Rossella Carter

Dohrmann, Martin, Göcke, Christian, Reed, John & Janussen, Dorte, 2012, Integrative taxonomy justifies a new genus, Nodastrella gen. nov., for North Atlantic " Rossella " species (Porifera: Hexactinellida: Rossellidae), Zootaxa 3383, pp. 1-13 : 3-4

Rossella Carter

Definition: Saccular Rossellinae with calycocomes among microscleres, microdiscohexasters concentrated near the atrial surface, and dermalia chiefly pentactins.

Diagnosis: Body is saccular, thick-walled, barrel-shaped with apical narrowing towards the osculum, mode of attachment is basiphytose or lophophytose. Choanosomal skeleton is composed of diactins and rarely accompanied by hexactins. Hypodermal spicules are pentactins, which can be differentiated into anchorate (which serve as basalia) and commonly with paratropal and orthotropal tangential rays. Prostalia lateralia if present are monaxons and sometimes outward protruding hypodermal pentactines. Dermalia are chiefly pentactins or combinations of them with some stauractins and hexactins. Atrialia are mainly hexactins, rarely together with pentactins or diactins. Microscleres have discoidal, tyloidal, rhopaloidal, oxyoidal rarely onychoidal terminations. Calycocomes always present, they have well-developed primary rays and are often accompanied by spherical ‘mesodiscohexasters’, discohexactins and microdiscohexasters. Mesodiscohexasters are concentrated near the dermal surface, microdiscohexasters are concentrated near the atrial surface. In most species, microdiscohexasters have secondary rays of unequal length (anisodiscohexasters). Oxyoidal spicules are combinations of hexasters, hemihexasters, hexactins and rarely other holactinoidal spicules.

1. Included here only for completeness; molecular data strongly suggest that the subfamily-division of Rossellidae is artificial (Dohrmann et al. 2008, 2012)

The body shape of Nodastrella is very variable, urn- to amphora- or trumpet-shaped depending on the size and ontogentic age (as illustrated by van Soest et al. 2007: Fig. 1 ). Young and smaller specimens are commonly tubular or urn-shaped, whereas larger specimens tend to become amphora- or trumpet-shaped. The adult body form is very similar to the typical shape of Asconema , another N Atlantic rossellid genus with which Nodastrella can easily be confused if no spicule analysis is carried out. Identification of Nodastrella is straightforward by the presence of calycocomes and discasters. However, these spicules can be very rare and might be overlooked; in that case the two genera can be distinguished by their dominant dermal megascleres, which are stauractins in Nodastrella and pentactins with distally directed unpaired ray in Asconema ( Tabachnick and Menshenina 2007) .

Etymology: The genus name is derived from the species name of the holotype, first described as Rossella nodastrella ( Topsent 1915) .

Figures

FIGURE 1. Nodastrella nodastrella USNM 1150046, specimen (A) and skeleton (B – G). (B – E, G) scanning electron micrographs; (F) light micrograph. (A) Deck photograph of specimen attached to Lophelia coral. (B) Dermal stauractin. (C) Detail of calycocome. (D) Cluster of calycocomes and a discaster (lower left). (E) Pappocome-like oxyhexaster with most secondary rays broken off. (F) Complete pappocome-like oxyhexaster. (G) Discaster.