Classification of Isodictya rigida by H.M. Reiswig

Identification of sponge fragment provided by G. Yahel, 15 June 2004, H. M. Reiswig, 26 July 2004 Label: “Iophon? 04.06.03 Race Rocks; Formalin 4%” First conclusion was tentative: Dictyonella sp., and unsatisfying since no species of this genus was known in B.C. waters; structure and body was more like Isodictya, but the rare isochelae spicules of that genus were not found in preliminary analysis.  After discussion with Bill Austin on Barkley Sound Cruise, I made a thorough examination of thick sections and found the rare isochela spicules, mainly in the atrial walls (older tissues).  I then made new spicule preparations of that region and was able to easily find 50 of the ‘rare’ spicules for measurement.

Revised conclusion (now with high confidence): Isodictya rigida (Lambe, 1893) [Originally Neoesperiopsis rigida; the same in Austin & Ott, 1997 (Kozlov)] Class: Demospongiae; Order: Poecilosclerida; Suborder: Mycalina;  Family: Isodictyidae; Genus: Isodictya Bowerbank, 1864