Echiniscus scabrospinosus Fontoura, 1982

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 : 42-48

Echiniscus scabrospinosus Fontoura, 1982

Figs. 1 , 2

Material examined: Portugal 46 specimens: one from Serra do Buçaco (Holotype), and 45 from Amarante; Tanzania: one specimen; Azores (Faial Island: Miradouro da Praia Norte): one specimen. Specimens collected from mosses and lichens. We do not consider here the specimens from China previously attributed to E. scabrospinosus by Beasley and Cleveland (1996) due to the fact that they do not belong to this species; neither the specimens recently reported by Yang (2008).

Type repository: The holotype, the African specimen, the specimen from the Azores and 3 other specimens from Portugal are deposited in the collection of Binda and Pilato (Museum of the Department of Animal Biology “Marcello La Greca”, University of Catania); the remaining 42 specimens from Portugal are deposited in the collection of P. Fontoura at the Department of Zoology and Anthropology, Faculty of Sciences, University of Porto.

New description: The new description is based essentially on the holotype, but some details are more visible in the other specimens.

Body length 218 µm long. Color reddish; eye spots red (visible in living specimens only). Median plate 3 absent but the corresponding area is sculptured. Cephalic plate with both anterior and posterior margin notched ( Fig. 1C ); neck plate narrow ( Fig. 1C ); scapular plate, 42.8 µm long, with a wide central portion and two small lateral portions with different ornamentation ( Figs. 1A, B and 2B ); two small thickened areas (intersegmental lateral plates) are present laterally to the median plate 1, to the median plate 2 and between the paired plate III and the terminal plate ( Fig. 1C ); terminal plate not faceted and with two posterolateral incisions. Median plates 1 and 2 divided into an anterior portion with only the anterior margin sculptured and a sculptured posterior portion ( Fig. 1A, C ). Paired plates II and III with a wide medial portion and a small lateral part with different ornamentation ( Figs. 1B and 2B ); the medial portion has an anterior part with two alternate sculptured and two smooth transversal bands and a larger sculptured posterior portion ( Fig. 1A–C ).

Neck plate, intersegmental lateral plates, lateral portions of scapular plate and of paired plates II and III with many very small dots and, at the same optical focus, few small, not well visible, light spots; other plates, or portions of plates, without small dots but with only large circular or elliptical light spots ( Figs. 1 and 2B ); each light spot with a central dark ring from which some dark stripes irradiate ( Fig. 1D ).

Largest light spots, with a diameter of 2.1 µm, on the scapular, median plates and on the posterior portion of the paired plates II and III. The terminal plate has light spots slightly smaller than those of the scapular plate, of the paired plates and of the median plates 1 and 2 ( Fig. 1A, B ). In some specimens, the terminal plate has three longitudinal and three clearly visible transversal smooth bands appearing as dark stripes ( Fig. 1A ) but in some specimens these bands, or some of them, are poorly visible ( Fig. 1B ). Cuticle of legs with very fine dots and without light spots. Ventral surface with very fine dots.

External and internal cephalic cirri 14.9 µm and 12.5 µm long respectively; cephalic papilla 6.5 µm long; clava 4.4 µm long ( Fig. 2A ); in addition to the lateral appendage A, lateral spines C, D and E and dorsal spines D d are present ( Fig. 1A ). The spines D d are more robust than the others, dagger–shaped with a round tip, and have margins not perfectly smooth. Filament A 33.2 µm long, spine C 11.0 µm, spine D 11.2 µm, spine E 15.6 µm, spine D d 21.8 µm. External and internal claws of the second pair of legs 10.1 µm and 10.9 µm long respectively; on the hind legs they are 12.0 µm and 13.2 µm long respectively. A small spine, 1.8 µm long, is present on the legs I ( Fig. 2A, B ); leg IV with a dentate fringe with 9 or 10 sharp triangular teeth of different sizes ( Fig. 1A ) and a papilla 4 µm long.

External claws smooth; internal claws with a long and thin spur oriented towards the claw base ( Fig. 2D ) (spur 3.3 µm long, inserted at 3.6 µm from the claw base in the largest specimen, 240 µm long).

The other specimens are similar to the holotype in both qualitative and metric characters ( Table 1 ); but the density of light spots (12–15 light spots / 100 µm 2 in some specimens, up to19–21 (or more, 26 was the maximum observed) light spots / 100 µm 2 in others) ( Table 2 ) and the appendages show a high degree of variability with asymmetries and very different lengths, and some of them (frequently D, very rarely D d) may be absent ( Table 3 ). The appendages also show a degree of variability in their shape, in fact some of them may have two or three tips. The number of teeth of the dentate fringe is comprised between 8 and 12.

