Halichondria loma, 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 : 178-181

Halichondria loma sp. nov.

Figures 18 , 19

Material examined. Holotype: CASIZ236654 / IZC00048445 , North Monastery Beach , Carmel, (36.52647, - 121.92730), 12–29 m, 9/22/21; paratypes: IZC00048444 , Butterfly House, Carmel, (36.53908, -121.93520), 9–20 m, 8/10/21; SBMNH700908 , Acropolis Street, Pacific Grove, (36.64183, -121.93060), 9–18 m, 8/9/21; SBMNH700913 , Fire Rock, Pescadero Point, Carmel, (36.55898, -121.95110), 10–22 m, 8/10/21; IZC00048442 , Inner Carmel Pinnacle, (36.55910, -121.96630), 10–18 m, 8/10/21; IZC00048443 , Wreck of the Ruby E, San Diego, (32.76680, -117.27620), 18–25 m, 5/16/21; SBMNH700925 , Six Fathoms, San Diego, (32.71000, -117.26860), 9–18 m, 5/15/21; SBMNH700914 , Goalpost, San Diego, (32.69438, -117.26860), 12–15 m, 2/8/20.

Etymology. Name inspired by Point Loma, the location where the first sample was found.

Morphology. Encrusting, bright yellow in life, white when preserved. Oscules prominent, flush with surface or atop low chimneys. Surface patterned with partially transparent mesh-like ectosomal network of fibers and vein-like sub-surface channels. Morphology is very similar to H. panicea and H. bowerbanki , but in contrast to these species, no individuals were found to form tendrils or occur in green.

Skeleton. Choanosome is a chaotic mass of oxeas in confusion, accompanied by paucispicular tracts; no apparent spongin. Ectosomal skeleton of tangential oxeas; in some regions of the sponge, these form a lattice of meandering, paucispicular tracts; in other regions the oxeas form a mat patterned only by circular gaps around pores.

Spicules. Oxeas of typical Halichondria form, thickest in the center, gradually tapering to hastate tips. Holotype 411–544–650 x 9–12–15 μm (n=40). Other samples average from 462 to 527 μm. All samples pooled: 298–509–650 x 5–11–16 μm (n=386). Only one size class of spicules present (length and width distributions are unimodal), but if spicule preparations are done for ectosome and choanosome separately, spicules are significantly shorter in ectosome (sample IZC00048442: ectosome 409–516–611 x 5–11–15 μm (n=49), choanosome 407–548–644 x 5–10–14 μm (n=50), Wilcoxon rank-sum test p=0.004).

Distribution and habitat. This species is uncommon but widespread on subtidal, natural reefs in Southern and Central California. It was found at 40% of the natural reefs investigated around the Monterey Peninsula, 40% of the natural reefs investigated around San Diego County in extreme Southern California, but not found at any sites between. It was also found on the wreck of the Ruby E, an artificial reef in the San Diego area. It was not common at any site where it was found.

Halichondria — H. panicea , H. bowerbanki , and/or undescribed species—are abundant in marinas and bays in California, but H. loma sp. nov. was not found at any of the 23 marinas investigated by the authors. There are also many intertidal Halichondria in Northern and Central California, but H. loma sp. nov. was not found at any intertidal sites investigated. Halichondria loma sp. nov. therefore seems to be limited to the subtidal, and occurs at low density, primarily on natural reefs.

Remarks. Two species of Halichondria are known in California: H. panicea and H. bowerbanki , and the new species is quite similar to both. Previous descriptions of these species in California ( de Laubenfels 1932; Lee et al. 2007) describe oxeas up to a maximum of 420 μm in length, while the new species is longer: the holotype averages 544 μm, with a maximum of 650 μm. This is a subtle difference, especially considering that H. bowerbanki in the United Kingdom has been described as having spicules of similar length ( Ackers et al. 2007). However, genetic data at mitochondrial and nuclear loci support the distinctiveness of the new species, with H. panicea , H. bowerbanki , and the new species all having 14–23% sequence divergence at 28S and 4–10% sequence divergence at cox1 (figure 18). The new species is therefore best identified using a combination of genetic and morphological data.

We have extensive collections of Halichondria from other locations in Central and Southern California, and these unpublished data support the existence of H. panicea and H. bowerbanki in the region; in addition to H. loma sp. nov., these data point to several other wide-spread undescribed species. These data will be detailed in an upcoming systematic revision of the family Halichondriidae for the region.

This species cannot be identified in the field, as the gross morphology cannot be differentiated from H. panicea or H. bowerbanki . Halichondria can be tentatively identified to the genus level in the field, but are easy to confuse with some other species, such as Mycale psila and Hymeniacidon perlevis .

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 19. Halichondria loma. Field photos of holotype (A) and SBMNH700925 (B). C: oxea from IZC00048442. D: crosssection and E: surface skeleton, both from SBMNH700914.