Etmopterus bigelowi

Common Name

Blurred Smooth Lanternshark

Year Described

Shirai & Tachikawa, 1993

Identification

This lanternshark is moderately slender with a fairly long snout (longer than mouth width but shorter than the distance from mouth to pectoral origin). Anterior nasal flap is short. There are two dorsal fins, the second being slightly larger than the first. Distance between them is greater than the snout-gill distance. Both have a spine on the anterior margin. First dorsal originates posterior to the rear margin of the pectoral fin and closer to it than the pelvic origin. Pectoral fin is squared off and small. Anal fin is absent. Pelvic fins originate well anterior to the second dorsal. Caudal fin is fairly long (about distance from snout to second gill slit). Rear margins of fins lack broad fringes. Teeth in lower jaw are broader than the upper jaw. Upper jaw teeth are narrow with a broad, erect central cusp and 2-4 pairs of lateral cusplets. The lower jaw teeth have low and oblique cusps with a lateral notch. Upper jaw: 19-24 teeth; lower jaw: 25-39 teeth. Denticles low without median spine (low, flat crowns and four-pointed bases) and randomly distributed. Skin smooth. Ventral photophores are smaller than skin denticles and scattered amongst them.

Color

Uniform gray to dusky brown body with a pale blotch on the top of the head (pineal spot). A bright metallic green lateral stripe in fresh specimens. There are scattered black markings on the lower head, the lower pectoral fin, the pelvic base, and the caudal base, but are not conspicuous. Fins dark anteriorly with a pale edge. Eye is green in life.

Size

Mature adults from 31-47 cm. Maximum size to ~67 cm.

Habitat

Benthic or oceanic over continental slopes and shelves from 110-1000 m. (shallower in open water). Feeds on small sharks and various bony fishes. Life history poorly known.

Range

Widely scattered records throughout the western Atlantic: the northern Gulf of Mexico, the Caribbean, Suriname, southeastern Brazil, Uruguay, and Argentina.

References

Castro, J.I. 2011. The Sharks of North America. Oxford University Press, 640 pp.

Compagno, L., M. Dando, and S. Fowler. 2005. Sharks of the World. Princeton University Press, 480 pp.

Other Notes

Often confused with Etmopterus pusillus, which is the only other Etmopterus with smooth denticles. Most of the records from the W. Atlantic appear to be E. bigelowi, but E. pusillus may occur in our area, especially in the Southern Hemisphere. Etmopterus pusillus is separated from E. bigelowi by having less turns in the intestinal valve (10-13 vs. 16-19) and more teeth (22-31/30-53 vs. 19-24/25-39) (Castro, 2011).