Parazoanthus Haddon & Shackelton, 1891

Low, Martyn E. Y., Sinniger, Frederic & Reimer, James Davis, 2016, The order Zoantharia Rafinesque, 1815 (Cnidaria, Anthozoa: Hexacorallia): supraspecific classification and nomenclature, ZooKeys 641, pp. 1-80 : 13-14

Parazoanthus Haddon & Shackelton, 1891

Heterozoanthus Verrill, 1870: 371 [nomen oblitum].

Parazoanthus Haddon & Shackleton, 1891a: 653, 654 [nomen protectum].

Type species.

Palythoa axinella Schmidt, 1862, by original designation.

Gender.

Masculine.

Diagnosis.

Originally described as well-developed canal system in the mesoglea of the column, forming a ring sinus. Zoantharians often associated with sponges but not Hydrozoa, lacking skeletal secretion ( Sinniger et al. 2010a). Examined species with endodermal sphincter muscle (=branchiform endodermal muscle [ Swain et al. 2015]), encrustations reaching to endodermal surface of mesoglea ( Swain and Swain 2014).

Remarks.

"The original morphological description of Parazoanthus mentions several characteristics such as diffuse endodermal sphincter, encircling sinus, endodermal canals, lacunae and cell-islets in the mesoglea, continuous ectoderm and bodywall incrusted with mineral particles, often with numerous sponge spicules present in the incrustations. As shown in Sinniger et al. (2005) and here, these morphological characteristics alone do not ascertain the monophyly of Parazoanthus . Morphological characteristics in zoanthids can often become artifactual due to both complications encountered in making thin cuttings of heavily sediment incrusted polyps, and in interpreting the results of such sections. In the past, the large majority of epizoic macrocnemic zoanthids were described as belonging to Parazoanthus despite clearly different ecologies in many cases.

Thus, the results of this study strongly suggest that only zoanthid species able to associate with sponges should remain in Parazoanthus , as the type species of this genus, Palythoa axinellae from the Mediterranean Sea, is regularly associated with demosponges." ( Sinniger et al. 2010a: 69).

There is a need for a new diagnosis of this genus-grouping. With the recent erection of Umimayanthus Montenegro, Sinniger and Reimer, 2015 and the resurrection of Bergia Duchassaing de Fonbressin and Michelotti, 1860 in Montenegro et al. (2015a), the genus Parazoanthus now consists only of the former phylogenetic grouping of Parazoanthus 'clade C’ sensu Sinniger et al. (2010a) and is monophyletic ( Montenegro et al. 2015a: 71). Parazoanthus can be distinguished from Bergia and Umimayanthus by 16S-rDNA sequences, lacking the unique 60 bp deletion of Bergia and the unique insertion and deletion of Umimayanthus . Thus, the molecular characters described in Sinniger et al. (2008, 2013) appear to be efficient in identifying to genus level and could be used as diagnostic characters.