Acanella rigida Wright & Studer, 1889

France, Scott C., 2017, A taxonomic review of the genus Acanella (Cnidaria: Octocorallia: Isididae) in the North Atlantic Ocean, with descriptions of two new species, Zootaxa 4323 (3), pp. 359-390 : 376

Acanella rigida Wright & Studer, 1889

Figure 10

Acanella rigida Wright & Studer, 1889: 31 , pl. 9, fig 4; Thomson & Henderson, 1906: 33

Acanella sibogae Nutting, 1910: 14 , pl. 3, figs, 2, 2a. pl. 5 fig 4; Kükenthal, 1915: 120; Kükenthal, 1924: 419; Grant, 1976: 26, figs. 23¯24; Bayer, 1990: 212, fig 5

Acanella jaPonica Kükenthal, 1915: 120; Kükenthal, 1919: 582, pl. 44, fig. 76; Grant, 1976: 25, figs. 20¯21

Type: Collected via dredge. Station 194, off Banda Islands , Indonesia. 220 fathoms depth. Deposited in the Natural History Museum, London. Reg no. 1889.5.27.22.

For description see: Wright & Studer 1889

Remarks: Specimens with Haplotype E ( Figure 10 ) match the description of A. rigida , with tall (4̄ 5 mm) polyps and long (3̄ 5 mm) curved fusiform sclerites that extend the length of the polyp, twisting around the body and protruding past the base of the tentacles. The sclerites are irregular in shape, large and all have more-or-less well-developed tubercles. A. rigida , A. robusta , and A. verticillata have similar characteristics, all with large obliquely placed sclerites that curve around the polyp body and project between the base of the tentacles, and Bayer (1990) suggested they might be the same species. However, Bayer (1990) and Grant (1975) note the following differences among the species: A. rigida has tall (4̄ 5 mm) polyps whereas the other two have short (2 mm) polyps; all three have sclerites strongly projecting between the tentacles but A. robusta has sclerites that are heavily covered by small sharp tubercles.

Distribution: Our collection expands the known range of A. rigida from off the coast of Japan, Philippines, and Indonesia, to east of Papua New Guinea; the depth range remains the same at 350̄ 700 m ( Figure 3 ).

Figures

FIGURE 3. Box and whisker plot depicting the depth range of the 8 different Acanella Haplotypes (A-H) among the 97 samples sequenced for this study; where n = 1 the line connects depth extremes of the trawl that collected the sample. The Haplotypes are arranged in order of decreasing depth and divided by collection location (Haplotype A was collected from both the Atlantic and Pacific). The dashed line demarcates the 200 m isobath, a conventional limit for the upper depth of the deepsea (200 m).

FIGURE 10. SEM images of Acanella rigida (Haplotype E, CP 3652 / 3). A) Tentacle sclerites. B) Coenenchyme sclerites. C) Polyp body sclerites.