Hymedesmia (Hymedesmia) promina, 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 : 160-162

Hymedesmia (Hymedesmia) promina sp. nov.

Figures 2 & 6

Material examined. Holotype: CASIZ236656 / IZC00048451 , Inner Carmel Pinnacle (36.55910, -121.96630), 10– 18 m, 8/10/2021.

Etymology. Named for both the pinnacle on which it was found and the raised, tower-like prominences decorating the surface.

Morphology. Thinly encrusting, 1 mm thick, with numerous oscula atop prominences 1–2 mm in diameter; prominences occur singly, in pairs, or as ridges of several in a line. Yellowish–orange in life; turns distinctly blue in ethanol. Prominences retract when preserved but remain visible as blue mounds, with the ectosome between them appearing wrinkled and grayish. Firm and incompressible.

Skeleton. Basal spongin plate; some acanthostyles singly erect on substrate, with heads embedded in spongin; other acanthostyles and some subtylotes laying horizontally along substrate. Tracts of subtylotes ascend from substrate and branch, but stop before reaching ectosome; numerous microscleres scattered throughout sponge. Ectosome contains abundant diatoms and scattered chelae, but no macroscleres.

Spicules. Long acanthostyles, short acanthostyles, subtylotes, arcuate isochelae, sigmas.

Long acanthostyles: Densely spined in head region, sparsely spined on shaft. 316–442–513 x 11–13–17 μm (n=17).

Short acanthostyles: Densely spined throughout; large spines on head curve towards tip, large spines on shaft curve towards head. 104–123–140 x 5–9–13 μm (n=25).

Subtylotes: Straight rods with slightly swollen, oblong tips. 244–282–404 x 3–6–12 μm (n=20).

Arcuate isochelae: Of typical shape for genus; curved shaft, three well delineated teeth, central tooth longer than lateral teeth. 27–31–37 μm (n=20).

Sigmas: C- or S-shaped, most rotated such that they are not in a single plane. 41–53–65 μm (n=23).

Distribution and habitat. Known only from the Carmel Pinnacles. Numerous individuals seen on initial dive, but only one sample taken; no individuals seen on second dive.

Remarks. Hymedesmia are thinly encrusting Hymedesmiidae with acanthostyles singly erect on the substrate and bundles of tornotes in the choamosome and/or ectosome (van Soest 2002). Genetic data indicate the genus is polyphyletic ( Redmond et al. 2013); the 'hymedesmoid' skeletal morphology is known to have evolved multiple times outside the family, so it is not surprising that it has also evolved repeatedly within the family (van Soest 2002). No genetic data is yet available for the type species of Hymedesmia , and data from few species are available at 28S or cox1. Surprisingly, however, H. promina appears to be more closely related to species placed in the Coelosphaeridae and Myxillidae than to other Hymedesmiidae (figure 2). As this species is clearly in Hymedesmia based on the morphological taxonomy, reconciling the taxonomy with the evolutionary history of hymedesmoid sponges must await genetic data from more species and a systematic revision.

Hymedesmia promina is easily differentiated from other described species known from the region. Hymedesmia (Stylopus) arndti ( de Laubenfels, 1930) is the only Hymedesmia described from the northeast Pacific, though there are also unpublished reports of H. (Stylopus) primitiva Lundbeck, 1910 occurring in British Columbia; neither species has chelae. An additional 11 sponges have been referred to as " Hymedesmia sp. " in various California surveys and remain undescribed ( Lee et al. 2007). Of these, an intertidal sample from the Farallon Islands in Northern California ( Klontz 1989) is the only potential match to H. promina sp. nov.. These previous undescribed sponges are vouchered but were not examined as part of this work.

Further work is required before this species can be confidently identified based on gross morphology in the field. Thinly encrusting orange sponges are numerous in California, but it is possible that the tower-shaped oscula of H. promina sp. nov. are diagnostic.

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 6. Hymedesmia promina. Field photos of holotype (A) and uncollected sample (B). C: Cross–section showing acanthostyles embedded in basal plate and horizontal spicules at sponge base. D: Large acanthostyle. E: Subtylote. F: Short acanthostyle. G: Sigma. H–I: Chelae. J: Cross–section showing ascending tracts of subtylotes, with diatoms visible at sponge surface. C–J from holotype.