Bindius triquetrus, Pilato, Giovanni, 2009

Pilato, Giovanni, 2009, Bindius triquetrus gen. nov. sp. nov. (Eutardigrada, Hypsibiidae) from Sicily (Italy), Zootaxa 2058, pp. 62-68 : 63-67

Bindius triquetrus gen. nov., sp. nov.

Fig. 1

Material examined: Sicily, Madonie Mountains: Geraci Siculo, Marcato d’Alfano (1200 m a.s.l.): holotype (slide N. 5240) and two paratypes; Petralia Sottana, Vallone Scopalacqua (1300 m a.s.l.): one paratype. All specimens were extracted from sphagnum samples.

Species diagnosis: Claws of Hypsibius type; bucco-pharyngeal apparatus of Diphascon model and of Bindius type. Buccal tube clearly shorter than the pharyngeal tube (its length is about 33.6% of the total length of the bucco-pharyngeal tube). Small pharyngeal apophyses and three rod-shaped macroplacoids present; a small, very faint microplacoid may be present or not; septulum absent. Claws of Hypsibius type, slender. The posterior claw of the hind legs clearly longer than the corresponding claws of the other pairs of legs. Lunules and other cuticular thickening on the legs absent.

Description of the holotype: Body length 200.0 µm, colorless, eye spots absent; cuticle smooth without pores and granulation on the legs. Bucco-pharyngeal apparatus ( Fig. 1 A, B), is a variant of the Diphascon model (i.e., the bucco-pharyngeal tube is subdivided into an anterior rigid portion (buccal tube) and a posterior flexible portion (pharyngeal tube) with a spiral thickening). Buccal tube without ventral lamina and with large dorsal and ventral apophyses for the insertion of the stylet mucles asymmetrical with respect to the frontal plane. Dorsal apophysis ( Fig. 1 A, B) triangular in shape with rectilinear margin and the posterior apex clearly distant from the buccal tube wall. The ventral apophysis ( Fig. 1 A) is similar to the hook shaped apophyses of Diphascon (but larger and with the apex more distant from the buccal tube wall). Postero-lateral processes of both those apophyses are well developed. Bucco-pharyngeal tube is 55.0 µm long, buccal tube 18.5µm (pbf = 33.6) and 1.7 µm wide externally (pt = 9.2). Stylet supports inserted on the buccal tube at 68.2% of its length (pt = 68.2). Peribuccal lamellae and papulae absent. Teeth in oral cavity absent (or not visible in light microscopy). Pharyngeal bulb ( Fig. 1 A, B) elongate (29.5 µm x 14.5 µm) with small pharyngeal apophyses and three rod-shaped macroplacoids. Microplacoid not visible (very faint microplacoid is visible in two paratypes). Septulum absent. Macroplacoid row 18.9 µm long (pt = 102.2), first macroplacoid 5.2 µm (pt = 28.1), second 5.6 µm (pt = 30.3) and third 8.6 µm long (pt = 46.5).

Claws of Hypsibius type ( Fig. 1 C, D), slender with accessory points on the main branches. Orientation of the holotype allowed the measurement of only the claws of the second and third pairs of legs ( Table 1 ); in a paratype we also measured the claws of the first and the fourth pairs of legs ( Table 1 ). It is evident that the posterior claws of the hind legs are clearly longer than the external claws of the other pairs of legs while the anterior claws are similar in length to the internal claws of the other pairs of legs. Lunules and other cuticular thickening on the legs absent. Eggs unknown.

smallest specimen (holotype) largest specimen Etymology: The name triquetrus refers to the shape of the dorsal apophysis for the insertion of the stylet muscles ( triquetrus = triangular in shape).

Differential diagnosis: For some characters of the bucco-pharyngeal apparatus (absence of a drop-shaped thickening between buccal tube and pharyngeal tube, the small dimensions of the pharyngeal apophyses) Bindius triquetrus sp. nov. is similar to the species of the subgenus Adropion of the genus Diphascon , but the shape of the apophyses for the insertion of the stylet muscles allows it possible to distinguish Bindius triquetrus sp. nov. from all the species belonging to this subgenus; in addition it differs from D. (A.) clavatum Bartoš, 1935 in having smooth cuticle; from D. (A.) greveni , D. (A.) gordonense , D . (A.) maucci Dastych, 1996, D. (A.) onorei , and D. (A.) linzhensis Li, 2007 in lacking septulum; from D. (A.) scoticum in lacking cuticular bars on the legs and in the shape of the claws. The species more similar to the new species are: D. (A.) prorsirostre ; D. (A.) arduifrons Thulin, 1928 ; D. (A.) marcusi ( Rudescu, 1964) ; D. (A.) carolae ; D. (A.) marcuzzii ( Mihelcic, 1971) ; D. (A.) montigenum ; D. (A.) modestum ; D. (A.) behanae Dastych, 1987 , Diphascon (A.) triodon ( Maucci, 1996) and D. (A.) tricuspidatum . Bindius triquetrus sp. nov. differs from each one of those species in other characters. It differs from D. prorsirostre and D. arduifrons in having the buccal tube shorter with respect to the total length of the bucco-pharyngeal tube (pbf = about 34 in Bindius triquetrus sp. nov, about 40 in D. prorsirostre and D. arduifrons ); the pharyngeal tube clearly longer than the pharyngeal bulb; longer placoid row with respect to the pharyngeal bulb length (its length is about 71% of the pharyngeal bulb length in the new species, about 50% in D. prorsirostre , and about 55% in D. (A.)

arduifrons ); more slender claws.

