (holotype and paratype) of Diphascon (D.) ziliense sp. nov., the holotype of Diphascon (D.) procerum, and one paratype of Diphascon (D.) ramazzottii. (In brackets the values of the ptd index).

Slide No. 5500 Holotype	5499 Paratype	3171 Holotype	1464 Paratype
µm	µm	µm	µm
Body length 286	158	358	346
Bucco-pharyngeal tube length 57.8	?	64.8	71.5
Buccal tube length 26.6 pbf =46	19.6 pbf =?	27.3 pbf =42.1	30.9 (pbf= 43.2)
External buccal tube width 2.3 (8.7)	1.7 (8.7)	2.2 (8.1)	2.4 (7.8)
Stylet supports insertion point (60.4)	(63.3)	(61.1)	(59.2)
Pharyngeal tube length 31.2	?	37.6	40.3
First macroplacoid 7.3 (27.4)	4.8 (24.5)	7.3 (26.7)	8.3 (26.9)
Second macroplacoid 5.8 (21.8)	4.0 (20.4)	6.9 (25.3)	6.1 (19.7)
Septulum 2.9 (10.9)	2.2 (11.2)	2.8 (10.3)	3.1 (10.0)
Placoids + septulum 16.5 (62.0)	11.3 (57.7)	17.3 (63.4)	18.2 (58.9)
Macroplacoid row 13.4 (50.4)	9.1 (46.4)	14.5 (53.1)	14.6 (47.2)
External claw I 11.4 (42.9)	? (?)	11.6 (42.5)	? (?)
% main branch / total claw length 8.2 71.9	??	9.3 80.2	??
Internal claw I 8.5 (32.0)	? (?)	7.7 (28.2)	? (?)
% main branch / total claw length 5.4 63.5	??	6.7 87.0	??
External claw II 12.0 (45.1)	9.4 (48.0)	? ?	10.9 (35.2)
% main branch / total claw length 9.6 80.0	??	??	8.5 77.9
Internal claw II 8.1 (30.4)	? (?)	9.1 (33.3)	8.2 (26.5)
% main branch / total claw length 5.4 66.7	??	8.1 89.0	6.2 75.6
External claw III 12.1 (45.5)	9.6 (49.0)	? (?)	10.3 (33.3)
% main branch / total claw length 9.7 80.2	??	??	8.1 78.6
Internal claw III 8.5 (32.0)	? (?)	? (?)	8.9 (28.8)
% main branch / total claw length 5.8 68.2	??	??	6.9 77.5
Posterior claw IV 13.4 (50.4)	10.0 (51.0)	14.0 (51.3)	13.5 (43.7)
% main branch / total claw length 10. 2 76.1	7.9 79.0	11.7 83.6	10.3 76.3
Anterior claw IV 10.2 (38.4)	7.7 (39.2)	9.7 (35.5)	? (?)
% main branch / total claw length 7.7 75.5	5.7 74.0	8.3 85.6	??