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

Pilato, Giovanni, Sabella, Giorgio & Lisi, Oscar, 2014, Two new tardigrade species from Sicily, Zootaxa 3754 (2), pp. 173-184 : 179-182

Diphascon (Diphascon) procerum sp. nov.

Figs. 4 , 5 .

Material examined: Cava San Giovanni Lo vecchio: Noto (Siracusa), holotype (slide No. 3171) and 9 paratypes (slides Nos. 3168-3170, 3172; 3253-3154 and 3266) (moss sample collected by Sebastiano Distefano in January 1980).

Type repository: Holotype and paratypes are deposited in the Binda & Pilato collection, Department of Biological, Geological and Environmental Sciences, Section of Animal Biology, University of Catania.

Specific diagnosis: Cuticle without gibbosities, with extremely fine tubercles that viewed vertically appear as dots; eye spots present; pharyngeal tube (measured from the caudal extremity of the drop-shaped thickening) slightly shorter than the pharyngeal bulb; two rod-shaped macroplacoids and septulum present; lunules absent; accessory points present; a cuticular bar present near the internal claw on legs I–III; two short cuticular bars present on legs IV, one near the base of the anterior claw and one between the anterior and posterior claws.

Description of the holotype: Body length 358 µm; colourless; eye spots present; cuticle with extremely small tubercles (visible as dots) ( Fig. 4 A), also present on the legs. Buccal-pharyngeal apparatus of Diphascon type (rigid buccal tube, without ventral lamina, and flexible, spirally thickened pharyngeal tube); drop shaped thickening is present between the buccal and the pharyngeal tube ( Fig. 4 B); mouth without peribuccal lamellae or papulae; no teeth visible in the buccal cavity; 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.

Buccal-pharyngeal tube length (measured from the anterior margin of the stylet sheaths to the caudal end, excluding pharyngeal apophyses), 64.8 µm; buccal tube length (measured from the anterior margin of the stylet sheaths to the caudal end of the drop-shaped thickening), 27.3 µm; expressed as a ratio of the total length of the bucco-pharyngeal tube, 42.1 % (pbf = 42.1); buccal tube external width 2.2 µm (ptd = 8.1); stylet supports inserted at 61.1 % of the buccal tube length (ptd = 61.1); pharyngeal tube length 37.6 µm.

Pharyngeal bulb with apophyses, two rod-shaped macroplacoids and septulum ( Fig. 4 B), microplacoid absent. First macroplacoid, with central constriction, 7.3 µm long (ptd = 26.7); second macroplacoid, with a preterminal constriction (see more clearly in Fig 5 A paratype), 6.9 µm long (ptd = 25.3); septulum length 2.8 µm (ptd = 10.3); entire placoid + septulum row length 17.3 µm (ptd = 63.4); entire macroplacoid row 14.5 µm (ptd = 53.1).

Hypsibius type claws ( Fig. 4 B–D), well developed with a short basal tract, broader in the external claws and particularly the posterior claws of legs IV (see more clearly in Fig. 5 B, C paratype); leg I external claw length, 11.6 µm (ptd = 42.5); internal claws on same leg 7.7 µm (ptd = 28.2); leg IV posterior claw length, 14 µm (ptd = 51.3) with indented basal margin; anterior claw on same leg 9.7 µm long (ptd = 35.5). Additional measurements are given in Table 4 . Thin accessory points present on all main claw branches ( Fig. 5 B); lunules absent; obvious cuticular bar present near the internal claws of legs I–III ( Figs. 4 C and 5C); two clearly visible, short cuticular bars are present on the hind legs, one near the base of the anterior claw and the second between the anterior and the posterior claws ( Figs. 4 D and 5B). Eggs not found.

Remarks: The paratypes are similar to the holotype in both qualitative and metric characters; measurable characters of the holotype and two paratypes are reported in Table 4 .

Etymolog y: The name procerum refers to the claw shape (the main branches are long with respect to the total claw length, and for this reason the claws appear slender; Latin: proceru s = long and slender).

Diphascon (D.) procerum sp. nov. D. (D.) ramazzottii

Slide No. 3253 3171 3170 1404

Paratype Holotype Paratype Paratype Differential diagnosis: Six species within the subgenus Diphascon (Diphascon) are reported to have an ornamented cuticle that is without gibbosities or reticular design, 2 macroplacoids and septulum. These are: D, (D) oculatum Murray, 1906 , D. (D.) rugocaudatum ((Rodriguez Roda, 1952), D. (D.) nodulosum ( Ramazzotti, 1957) , D. (D.) ramazzottii ( Robotti, 1970) , D. (D.) granifer Greven, 1972 and D. (D.) burti Nelson, 1991 .

Diphascon (D.) procerum sp. nov. differs from D. (D.) oculatum and D. (D.) rugocaudatum in having cuticular tubercles on the entire dorsal body surface and not limited to the caudal region; in addition, it differs from D. (D.) oculatum in having shorter pharyngeal tube and longer macroplacoids.

