Taxonomic inflation or hidden diversity: unveiling the fact surrounds Lytocestus indicus (Cestoda: Caryophyllidea).

Abstract

The tapeworms belonging to the order Caryophyllidea (Platyhelminthes, Eucestoda) represent a widespread group of intestinal parasites found in cypriniform and siluriform fishes. This group comprises four families (Balanotaeniidae, Capingentidae, Caryophyllaeidae, Lytocestidae), 42 genera and approximately 130 described species. Additionally, over a hundred new taxa have been reported from India. While many of these taxa are endemic and have unique evolutionary importance, a considerable number of putative new taxa were also invalidated because the quality and reliability of the published data did not meet the requirements. Various researchers have synonymised 28 species into a single representative, Lytocestus indicus (Moghe, 1925) Woodland, 1926. Consequently, L. indicus was chosen as a model organism to investigate whether there is taxonomic inflation or hidden diversity. Newly collected specimens of L. indicus were subjected to various fixatives for morphological assessment, and hologenophores of the same were obtained to determine whether true variations exist in their genotype or if they are merely fixation-induced variations. Despite morphological variations associated with fixation, molecular data indicated that they were indeed the same specimens. The taxonomic status of 43 new taxa was critically evaluated, with most of them tentatively synonymised with L. indicus. Others were also found to be conspecific with L. indicus but were classified as unavailable names based on their first description in unpublished dissertations.