Holotype smallest specimen largest specimen Papilla on legs IV 4.0 1.8 9.3 2.5 1.5 6.6 4.3 1.8 10.1 Differential diagnosis: Considering the species of Echiniscus having a similar plate ornamentation and the same lateral and dorsal appendages present in E. scabrospinosus (also their individual variability considered), we think it opportune to compare to it: Echiniscus crassispinosus Murray, 1907 ; Echiniscus canedoi Da Cunha & Do Nascimiento Ribeiro, 1962; Echiniscus manuelae Da Cunha & Do Nascimiento Ribeiro, 1962, Echiniscus angolensis Da Cunha & Do Nascimiento Ribeiro, 1964; E. spinulosus , E. spiniger and, overall, E. marginatus .

Echiniscus scabrospinosus differs from E. crassispinosus in details of the plate ornamentation and in having, according to the literature ( Marcus, 1936; Ramazzotti and Maucci, 1983) internal claws with longer and straight spurs.

FIGURE 3. Echiniscus spinulosus . A, anterior portion of the body; the narrow neck plate and the scapular plate are shown; the arrow indicates the lateral portion of scapular plate with light spots; B, the dorsal appendages C d and D d are shown; arrow indicates light spots present on the legs; C, claws of the first pair of legs; D, claws of the fourth pair of legs. Scale bar = 10 µm.

It is also similar to E. canedoi but it differs from this species in lacking spine E. Unfortunately the description of E. canedoi is not detailed as to the plates’ ornamentation and it is not specified whether a spine on the first pair of legs, a papilla on the hind leg and spurs on the claws are present or absent.

E. scabrospinosus differs from E. manuelae in lacking C d, in having filament A slightly longer and spine E smooth; unfortunately the description of E. manuelae is not detailed as to the plates ornamentation, and it is not specified whether spurs are present or not on the claws.

FIGURE 4. Echiniscus spiniger . A, anterior portion of the body; the narrow neck plate and the scapular plate are shown; the arrow indicates the lateral portion of scapular plate with light spots; B, the dorsal appendages C d and D d are shown; C; terminal plate; its light spots are not smaller than those of the other plates (photos A, B and C from the same specimen); D, claws of the first pair of legs; E, claws of the fourth pair of legs. Scale bar = 10 µm.

E. scabrospinosus differs from E. angolensis in lacking the median plate 3, in details of the plate ornamentation and, according to the description but not to the figure, in having a spine C d.

We noted the presence of a dark ring, from which some dark stripes irradiate, in the center of the light spots also in E. spinulosu s, in E. spiniger and in E. marginatus .

E. spinulosus and E. spiniger , when the lateral appendage B and the dorsal appendage C d are absent, have the same appendages as E. scabrospinosus . But this species differs from E. spinulosus and from E. spiniger in having small dots only in the neck plate, in the lateral portion of the scapular plate and of paired plates, and on the intersegmental lateral plates (in E. spinulosus and in E. spiniger they are present in all plates); in lacking light spots on the neck plate ( Fig. 1C ) and on lateral portions of the scapular plate and of the paired plates II and III ( Fig. 1B ; 2B) while in E. spinulosus (Fig. 3A) and in E. spiniger (Fig. 4A, C) they are present and well visible; in having light spots of the terminal plate smaller than those of other plates; in lacking light spots on the cuticle of the legs (present and well visible in E. spinulosus and in E. spiniger ); in having longer lateral spines than E. spinulosus ; dorsal appendages D d (only exceptionally absent) wider than the other appendages ( Fig. 1A, B ) while in E. spinulosus (Fig. 3B) and in E. spiniger (Fig. 4B) they are similar to the other appendages; internal claws with a thin spur (those of the legs I–III are slightly smaller than those of the hind legs, Fig. 2C, D ) while in E. spinulosus (Fig. 3C, D) and in E. spiniger (Fig. 4D, E) the difference in size is more marked; in addition in E. scabrospinosus the spurs are clearly oriented towards the claw base, while in E. spinulosus and in E. spiniger they form an almost right angle with the claw.

