Echiniscus bigranulatus Richters, 1908

Michalczyk, Łukasz & Kaczmarek, Łukasz, 2006, Revision of the Echiniscus bigranulatus group with a description of a new species Echiniscus madonnae (Tardigrada: Heterotardigrada: Echiniscidae) from South America, Zootaxa 1154, pp. 1-26 : 2-8

Echiniscus bigranulatus Richters, 1908 ( Figs. 1–20 , 72 )

Material examined

Neotype – 1 adult female from Tierra del Fuego, Argentina, South America (from the Binda & Pilato Collection, University of Catania, Italy, slide no. 4414); 14 adults (7 mounted in Hoyer’s medium and 7 prepared for SEM) from Costa Rica, Central America (near the road from Pacayas to Turrialba, 27.5 km before Turrialba; moss from soil); 1 adult from Pichinchia, Ecuador, South America (from the Binda & Pilato Collection, University of Catania, Italy, slide no. 4779); 1 adult from Cistre, Argentina, South America (from the Reinhardt Møbjerg Kristensen Collection, University of Copenhagen, Denmark).

Redescription

Adult female (measurements of the neotype): Body length 202.4 ( Figs. 1–4 ). Body red. Red eyes visible in living specimens only. Internal cirrus 13.8 long, external cirrus 18.1 long; internal/external cirrus ratio = 0.76. Cephalic papilla 7.6 long. Apart from head cirri and cirrus A no other appendices present. Cirrus A 47.5 long, ending in a point. Cirrus A/body ratio = 0.23. Clava 6.7 long.

Dorsal (plate) cuticle with true pores and without granulation ( Figs. 5–12 ). Cuticle appearance in SEM: surface smooth without granules, strongly porous. Pores large (1.0 in diameter) ( Figs. 7–8 ), smaller on the anterior portion of median plate II (0.5 in diameter).

‘Sponge layer’ absent, large pillars present ( Figs. 11–12 , 72 ). Undeveloped pillars in shape of blunt projections visible under pores. Cuticle visible in PCM: pores visible as bright fields, cuticular pillars appear as dark dots. Pores on the same focus level as pillars ( Figs. 5–6 ). Both pores and cuticular pillars very well focusable. Ventral cuticle with very fine, dense and regular granulation.

All plates well developed with the same sculpture, but anterior part of median plate II with smaller pores (ca. 0.5 in diameter) ( Figs. 13–14 ). Head and scapular plates not faceted. In LM lateral portions of scapular plate seem to be detached from the dorsal plate and form small shoulder plates (one on each side of the body) divided from the scapular plate by a thin bright stripe. This false division is caused by a bend of plate where cuticle is thinner; in SEM this division is not visible. Third median plate present and well developed ( Figs. 15–16 ). Terminal plate faceted. Notches 19.0 long.

Spine on legs I in shape of narrow triangle, 2.9 long. Papilla on legs IV finger­like, 4.8 long ( Figs. 17–19 ). Dentate collar with fine granulation in LM (small, shallow depressions in SEM), and with 12 sharp, triangular teeth ( Figs. 17–19 ).

Claws of legs IV 11.0 long. External claws of all legs without spurs, internal claws of all legs with spur, directed downwards, growing out of claw at ca. 35o ( Figs. 18–20 ). Spur on claws of legs IV relatively large (2.7 long; spur/claw ratio = 0.25). Claws of legs I–III slightly shorter.

Remarks

Results of simple statistical analysis of measurements of selected morphological structures for 7 specimens from Costa Rica are given in Table 1 . No males, juveniles, larvae and eggs were found.

All of the specimens found across South and Central America are very similar, therefore we have assumed that the intraspecific variability in E. bigranulatus is low.

According to the original description claws are devoid of the spurs, while all specimens that we have examined had spurs on internal claws of all legs. We think that spurs could have been overlooked, due to a relatively low angle in which they grow out of the claw. Sometimes, when claws are very closely arranged to each other, spurs are difficult to identify.

Geographic distribution

Known from South and Central America. Records of this species in Africa need to be reconfirmed, however it seems to be very likely that the South African specimens belong to a different species.

Type depositories

Neotype and 3 specimens from Costa Rica are preserved at the Natural Sciences Collection, Faculty of Biology, A. Mickiewicz University, Umultowska 89, 61–614 Poznań, Poland; 3 specimens from Costa Rica are preserved in the collection of Ł. Michalczyk.

Etymology

The name ‘ bigranulatus ’ was given by Ferdinand Richters as he probably thought that dorsal plates are covered with ‘double granulation’.

Differential diagnosis

For comparisons with other species of the bigranulatus group see Tables 7–8.

Figures

FIGURES 1 – 4. Echiniscus bigranulatus — habitus (2 — neotype, the rest of the specimens is from Costa Rica); 1, dorso­lateral view (DIC), 2, dorso lateral view (PCM, neotype), 3, lateral view (SEM), 4, dorsal view (SEM).

FIGURES 5 – 8. Echiniscus bigranulatus — dorsal plate cuticle; 5, DIC, 6, PCM, 7 – 8, SEM; 5 and 6 show the same fragment of cuticle.

FIGURES 9 – 12. Echiniscus bigranulatus — cuticle; 9, anterior plates (SEM), 10, posterior plates (SEM), 11 – 12, structure of dorsal plate cuticle (SEM) (see also Fig. 72).

FIGURES 13 – 16. Echiniscus bigranulatus. 13 – 14, second median plate (PCM and SEM, respectively), 15 – 16, third median plate (PCM and SEM, respectively). Not scaled.

FIGURES 17 – 20. Echiniscus bigranulatus. 17, papilla and dentate collar on the IV pair of legs (PCM), 18, dentate collar and claws of the IV pair of legs (PCM), 19, papilla, dentate collar and claws on the IV pair of legs (SEM), 20, claws on the III pair of legs (SEM).

FIGURES 72 – 74. Structure of dorsal plate cuticle in three species of the bigranulatus group (semischematic section based on SEM observations); 72, E. bigranulatus (see also Figs. 11 – 12), 73, E. ollantaytamboensis (see also Figs. 53 – 54), 74, E. madonnae sp. nov. (see also Figs. 31 – 32); abbreviations: bc — body cavity, cs — cuticle surface, pi — pillar, po — pore, pp — pseudopore, sl — ‘ sponge’ layer, up — undeveloped pillar. Not scaled.

Tables

TABLE 1. Lengths [in µm] and length ratios of selected morphological structures of adults of Echiniscus bigranulatus Richters, 1908 from Costa Rica mounted in Hoyer’s medium (MIN and MAX refer to the smallest and the largest structure found among all measured specimens; SD — Standard Deviation, N — number of specimens / structures measured).

Neotype locality
South America, Argentina; Tierra	del Fuego,	Isla	Nueva;	moss	from	soil;	15	January
1990; leg. Francesco Lombardo.