Iophon frigidus var. gracilis Hentschel, 1929

Van Soest, Rob W. M., 2024, Correcting sponge names: nomenclatural update of lower taxa level Porifera, Zootaxa 5398 (1), pp. 1-122 : 69

Iophon frigidus var. gracilis Hentschel, 1929

Iophon frigidus var. gracilis Hentschel, 1929: 884 (no illustration).

The variety described by Hentschel from North Spitsbergen, 1 mile N of Ross Island, 80.8°N 20.3833°E, depth 85 m (holotype in ZMH), and the White Sea, 66.6°N 41.3833°E, depth 54 m (collected by the ‘Deutschen Expedition in das N̂rdliche Eismeer im Jahre 1898’) was erected primarily on the basis of a single character: the possession of bipocillae, which were lacking in the typical variety described by Lundbeck (1905: 183) from the East Greenland shelf, 72.4167°N 19.55°W, depth 256 m, syntypes ZMUC DEM 18 and 26), and by Levinsen (1887: 360 as Esperella picea ) from the Kara Sea, and by Hentschel (1916: 10) from Spitsbergen. Further differences were more subtle: slightly smaller megascleres and anisochelae with a narrow upper half distinct from the broader shape in the typical variety.

Burton (1932: 348) discussed the global diversity of species of Iophon and in a footnote he synonymized I. frigidus , (ignoring I.f. var. gracilis ), and I. dubius Hansen, 1885 with I. piceum ( Vosmaer, 1885) citing observations of the variability in spiculation in species from the southern oceans [ I.radiatum Topsent, 1901 and I. proximum ( Ridley, 1881) ] as evidence for this conclusion.

Koltun (1959: 151) largely followed Burton’s example but proposed a more differentiated widespread Arctic species Iophon piceum five ‘subspecies’. Of these, he confirmed that Iophon frigidus and the variety I. f. var. gracilis were synonymous with I. piceum dubium ( Hansen, 1885) rather than with the typical subspecies. Remarkably, he proposed a subspecies Iophon piceum abipocillum , for a specimen which lacked bipocillae similar to I. frigidum . Koltun’s proposed diversity of largely sympatric ‘subspecies’ is not consistent with current hypotheses about subspecies.

I am not convinced that Iophon piceum is the senior synonym of I. frigidum , as no comparative studies have been published. Burton’s and Koltun’s opinions are not sufficiently underbuilt.

If I. frigidum is a distinct species, I.f. var. gracile cannot be synonymized and prudence dictates a possibly temporary elevation in rank to species level, since the difference (possession of bipocillae) precludes synonymy. Accordingly, I propose to name the present variety Iophon gracile Hentschel, 1929 .