Neopodospongia, Sim-Smith, Carina & Kelly, Michelle, 2011

Sim-Smith, Carina & Kelly, Michelle, 2011, Two new genera in the family Podospongiidae (Demospongiae: Poecilosclerida) with eight new Western Pacific species, Zootaxa 2976, pp. 32-54 : 40-41

Genus Neopodospongia gen. nov.

Type species: Neopodospongia pagei gen. et sp. nov., here designated.

Diagnosis. Thinly encrusting Podospongiidae with simple, raised, regularly spaced oscules. Surface like cellophane or thin translucent leather, easily detached from underlying choanosome, enabling the sponge to be ripped off the substrate in a sheet. Megascleres are strongyloxeas with various modifications that form fine single or multiple tracts that emerge as sprays of secondary tracts or brushes in the ectosome. Microscleres are aciculospinorhabds in up to two size categories in which the apex is a ragged spire of merged, sculpted spines. Ectosome is highly collagenous and densely packed with microscleres. Protospinorhabds are sigmoidal.

Etymology. Named as a new, encrusting form of sponge that resembles the stipitate genus Podospongia (neo = Greek for new).

Remarks. Species of Podospongia were traditionally understood to be typically stipitate, with the exception of the thinly encrusting Irish species Latrunculia normani , transferred to Podospongia by Kelly & Samaai (2002, p. 698). These authors considered that the species normani was most probably a species of Podospongia because of the presence of aciculospinorhabds, although the thinly encrusting habit did not conform to the diagnosis of the genus. Since 2002, two additional papers ( Cristobo et al. 2009; Samaai & Kelly 2006) listed the species as Podospongia with no further explanation.

Podospongia normani from northwest Ireland is remarkably similar to the New Zealand Neopodospongia gen. nov. species despite the obviously disjunct distribution of the species. Podospongia normani is described by Stephens (1915) as very thinly encrusting with a smooth surface interspersed by ‘minute hillocky elevations’ which may be contracted oscules. The choanosomal skeleton was described as consisting of ‘strong fibres made up of closely-packed multiserially arranged styli (those illustrated in Stephens, 1915, Pl. V, Fig. 2 a–d are polytylote strongyloxeas with exactly the same morphology as those of the New Zealand species), which run upwards through the sponge, and which are continued in a horizontal direction beneath the dermal layer of ‘dicasters’’ (= spinorhabds). We think that the horizontal orientation of the tracts may be due to desiccation or squashing as the same was observed in the extremely thin, soft N. exilis gen. nov. sp. nov., described below. The ectosome was described as consisting of a ‘single layer of vertically placed dicasters which are set closely together’ and they were found by Stephens to be scattered throughout the choanosome. This is also a characteristic of the New Zealand species. The aciculospinorhabds are very similar in shape to those of N. exilis gen. nov. sp. nov. described below, in that they have a four-spined basal whorl, a horizontal whorl of trifurcate spines in the middle, and an apical whorl of serrated spines from which emerges a conical spire with serrated edges ( Stephens, 1915; Pl. V, Fig. a–c).

The key characters that link P. normani and the three New Zealand species of Neopodospongia gen. nov. are the possession of a different form of aciculodiscorhabd, and the encrusting morphology. In Neopodospongia gen. nov. the large aciculorhabd is a ragged spire of fused spines, not just simple or bifurcate spines extending from the apical whorl as in Podospongia . They also form smooth encrustations, some of which may be extensive. Moreover, these four species have only a single form of megasclere, the strongyloxea, unlike Podospongia which has an additional form in the stalk, a distinctive short thick anisostrongyle. Thus, for these five species at least, thin encrusting morphology is not just a developmental form of Podospongia , as was previously thought when Vacelet (1969) attributed several thin encrusting sponges to P. loveni . It would be of benefit to examine these specimens in the light of what we now know about Neopodospongia gen. nov. before it can be concluded that they are indeed encrusting forms of Podospongia . It should be noted here that the informally named shallow water Chilean species, S igmosceptrella tupecomareni , illustrated in Willenz et al. (2009). is also clearly a species of Neopodospongia gen. nov, with two size categories of aciculospinorhabds.

The discovery of three thinly encrusting species of Podospongiidae in New Zealand, with aciculospinorhabds that are remarkably similar to those of P. normani from Ireland, raises the question of the integrity of the genus Podospongia as it presently stands. Although the disjunct distribution may be considered unusual, it has precedents in the relatively well known genera Latrunculia du Bocage, 1869 and Polymastia Bowerbank, 1864 , which occur in both hemispheres. Because of the considerable similarity of the forms of the Irish and New Zealand species we have little hesitation in hereby transferring Podospongia normani to Neopodospongia gen. nov.

Neopodospongia gen. nov. can be compared to other Podospongiidae genera, including encrusting species of Sigmosceptrella , but is clearly differentiated from these by the presence of characteristic aciculospinorhabds. While the generalised skeletal arrangement in Neopodospongia gen. nov. is reminiscent of that of Sigmosceptrella , the latter has well defined thick plumose divergent tracts with frequently dumbbell-shaped spinorhabds (Kelly- Borges & Vacelet 1995). Species of Diacarnus are highly diverse with barrel-shaped, spherical, and branching forms, but all have exquisite umbelliform or candelabra-like plumose fibres, spinorhabds, and linear microsclere protorhabds. Negombata is a western Indian and Southeast Asian genus and is characterised by beautiful orange red colouration in life and a spongin bound plumoreticulation of two forms of megascleres within the choanosome. In comparison to other Podospongiidae genera, Neopodospongia gen. nov. has a relatively simple skeletal architecture.

Figures

FIGURE 2. Generalised skeletal architecture of new Podospongiidae genera and species: A. Podospongia virga, with secondary tract formation evident within the globular part of the body; B. Podospongia colini, with dendritic non-divergent tracts within the globular part of the body; C. generalised skeletal architecture of Neopodospongia species; D. generalised skeletal architecture of Diplopodospongia species.