Euplectella Owen (1841)

Castello-Branco, Cristiana, Collins, Allen G. & Hajdu, Eduardo, 2020, A collection of hexactinellids (Porifera) from the deep South Atlantic and North Pacific: new genus, new species and new records, PeerJ 8, pp. e 9431-e 9431 : 6-7

Genus Euplectella Owen (1841)

Diagnosis

The body is tubular with numerous lateral oscula and usually possesses a colander-like sieve-plate. Lophophytous, attached to substratum with anchor-like basalia. Principal choanosomal spicules (large) are chie fl y stauractins usually with hexactins or pentactins.

The distal rays of these hexactins and pentactins are rough; the proximal rays in hexactins are always rudimentary. Additional choanosomal spicules are diactins, tauactins and rarely stauractins together with rare derivatives. The choanosomal spicules form longitudinal and circular skeleton beams. The sieve-plate, when present, contains hexactin derivatives that vary in different species. Basalia are anchor-like spicules with four or more teeth. Dermalia are hexactins. Atrialia are pentactins. Microscleres are fl oricomes and graphiocomes, sometimes hexasters and small sigmatocomes, rarely discohexasters, hemihexasters, hexactins and onychasters (modi fi ed from Tabachnick, 2002).

Remarks: We emended the diagnosis to include the present new species which lacks a sieve-plate. The new species fi ts with all the remaining aspects of the previously accepted diagnosis of Euplectella (cf. Tabachnick, 2002).

Considering the remaining genera of Euplectellinae , the new species described below does not fi t with Acoelocalyx Topsent (1910) because it has hexactins, pentactins and rarely stauractins as choanosomal spicules, as well as discohexaster microscleres. It differs from Chaunangium Schulze (1904) by the presence, in the latter, of several distinctly separated tufts of basalia, diactins as choanosomal spicules, and discohexasters and plumicomes as microscleres. Docosaccus Topsent (1910) differs by the presence of diactins in the choanosoma and possession of a varied set of microscleres including hexactins, hemihexasters, hexasters, fl oricomes and discohexasters. It does not fi t with Holascus Schulze (1886) because species of this genus have pinular hexactines as dermalia and atrialia, and lack fl oricomes. Malacosaccus Schulze (1886) presents choanosomal spicules which are chie fl y hexactins, pinular hexactins as dermalia and atrialia, and hexaster microscleres. To the latter, hemihexasters and hexactins, discohexasters, fl oricomes and onychasters may sometimes be added. Finally, Placopegma Schulze (1896) differs by its choanosomal diactins and discohexaster microscleres, occasionally combined with plumicomes, hexasters, hexactins and discohexactins.