Resurrection and redescription of Squalus suckleyi (Girard, 1854) from the North Pacific, with comments on the Squalus acanthias subgroup (Squaliformes: Squalidae)

Abstract

A taxonomic re-evaluation of the status of the North Pacific Squalus suckleyi (Girard, 1854) combining the use of meristic, morphological and molecular data reveal this species to be clearly distinct from the widespread Squalus acanthias (Linneaus, 1758). Differences in the external morphology between S. acanthias and S. suckleyi are subtle and are likely to be masked by intraspecific variation within individuals. However, we found S. suckleyi to differ from S. acanthias based on the following morphological and meristic characteristics: a short, broadly-rounded to acute snout; first dorsal-fin midpoint more posterior to pectoral-fin insertion; pelvic-fin origin closer to second dorsal fin than first dorsal fin; total vertebral counts average 99 (97–106). Molecular analysis of approximately 650 bp of the CO1 mitochondrial gene (DNA barcode region) showed separation of S. suckleyi and S. acanthias into two distinct genetic clades with 98% bootstrap support. Within species genetic diversities were 0.109±0.036% and 0.176±0.041% for S. suckleyi and S. acanthias respectively; between species diversity was 5– 6 fold greater at 0.765+0.307%. Squalus suckleyi is thus resurrected and a neotype for this endemic North Pacific Squalus species is designated.

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

“…But a lack of shared haplotypes, plus variation between species that is generally an order of magnitude higher than variation within species, is a consistent pattern reported in many elasmobranch species descriptions (Spies et al 2006; Ward et al 2007; Veríssimo et al 2014; Daly-Engel et al 2018; Pfleger et al 2018). Among the four closely-related species we studied, average concatenated sequence divergence between species (1.045±0.183%) was nearly fourteen times the average within-species divergence (0.075±0.026), and therefore consistent with species-level differences reported for other elasmobranchs, including Squalus (Ward et al 2007; Ebert et al 2010; Viana et al 2016). …”

“…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). Findings from several studies have shown a mix of low genetic distances between well-established morphological species, and deep genetic splits between animals identified as conspecifics (Daly-Engel et al 2010; Veríssimo et al 2017; Daly-Engel et al 2018; Pfleger et al 2018; Daly-Engel et al submitted).…”

“…Such complexes are not unusual in nature, having been observed across a variety of phyla from insects (Perring 2001) and nematodes (Chilton et al 1995) to bony fishes (Barluenga and Meyer 2004), and have been shown to harbor “cryptic” diversity not always apparent from morphology alone (Daly-Engel et al Submitted). Taxonomic reevaluation of Squalus in the Indo-Pacific and elsewhere has revealed many undescribed species that were historically lumped together under a single name (Ward et al 2007; Naylor et al 2012; Viana et al 2016; Pfleger et al 2018): although the relatively shallow spiny dogfish Squalusacanthias Linnaeus comprises just one wide-ranging species apart from the North Pacific (Ebert et al 2010; Veríssimo et al 2010), we now know that both the Shortspine dogfish shark Squalusmitsukurii Jordan & Snyder and the shortnose dogfish shark Squalusmegalops Macleay comprise global species complexes (Veríssimo et al 2010; Naylor et al 2012; Veríssimo et al 2017; Pfleger et al 2018; Daly-Engel et al Submitted). …”

Who let the dogfish out? A review of management and socio-economic aspects of spiny dogfish fisheries

“…These results are in accordance with reported differences in life histories between the North Pacific and Atlantic spiny dogfish populations. These differences in genetic and life histories led to recent resurrection of the North Pacific spiny dogfish (Squalus suckleyi) as a species different from Squalus acanthias (Ebert et al 2010). The S. suckleyi reaches sexual maturity between 29-35 years and 92-100 cm in total length (TL) for females, and between 16-19 years and 70-80 cm TL for males, with maximum reported size and ages of 130 cm TL and 81 years (Ketchen 1972(Ketchen , 1975Jones and Geen 1977;Saunders and McFarlane 1993).…”

Exposure to Acute Severe Hypoxia Leads to Increased Urea Loss and Disruptions in Acid-Base and Ionoregulatory Balance in Dogfish Sharks (Squalus acanthias)

“…Note that we retain the name Squalus acanthias suckleyi while recognizing that Ebert et al (2010) have recently proposed that these northeast Pacific elasmobranchs are a separate species (Squalus suckleyi) distinct from Squalus acanthias. In series 1 and 2, sharks were caught off the west coast of Vancouver Island, near Bamfield, British Columbia, Canada, and were held in a large indoor tank containing approximately 150,000 L of circulating, well-aerated Bamfield Marine Station seawater (12ЊC, 30 ppt salinity) for approximately 1 mo prior to experimentation.…”