Introduction Caloneis egena is a species of diatom originally described from Campeche Bay (Mexico) that is regarded as cosmopolitan, with several reports from the Pacific region. Methods A strain of diatom from the genus Caloneis was isolated from the Gulf of Tomini, Sulawesi (Indonesia). It was subjected to an integrated approach combining microscopy, genomic analyses, and phylogeny. Results Although looking similar to C. egena , the strain from Tomini was found to be a new species, hereby described as Caloneis paraegena sp. nov. The complete mitochondrial and plastid genomes were sequenced and annotated and represent the first organellar genomes made available for the genus Caloneis . The multigene phylogeny inferred from these results positions C. paraegena as sister to a clade that associates Caloneis fontinalis , C. silicula , and C. lewisii . Discussion A survey of the literature dedicated to C. egena led to questioning its distribution, suggesting that records from the Pacific region might, in fact, represent C. paraegena based on morphology. Because of the absence of a molecular reference for C. egena , the exact relationship between these two species remains to be verified.
Arsad et al. (2026) studied this question.