Corallizoanthus Reimer

Swain, Timothy D. & Swain, Laura M., 2014, Molecular parataxonomy as taxon description: examples from recently named Zoanthidea (Cnidaria: Anthozoa) with revision based on serial histology of microanatomy, Zootaxa 3796 (1), pp. 81-107 : 84-85

Genus Corallizoanthus Reimer in Reimer, Nonaka, Sinniger & Iwase, 2008

Type species. Corallizoanthus tsukaharai Reimer in Reimer, Nonaka, Sinniger & Iwase, 2008, by original designation.

Diagnosis. Parazoanthidae (?) associated with Alcyonacea and lacking scleroprotein skeleton (diagnosis of Reimer et al. 2008a). Known from temperate regions at 194–1763 m. Azooxanthellate. Polyps white to yellow, expand to 7.7 mm wide and 12 mm long, with 11–14 capitular ridges. Marginal musculature cyclically transitional, 323–793 Μm in length, composed of 9–32 attachment points. Encrustations of the column to the center of mesoglea (diagnosis expanded using data presented here and Swain 2010).

Remarks. Creation of Corallizoanthus was based on intraspecific monphyly of C. tsukaharai specimens within a polytomy of species representing Savalia (= Gerardia ) and Parazoanthus (Figs. 5–7 of Reimer et al. 2008a), and on the supposition that no described zoanthid genus lacks a skeleton and associates with Alcyonacea (however, Parazoanthus lucificum Cutress & Pequegnat, 1960 and Epizoanthus induratum Cutress & Pequegnat, 1960 both appear to meet these criteria). A more comprehensive (in terms of taxa and data) molecular phylogeny supports reciprocal monophyly for species related to Corallizoanthus and Savalia ( Swain 2010) and may offer justification for the retention of this genus; although no non-molecular characters yet differentiate Corallizoanthus from Savalia (which appears to include the scleroprotein skeleton-free P. lucificum: Sinniger et al. 2008 ). Additionally, the marginal musculature of C. tsukaharai described here (as cyclically transitional) seems to exclude Corallizoanthus from the current definition of Parazoanthidae , which is limited to macrocnemic Zoanthidea with endodermal marginal musculature. Resolving these issues will require reexamination of the Corallizoanthus, Savalia , Parazoanthus , and Epizoanthus taxa that form these clades (see Fig. 1 of Swain 2010).

Although more research is required and a complete resolution of all issues plaguing these taxonomic concepts is beyond the scope of this submission, we can make some clarifications and suggestions here. The specimens of Epizoanthus with phylogenetic affinities to C. tsukaharai ( Epizoanthus aff. tsukaharai [CA] and Epizoanthus aff. tsukaharai [ NZ] sensu Swain 2010) were conservatively assigned to genus Epizoanthus (because of their largely mesogleal marginal musculature) in the absence of morphological data on Corallizoanthus (which should have an entirely endodermal marginal musculature if Corallizoanthus belongs to Parazoanthidae ). With the data presented here on C. tsukaharai , and a review of the morphbank images (collections 476540 & 476539) and histological slides of Swain 2010, we interpret the morphology of these specimens (particularly the marginal musculature) to be consistent with (but not identical to) C. tsukaharai and therefore reassign them to the revised Co rallizoanthus. Whether the definition of Parazoanthidae should be expanded to include cyclically transitional marginal musculatures or whether Corallizoanthus (and potentially Savalia ) should be reassigned to a different family is not yet clear. The marginal musculature of Savalia is defined as transitional ( Ocaña et al. 1995), an interpretation that would be made by observing almost any single section of a cyclically transitional marginal musculature (see below), and could be one of the characters that unifies Savalia and Corallizoanthus (also supported by phylogeny, see Fig. 1 of Swain 2010) in a new family or a reinstated Savaliidae Nardo, 1844 (= Gerardiidae Roche & Tixier- Durivault, 1951). Although Sinniger et al. 2008 suggest (but did not offer documentation) that Parazoanthus lucificum secretes its own skeleton (an important character for identifying Savalia ) and reassigned P. lucificum to Savalia (as Savalia lucifica ), the original description ( Cutress & Pequegnat 1960) makes no mention of this character and describes the marginal musculature as endodermal (not transitional as in Savalia ). The resolution of these apparent discrepancies is also not clear and would require the reexamination of internal microanatomy of the type specimens of Savalia savaglia (Bertoloni, 1819) and Parazoanthus lucificum in order to determine if specimens have been misidentified in recent research (e.g., E. induratum has the superficial appearance of P. lucificum , but its marginal musculature seems much more similar to Savalia ) or if taxon definitions must be further revised.

Figures

FIGURE 1. Histology of Corallizoanthus tsukaharai (10 Μm sections). Labeled features include actinopharynx (A), endodermal marginal musculature (EMM), lacunae formed by dissolution foraminifera tests (L-FT), mesogleal marginal musculature (MMM), oral disk (OD), peristome (P), tentacles (T); measurements of capitular tissue width made at black arrow. A. Longitudinal section of contracted polyp at capitulum showing endodermal portion of cyclically transitional marginal musculature. B. Longitudinal section of contracted polyp at capitulum showing mesogleal portion of cyclically transitional marginal musculature. C. Longitudinal section of contracted polyp.