Minibiotus weglarskae, Michalczyk & Kaczmarek & Claxton, 2005

Michalczyk, Łukasz, Kaczmarek, Łukasz & Claxton, Sandra K., 2005, Minibiotus weglarskae, a new species of Tardigrada (Eutardigrada: Macrobiotidae) from Mongolia, Zootaxa 1008 (1), pp. 47-56 : 48-55

Minibiotus weglarskae sp. nov. ( Figs. 1–18 )

TYPE MATERIAL: The holotype (adult) and 10 paratypes are preserved at the Zoological Museum of Jagiellonian University (ul. Ingardena 6, 30­060 Kraków , Poland); 10 paratypes are preserved in the collection of L. Michalczyk ( Jagiellonian University ); 11 paratypes are preserved at the Department of Animal Taxonomy and Ecology, A. Mickiewicz University, Poznañ, Poland ; 8 paratypes and two eggs are preserved in the collection of Sandra K. Claxton (Macquarie University, Australia) .

Description. Adult (Holotype): Body length 242.3 ( Figs 1–7 ). Body white or transparent. Posterior eyes present. Cuticle with pores arranged in ten transverse bands ( Figs 1– 2 ). Pores small round and oval (1.0– 1.5 in diameter) on ventral surface becoming larger (1.5–2.0 in diameter) and more irregular in shape (bilobed, trilobed and sometimes starshaped) over dorsal and lateral surfaces and on outside of each leg. Ten larger (2.4–3.8 long and 1.4–2.9 wide) irregularly shaped pore­like areas enclosing fine granulation on dorsal cuticle only ( Figs 1 , 3 ); these are probably external evidence of muscle attachments (cribriform areas). Cribriform areas arranged in two longitudinal rows along main axis of body: first pair on head, second to fourth pairs of large pores at level of first three pairs of legs and fifth pair between third and fourth pair of legs. Ring of round or oval pores around mouth below sensory fields absent. Three to five large triangular or irregularly shaped pores present on dorsal cuticle of hind legs ( Figs. 9–11 ).

Mouth antero­ventral. Buccal tube 21.9 long and 1.0 [4.3] wide, with two bends (anterior and posterior) ( Figs. 12 , 14–15 ). Buccal tube walls 0.5 m thick at the level of the stylet support insertion point and slightly thicker below that point (not evident in smaller specimens). Stylet supports inserted on buccal tube at 12.4 [56.5]. Ventral support very short. Pharyngeal apophysis triangular, very near first macroplacoid and about same size as it. First macroplacoid largest, pear­shaped, (1.9 [8.7] long), second smallest, round (1.4 [6.5] long) and third round (1.9 [8.7] long). Macroplacoid row 5.7 [26.1] long. Placoid row 6.7 [30.4] long. Small round microplacoid 0.5 [2.2] long, very close to third macroplacoid. Pharyngeal bulb slightly oval ( Fig. 12 ).

Claws short and robust, accessory points rising high above primary branch ( Figs. 13 , 16 ). Fine granulation near claws on all legs. Granulation arranged in small patches above claws on outside of first three pairs of legs, not clearly visible even with highest magnifi­ cation. Granulation well developed on fourth pair of legs. Primary branch (pb) with basal claw of first pair of legs 5.7 [26.1] long, secondary branch (sb) 3.8 [17.4] long; of second pair, pb. 5.7 [26.1], sb. 4.8 [21.7]; of third pair, pb. 5.7 [26.1], sb. 4.8 [21.7]; of fourth pair, pb. 6.7 [30.4], sb. 4.8 [21.7]. Bars and other cuticular thickenings on legs absent. All claws with smooth­edged lunules, better developed on fourth pair of legs.

Egg: See ‘Remarks’.

Remarks. Eyes were lacking in only two (8%) of specimens examined.

The results of simple statistical analysis of measurements and pt values for 23 randomly chosen specimens are given in Table 1.

