Cladorhiza mirabilis

Cladorhiza mirabilis (Ridley & Dendy, 1886)

Figure 11, Tables 5 & 8

Trochoderma mirabile Ridley & Dendy, 1886: 344.

Axoniderma mirabile Ridley & Dendy, 1886: 493.

Axoniderma mirabile Ridley & Dendy, 1887: 97–98, Pl. XX, Fig. 5, Pl. XXI, Figs. 8, 9, 10.

Axoniderma mirabile: Koltun, 1970: 187, Fig. 13, 5–8

Material Examined: Histological slides of Types BMNH 1887.5.2.141 and BMNH 1891.10.3.49: south of Easter Island, South Pacific, Station 291, H.M.S. Challenger, 27/x/1875; 39° 13’S, 118° 49’ W, 4115 m depth, red clay substrate.

Distribution: This species is presently known only from the South and North Pacific.

Description:

Growth form: Pedunculate erect, ‘crinorhizoid’ parasol-shaped with conical cap-shaped body with terminal papillae, perched on the end of a long slender stem, with numerous long filaments surrounding the body, basal attachment not recorded. Ridley & Dendy (1887) record the height of the specimen (with broken stem) as 54 mm.

Ectosomal skeleton: The ectosomal skeleton of the filaments consists of granular collagen membrane containing predominantly larger pseudoamphiasters embedded vertical to the axial bundles of styles, and interspersed with smaller unguiferate anisochelae (Fig. 11 D).

Endosomal skeleton: Axis of filaments cored by small bundles of 4-5 larger styles-mycalostyles and tracts of few smaller styles running parallel to the axis (Fig. 11 D). Axis of stem and body with thick multispicular bundles of styles-mycalostyles that appear to consist mainly of the larger size class, with single or a few larger styles projecting on the terminal papillae at right angles to the axis (Fig. 11 E), and a thick cortex encrusted with pseudoamphiasters and other microscleres.

Megascleres: Styles in two categories, very large styles-mycalostyles ranging up to 6mm in length (mostly broken in the histological slide of the lectotype), and thinner supporting styles up to 300 µm long and 5 µm wide. Both sizes are styles occur together in the stem and filaments.

Microscleres: Pseudoamphiasters (127-(191)-295 x 8-(13)-18 μm, n=50), with 4-6 alae. Anisochelae (31-(40)- 48 x 2-(4)-8 μm, n=50), Sigmas (88-(106)-114 x 2-(4)-5 μm, n=9).

Remarks: The redescription of C. mirabilis from its microscope slide type clarifies some uncertainties in the original measurements of spicules provided by Ridley & Dendy (1887), and its possession of larger and smaller categories of styles-mycalostyles as structural and supporting megascleres, respectively (Table 8).

Koltun’s (1970) also records this species from the North Pacific, listing a range of measurements for anisochelae and pseudoamphiasters, although it is unclear in his reference to pseudoamphiasters (“sometimes up to 0.230 mm long”), whether he was referring to additional spicules he observed in his material, or referring to Ridley and Dendy’s (1887) measurements, or both. He noted his material only differed from the 2 specimens described by Ridley & Dendy in lacking sigmas.

Re-examination of the data from the holotype of C. hubbsi during this study also revealed the range of anisochelae to be: 23-31-35 μm, pseudoamphiasters: 120-(136)-153 μm, styles (in three classes, 4041-(5067)-7142 x 52-(71)-96, 3419-(4172)-5146 x 25-(61)-102, 1518-(2565)-3330 x 14-(44)-79 μm and sigmancistras: 75-(98)-121 μm. The shape of the parasol apparently diagnostic for C. hubbsi (Lundsten et al. 2017: Fig. 6A) has the same vertical orientation of the filaments as does C. mirabilis in Koltun’s (1970) Plate 6 figure 7. Consequently, it would be informative to re-examine the maximum dimensions of the pseudoamphiaster in Koltun’s (1970) specimen, which may show it to be conspecific with C. hubbsi, and thus, suggest a pan North Pacific distribution, or as it currently is, a North-South Pacific continuum.

Unfortunately, neither the holotype of C. hubbsi nor Koltun’s (1970) C. mirabilis was available for us to reexamine. Re-examination of the type of C. mirabilis under an SEM or using molecular techniques would also be useful. In any case, a population genetic approach based on fresh specimens from the North and South Pacific would test the connectivity between temperate Pacific Ocean waters both sides of the equator, and even both sides of the International Date Line.

Lundsten et al. (2017) appear to have misinterpreted Ridley & Dendy’s (1887) description, with the original description of C. mirabilis having a basal width of 6 mm, compared to 11 mm in C. hubbsi. The lateral processes in C. mirabilis were listed as about 31 mm by Ridley & Dendy (1887) and these compare to 42–51 mm in C. hubbsi by Lundsten et al. (2017).

Unfortunately, also, both Lenhert et al. (2005) and Lopes & Hajdu (2014) mistakenly list Ridley and Dendy’s (1887) measurements of the pseudoamphiasters in C. mirabilis as 23 µm instead of 230 µm.