Errina labrosa Pica, Cairns & Puce

Pica, Daniela, Cairns, Stephen D., Puce, Stefania & Newman, William A., 2015, Southern hemisphere deep-water stylasterid corals including a new species, Errinalabrosa sp. n. (Cnidaria, Hydrozoa, Stylasteridae), with notes on some symbiotic scalpellids (Cirripedia, Thoracica, Scalpellidae), ZooKeys 472, pp. 1-25 : 6-10

Taxon classification Animalia Anthoathecata Stylasteridae

Errina labrosa Pica, Cairns & Puce sp. n. Figures 3, 4, 5

Holotype.

BNHM 1977.8.10.2: four branches of a single colony, Discovery Expedition Sta 6, Tristan da Cunha, 3 miles N 30° E of Settlement, 80-140 m depth, 1 February1926 (in ethanol).

Paratypes.

MNA 3085: two colonies, Cruise Icefish 2004 (dry); MNA 3087: several fragments (dry).

Diagnosis.

The new species has a characteristic abcauline lip, ring palisade and one type of dactylopore with very elongated spines.

Description.

The holotype (Figure 3a) is composed of several branches of a single colony. The larger branch is about 10 cm long and 9 cm wide. The other specimens (Figure 3b) consist of two large colonies and one small and broken colony attached to a black coral. All colonies have an wide base from where flabellate and uniplanar branches arise. Their bases are elliptical in cross-section and the axis of the largest colony is 6 by 4 mm. The apexes are up to 1 mm in diameter. The branches are irregularly sparse and unequal, without anastomosis.

The gastropores and the dactylopores are predominantly concentrated on the terminal branches (Figure 3c) and decrease in abundance towards the base (Figures 3 d–f). In this region the pores remain confined to the lateral branch edges where the gastropores are aligned and surrounded by dactylopores characterised by a small spine.

The coenosteum is white-cream in colour and the texture is reticulate-granular with poorly-defined granules (Figure 3g). The strips are irregular in shape, 21-79 µm wide. The surface appears uniformly lumpy.

The gastropores are circular in shape (Figures 3 h–i), 80-150 µm in diameter. Predominantly in the apical region of the colony they are bordered by a well-pronounced abcauline lip (Figure 3h). This lip is porous and rounded to rectangular in shape, up to 273 µm wide, and may bear one or two dactylopore spines. The gastropore tubes are cylindrical and shallow, gastrostyles are visible at the surface. The gastrostyle (Figure 4a) has a spindle shape, ornamented with multi-tipped bifurcating spines (Figure 4b) in the apical portion, while the basal region presents a small smooth constriction. They measure 205-289 × 68-114 µm (L:D=2.3-3.4). The wall of the gastropore tube bears a diffuse ring palisade (Figure 4c) composed of irregularly shaped elements up to 20 µm in diameter. Tabulae are absent.

Dactylopores are of one kind. In the apical branches they are adcauline and bordered by well-defined spines (Figures 4 d–f; 5a). These spines are 104-244 µm long and 158-223 µm wide, truncate, with a long groove (the dactylotome) 300-550 µm long, which is oriented with an angle up to 45° with respect to the branch surface. Laterally, the spines show the same texture as the surface, while the internal wall is characterised by rudimentary dactylostyles, uniformly distributed on all surfaces (Figure 5b). The dactylostyle elements are rounded and 2-6 µm in diameter. The dactylotome is 48-73 µm wide. Proximally, the dactylopore spines are shorter with a smaller groove. In this region the spines are oriented in all directions and they are located mainly on the lateral side of the branches around the gastropores.

The ampullae (Figures 5 c–d) are distributed homogenously over the colony. In the apical branches they are external while in the basal branches they are predominantly internal. The female ampullae, 550-842 µm in diameter, are round in shape but appear hemispherical from outside, and may have some dactylopores above them (Figure 5c) and an efferent pore on one side (Figure 5c). The male ampullae, 400-500 µm in diameter, are also round in shape (Figure 5d). No efferent pores were observed for them.

Remarks.

Among the 25 known species of Errina , the only two other species having a gastropore lip, ring palisade and one type of dactylopore, as in our species, are Errina cheilopora Cairns, 1983 and Errina reticulata Cairns, 1991. The gastropore lip of these two species projects over the gastropore ( Cairns 1991) and therefore differs in shape with respect to the lip observed in our specimens. In addition, both species have large gastropores (180-330 µm and 140-200 µm, respectively) and mainly show a linear-granular texture ( Cairns 1991). Our specimens show a characteristic gastropore lip and very elongated dactylopore spines, which distinguish Errina labrosa easily from the other species. Moreover, from a geographic point of view, Errina labrosa together with Inferiolabiata spinosa (see above) represent the first identified stylasterids from the Tristan da Cunha Archipelago in the central part of the South Atlantic Ocean.

Errina was reported earlier from Tristan da Cunha by Moseley (1881) based on a specimen dredged by the Challenger Expedition (Sta. 135), which was identified as Errina labiata (now Inferiolabiata labiata ). Boschma (1964) doubted this identification because he noted that the openings of the groove spines of the dactylopores are turned toward the basal part of the colony instead of the apical part, as in Inferiolabiata labiata . He identified the specimen as Errina gracilis . Subsequently Cairns (1983a), reviewing the stylasterids from the Antarctic and Subantarctic region, reidentified the same specimen as Errina (Errina) sp. to because its poor description that did not allow a correct identification and therefore a comparison with our specimen is impossible.

Etymology.

From the Latin word labrum (meaning lip) for the characteristic abcauline lip of the gastropores.