Plocamionida microcionides var. achelata Topsent, 1928

Van Soest, Rob W. M., 2024, Correcting sponge names: nomenclatural update of lower taxa level Porifera, Zootaxa 5398 (1), pp. 1-122 : 72

Plocamionida microcionides var. achelata Topsent, 1928

Plocamionida microcionides var. achelata Topsent, 1928: 304 (no illustrations).

The variety was erected by Topsent for several specimens collected north of the Azores by the Prince Albert 1 er Monaco Cruises Stat. 1420, 42.9°N 28.5°W, depth 2460 m, and Stat. 3144, 37.675°N 25.9667°W, depth 919 m (syntypes in MOM, with slides in Paris registered as MNHN DT 1154). It has similar spicular characters as the typical variety of Plocamionida microcionides ( Carter, 1876: 390 as Hymeraphia , from Cape St. Vincent, Portugal, ‘Porcupine’ Stat. 25, 37.1833°N 9.1167°W, depth 684 m, presumed type slide BMNH 1954.3.9.152), but it lacks the chelae. The variety differs furthermore from the type of the typical variety in spicule lengths and thickness: Carter’s description lists styles of 720 x 11 µm, acanthostyles 115 x 7 µm, acanthostrongyles 72 x 3.5, but the tornotes were apparently overlooked by Carter. Topsent described var. achelata as having tornotes of 385–453 x 10–11 µm, styles 770– 1000 x 23–25 µm, acanthostyles 195–265 x 10–11 µm and acanthostrongyles of 110–125 x 10–11 µm, considerably more robust than Carter’s material. However, Stephens (1921: 58) re-examined Carter’s type slides and found the tornotes of 275–400 µm in the type and her own specimens from Irish deep Lophelia reefs combined. Stephens reported the size of the other spicules to be in excess of those of Carter’s type: styles 400– 2300 x 30 µm, acanthostyles 150–250 x 13 µm, acanthostrongyles 90–125 x 8–10 µm. These spicule data thus overlap between the varieties. Chelae in the typical variety are 25 µm ( Carter 1876), 24–27 µm ( Stephens 1921). Topsent (1904, 1928) mentioned the occurrence of the typical variety in the material of several other Prince Albert 1 er Monaco Cruises stations, misidentified as Plocamionida ambigua ( Bowerbank, 1866) : Stat. 702 (39.3556°N 31.0981°W, depth 1350 m) and 1052 (65.6833°N 9.5°W, depth 440 m). Reveillaud et al. (2011: 9) suggested the var. achelata to be a possible separate species. In view of the near-sympatric occurrence in the North Atlantic of both varieties and because several specimens from disparate depths of the two have been found, I propose to follow Reveillaud et al. by elevating the var. achelata to species, to be named Plocamionida achelata Topsent, 1928 .