Bindius triquetrus sp. nov. differs from D. marcusi in having pharyngeal tube longer than pharyngeal bulb (in the holotype of Bindius triquetrus sp. nov. the pharyngeal tube is 36.5 µm long and the pharyngeal bulb 29.5 µm long; in D. marcusi the pharyngeal tube is almost as long as the pharyngeal bulb); less elongate pharyngeal bulb (ratio length/width = 2 in Bindius triquetrus sp. nov., 3 in D. marcusi ); pharyngeal apophyses present; small microplacoid very faint or absent.

The new species differs from D. carolae in having slightly longer placoid row with respect to the pharyngeal bulb (its length is about 71% of the pharyngeal bulb length in the new species, about 67% in D. carolae ); and longer claws with slightly longer basal portion and longer secondary branches.

Bindius triquetrus sp. nov. differs from D. marcuzzii in having more elongate pharyngeal bulb (ratio length/width = 2 in Bindius triquetrus sp. nov., 1.6 in D. marcuzzii ); smaller pharyngeal apophyses; less marked difference in length between first and second macroplacoid (in D. marcuzzii the second macroplacoid is twice the length of the first one); small microplacoid faint or absent; main branches of the claws with accessory points.

The new species differs from Diphascon modestum in having slightly wider bucco-pharyngeal tube (1.7–1.9 µm in specimens of Bindius triquetrus sp. nov. about 200 µm long, 1.2–1.3 µm in specimens of D. modestum about 155 µm long); pharyngeal apophyses present, longer claws (anterior and posterior claws of hind legs 7.9 µm and 12.7 µm long, respectively in specimens of Bindius triquetrus sp. nov. about 200 µm long; 4.1 µm and 6.7 µm, respectively, in specimens of D. modestum about 155 µm long).

The new species clearly differs from D. montigenum in having more elongate pharyngeal bulb (ratio length/width = 2 in Bindius triquetrus sp. nov., 1.2 in D. montigenum ); longer placoids (rod-shaped in Bindius triquetrus sp. nov., oval granules in D. montigenum ) and longer claws with longer basal portion (posterior claws of hind legs 12.7 µm long in specimens of Bindius triquetrus sp. nov. about 200 µm long, 9.6 µm in specimens of D. montigenum about 250 µm long).

Bindius triquetrus sp. nov. differs from D. behanae in having smooth cuticle, longer buccal tube with respect to the total length of the bucco-pharyngeal tube (pbf = 33.6 in Bindius triquetrus sp. nov., about 42 in D. behanae , according to the measurements provided by Dastych, 1987); pharyngeal bulb more elongate in shape (ratio length/width = 2 in Bindius triquetrus sp. nov., 1.4–1.5 in D. behanae according to the measurements of Dastych (1987)); second macroplacoid longer than the first one, and small microplacoid very faint or absent.

The new species differs from D. tricuspidatum in having very different pharyngeal bulb in shape (ratio length/width = 2 in Bindius triquetrus sp. nov., 1.4 in D. tricuspidatum ); longer macroplacoids (pt of placoid row 102.2–110.7 in Bindius triquetrus sp. nov. 47.3– 44.9 in D. tricuspidatum ), microplacoid very small and faint or absent, and external claws’ accessory points not divergent.

Bindius triquetrus sp. nov. differs from D. triodon in having shorter buccal tube (pbf = 33.6 in the new species, 48.8 in D. triodon ); stylet supports inserted in a more caudal position (pt = 66.3–68.2 in the new species, about 62 in D. triodon ) and claws different in shape (overall in having longer and more slender common basal portion).

Figures

FIGURE 1. Bindius triquetrus gen. nov. sp. nov. A, bucco-pharyngeal apparatus (holotype); the asymmetry (due to the different shape of the dorsal (arrow) and ventral apophyses for the insertion of the stylet muscles) is evident. B, buccopharyngeal apparatus of he holotype; the dorsal apophysis, the stylet supports (arrow) and the placoids are focused. C, claws of the second pair of legs (holotype). D, claws of the fourth pair of legs (paratype). Scale bars = 10 µm.

Tables

TABLE 1. Length (in µm) of some structures of the smallest and the largest measured specimens of Bindius triquetrus gen. nov. sp. nov.

Body length	200.0	208.0
Bucco-pharyngeal tube	55.0	?
Pharyngeal tube	36.5	?
Buccal tube	18.5	19.7
pbf	33.6	?
Buccal tube external width	1.7	1.9
pt	9.2	9.6
Stylet supports pt	68.2	66.3
Macroplacoid row	18.9	21.8
pt	102.2	110.7
First macroplacoid	5.2	5.5
pt	28.1	27.9
Second macroplacoid	5.6	6.2
pt	30.3	31.4
Third macroplacoid	8.6	9.2
pt	46.5	46.7
Microplacoid	not visible	1.5
pt	?	7.6
External claw I	?	9.2
pt	?	46.7
Internal claw I	?	7.2
pt	?	36.6
External claw II, III	10.1	10.6
pt	54.6	53.8
Internal claw II, III	7.6	7.8
pt	41.1	39.6
Posterior claw IV	?	12.7
pt	?	64.5
Anterior claw IV	?	7.9
pt	?	40.1