Taxonomy is important. And it is important to name organisms correctly to avoid confusion. Next question is what is “correctly”. Two main approaches are possible: go by the rules and go by the usage. The rules are clear: the name in the original description has the priority, unless later revisions change the name; this includes spelling versions. The usage is clear too, since 1989 every publication referenced in WoS and Biological Abstracts call the famous Baikal copepod Epischura baicalensis and no other way.
Recently I noticed that, current usage of “Epischura baicalensis” notwithstanding, several taxonomic databases, including WoRMS, IUCN Red List and EoL, as well as Wikipedia, list our beloved organism as “Epischura baikalensis“. I e-mailed curators of these resources raising a concern about misnomer and, thanks to IUCN’s Janet Scott, the truth has been established. An inconvenient truth perhaps. “Epischura baikalensis” is not a misnomer, “Epischura baicalensis” is. Sars (1900) described the Baikal species of Epischura as Epischura baikalensis G.O. Sars n.sp. and this nomen is to be used in all publications.
Now, proponents of “baicalensis” might argue that Sars violated the rules of usage of Latin in taxonomic names. Indeed, Baikal should be spelled Baical according to formal Latin rules (the Empire’s soldiers never reached that far east, so we do not know how Romans would have called the Lake). Yet, there is another rule: if the name is based on an existing proper name in languages other than Latin, the native and not Latin spelling should be used. Already at Sar’s time the spelling Baikal prevailed in English literature and hence the k in baikalensis.
Figure 1. Epischura baiKalensis
Figure 2. Sars, 1900.
In addition to this post, I made notes in both the English and the Russian wikipedia pages on E. baikalensis.
G. O. Sars (1990). “On Epischura baikalensis, a new Calanoid from Baikal Lake”. Annuaire du Musée Zoologique de L’Académie Impériale des Sciences de St.-Pétersbourg vol. V, pp. 226-240.