Thursday, December 14, 2017

[Ichthyology • 2017] Pseudoliparis swirei • A Newly-Discovered Hadal Snailfish (Scorpaeniformes: Liparidae) from the Mariana Trench

Pseudoliparis swirei
Gerringer, Linley, Jamieson, Goetze & Drazen, 2017


Pseudoliparis swirei sp. nov. is described from 37 individuals collected in the Mariana Trench at depths 6898–7966 m. The collection of this new species is the deepest benthic capture of a vertebrate with corroborated depth data. Here, we describe P. swirei sp. nov. and discuss aspects of its morphology, biology, distribution, and phylogenetic relationships to other hadal liparids based on analysis of three mitochondrial genes. Pseudoliparis swirei sp. nov. is almost certainly endemic to the Mariana Trench, as other hadal liparids appear isolated to a single trench/ trench system in the Kermadec, Macquarie, South Sandwich, South Orkney, Peru-Chile, Kurile-Kamchatka and Japan trenches. The discovery of another hadal liparid species, apparently abundant at depths where other fish species are few and only found in low numbers, provides further evidence for the dominance of this family among the hadal fish fauna.

Keywords: Pisces, snailfish, Notoliparis, description, taxonomy, phylogenetics

[upper] FIGURE 2. A) In situ photograph of Pseudoliparis swirei sp. nov. at 6,198 m. B) a group at 7,485 m. C) Deck photograph of SIO 16-82/HADES 200049. D) Radiograph of SIO 16-86/HADES 200141. Image by Sandra Raredon. Scale indicator 5 cm.
[lower] FIGURE 3. Lateral view of Pseudoliparis swirei sp. nov.. Combined representation of holotype, paratypes, and freshly captured images of paratype USNM 438985/HADES 200133, juvenile, 151 mm. Drawings by Thomas D. Linley.

Pseudoliparis swirei Gerringer & Linley sp. nov. 
Mariana snailfish: Linley et al. 2016 (page 105, Figure 4a)
Mariana snailfish: Linley et al. 2017 (page 42, Figure 6.43)
Mariana snailfish/Mariana liparid: Gerringer et al. 2017a (page 111)
Mariana liparid/Liparidae sp. nov: Gerringer et al. 2017b (page 137)

Diagnosis. Andriashev and Pitruk (1993) define the genus Pseudoliparis as having a well-developed disk and one pair of nostrils and lacking pseudobranchia and pleural ribs, with four radials in the pectoral girdle, which has neither notches nor fenestrae. In this genus, the hypural plate is divided by a distal slit (Andriashev and Pitruk, 1993). Like the other in this genus, Pseudoliparis swirei sp. nov. (Figures 2, 3) displays these characters, including a moderately well-developed disk, although this is easily damaged in collection. Pseudoliparis swirei sp. nov. can be distinguished from the two other known Pseudoliparis species with the following characters. Pseudoliparis swirei sp. nov. differs from P. belyaevi in the presence of a distinct lower pectoral-fin lobe, similar to that seen in P. amblystomopsis (Andriashev, 1955). Pseudoliparis swirei has more dorsal-fin rays 55 (51–58) than P. amblystomopsis 49 (49–52), more anal-fin rays 48 (43–49) compared to 43 (42–45), and more vertebrae 61 (56– 62), compared to 55–57, although these ranges somewhat overlap. Head length is shorter in P. swirei sp. nov. (17.0–21.7 %SL) than Pamblystomopsis (21.6–24.0 %SL). Comparisons were made according to ranges presented by Andriashev & Pitruk (1993). Pseudoliparis belyaevi is known only from the Japan Trench, P. amblystomopsis from the Japan and Kurile-Kamchatka trenches, P. swirei only from the Mariana Trench.

FIGURE 2. A) In situ photograph of Pseudoliparis swirei sp. nov. at 6,198 m. B) a group at 7,485 m. C) Deck photograph of SIO 16-82/HADES 200049. D) Radiograph of SIO 16-86/HADES 200141.

Image by Sandra Raredon. Scale indicator 5 cm.

Distribution. Known only from the Mariana Trench at capture depths from 6,898–7,966 m, individuals likely this species were recognized in video at depths 6,198–8,098 m (Linley et al. 2016; Jamieson & Linley, unpublished data).

 Etymology. The Mariana Trench famously houses the ocean’s deepest point, at Challenger Deep, named for the HMS Challenger expedition which discovered the trench in 1875. Their deepest sounding of 8,184 m, then the greatest known ocean depth, was christened Swire Deep after Herbert Swire, the ship’s First Navigating Sublieutenant (Corfield 2003). We name this fish in his honor, in acknowledgment and gratitude of the crew members that have supported oceanographic research throughout history. 

A CT scan of the Mariana snailfish. The green shape, a small crustacean, is seen in the snailfish’s stomach.Adam Summers/University of Washington

Mackenzie E. Gerringer, Thomas D. Linley, Alan J. Jamieson, Erica Goetze and Jeffrey C. Drazen. 2017.  Pseudoliparis swirei sp. nov.: A Newly-Discovered Hadal Snailfish (Scorpaeniformes: Liparidae) from the Mariana Trench. Zootaxa.  4358(1); 161–177. DOI:  10.11646/zootaxa.4358.1.7

There's a deeper fish in the sea
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Thomas D. Linley, Mackenzie E. Gerringer, Paul H. Yancey, Jeffrey C. Drazen, Chloe L. Weinstock and Alan J .Jamieson. 2016.  Fishes of the hadal zone including new species, in situ observations and depth records of Liparidae. Deep Sea Research Part I: Oceanographic Research Papers.  114; 99-110.  DOI: 10.1016/j.dsr.2016.05.003


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