Description and distribution of Desmacella hyalina sp. nov. (Porifera, Desmacellidae), a new cryptic demosponge in glass sponge reefs from the western coast of Canada

Abstract

Glass sponges (Porifera, Hexactinellida) form globally unique reefs that support deep-sea biodiversity in the Canadian northeast Pacific. In February 2017, the largest known reefs were protected within the Hecate Strait and Queen Charlotte Sound Glass Sponge Reefs Marine Protected Area (HSQCS-MPA). Many studies that have established baseline biodiversity data for the MPA have focused on describing the crustaceans and fish living in the reefs, but the relationship between glass sponges and sponge epibionts has often been overlooked. We studied one of the more conspicuous sponge epibionts of the genus Desmacella Schmidt, 1870, a demosponge that encrusts the surface of reef-forming glass sponges. Using a remotely operated vehicle, samples of an encrusting sponge with three color morphotypes (yellow, white, and mauve) were collected from the northern reef complex of the HSQCS-MPA. Spicule and DNA analyses of COI sequences revealed the white morphotype to be distinct from the previously described species, D. austini Lehnert, Conway, Barrie & Krautter, 2005. Comparisons with other Desmacella samples collected from other regions in British Columbia waters since 1976 confirmed this to be a new species, which we describe here as Desmacella hyalina sp. nov. We also mapped the spatial distribution of the color morphotypes on the reefs and found that Desmacella spp. formed nearly 20% of live sponge cover at some sampling sites indicating its potential importance in the reefs. Our results expand on knowledge of the diversity of sponge epibionts in glass sponge reefs and highlight the importance of understanding cryptic species diversity especially for future monitoring in marine protected areas.