Phorbas nebulosus, Turner & Lonhart, 2023

Turner, Thomas L. & Lonhart, Steve I., 2023, The Sponges of the Carmel Pinnacles Marine Protected Area, Zootaxa 5318 (2), pp. 151-194 : 156-159

Phorbas nebulosus sp. nov.

Figures 2–4 .

Material examined. Holotype: CASIZ236661 / IZC00048467 , Inner Carmel Pinnacle, (36.55910, -121.96630), 10–18 m, 8/10/21 ; Paratype: SBMNH700928 , Wycoff Ledge , San Miguel Island, (34.02132, -120.38710), 9–19 m , 8/25/19.

Etymology. Named for its resemblance to supernova remnants such as the crab nebula.

Morphology. Thickly encrusting; holotype is 2 cm thick, paratype is 7 mm thick. Pale orange when alive, beige when preserved. Sponge surface is nearly covered in areolae, with scattered oscula also present. Areolae flush with surface, but oscula slightly raised.

Skeleton. Choanosomal skeleton with plumose dendritic columns of acanthostyles rising towards the surface; tracts are loose and confused, with many individual spicules also in confusion. Ectosomal skeleton of upright and tangential tornote bouquets. Chelae present throughout, but most dense in ectosome.

Spicules. Long acanthostyles, short acanthostyles, tornotes, arcuate isochelae. Measurements below are for both samples pooled.

Long acanthostyles: moderately spined throughout, usually most densely spined at head. 224–283–317 x 7–11– 15 μm (n=11).

Short acanthostyles: spines average larger and more dense than large acanthostyles, but with some overlap. 127–166–182 x 6–10–12 μm (n=17).

Tornotes: straight rods with both ends tapering to points; points variable, but most smoothly tapering, resembling oxeas; many appear symmetrical, while others are slightly asymmetrical, with one point more abruptly tapering than the other. 205–245–284 x 5–6–9 μm (n=40).

Arcuate isochelae: curved shaft, three alae; center ala slightly longer than side alae, and variably rounded or slightly pointed. 14–18–21 μm (n=32).

Distribution and habitat. Known from two samples, one from the Carmel Pinnacles and one from San Miguel Island (Southern California); both locations were natural, rocky subtidal reefs. The species is likely to be rare in the investigated region, as it is visually distinctive and has not been seen at any other site.

Remarks. The arcuate isochelae, areolated pore fields, plumose tracts of acanthostyles, and tangential ecotosomal brushes of tornotes lead to placement in Phorbas . The genetic data are unable to strongly support or refute this placement, as the genus appears highly polyphyletic (figures 2 & 3). Genetic data from the type species, P. amaranthus Duchassaing & Michelotti, 1864 , are available at 18S, and place the type species in a poorly supported clade near Lissodendoryx fibrosa , Crella elegans , and Hemimycale columella ( Redmond et al. 2013) . Our phylogenies share some species in common with the published 18S phylogeny (but not P. amaranthus ), and appear to place P. nebulosus sp. nov. in this same large clade, albeit closer to Crella elegans than to any other Phorbas . The genus Crella also has areolated pore fields, but is currently defined by having a tangential crust of spiny oxeas, anisoxeas, or styles (van Soest 2002). The genus Crella would therefore have to undergo substantial revision to house P. nebulosa sp. nov.

Two other California species are currently placed in the genus Phorbas : P. californianus ( de Laubenfels, 1932) and P. hoffmani ( Bakus, 1966) . Both are easily differentiated from the new species by multiple spicular characters including the absence of chelae. The only other Phorbas known from the Northeast Pacific is P. reginae Aguilar-Camacho & Carballo 2012 , from the Gulf of California, Mexico. This last species is well differentiated from the new species by multiple spicular characters including possession of tylotornotes and differently shaped chelae. Phorbas reginae also has much smaller acanthostyles, with the larger class averaging less than half as long as P. nebulosus and the small acanthostyles only a third as long as P. nebulosus . Morphology also differs, with P. reginae being black in ethanol and lacking of visible ostia and oscules, but these differences could be due to the greater age of the P. reginae specimen ( Aguilar-Camacho & Carballo 2012).

Phorbas nebulosus sp. nov. can be tentatively identified in the field based on color and being completely covered in roughly circular pore fields. Hemimycale polyboletus comb. nov., nom. nov. (see below) is similar, but the pore fields of that species (and P. hoffmani ) are usually elevated on papillae. Known samples of P. californianus are white or blue, not orange, and the pore fields are larger and amorphous. There are also one or more undescribed species covered in circular areolae in California, similar in color to P. nebulosus , but these species are thinly encrusting rather than thickly encrusting and globular.

Figures

FIGURE 2. Maximum likelihood phylogeny of the 28S locus for the Poecilosclerida. Genbank accession numbers are shown; bold indicates new sequences. Node confidence is based on bootstrapping. Scale bar indicates substitutions per site. Colors indicate clades containing new taxa, as referenced in the text.

FIGURE 3. Maximum likelihood phylogeny of the cox1 locus for the Poecilosclerida. Genbank accession numbers are shown; bold indicates new sequences. Node confidence is based on bootstrapping. Scale bar indicates substitutions per site. Colors indicate clades containing new taxa, as referenced in the text.

FIGURE 4. Phorbas nebulosus. A: Holotype in the field. B: Field photo of SBMNH700928. C: Choanosomal skeleton. D: Ectosomal skeleton. E–F: Chelae. G: Long and short acanthostyles. H: Tornote. C–H from holotype.