Echiniscus lineatus, Pilato, Giovanni, Fontoura, Paulo, Lisi, Oscar & Beasley, Clark, 2008

Pilato, Giovanni, Fontoura, Paulo, Lisi, Oscar & Beasley, Clark, 2008, New description of Echiniscus scabrospinosus Fontoura, 1982, and description of a new species of Echiniscus (Heterotardigrada) from China, Zootaxa 1856, pp. 41-54 : 49-53

Echiniscus lineatus sp. nov

Figs. 6 , 7

Material examined: China, Yunnan Province, Menglun (21° 55’N, 101°14’E) within the Xishuangbanna Tropical Botanic Garden: 1 specimen from bamboo litter, 6 specimens from lichen sample. The holotype (slide N. 5222, and 6 paratypes are deposited in the collection of Binda & Pilato, Museum of the Department of Animal Biology, University of Catania, Italy).

Specific diagnosis: Unpaired plate 3 absent but the corresponding area sculptured; all plates with many small dark polygons and a few light spots many of which forming transverse stripes; lateral portions of scapular plate and paired plates II and III with dark polygons but without light spots; ventral surface without plates and with very fine dots difficult to see; the appendages are: lateral filaments A, spines B, C, D, E and dorsal spines C d and D d; internal claws with a long, sharp spur oriented towards the base.

Description of the holotype: Body length 208 µm; color reddish; eye spots red; neck plate narrow; the lateral margins of the median plate 3 are not visible but the area between the paired plate III and the terminal plate is strongly sculptured as the other plates; terminal plate faceted and with two incisions. Ventral plates absent. All dorsal plates with a double sculpture: many small polygonal dots are present and fewer circular or elliptical light spots, often fused to one another, forming some transverse stripes ( Fig. 6 A–C). The small polygons are present also where the light areas are present ( Fig. 6 D). The largest polygonal dots (diameter up to 1.1 µm) are present on the posterior portion of the scapular plate and on the central portion of the terminal plate. Two transverse smooth bands are present on the paired plates II and III ( Fig. 6 A, B), and one on the median plate 2 and on the area corresponding to the plate 3. The lateral portions of scapular plate and paired plates II and III have only small dark polygons and lack light spots ( Fig. 6 A). The cuticle between the plates and the ventral surface has very fine dots difficult to see. On the legs only very fine dots, smaller than the polygons, are present; light spots are absent.

Internal cephalic cirri 15.2 µm long; external ones 17.6 µm; cephalic papilla 7.1 µm long; clava 6.8 µm long. In addition to the lateral appendage A (33.9 µm long), also lateral spines B, C, D, and E are present, and dorsal spines C d and D d (Fig. 7A, B). Spine B, 13.1 µm long; C, 23.7 µm; D, 25.4 µm; E (with a slight asymmetry), 26.4 µm on a side and 27.6 on the other; spines C d 6.2 µm long and spines D d, wider than the other appendages, dagger-shaped, 22.5 µm long (Fig. 7B). A spine, 3.5 µm long, is present on the first pair of legs (Fig. 7C); hind legs with a papilla 4.2 µm long and a dentate fringe (Fig. 7D) with many triangular, regular teeth (10 on one leg, 15 on the other).

External claws on second and third pairs of legs 10.1 µm and 10.9 µm long respectively; external and internal claws on the fourth pair of legs 11.2 µm and 12.2 µm long respectively. A long, sharp spur oriented towards the base is present on the internal claws (Fig. 7E, F). The spurs of the legs IV are more developed than those of the legs I–III but similar in shape and orientation.

The paratypes are similar to the holotype in both qualitative and metric characters, but as shown in Table 4 , a degree of variability may be noted in the length of the lateral and dorsal appendages with a low degree of asymmetries. The spine B (from 3.6 to 13.1µm long), and the spines D d (from 14.7 to 22.5 µm) are the most variable appendages.

smallest paratype second paratype holotype Remarks: Many species of Echiniscus have the same pattern of lateral and dorsal appendages as E. lineatus sp. nov., but this species differs from them in the characters indicated below.

It differs from E. scabrospinosus in some characters of the plate ornamentation (well evident polygonal dots are present in addition to the light spots; lower number of light spots forming transverse stripes; dark ring into the centre of light spots absent; smooth bands on terminal plate absent); in lacking intersegmental lateral plates; in having also the lateral appendage B and the dorsal appendage C d; in having (A excluded) slightly longer lateral appendages; dentate fringe with thinner teeth.

The new species differs from Echiniscus pooensis Rodriguez-Roda, 1948 , in having a different color, different plate ornamentation and more developed spur on the internal claws; it differs from Echiniscus divergens Marcus, 1936 , in the plate ornamentation and in having spines D d that are not very divergent.

Echiniscus lineatus sp. nov. differs from E. spinulosus and E. spiniger in having the terminal plate more clearly faceted; in having a different plate ornamentation (in the new species many small dark polygons are present and few light spots forming some transverse lines ( Fig. 6 A–C), while E. spinulosus and E. spiniger (Figs. 3A, B and 4A–C) have much smaller dark dots and more dense and irregularly distributed light spots); in addition in E. lineatus sp. nov. the small polygons are present also where the light spots are present ( Fig. 6 D) while in E. spinulosus the light spots have a central dark ring; in lacking light spots on the neck plate and on the lateral portions of the scapular plate and of the paired plates II and III ( Fig. 6 A) while in E. spinulosus (Fig. 3A) and E. spiniger (Fig. 4A) they are present and very visible. On the legs of E. lineatus sp. nov. only very fine dots are present while in E spinulosus and E. spiniger (Fig. 4C) also light spots are very evident.

