Haliclona (Flagellia) Van Soest 2017, sp. nov.

Subgenus Haliclona (Flagellia) Van Soest, 2017 Haliclona (Flagellia) xenomorpha sp. nov. urn:lsid:zoobank.org:act: 83A1F469-C799-4D43-865F-C9D9C593E7BA Type specimens. Holotype: ARC 81426, north of Brion Island, Canada (48.0568N, 61.50641W), 69 m depth, DFO CCGS Teleost RV Survey, September 17, 2018. Paratypes: ARC 81427, central Gulf of St. Lawrence, Canada (47.9871N, 63.0248W), 63.5 m depth, DFO CCGS Teleost RV Survey, September 13, 2018; ARC 81428, East of Cap d’Espoir, Canada (48.3587N, 63.6829W), 49 m depth, DFO snow crab survey aboard the Jean Mathieu, August 17, 2018. External morphology. (Fig. 1 A–D). Massively encrusting with raised oscula. The sponge is very friable and is thus often broken into pieces upon collection. The largest specimens are over 10 cm in diameter, but no consistent growth form is apparent. Larger specimens are often seen fully encrusting small pebbles and may have shell fragments incorporated into the tissue. The surface is generally smooth in more intact specimens, while fragments are more irregular and porous. In less damaged specimens, a fine transparent mesh covers the surface, but this often collapses after collection. Oscula are <0.5 cm wide and are raised above the surrounding tissue. Below the surface, the sponge tissue is irregularly punctate. The consistency of large pieces is firm, compressible, but very brittle if pressure is applied, resulting in small crumbled pieces. The colour is pale yellow to light brown, with some specimens appearing pinkish. Skeleton. (Fig. 1 E, F). Confused, with a loose reticulation of paucispicular tracts which are irregularly connected by single spicules. Thick and thin oxeas do not appear to be localized in the skeleton. There is no surface specialization of spicules, but a layer of thick spongin is present at the surface in undamaged specimens. Flagellosigmas and sigmas are found throughout the choanosome, with regular sigmas often occurring in groups, especially evident near canal openings. Spicules. (Fig. 2 A–J). Megascleres are oxeas in two size categories. Thick oxeas are often slightly bent and have sharp tapered points, 250– 271 –298 × 12– 13 – 17 µm. Thin oxeas are similarly shaped but with sharper ends which taper further along the shaft, 183– 219 –245 × 3.6– 6.1 –9.0 µm. Microscleres are flagellosigmas in two size categories and abun- dant normal sigmas. The distinctive thick category of flagellosigmas consists of spicules with curved ends that may be steeply curved (Fig. 2 C, D), branched into two or more points (Fig. 2 D–F), or not curved at all with endings pointing outwards, length of long endings 56– 68 –108 μm, of short endings 46– 57 –73 μm, width 58– 72 –98 μm, thickness 6.5– 9.0 –13 μm. Normal flagellosigmas are ovoid with widely curved ends, but are variable in size and overall shape, length of long endings 32– 51 –95 μm, of short endings 26– 42 –56 μm, width 40– 58 –77 μm, thickness 2.7– 4.1 –5.6 μm. Regular sigmas are variable in size, and have incurved apices, 39– 62 – 82 µm in length and 3.2– 5.1 – 7.1 µm thick. In some specimens thick flagellosigmas may appear more sigma-like with ends of similar lengths and a crescent shape, but these spicules may also have irregular ends (Fig. 2 F). Distribution and ecology. Several specimens were collected along the American Bank near the Gaspé Peninsula and southern fringe of the Laurentian Channel. The holotype was collected north of Brion Island (Magdalen Island archipelago) near the shelf edge and was encrusting a rock. The species was collected at depths ranging from 41– 89 m. Multiple specimens were collected in single trawls (Fig. 1 D), but only single individuals from trawls were retained for taxonomic analysis. Etymology. From the Greek xénos meaning alien or strange and morphḗ meaning shape, in reference to the thick and often irregular flagellosigmas. These spicules also resemble the derelict spacecraft from the 1979 film Alien directed by Ridley Scott, and the name pays homage to the titular antagonist of the series. Discussion. Global representative members of the subgenus are reviewed in Van Soest (2017). Most species in the subgenus are thin and encrusting, however, H. (F.) indonesiae Van Soest, 2017 and H. (F.) edaphus De Laubenfels, 1930 have plate-like growth forms and H. (F.) hamata (Thiele, 1903) has an erect, arborescent habit. Haliclona (Flagellia) porosa (Fristedt, 1887) is most similar to H. (F.) xenomorpha sp. nov. and is described as attaining a large size of up to 9 cm in diameter by Fristedt (1887, as Desmacella porosa) and larger than 5.5 cm broad and 2 cm high by Lambe, (1896, as Gellius flagellifer Ridley & Dendy, 1886). An Arctic specimen of H. (F.) porosa reported by Dinn & Leys (2018) has a soft consistency and has a thick transparent surface whereas H. (F.) xenomorpha sp. nov. specimens from the Gulf of St. Lawrence have dense tissue and are uniform in colour with a very thin transparent surface. The congeneric H. (F.) porosa has been previously reported from the Gulf of St. Lawrence (Lambe 1896) and further north in Baffin Bay/ Davis Strait (Fristedt 1887; Dinn & Leys 2018), usually in deep water.Drawings of specimens and spicules by Lambe (1896) are reminiscent of H. (F.) xenomorpha sp. nov., however, the presence of rare, small (ca. 26 µm) normal sigmas and no mention of thick flagellosigmas suggest that the species are indeed very different. Specimens of Haliclona (Flagellia) xenomorpha sp. nov. collected from the Gulf of St. Lawrence also have abundant normal sigmas that vary considerably in size, a clear departure from H. (F.) porosa (Van Soest 2017). Flagellosigmas of H. (F.) porosa can be much longer and wider, extending beyond 100 µm for short and long endings and overall width (Van Soest 2017), but never attain a similar thickness to the flagellosigmas of H. (F.) xenomorpha sp. nov. Additional spicule measurements of an Arctic specimen identified as H. (F.) porosa by Dinn & Leys (2018) are reported here (Table 1). The unique features of Haliclona (Flagellia) xenomorpha sp. nov. are the presence of thick flagellosigmas and two categories of oxeas. The thickness of the flagellosigma spicules exceed, and in most cases more than double the maximum thickness of spicules from other members of the genus (Van Soest 2017). The flagellosigmas in H. (F.) xenomorpha sp. nov. reach a maximum thickness 13 µm, while flagellosigmas of H. (F.) porosa reach a maximum thickness of 5 µm reported by Van Soest (2017), but up to 6.3 µm in an Arctic specimen (Dinn & Leys 2018). Thick flagellosigmas are common in the skeleton, and are thus considered as a second size category, though there may be intermediately sized flagellosigmas which are difficult to place in either size category. The consistently irregular endings of the thick flagellosigmas are also a defining character of the species.

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