Shedding light on the Chimaeridae taxonomy: the complete mitochondrial genome of the cartilaginous fish Hydrolagus mirabilis (Collett, 1904) (Holocephali: Chimaeridae)

Abstract

Cartilaginous fish are fascinating taxa, present in the folklore and art of many different cultures. Moreover, they display several unique anatomical, physiological, molecular, and behavioral characteristics making them extremely interesting from a biological perspective. Nevertheless, some crucial knowledge gaps remain, including phylogenetic relationships among extant species. Here, we produced the complete mitogenome sequence of the large-eyed rabbitfish, Hydrolagus mirabilis (Chimaeriformes). The complete mitogenome is 19,435 bp long and shows the same overall content, i.e. 13 protein-coding genes, 22 transfer RNA, and two ribosomal RNA genes, as all other examined Chondrichthyan mitogenomes. Phylogenetic reconstructions including 12 Holocephalan and three outgroup Elasmobranch mitogenomes place the H. mirabilis within the family Chimaeridae but revealed paraphyletic Hydrolagus and Chimaera, in line with a previous study, highlighting the importance for collecting additional molecular data to improve phylogenetic reconstruction in this group of vertebrates.

The Paleozoic assembly of the holocephalian body plan far preceded post-Cretaceous radiations into the ocean depths

“…Chimaeridae includes species traditionally placed in the genera Chimaera and Hydrolagus (Figure 2; Figure S3). However, as in previous studies we fail to resolve the reciprocal monophyly of these genera (Figure S3) [34,49,75,76]. Instead, we resolve four major clades in Chimaeridae, two of which necessitate the resurrection of available generic names.…”

“…We resurrect two genera, Bathyalopex and Phasmichthys, for clades in Chimaeridae that diverged from recognized lineages in the Jurassic and Cretaceous (Figure 2). This clarifies the systematics of living holocephalians, particularly confusion surrounding the classification of species traditionally placed in the chimaerid genera Chimaera and Hydrolagus [75,76]. Our placement of species in the genera †Ischyodus and †Elasmodectes on the stems of two lineages in crown Holocephali with strong nodal support across different analyses also provides a starting point for a reinterpretation of the fossil record of post-Paleozoic holocephalian fishes, which consists almost entirely of isolated tooth plates [83][84][85][86][87][88][89][90][91], on the basis of skeletal remains.…”

A mitochondrial genome assembly of the opal chimaera, Chimaera opalescens Luchetti, Iglésias et Sellos 2011, using PacBio HiFi long reads

“…However, as previously observed (Gomes-dos-Santos et al. 2020 , 2021 ), neither Hydrolagus nor Chimera genera were recovered as monophyletic, which highlights the importance of revising the taxonomy. Indeed, previous authors had already suggested that the distinction between Chimera and Hydrolagus based on the presence or absence of a notch separating the anal from the caudal fin, respectively, needed revision (Didier et al.…”

The complete mitogenome of the Atlantic longnose chimaera Rhinochimaera atlantica (Holt & Byrne, 1909)

“… 2010 ), MW029477 ( H. mirabilis ) (Gomes-dos-Santos et al. 2021 ), HM147139 ( H. lemures ) (Inoue et al. 2010 ), KP006329 ( C. phantasma ) (unpublished), KP006330 ( R. africana ) (unpublished), HM147141 ( R. pacifica ) (Inoue et al.…”