Description of a new deep-water dogfish shark from Hawaii, with comments on the Squalusmitsukurii species complex in the West Pacific.

Charles F Cotton,Amber Koch,R Dean Grubbs,Toby S Daly-Engel,James M Anderson

doi:10.3897/zookeys.798.28375

Abstract

Dogfish sharks of the genus Squalus are small, deep-water sharks with a slow rate of molecular evolution that has led to their designation as a series of species complexes, with low between-species diversity relative to other taxa. The largest of these complexes is named for the Shortspine spurdog (Squalusmitsukurii Jordan & Snyder), a medium-sized dogfish shark common to warm upper slope and seamount habitats, with a putative circumglobal distribution that has come under investigation recently due to geographic variation in morphology and genetic diversity. The Hawaiian population of Squalusmitsukurii was examined using both morphological and molecular analyses, putting this group in an evolutionary context with animals from the type population in Japan and closely-related congeners. External morphology differs significantly between the Hawaiian and Japanese S.mitsukurii, especially in dorsal fin size and relative interdorsal length, and molecular analysis of 1,311 base pairs of the mitochondrial genes ND2 and COI show significant, species-level divergence on par with other taxonomic studies of this genus. The dogfish shark in Hawaii represents a new species in the genus, and the name Squalushawaiiensis, the Hawaiian spurdog, is designated after the type location.

Highlights

Deep-water sharks like the dogfish sharks (Squaliformes, Squalidae) and the gulper sharks (Squaliformes, Centrophoridae) have proven confounding groups for systematists to resolve due to their highly conserved morphology, wide ranges, and patchy, infrequently-sampled distributions (Veríssimo et al 2014; Cotton and Grubbs 2015; Veríssimo et al 2017; Daly-Engel et al submitted)
Genetic examination of 130 tissue samples from 25–30 Squalus dogfish species has shown that S. cf. mitsukurii from Hawaii clustered closely with S. nasutus Last, Marshall, & White from Australia, S. japonicus Ishikawa from Japan and elsewhere, and S. mitsukurii from Japan (Daly-Engel et al Submitted), and well apart from other congeners in the region; the current analysis focuses on these species
Mitochondrial DNA sampled from four conspecific shark taxa in the genus Squalus from the Central and West Pacific

Summary

Introduction

Deep-water sharks like the dogfish sharks (Squaliformes, Squalidae) and the gulper sharks (Squaliformes, Centrophoridae) have proven confounding groups for systematists to resolve due to their highly conserved morphology, wide ranges, and patchy, infrequently-sampled distributions (Veríssimo et al 2014; Cotton and Grubbs 2015; Veríssimo et al 2017; Daly-Engel et al submitted). Recent years have shown that DNA sequencing in conjunction with morphological analyses is an effective approach for elucidating the alpha taxonomy of deep-water sharks (Avise 2004; Ward et al 2005; Last et al 2007c; Ebert et al 2010; Veríssimo et al 2014; Pfleger et al 2018). Taxonomic delineation that incorporates DNA analysis has often relied upon consistencies among within- and between-species divergences in the barcoding gene (COI), as measured by percent nucleotide sequence variation (Avise 2004; Ward et al 2005; Naylor et al 2012). A number of investigators have found the more-rapidly evolving ND2 gene to be an effective genetic marker for estimating both inter- and intraspecific variation in dogfish sharks (Veríssimo et al 2010; Naylor et al 2012; Veríssimo et al 2017; Pfleger et al 2018)

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Discussion

Conclusion