Echiniscus lineatus sp. nov. also differs from E. spinulosus and E. spiniger in having dorsal spine D d wider than the other appendages (Fig. 7B) while in E. spinulosus (Fig. 3B) and in E. spiniger (Fig. 4B) they are similar to the other appendages (from E. spinulosus also in having longer lateral appendages); in E. lineatus sp. nov. internal claws have thinner spurs oriented toward the base (Fig. 7E, F) while in E. spinulosus (Fig. 3C, D) and E. spiniger (Fig. 4D, E) the spurs form almost a right angle with the claw; in addition in E. lineatus sp. nov. the spurs on the legs I–III are slightly smaller than those of the hind legs (Fig. 7E, F) while in E. spinulosus (Fig. 3C, D) and E. spiniger (Fig. 4D, E) the difference in size is more marked.

The new species ( Figs. 6 , 7) differs from E. clevelandi ( Fig. 8 ) in having a different cuticular ornamentation (dark polygons slightly smaller and more numerous; light spots less numerous, more spaced, and forming FIGURE 7. Echiniscus lineatus sp. nov. A, anterior portion of the body of a paratype; the cephalic cirri, lateral cirrus A, clava, lateral cirri B and C are visible; B, posterior portion of the body of the holotype; it is evident that the dorsal cirrus D d is wider than the other appendages; C, anterior portion of the body of the holotype; the arrow indicates the spine on the first pair of legs; D, dentate fringe and papilla on the fourth pair of legs of the holotype; E, claws of the first pair of legs of a paratype; F, one internal claw of the fourth pair of legs of a paratype. (Scale bar = 10 µm).

stripes); dots on the legs smaller and denser; in addition, the spines D d are clearly wider than the other appendages; internal claws with better developed spur; dentate fringe with more numerous teeth (10–15 in E. lineatus sp. nov., 7–11 in E. clevelandi ).

Echiniscus lineatus sp. nov. differs from E. tropicalis in having a different plate ornamentation (the new species has a double ornamentation with small dark polygons and light spots forming stripes, while in E. tropicalis dark polygons are lacking and more numerous irregularly distributed light spots are present; dark ring in the center of each light spot is more evident); lateral portion of scapular plate and of paired plates and legs without light spots; longer lateral and dorsal appendages; spines D d larger than the other appendages.

The new species differs from E. marcusi in having a different plate ornamentation; longer lateral and dorsal appendages; appendages D d larger than the other appendages; spine on legs I smaller.

Figures

FIGURE 6. Echiniscus lineatus sp. nov. A, B, cuticular ornamentation of some plates of the holotype; many light spots form transverse stripes; In A the arrows indicate the lateral portions of the paired plates where light spots are absent; in B the arrows indicate the smooth bands of some plates; C, scapular plate of a paratype; small dark polygons, light spots forming transverse stripes are shown; D, detail of the cuticular ornamentation; arrows indicate small dark polygons present also in correspondence of light spots. Scale bar = 10 µm.

FIGURE 8. Echinicus clevelandi. A, habitus; B, detail of the cuticular ornamentation; the arrow indicates small dark polygons present also in correspondence of the light spots. (Scale bar = 10 µm).

Tables

TABLE 4. Measurements (in µm) of some structures of three specimens (two paratypes and the holotype) of Echiniscus lineatus sp. nov. (% bo = percentage of body length; % sc = percentage of scapular plate length; when appendage asymmetry occurred the two measures are reported).

Character Body length	µm 180	%bo	%sc	µm 193	%bo	%sc	µm 208	%bo	%sc
Scapular plate length Int. ceph. cirrus	37.9 16.6	21.1 9.2	43.8	42.2 16.0	21.9 8.3	37.9	44.5 15.2	21.4 7.3	34.2
Ext. ceph.cirrus Ceph. Papilla Clava	17.0 6.1 5.8	9.4 3.4 3.2	44.8 16.1 15.3	16.8 6.4 6.2	8.7 3.3 3.2	39.8 15.1 14.7	17.6 7.1 6.8	8.5 3.4 3.3	39.6 16.0 15.3
Appendage A Appendage B Appendage C	32.7 3.6 19.6–20.0	18.2 2.0 10.9–11.11	86.3 9.5 51.7–52.8	33.4 7.9–10 21.8–23.4	17.3 4.1–5.2 11.3–12.1	79.2 18.7–23.7 51.7–55.4	33.9 13.1 23.7	16.3 6.3 11.4	76.2 29.4 53.3
Appendage D Appendage E	21.2 23.6	11.8 13.1	55.9 62.3	22.3–22.9 22.4–24.5	11.6–11.9 11.6–12.7	52.8–54.3 53.1–58.1	25.4 26.4–27.6	12.2 12.3–13.3	57.1 59.3–62.0
Appendage C d Appendage D d Spine on legs I Int. claws II/III Ext. claws II/III	4.5 14.7 3.6 9.3 8.6	2.5 8.2 2.0 5.2 4.8	11.9 38.8 9.5 24.5 22.7	4.4 18.6 3.6 9.6 9.4	2.3 9.6 1.9 5.0 4.9	10.4 44.1 8.5 22.8 22.3	6.2 22.5 3.5 10.9 10.1	3.0 10.8 1.7 5.2 4.9	13.9 50.6 7.9 24.5 22.7
Int. claws IV Ext. claws IV Papilla on legs IV	11.4 10.9?	6.3 6.1?	30.1 28.8?	11.9 11.8 3.7	6.2 6.1 1.9	28.2 28.0 8.8	12.2 11.2 4.2	5.9 5.4 2.0	27.4 25.2 9.4