Two unembryonated eggs were found with these specimens ( Figs. 17–18 ) and it is very likely that they belong to the new taxon as no other tardigrade species were found in the sample. The processes of these eggs bear a strong resemblance to those of Minibiotus floriparus Claxton. The diameter with processes is 50.0, without processes 40.0. There are ca 24 processes around the circumference and ca. 50 in a hemisphere. Processes are shaped like the head of a screw and each process is covered by a separate membrane. The height of processes is 5.0–5.5, base diameter 1.6–2.0, diameter of the distal disk 5.0–5.5 and processes are 3.0 apart. The distal disk appears to be made up of a number of small compartments like the disk of M. floriparus .

The presence and disposition of pores have been used extensively as taxonomic characters to differentiate species in some genera of eutardigrade, e.g., Macrobiotus and Minibiotus . The presence of cribriform areas in the cuticle of species in the families Macrobiotidae and Milnesiidae has previously been reported (e.g., Schuster et al. 1975) but is rarely acknowledged in descriptions of species and never used as a taxonomic character. Large and very well visible cribriform areas, as found in M. weglarskae sp. nov., have not been recorded for any other Minibiotus species. The significance of such an appearance is unclear at this point.

Etymology. The species is named for Professor Barbara Węglarska of the Jagiellonian University, Kraków, Poland in appreciation of her contribution to tardigrade science.

Type locality. Northern Mongolia; Archangaj Ajmag; Tehijn Cagan Nuur National Park ; 2700 m asl; 19.07.2000; lichen sample from rock; leg. Ł. Kaczmarek.

Differential diagnosis. Minibiotus weglarskae sp. nov. is similar to Minibiotus bisoctus (Horning, Schuster & Grigarick) in having ten transverse bands of pores of irregular shape although the bands in the former are not as clearly defined as in the latter. It differs from that species by having a narrower buccal tube, a shorter macroplacoid row length both absolutely and relative to the buccal tube length (23% in the new species, 31% in M. bisoctus ). M. weglarskae sp. nov. also has much shorter claws than M. bisoctus ( Table 1). The microplacoids of the two species are different, being round and solid in the new species but lens­shaped and not solid in M. bisoctus . Although only a single specimen of the latter species was examined in this comparison ( Table 1), the differences appear to be sufficiently great as to warrant a new species for the specimens from Mongolia.

The eggs found with adult specimens are very similar to those of M. floriparus , however the adults of M. floriparus differ from those of M. weglarskae sp. nov. by lacking pores in the cuticle.

Figures

FIGURES 1–2. Minibiotus weglarskae sp. nov. — habitus; 1—dorsal view, 2 — ventral view (paratypes).

FIGURES 3–4. Minibiotus weglarskae sp. nov. — habitus, dorsal cuticle; 3 — small pores have been removed to give the clearer pattern of the cribriform areas and larger triangular pores on the hind legs; 4 — cribriform areas and larger triangular pores on the hind legs have been removed to give the clearer pattern of the small pores (paratype).

FIGURES 5–6. Minibiotus weglarskae sp. nov. — habitus; 5 — dorso­lateral view, 6 — ventrolateral view (paratypes) (DIC).

FIGURES 7. Minibiotus weglarskae sp. nov. 7 — habitus (middle section) (paratype) (DIC).

FIGURES 8–11. Minibiotus weglarskae sp. nov. 8 — one of five pairs of cribriform areas on the dorsal cuticle (PCM); 9–11 — larger, triangular pores on the dorsal side of the hind legs (paratypes) (DIC).

FIGURES 12–13. Minibiotus weglarskae sp. nov. 12 — buccal apparatus (note the thickened wall of the buccal tube below the stylet support insertion points); 13 — claws of IV pair of legs (paratype).

FIGURES 14–16. Minibiotus weglarskae sp. nov. 14 — furcae (PCM); 15 — buccal apparatus (lateral view), note the two bends of the buccal tube; 16 — hind legs (ventral view) (paratype) (DIC).

FIGURES 17–18. Eggs found in the sample with specimens of Minibiotus weglarskae sp. nov. (PCM)