Etmopterus lucifer has a slender body with brown coloration on the top and black coloration on the bottom.
E. lucifer is shown to have a higher amount of poresassociated with sensory
ampullae of Lorenzinion its ventral side than dorsal side, meaning the species likely closes in on prey from above. Black markings are also featured around the pelvic, or ventral, fins and at the base of the caudal, or tail, fin. The blackbelly lanternshark has two dorsal fins, the second of which is larger, and a caudal, or tail, fin, which is relatively long.
E. lucifer has relatively long gills, as well as five
branchial arches. Teeth are around 2 mm in length. Photophores are located across the body of
E. lucifer in distinct arrangements, but are found in much higher density on the ventral side of the shark where they are oriented downward.
E. lucifer also displays photophores in clade specific lateral markings as well as along its pectoral fins and
claspers. Bioluminescence in blackbelly lanternsharks and other
Etmopteridae sharks has been found to be controllable through manipulation of hormones including
melatonin (MT),
α-melanocyte-stimulating hormone (α-MSH), and
adrenocorticotropic hormone (ACTH). MT was found to induce light emission in the photophores of
E. lucifer, a process that simultaneously occurred with the opening of the iris-like structure (ILS) leading researchers to conclude that both the bioluminescent chemical reaction occurring in photocytes and the ILS appear to be involved in the control of light emissions. α-MSH and ACTH were both found to decrease light emissions in the photophores of
E. lucifer. Additional information on the biochemical mechanism for bioluminescence in sharks is still being researched. Studies have attempted to link bioluminescence to known
luciferins, chemicals that produced light when oxidized by a
luciferase enzyme, but it has been suggested that a novel photoprotein or luciferase might be present in sharks. == Biology and ecology ==