Hymeniacidon fusiformis, 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 : 181-182

Hymeniacidon fusiformis sp. nov.

Figures 18 & 20

Material examined. Holotype: CASIZ236657 / IZC00048452 , Inner Carmel Pinnacle, (36.55852, -121.96820), 10–24 m, 9/22/21.

Etymology. Named for its slightly fusiform styles.

Morphology. Growing as an irregular mass, thickly encrusting with many projecting fingers and lobes, heavily fouled by hydroids and other animals. Sampled portion is 1 cm thick, but sponge was thicker in life. Firm and barely compressible; oscules and pores not evident.

Skeleton. Choanosome a chaotic halichondrid reticulation with vague multispicular tracts meandering towards the surface. Spicule density high; spongin not apparent. Ectosome a dense mat of tangential styles approximately 200 μm thick, unstructured in some regions, and patterned into a semi-regular mesh in other regions. Large subectosomal spaces present, bridged by spicule tracts to support ectosome.

Spicules. Styles: most are very slightly fusiform, so that they are thicker in the center than near the head of style. Length and width are both highly variable; distributions are continuous but bimodal, 186–281–409 x 4–10–18 μm (n=345), length modes 260 and 330 μm, width modes 8 and 13 μm. When spicule preps are done separately for ectosome and choanosome, no differences are found in spicule sizes by domain: ectosome 217–286–372 x 4–11–18 μm (n=68), choanosome 206–285–370 x 6–10–18 μm (n=62), Wilcoxon rank-sum test p = 0.863.

Distribution and habitat. Known only from the Carmel Pinnacles.

Remarks. Of the three Hymeniacidon known from the region, H. actites ( Ristau, 1978) and H. ungodon de Laubenfels 1932 have much smaller spicules, with less variation in spicule dimensions. Hymeniacidon perlevis ( Montagu, 1818) have spicules of similar length, and also have high variation in spicule length. However, H. perlevis spicules vary little in width and are not fusiform. The new species also differs from H. perlevis in coloration: though H. perlevis can be yellow, orange, or red, it is not known to occur in white. Finally, H. perlevis spicules differ in having a unimodal distribution for both length and width, and being significantly smaller in the ectosome than the choanosome. These species are also genetically differentiated at the 28S locus, as shown in figure 18. It is unlikely that this species can be identified in the field.

Figures

FIGURE 18. Maximum likelihood phylogenies for the Halichondriidae. A: 28S locus, B: cox1 locus. Genbank accession numbers are shown; bold indicates new sequences. Node confidence is based on bootstrapping. Scale bar indicates substitutions per site.

FIGURE 20. Hymeniacidon fusiformis. A: field photo. B: cross-section at sponge surface. C: ectosomal skeleton. D: oxea. All images of holotype.