Xerobiotus euxinus, Pilato, Giovanni, Kiosya, Yevgen, Lisi, Oscar, Inshina, Valentina & Biserov, Vladimir, 2011

Pilato, Giovanni, Kiosya, Yevgen, Lisi, Oscar, Inshina, Valentina & Biserov, Vladimir, 2011, Annotated list of Tardigrada records from Ukraine with the description of three new species, Zootaxa 3123, pp. 1-31 : 9-12

Xerobiotus euxinus sp. nov.

( Fig. 5 )

Materal examined. Kherson Oblast, Chernomorsky biosphere reserve, pine forest, vicinity of “Volyzhin forest” (approx. 46°30ʹ N, 31°48ʹ E), collectors M. O. Kravchenko, D.A. Shabanov, moss on soil, May 2008; Holotype, eight paratypes and an additional 23 specimens and nine eggs.

Type repository. Holotype (slide No. 5431) and eight paratypes (slide No. 5431) are deposited in the collection of Binda & Pilato (Museum of the Department of Animal Biology “Marcello La Greca”, University of Catania, Italy). Other specimens are deposited in the Kiosya's collection (School of Biology, V.N. Karazin Kharkiv National University, Ukraine).

Specific diagnosis. Eye spots present; cuticle smooth without pores; dorsal transverse ridges of the buccal armature probably joined to one another forming a continuous arc; pharyngeal bulb with two macroplacoids and microplacoid. Claws of the Xerobiotus - type ( Bertolani & Biserov, 1996); lunules absent on the first three pairs of legs; present on the hind legs; no cuticular bar present on the legs.

Description of the holotype. Body length 443 µm; colorless, cuticle smooth; without pores or dots. Eye spots present. Bucco-pharyngeal apparatus of Macrobiotus type ( Fig. 5A ). Mouth terminal with ten small peribuccal lamellae; buccal cavity small with a posterior ring of small teeth and a system of dorsal and ventral transverse ridges; the dorsal ridges seemed to be joined to one another forming a continuous arc (but this character needs to be confirmed). Rigid buccal tube 40.3 µm long and 4.8 µm wide externally (pt = 11.9). Ventral lamina about 23.5 µm long (pt = 58.3); stylet supports inserted on the buccal tube at 77.4 % of its length (pt = 77.4). Pharyngeal bulb with apophyses, two macroplacoids and microplacoid.

First macroplacoid 10.0 µm long (pt = 24.8), second 6.9 µm (pt = 17.1), microplacoid 3.6 µm long (pt = 8.9); entire placoid row length 21.8 µm (pt = 54.1); macroplacoid row length 18.2 µm (pt = 45.2).

Claws of the Xerobiotus - type ( Fig. 5B ), i. e. with a small, thin basal portion, not subdivided by septum into distinct basal stem and distal portion, and secondary branch rigidly joined to the primary branch. External and internal claws of second pair of legs 9.7 µm (pt = 24.1) and 9.0 µm long (pt = 22.3) respectively; posterior claws of the hind legs 9.9 µm long (pt = 24.6); the orientation of the internal claws prevented measurement. Main branches with accessory points. Lunules absent on the first three pairs of legs ( Fig. 5B ), present on the hind legs ( Fig. 5C ). No cuticular bar present on the legs.

Description of the eggs. Three eggs, similar to those of Xerobiotus pseudohufelandi , were found together with the specimens of X. euxinus sp. nov., but none of them had developed embryo and therefore their attribution to the new species needs to be confirmed.

Remarks. The paratypes were similar to the holotype in both qualitative and metric characters. The measurements of some structures of two specimens are reported in Table 3 .

X. euxinus sp. nov. X. euxinus sp. nov. X. pseudohufelandi X. xerophilus No. slide 5431 5431 2504 2785

paratype holotype paratype Etymology. The specific name euxinus refers to 'Pontus euxinus' – the Latin name of the Black Sea which is situated very close to the type locality of this species.

Differential diagnosis. Previously, two species were known to belong to the genus Xerobiotus : X. pseudohufelandi ( Fig. 6A –C) and X. xerophilus ( Fig. 6 D, E). The new species differed from X. pseudohufelandi in having clearly narrower and more slender buccal tube ( Table 3 ; Figs. 5A and 6A ); stylet supports inserted on the buccal tube in a slightly more cephalic position ( Table 3 ); and, very probably, in having the dorsal transverse ridges in the buccal armature joined to form a continuous arc. The new species differed from X. xerophilus in having longer placoids ( Table 3 ), and clearly longer claws ( Table 3 ; Figs. 5B, C and 6 E).

Figures

FIGURE 5. A – C, Xerobiotus euxinus sp. nov.: A, Bucco-pharyngeal apparatus of a parataype (slide N. 5431). B, Claws of the second pair of legs holotype (slide No. 5431). C, Claws of the hind legs; arrow indicates one visible lunula (paratype on slide No. 5431). (Scale bars = 10 µm).

FIGURE 6. A, B, C, Xerobiotus pseudohufelandi (slide No. 2504): A, Bucco-pharyngeal apparatus. B, Claws of the second pair of legs; C, claws of the third pair of legs. D, E, Xerobiotus xerophilus (paratype, slide No. 2785): D, Bucco-pharyngel apparatus. E, Claws of the first and second pairs of legs. (Scale bars = 10 µm).

Tables

TABLE 3. Measurements of some structures of the holotype and a paratype of Xerobiotus euxinus sp. nov., an Italian specimen of X. pseudohufelandi and a paratype of X. xerophilus.

Body length 418	443	400	380
Buccal tube 38.3	40.3	39.7	39.0
Buccal tube width 4.5	4.8	6.2	4.6
pt 11.8	11.9	15.6	11.8
Stylet supports insertion point pt 77.8	77.4	79.8	79.3
Placoid row 20.1	21.8	22.3	18.2
pt 52.5	54.1	56.2	46.7
Macroplacoid row 16.8	18.2	18.3	14.7
pt 43.9	45.2	46.1	37.7
First macroplacoid 9.8	10.0	10.9	8.4
pt 25.6	24.8	27.5	21.5
Second macroplacoid 6.3	6.9	7.3	5.3
pt 16.5	17.1	18.4	13.6
Microplacoid 3.4	3.6	3.3	3.1
pt 8.9	8.9	8.3	7.9
External claws II 9.8	9.7	10.3	?
pt 25.6	24,1	25.9	?
Internal claws II 9.4	9.0	?	5.2
pt 24.5	22.3	?	13.3
External claws III?	?	10.4	5.4
pt?	?	26.2	13.8
Internal claws III 9.7	?	9.7	?
pt 25.3	?	24.4	?
Posterior claws IV 9.8	9.9	10.2	?
pt 25.6	24.6	25.7	?
Anterior claws IV?	?	10.1	4.2
pt?	?	25.4	10.8