Trypanosoma rangeli, Tejera, 1920

Molinari, Jesús & Moreno, S. Andrea, 2018, The correct subgeneric name of Trypanosoma rangeli Tejera, 1920 (Euglenozoa: Trypanosomatidae), a human-infective endoparasite of neotropical mammals, Zootaxa 4418 (1), pp. 98-100 : 98-99

Subgeneric nomenclature of Trypanosoma rangeli

“In the genus group, two or more available names established with the same spelling are homonyms” [Code, Article 53.2], and “A junior homonym … must be rejected and replaced either by an available and potentially valid synonym … or, for lack of such a name, by a new substitute name … with its own author and date” [Code, Articles 60.1, 60.3].

Surprisingly, trypanosome researchers have failed to notice that: 1) the subgeneric name Tejeraia Añez, 1982 is a junior homonym of the generic name Tejeraia Díaz-Ungría, 1963 , in use for Tejeraia mediospiralis (Molin, 1860) (Nematoda: Secernentea: Spirurida : Spirocercidae ), a parasitic roundworm infecting the stomach wall of the neotropical rodent, Cuniculus paca (Linnaeus, 1776) (Mammalia: Rodentia : Cuniculidae ) ( Díaz-Ungría 1963; Smales 2004); and 2) based on the provisions of the Code (Articles 53.2, 60.1, 60.3), Aneza Özdikmen, 2009 is the mandatory substitute name of Tejeraia Añez, 1982 .

“If there is in the original publication itself … clear evidence of an inadvertent error, such as a lapsus calami or a copyist’s or printer’s error, it must be corrected” [Code, Article 32.5.1]. The genus-group name Aneza is a patronym “dedicated to N. Anez who is the author of the preexisting subgenus Tejeraia ” ( Özdikmen 2009). It was constructed by adding the suffix -a instead of the usual -ia to Anez (= Añez). The original publication ( Özdikmen 2009) contains numerous mistakes and inconsistencies (e.g., “ Tripanosoma ” instead of Trypanosoma , “N. Anez” instead of N. Añez, referring to Protozoa as “animals”, use of the suffix -ia for other substitute names), which represent a latent temptation for subsequent authors to emend [Code, Article 33.2] Aneza by replacing -a with -ia.

The spiny subject of emendation of scientific names [Code, Article 33.2.3], which in countless cases has resulted in unjustified changes, has been lucidly discussed elsewhere ( Moore et al. 1942; Dubois 2007). Two conclusions can be reached. First, any word (e.g., Aneza ) may be used for a genus-group name provided that: a) it contains two or more letters, the first one in upper-case, all of them taken from the Roman alphabet; b) it is printed in a type-face font (normally italics) different from that of the text; and c) it is treated as a Latin noun in the nominative singular [Code, Appendix B6, Articles 11.2, 11.8]. Second, an ‛inadvertent error’ [Code, Article 32.5.1] must be of such nature that it is equally evident to all readers, which certainly is not the case of Özdikmen’s (2009) work. Hence, Aneza is a valid genus-group name that shall not be emended.

Should the name combination Trypanosoma (Aneza) rangeli be used?

Because from the nomenclatural perspective T. (Herpetosoma) rangeli Tejera, 1920 and T. (Aneza) rangeli Tejera, 1920 are available name combinations, the decision on which one to use does not depend on the Code, but on evolutionary and taxonomic considerations. Phylogenetic studies based on genetic markers (e.g., Stevens et al. 1999; Hughes & Piontkivska 2003; Maia da Silva et al. 2004; Fraga et al. 2016) have shown T. rangeli , and members of the subgenus Herpetosoma Doflein, 1901, to be more closely related to T. cruzi than to salivarian trypanosomes (i.e., the salivarian condition of T. rangeli most likely is independently evolved). These studies have also shown that Herpetosoma (subsuming T. rangeli ) is polyphyletic, with T. rangeli being more closely related to T. cruzi than to Trypanosoma lewisi (Kent, 1880) .

The type species of the subgenus Herpetosoma is precisely T. lewisi , an obligatory endoparasite of rodents (though it sometimes infects humans) transmitted by rat fleas ( Lin et al. 2015). The polyphyly of Herpetosoma (subsuming T. rangeli ) motivated Stevens et al. (1999; see also Fraga et al. 2016) to propose the subgenus to be ‛discontinued’ owing to ‛lack of evolutionary and taxonomic relevance’. This conclusion appears to be based on the perception that all species originally assigned to a genus (or subgenus) are its inseparable members. In fact, the type species is the only indispensable member of supraspecific taxa [Code, Article 61.1]. Other species can be and customarily are transferred among genera and subgenera based on evolutionary and taxonomic considerations, the most important of which is avoiding polyphyly.

Based on current phylogenetic evidence, T. rangeli must be excluded from the therefore monophyletic Herpetosoma. This subgenus (excluding T. rangeli ) designates a deep-rooted, thus evolutionarily and taxonomically relevant clade within the genus Trypanosoma . Regarding T. rangeli , users of trypanosome taxonomy have two options for its subgenus: T. (Schizotrypanum) rangeli Tejera, 1920 , if the close phylogenetic relationship of the species with T. cruzi needs to be emphasized (see Stevens & Brisse 2004); or T. (Aneza) rangeli , if the species is judged to be sufficiently divergent from other neotropical trypanosomes (see Gibson 2016).