Isohypsibius zappalai, Pilato, Giovanni, Sabella, Giorgio & Lisi, Oscar, 2015

Pilato, Giovanni, Sabella, Giorgio & Lisi, Oscar, 2015, Two new freshwater eutardigrade species from Sicily, Zootaxa 3918 (2), pp. 273-284 : 278-283

Isohypsibius zappalai sp. nov.

Type locality. Anapo River (Pantalica, Siracusa); 37° 08′N, 14° 59′E; 450 a.s.l.

Material examined. Holotype (slide No. 5551) collected by Angelo Zappalà, 19.2. 1974.

Specific diagnosis. Aquatic; colourless; eye spots present; entire body surface with small, rounded tubercles, relatively uniform in size and tending to form transverse lines; bucco-pharyngeal apparatus of the Isohypsibius type; buccal armature consisting of a band of small teeth and transverse ridges in the caudal portion of the cavity; pharyngeal bulb with apophyses and two rod-shaped macroplacoids; microplacoid absent; claws well developed with a long cammon basal portion and wide proximal portion to both main and secondary branches; small, flexible lunules present; cuticular bars on the legs absent.

Description of the holotype. Colourless; body length 396 µm; eye spots present before mounting. Entire body surface closely ornamented: numerous small tubercles are present ( Fig. 5 A–C ), most of which are rounded and fairly uniform in size (diameter up to 2 µm); the tubercles are spaced very densely (or in contact) and form transverse lines ( Fig. 5B, C ) but without a reticular design. The ornamentation, also present on the legs, is less visible on the ventral body surface.

Bucco-pharyngeal apparatus of the Isohypsibius type ( Fig. 5D ): mouth without peribuccal lamellae, buccal tube rigid without ventral lamina and with dorsal and ventral ridge-shaped apophyses for the insertion of the stylet muscles. In the caudal portion of the buccal cavity a band of small teeth and thin transverse ridges are present; there also appears to be a faint band of very small teeth present in the anterior portion of the buccal cavity, but this character needs to be confirmed.

Rigid buccal tube 40.9 µm long and 5.8 µm wide externally (pt = 14.2); stylet supports inserted on the buccal tube wall at 71.0 % of its length (pt = 71.0).

Pharyngeal bulb with apophyses and two rod-shaped macroplacoids; microplacoid absent. First macroplacoid, with a marked central constriction, 10.1 µm long (pt = 24.7), second 6.8 µm long (pt =16.6). Macroplacoid row length 17.6 µm (pt = 43.0).

The claws, of the Isohypsibius type, are well developed and have a long common basal portion and a wide proximal portion to both main and secondary branches ( Fig. 5D, E ). The orientation in the slide made the measurements of the total claw length difficult and for this reason we have included separate measurements for the main branch length. The orientation of the holotype meant we were only able to measure the claws of the first pair of legs and the claws of the hind legs ( Table 1). Main branches with accessory points ( Fig. 5E ). Small, flexible lunules present ( Fig. 5E ). Cuticular bars on the legs absent.

We did not find eggs attributable to the species.

Differential diagnosis. Excluding Isohypsibius species with smooth cuticle, gibbosities or reticular ornamentation, those with three macroplacoids or microplacoid, and those with cuticular bars on the legs, reduced the number of comparative species to: I. gilvus , I. verae , I. barbarae , I. annulatus , I. pauper , I. fuscus , I. sculptus and the above described I. rusticus sp. nov.

The new species differs from Isohypsibius gilvus in having uniform cuticular ornamentation while in I. gilvus sculptured bands alternate with unsculptured bands ( Figs. 5A, C and 3A ); in addition Isohypsibius zappalai sp. nov. has stylet supports inserted on the buccal tube in a more caudal position (pt = 71.0 in I. zappalai sp. nov., 64.3 in I. gilvus ); first macroplacoid clearly longer than the second and clearly differently shaped claws ( Figs. 5D, E and 3C ).

