On the uncertainty beneath the name Oithona similis Claus, 1866 (Copepoda, Cyclopoida)

Abstract

The marine cyclopoid Oithona similis sensu lato Claus, 1866, is considered to be one of the most abundant and ubiquitous copepods in the world. However, its minimal original diagnosis and the unclear connection with its (subjective) senior synonym Oithona helgolandica Claus, 1863, may have caused frequent misidentification of the species. Consequently, it seems possible that several closely related but distinct forms are being named Oithona similis or Oithona helgolandica without explicit and accurate discrimination. Here the current situation concerning the correct assignment of the two species is revised, the morphological characters commonly used to identify and distinguish each species are summarized, and the nomenclatural implications of indiscriminately using these names in current taxonomic and ecological practice is considered. It is not intended to upset a long-accepted name in its accustomed meaning but certainly the opposite. “In pursuit of the maximum stability compatible with taxonomic freedom” (International Commission of Zoological Nomenclature), we consider that reassessment of the diagnostic characters of Oithona similis sensu stricto cannot be postponed much longer. While a consensus on taxonomy and nomenclatural matters can be attained, we strongly recommend specifically reporting the authority upon which the identification of either Oithona similis s.l. or Oithona helgolandica s.l. has been accomplished.

Composition, Spatial Distribution, and Trophic Structure of the Zooplankton Community in San Jorge Gulf, Southwestern Atlantic Ocean

“…The copepod assemblage was dominated by medium-sized adult copepods Ctenocalanus vanus (36%), followed by copepodites stages (29%) of Clausocalanidae (C. vanus, Drepanopus forcipatus and Clausocalanus brevipes) and Paracalanus parvus. Adults of P. parvus, the ubiquitous Acartia tonsa, and the small-sized cyclopoid Oithona helgolandica (= O. similis; Cepeda et al, 2016) contributed 8%, 5%, and 3% to the total zooplankton community, respectively. Large-sized individuals of the family Calanidae (adults of Calanoides carinatus and Calanus australis and their copepodites) were the least abundant, representing less than 1% of zooplankton composition.…”

Large-scale geographic patterns of pelagic copepods in the southwestern South Atlantic

“…Except for data reported by Goberna (1986;Mazzochi andIanora (1991), the remaining data (83%) were produced by different researchers at the Zooplankton Laboratory of INIDEP, who employed similar identification and laboratory protocols. The scientific nomenclature of the species was updated following WoRMS (2018) and Cepeda et al (2016). To relate copepods' distributions to water masses, we employed historical hydrographic data retrieved from the World Ocean Atlas (https://www.nodc.noaa.gov/OC5/woa18/woa18data.html).…”

Investigating population‐scale allelic differential expression in wild populations of Oithona similis (Cyclopoida, Claus, 1866)

“…Particularly, marine species populations belonging to plankton face a large panel of physico-chemical changes in open ocean, (Guinder & Molinero, 2013;Pelejero, Calvo, & Hoegh-Guldberg, 2010) and gene expression variations have been observed in several studies (Lauritano, Procaccini, & Ianora, 2012;Salazar et al 2019). However, taxonomic identification (Cepeda, Sabatini, Scioscia, Ramírez, & Viñas, 2016), DNA and mRNA extraction of small marine eukaryote species due to their complex genomes (Bucklin et al, 2018) still constitute an obstacle to conduct proper studies focusing on gene expression and selection in natural populations.…”