Diplopodospongia, 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 : 46

Genus Diplopodospongia gen. nov.

Type species: Diplopodospongia rara gen. nov. sp. nov., here designated.

Diagnosis. Thinly encrusting deep-water Podospongiidae with a thin, granular, leathery, wrinkled surface that is not easily removed from the underlying crumbly choanosome. Oscules are not visible in life. Megascleres are anisoxeas, frequently centrotylote or polytylote, occasionally slightly sinuous, forming thick loose swathes that emerge from the base of the sponge and meander towards the surface, bifurcating at least once, and forming rough brushes at the surface. Microscleres are symmetrical diplospinorhabds in which the basal spine(s) and basal whorl, and apical whorl and apical spine(s), are similar in ornamentation and orientation, but one whorl might be slightly wider than the other. Protospinorhabds are linear, and shaped like a bow-tie. Microscleres form a thick crust in the ectosome and are abundant in the choanosome.

Etymology. Named for the characteristic dumbbell- or diplaster-shaped microscleres, the ends of which are not always identical, but very similar (diplo =Latin for double).

Remarks. Diplopodospongia gen. nov. has diplospinorhabd microscleres with linear or bow-tie-shaped protorhabds, with barely discernible tract development compared to that of other podospongiids; Diacarnus , Sigmosceptrella , Negombata , and Neopodospongia gen. nov. have a range of plumose fibre development with Diacarnus having the most complex and Neopodospongia gen. nov. having the least complex arrangement. In general terms, the diplospinorhabd microscleres are reminiscent of the dumbbell forms of spinorhabds in S. fibrosa , but the microscleres of this species are quite regular with only rare, if any, bifurcation of the spines in the apex, and are more like those of Diacarnus spp. The protospinorhabds of Diplopodospongia gen. nov. are linear as in Diacarnus , with expansions at each end, not sigmoidal as in Sigmosceptrella , Negombata , Podospongia , and Neopodospongia gen. nov., indicating quite a different development path for these microscleres.

In the initial study of specimens, acanthostyles were occasionally present in almost all spicule preparations and sections of Diplopodospongia gen. nov. sp. nov., suggesting affinity with Acanthancora Topsent, 1927 ( Poecilosclerida : Hymedesmiidae ); two species, A. aenigma ( Lundbeck 1910) and A. cyanocrypta (de Laubenfels 1930), have diplaster-like microscleres amongst the highly ornate, highly modified arcuate chelae. However, further examinations confirmed that they were foreign inclusions, and there is no evidence whatsoever of the microscleres of Diplopodospongia being derived from chelae. The diplospinorhabds are also highly reminiscent of microscleres in the hadromerid genera Diplastrella Topsent, 1918 , and the ‘sclerosponge’ genera Acanthochaetetes Fisher, 1970 , and Willardia Willenz & Pomponi, 1996 , but all have spiraster-like microscleres in addition to diplasters, and the principal megascleres are tylostyles. The latter genera also have a basal calcareous skeleton.