Heterotardigrada

Carphania fluviatilis Binda, 1978 Saracena Torrent (Randazzo) Eutardigrada .. ....continued on the next page Isohypsibius zappalai sp. nov. differs from I. verae in having cuticular tubercles, whilst I. verae has dots; stylet supports inserted on the buccal tube in a more caudal position (pt = 71.0 in I. zappalai sp. nov., 66.6 in I. verae ); claws slightly stouter, with shorter basal portion ( Figs. 5D, E and 3 E) and higher ratio between the main branch length and the total claw length ( Table 1); another difference is the presence of lunules in the new species.

The new species differs from I. barbarae in lacking transverse cuticular undulations ( Figs 5A, C and 4A ); in having the stylet supports inserted on the buccal tube in a slightly more caudal position (pt = 71.0 in the new species, 67.9 in I. barbarae ); first macroplacoid clearly longer than the second, and longer claws with longer common basal portion ( Figs. 5D, E and 4 D).

Isohypsibius zappalai sp. nov. differs from I. annulatus in having apparently smaller cuticular tubercles (diameter up to 2 µm in the new species, up to 4 µm in I. annulatus ), first macroplacoid clearly longer than the second, and lunules present.

The new species differs from I. pauper in having eye spots, buccal tube longer than the pharyngeal bulb, first macroplacoid markedly longer than the second. Mihelčič’s (1971) description of I. pauper did not include lunules in report or drawing; a character present in Isohypsibius zappalai sp. nov.

Isohypsibius zappalai sp. nov. differs from I. fuscus in having buccal tube longer than the pharyngeal bulb, first macroplacoid only about half again the length of the second, not three times the length of the second. According to Ramazzotti & Maucci (1983) I. fuscus claw accessory points are present but the original description (Mihelčič, 1971) recorded, “accessory points were not observed”. In Isohypsibius zappalai sp. nov. these structures are present.

The new species differs from I. sculptus in having proper cuticular tubercles and not pillars as reported by Dastych (1997) for the latter species; eye spots present, longer claws.

Isohypsibius zappalai sp. nov. differs from I. rusticus sp. nov. in having a different cuticular ornamentation (it is more dense and regular with all tubercles of almost the same size); the stylet supports are inserted on the buccal tube in a more cephalic position (pt = 71.0 in I. zappalai sp. nov. 76.0 in I. rusticus sp. nov.); apparently, lower pt value relative to the first macroplacoid ( Table 1) and lower pt value relative to the entire macroplacoid row ( Table 1); the claws are shaped differently with clearly wider proximal portion of the branches ( Figs. 5D, E and 2A–C ).

Etymology. The specific name is in honour to Mr. Angelo Zappalà who collected the sample from which the new species was found.

Figures

FIGURE 5. A – E, Isohypsibius zappalai sp. nov. (holotype, slide No. 5551). A B, C, Cuticular ornamentation (A, the anterior portion of the body, B, the posterior portion), and C, shows the tubercles form transverse lines (arrows )). D, Bucco-pharyngeal apparatus and claws of the first pair of legs. E, Claws of the fourth pair of legs (arrow a indicates an accessory point, b indicates a lunule). Scale bar = 10 µm.

FIGURE 3. A – C, Isohypsibius gilvus (paratype, slide No. 3571). A, cuticular ornamentation, B, Bucco-pharyngeal apparatus. C, Claws of the second and third pair of legs. D, E, Isohypsibius verae (holotype, slide No. 3679). D, Bucco-pharyngeal apparatus. E, Claws of the first and second pair of legs. Scale bar = 10 µm.

FIGURE 4. A, Isohypsibius barbarae (paratype slide No. 3678). A, Cuticular undulations are visible. B, Bucco-pharyngeal apparatus (paratype, slide 4820). C, Claws of the second pair of legs (holotype, slide 4820). D, Claws of the fourth pair of legs (holotype, slide 4820). The accessory points (arrow) and the lunules are visible. Scale bar = 10 µm.

FIGURE 2. A – D Isohypsibius rusticus sp. nov. (holotype, slide No. 5540). A, Claws of the first pair of legs. B, Claws of the second pair of legs. C, D, Claws of the fourth pair of legs (one lunule is visible: arrow). Scale bar = 10 µm.