Lasiognathus dinema

description

Description. — Length of illicium 15 – 47 mm (49.5 – 50.0 % SL); illicium of three known specimens fully extended anteriorly, cutaneous sheath surrounding posterior extension of illicial pterygiophore fully internalized (Pietsch, 2009: 84, fig. 85). A cylindrical, internally pigmented, anterior escal appendage (a light-guiding structure, without a homolog in any other known species of Lasiognathus; Pietsch, 2009: 237, figs. 245, 248), rounded distally in holotype, more elongate and tapering to a point in paratypes, length 1.3 – 2.8 mm (4.3 – 2.9 % SL). A thin, translucent, broad-based, antero-posteriorly compressed, posterior escal appendage, length 0.9 – 2.2 mm (3.0 – 2.3 % SL), with a scalloped or rounded distal margin, emerging from below escal pore. Distal escal appendage cylindrical, with narrow base and distal swelling, length 1.9 – 4.8 mm (6.3 – 5.0 % SL), bearing three lightly pigmented, strongly curved, bony hooks: one somewhat larger, length 2.0 – 2.2 mm (6.7 – 2.2 % SL), emerging from distal tip, directed posteriorly; and a pair of near equal size, length 1.4 / 1.6 – 1.4 / 1.9 mm (5.0 / 5.3 – 1.9 / 2.0 % SL), situated somewhat below, directed anteriorly. A pair of elonga

A New Species of the Ceratioid Anglerfish Genus Lasiognathus Regan (Lophiiformes: Oneirodidae) from the Northern Gulf of Mexico

diagnosis

Diagnosis. — Escal bulb with an elongate, cylindrical, internally pigmented anterior appendage; distal escal appendage a short cylindrical stalk, with an expanded distal end and a pair of tapering, filamentous prolongations emerging anteriorly from bases of escal hooks; distal escal appendage bearing three, lightly pigmented, bony, hook-like denticles; posterior escal appendage membranous, antero-posteriorly compressed, with a scalloped or rounded distal margin (Figs. 2, 3).

A New Species of the Ceratioid Anglerfish Genus Lasiognathus Regan (Lophiiformes: Oneirodidae) from the Northern Gulf of Mexico

discussion

DISCUSSION The specimens for this study were collected as part of an ongoing Natural Resource Damage Assessment Process conducted by the National Oceanic and Atmospheric Administration (for more information, see http: // www. darrp. noaa. gov / about / nrda. html) pursuant to the Deepwater Horizon Oil Spill (DWHOS). The stations at which the type specimens were collected were within a 250 km radius of the Macondo wellhead, at depths between 800 – 1300 m. The depths coincided with the depths of massive horizontal intrusions of hydrocarbons during and after DWHOS (~ 800 – 1200 m; Camilli et al., 2010; Valentine et al., 2010; Kessler et al., 2011), though the specimens described herein were not necessarily exposed. The finding of a new species in this region adds to our knowledge of the deep-pelagic Gulf in particular, and to the bathypelagic zone in general, which post-Census of Marine Life surveys have identified as the most chronically under-sampled environment on earth (Webb et al., 2010). In addition to describing a new species, this report is the first record of the genus Lasiognathus in the Gulf. Like the majority of ceratioid anglerfishes, examination of all available material

A New Species of the Ceratioid Anglerfish Genus Lasiognathus Regan (Lophiiformes: Oneirodidae) from the Northern Gulf of Mexico

etymology

Etymology. — The name dinema, is derived from the Greek, di, a prefix meaning ‘‘ two, ’’ and nema, ‘‘ thread, ’’ in allusion to the two elongate, thread-like prolongations emerging anteriorly from the bases of the escal hooks of this species (Figs. 1 – 3).

A New Species of the Ceratioid Anglerfish Genus Lasiognathus Regan (Lophiiformes: Oneirodidae) from the Northern Gulf of Mexico