Afrindella

The genus Afrindella was erected by Annandale in Annandale & Kemp (1912) as a subgenus to Plumatella. It is based on the idea that in certain species, when the polypide is retracted, a pair of slightly stiffened regions of the tentacle sheath come together like valves to form a flat barrier closing off the orifice. As the type species for Afrindella Annandale designated Plumatella tanganyikae, by which he probably meant Plumatella bombayensis. I believe this because at that time the ZSI had four specimens of P. bombayensis, all labeled as P. tanganyikae, and Annandale considered the two species indistinguishable (Annandale & Kemp 1912). Also included in the Afrindella subgenus were P. philippinensis Kraepelin, 1887, P. testudinicola, and later P. persica, now recognized as P. casmiana. Borg (1936) objected to the subgenus Afrindella because it was based on just a single feature, the closure of the orifice. However, Marcus (1942) elevated Afrindella to the level of a full genus and expanded the definition to include a strong and rigid chitinous ectocyst, tubules lying close to the substrate with little incrustation, and the lack of upright branches. Marcus made it clear that the genus did not imply any phylogenetic significance but was simply a way of grouping species with similar features. The concept of Afrindella was fully endorsed by Wiebach (1970, 1974, 1975). However, the features Marcus ascribed to Afrindella are variable. In P. bombayensis and P. casmiana the ectocyst can be rigid, dark and clear, but it can also be thin, fragile and heavily incrusted. In the only known specimens of P. tanganyikae and P. testudinicola the ectocyst is not even very strong or chitinous. The mechanism by which the orifice is closed has not been studied in detail but appears to be a simple consequence of heavy sclerotization of the ectocyst. While I recognize the appeal of breaking up the large genus Plumatella, it seems unwise to establish a genus on features that are so inconsistent.