Echiniscus scabrospinosus is extremely similar to E. marginatus Binda & Pilato, 1994 that generally has the same appendages as E. scabrospinosus , and only a careful comparison confirmed that this species is not a synonym of E. scabrospinosus . We noted that the description of E. marginatus includes a misunderstanding: the anterior margin of the paired plates II and III, of the median plate 2 and the area corresponding to the absent median plate 3 are strongly sculptured, but due to the partial overlapping of the plates, they had been erroneously considered as a marginal crenate stripe of the median plates 1 and 2 and of the paired plates II and III respectively ( Fig. 5 A, B). We also noted that in E. marginatus the light spots have a central dark ring not recorded in the description of the species. Notwithstanding these resemblances, we confirm that E. marginatus is a bona species; it differs from E. scabrospinosus in lacking a neck plate ( Figs. 5 A and 1C); in having light spots more variable in size ( Figs. 5 A–C and 1A–C); light spots of terminal plate not smaller than those of other plates ( Fig. 5 A, B and Fig. 1A, B ); less evident (probably absent) intersegmental lateral plates; lateral portions of paired plates with light spots ( Fig. 5 C) absent in E. scabrospinosus ( Figs. 1A, B , 2B ).

Figures

FIGURE 5. Echiniscus marginatus. A, anterior portion of the body of the holotype; B, posterior portion of the body of the holotype; C, detail of the cuticular ornamentation (paratype); arrow indicates light spots present also in the lateral portions of the paired plates; D, claws of the first pair of legs of a paratype; E, claws of the fourth pair of legs of the holotype. Scale bar = 10 µm.

FIGURE 1. A – D, Echiniscus scabrospinosus. A, B, habitus (A, specimen from Amarante, Portugal; B, specimen from Faial Island, Azores); arrows indicate the lateral portions of scapular plate and paired plates lacking light spots; C, anterior portion of the body of a specimen from Amarante (Portugal); the arrow indicates a pair of intersegmental lateral plates; D, detail of the plate ornamentation of the holotype; arrows indicate the dark ring present in the centre of each light spot. Scale bar = 10 µm.

FIGURE 2. A – D, Echiniscus scabrospinosus. A, B, anterior portion of the body of two specimens from Amarante (Portugal); arrows indicate the small spine on the first pair of legs and the lateral portion, lacking light spots, of scapular plate and paired plates; C, claws of the third pair of legs of a specimen from Amarante (Portugal); D, claws of the fourth pair of legs of a specimen from Faial Island (Azores). Scale bar = 10 µm.

Tables

TABLE 1. Measurements (in µm) of some structures of the holotype, the smallest and the largest measured specimens of E. scabrospinosus (% bo = percentage of body length; % sc = percentage of scapular plate length; when appendage asymmetry occurred the two measures are reported; a = absent).

Character µm	%bo	%sc	µm	%bo	%sc	µm	%bo	%sc
Body length 218	-	-	172.3	-	-	240.2	-	-
Scapular plate 42.8 length	19.6	-	37.6	21.8	-	42.6	17.7	-
Internal cephalic 12.5 cirrus	5.7	29.2	11.7	6.8	31.1	12.9	5.4	30.3
External cepha- 14.9 lic cirrus	6.8	34.8	14.3	8.3	38.0	15.9	6.6	37.3
Cephalic papilla 6.5	3.0	15.2	6.5	3.8	17.3	6.2	2.6	14.6
Clava 4.4	2.0	10.3	5.1	3.0	13.6	4.6	1.9	10.8

TABLE 2. Density of light spots in the scapular plate of E. scabrospinosus (estimated in 20 adult specimens).

Density on scapular plate	Number	of specimens	and	%
12–15 light spots / 100 µm2	8 (40%)
16–18 light spots / 100 µm2	7 (35%)
19–21 light spots / 100 µm2	4 (20%)
> 21 light spots / 100 µm2	1 (5%)

TABLE 3. Morphotypes recognizable in E. scabrospinosus as a consequence of the presence or absence of the lateral and dorsal appendages at least in one side of the body (43 adults and 1 larva).

Morphotype Specimens n (%)	A	C	D	E	D d
1 27 (62.8%)	+	+	+	+	+
2 8 (18.6%)	+	+	-	+	+
3 3 (7.0%)	+	-	-	+	+
4 3 (7.0%)	+	+	-	-	+
5 1 (2.3%)	+	-	-	-	+
6 1 (2.3%)	+	+	-	-	-
larva 1	+	-	-	+	-