Errina fissurata (Gray, 1872)

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 : 4-6

Taxon classification Animalia Anthoathecata Stylasteridae

Errina fissurata (Gray, 1872) Figure 2

Madrepora fissurata Stokes 1847: 336

Errina fissurata Gray 1872: 745; Moseley 1879: 479; 1881: 84; Boschma 1957: 53; 1964: 284; Boschma and Lowe 1969: 15; Cairns 1983a: 89.

Labiopora fissurata Hickson 1912: 878.

Errina (Eu-Errina) fissurata Broch 1942: 38.

Errina (Eu-Errina) antarctica Broch 1951: 35 (part of material from sta. 1948).

Errina (Errina) fissurata Boschma 1963: 337; Cairns 1983a: 89.

Errina antarctica Boschma 1966: 109 (part of material from sta. 30).

Material studied.

MNA 3070, MNA 3071: two colonies, Cruise Carbonant 2002, Sta. 24, 72°30'456"S, 174°05'552"E, 438 m depth, 13 January 2002 (in ethanol); MNA 3079, MNA 3080, MNA 3081, MNA 3082, MNA 3086: a total of five colonies, Cruise Tangaroa 2004, Sta. 77, 72°07'47"S, 172°42'36"E, 499 m depth, 14 February 2004 (dry); BNHM 1977.8.10.26: one colony, Discovery Expedition, Sta. 1948, 60°49'24"S, 52°40'00"W, 490-610 m depth, 4 January 1937 (in ethanol).

Description.

Specimens consist of up to 16.4 cm long broken branches of uniplanar colonies, all lacking the base (Figure 2a). The branching pattern is irregular and dichotomous, most branches oriented nearly parallel (Figure 2a). They are oval in cross-section and up to 6 mm in diameter. The blunt tips are 2-3 mm in diameter (Figure 2b).

The colour of the coenosteum is pale orange (Figure 2a) with the core of the branches white. The texture is reticulate-granular with small and rounded granules 1.4-10 µm in diameter (Figures 2c, d). On the surface there are non-linear slits, up to 140 µm wide and provided with teeth projecting inward (Figure 2d). They connect the coenosteal pores, 20-30 µm in diameter (Figure 2d).

The gastropores and dactylopores are scattered over the coenosteum (Figure 2b). They are decreasing in abundance and density from the tip of each branch towards the base, being mainly present on the lateral branch edges and almost absent on the faces while they are generally lacking in the basal region. The round gastropores, 100-300 µm in diameter, are not lipped and the gastrostyle tips are visible from the coenosteum surface (Figure 2b). The gastrostyles are robust and lanceolate without ridges and have multi-tipped bifurcating spines (Figures 2e, f). They are up to 470 µm long and up to 220 µm in diameter (L:D=1.7-2.9). Ring palisades and tabulae are not recorded (Figure 2e).

The coenosteum surface contains two kinds of dactylopores, with either large or small spines, which protrude perpendicularly from it (Figure 2g). The large spines are U-shaped in cross-section and have an adcauline opening; they are mainly present in the distal portion of the branches (Figures 2 h–j). They are 250-400 µm long with a diameter of 250-500 µm and are characterised by a thick porous wall (Figure 2h). Laterally they are composed of smooth overlapping platelets, while the internal wall is characterised by the typical reticulate texture (Figures 2i, j). The dactylotome is 60-110 µm wide (Figure 2j). From the apex to the base, the large dactylopore spines tend to become flush with the coenosteum and to disappear from the colony faces, remaining only on the lateral branch edges. The small spines are scattered between the large ones (Figures 2g, h, k), and, toward the base of the colony they become increasingly difficult to distinguish from the large dactylopores. Their external wall is smooth or reticulate and measures 60-140 × 60-85 µm in diameter and up to 70 µm in length (Figures 2h, k). The dactylotome is randomly oriented (Figure 2h). Dactylostyles are present only in the large spines (Figure 2j). They are composed by rudimentary elements up to 35 µm long and are arranged in two linear series on the lateral internal wall of the spine.

Large round pores (50-90 µm in diameter) almost flush with the coenosteum. They are scattered over the coral surface between the dactylopore spines (Figures 2g, h).

The colonies present sexual dimorphism in both size and position of the ampullae. The female colonies have round ampullae (up to 1 mm in diameter) that protrude from the coenosteum surface (Figure 2l). Small dactylopores are frequently present over the ampullae. The efferent pores are up to 175 µm in diameter and may be visible laterally. Male colonies have smaller, round to elliptical ampullae (up to 500 µm in diameter), which are partially embedded in the coenosteum and almost no detectable at the surface (Figure 2m).

Remarks.

In the Antarctic and Sub-Antarctic region 11 Errina species have been recorded ( Cairns 1983b, 1991). Among them, Errina fissurata and Errina antarctica are very similar to our specimens in various characters such as coenosteum colour and texture, non-lipped gastropore, and in having two kinds of dactylopores. The characteristic shape of the large dactylopore spines, the shape of the gastrostyles and the dimorphism of the ampullae reported in Errina fissurata clearly match with our Antarctic specimens. Moreover, Errina fissurata and Errina antarctica show a distinct geographical and bathymetric distribution: Errina fissurata is described around continental Antarctic, and almost exclusively at> 300 m depth, whereas Errina antarctica is only known from South America and usually reported from <300 m depth.

Our specimens compare favourably with samples described by Cairns (1983a), but differ in having the coenosteal pores distinguishable at the coenosteum surface, the presence of large pores at the surface, and having dactylostyles in the large dactylopores, never described before for this species. To date, the only other Errina species described with dactylostyles is Errina capensis Hickson, 1912 from South Africa ( Cairns and Zibrowius 2013).