From D. (D.) nodulosum the new species differs in the markedly smaller size of the cuticular tubercles, and from D. (D.) burti in lacking the pseudoseptulum and in having obvious cuticular bars on the legs.

Diphascon (D.) procerum sp. nov., differs from D. (D.) granifer in: having clearer cuticular tubercules or dots, eye spots present, and having obvious cuticular bars on the legs.

The new species differs from D. ramazzottii in having: smaller and more wide-spaced cuticular tubercles (visible as dots) (in D. ramazzottii the cuticular tubercles are near neighbour polygonals with the appearance of a reticular design (Pilato & Binda, 1977)). In addition, the new species has: slightly more caudally positioned stylet supports ( Table 4 ), longer second placoid and, as a consequence, longer placoid row ( Table 4 ), clearly longer claws ( Table 4 ); main branch of each claw longer with respect to the total claw length ( Table 4 ; Figs. 5 B, C and 5D).

Conclusions. The tardigrade fauna of the relatively small region encompassed by Sicily and the associated archipelegos could be considered well known with 24 papers spaced over 50 years and a current species list of 96 species. However, this study has described new species, Macrobiotus insuetus sp. nov. and Diphascon (D.) procerum sp. nov., from separate Sicilian localities, which indicates there are still a large number of microenvironments in this area waiting to be studied.

Figures

FIGURE 4. A-D, Diphascon procerum sp. nov. A, Paratype cuticular ornamentation detail (arrows) (slide 3253). B, Holotype buccal-pharyngeal apparatus. C, Holotype claws of leg III. Arrow indicates the cuticular bar near the base of the internal claw. D, Holotype claws of leg IV. Arrows indicate the cuticular bars near the base of the claws. Scale bar = 10 µm.

FIGURE 5. A-C. Diphascon procerum sp. nov. A, Paratype buccal-pharyngeal apparatus and claws of leg I (slide No. 3253). The eyes are visible. B, Paratype (as in A) claws of leg IV (slide No. 3253). Cuticular bars near the base of both claws are visible. Arrow indicates the thin accessory points. C, Paratype (as in A) claws of leg II (slide No. 3253). D, Diphascon ramazzottii. Paratype claws of leg II (slide No. 1464). Scale bar = 10 µm.

Tables

TABLE 4. Measurements (in µm), and other morphological parameters, for Diphascon (D.) procerum sp. nov. holotype and two paratypes, compared with a similar sized paratype of Diphascon (D.) ramazzottii. (ptd index values in brackets).

µm	(ptd)	µm	(ptd)	µm	(ptd)	µm	(ptd)
Body length 346		358		369		346
Buccal-pharyngeal tube length 61.8		64.8		68.8		71.5
Buccal tube length 28.4		27.3		29.1		30.9
pbf ratio 46.0		42.1		42.3		43.2
Pharyngeal tube 33.7		37.6		39.9		40.3
External buccal tube width 2.5	(8.8)	2.2	(8.1)	2.3	(7.9)	2.4	(7.8)
Stylet supports insertion point	(61.8)		(61.1)		(62.4)		(59.2)
First macroplacoid 8.2	(28.8)	7.3	(26.7)	9.2	(31.6)	8.3	(26.9)
Second macroplacoid 6.2	(21.8)	6.9	(25.3)	6.8	(23.4)	6.1	(19.7)
Septulum 3.0	(10.5)	2.8	(10.3)	3.2	(11.1)	3.1	(10.0)
Placoids + septulum 18.1	(63.5)	17.3	(63.4)	19.1	(65.6)	18.2	(58.9)
Macroplacoid row 14.9	(52.3)	14.5	(53.1)	15.7	(54.0)	14.6	(47.2)
External claw I?	?	11.6	(42.5)	?	?	?	?
% main branch/ total claw length?	?	9.3	(80.2)	?	?	?	?
Internal claw I 8.3	(29.1)	7.7	(28.2)	?	?	?	?
% main branch/ total claw length 7.6	91.6	6.7	87.0	?	?	?	?
External claw II?	?	?	?	12.2	(41.9)	10.9	(35.2)
% main branch/ total claw length?	?	?	?	10.5	86.1	8.3	76.1
Internal claw II 8.9	(31.2)	9.1	(33.3)	?	?	8.2	(26.5)
% main branch/ total claw length 7.9	88.8	8.1	89.0	?	?	6.2	75.6
External claw III?	?	?	?	?	?	10.3	(33.3)
% main branch/ total claw length?	?	?	?	?	?	8.1	78.6
Internal caw III 9.4	(33.0)	?	?	10.6	(36.7)	8.9	(28.8)
% main branch/ total claw length 8.5	90.4	?	?	9.5	89.6	6.9	77.5
Posterior claw IV 15.2	(53.3)	14.0	(51.3)	?	?	13.4	(43.4)
% main branch/ total claw length 12.4	81.6	11.7	83.6	?	?	10.5	78.4
Anterior claw IV 10.7	(37.5)	9.7	(35.5)	11.5	(39.5)	?	?
% main branch/ total claw length 8.9	83.2	8.3	85.6	9.8	85.2	?	?