Quick Facts Conservation status, Scientific classification ...

Blackbelly lanternshark
Drawing by Dr Tony Ayling
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Elasmobranchii
Subdivision:	Selachimorpha
Order:	Squaliformes
Family:	Etmopteridae
Genus:	Etmopterus
Species:	E. lucifer
Binomial name
Etmopterus lucifer D. S. Jordan & Snyder, 1902
Range of the blackbelly lanternshark (in blue)

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The blackbelly lanternshark or lucifer shark (Etmopterus lucifer) is a shark of the family Etmopteridae found around the world in tropical and temperate seas at depths between 150 and 1,250 meters.^[2] Compared to other mesopelagic fish predators and invertebrates, the blackbelly lanternshark is thought to reside in shallower, more southern waters.^[3] E. lucifer can reach up to 47 centimeters in length^[2] and consumes mesopelagic cephalopods, fish, and crustaceans.^[4] Blackbelly lanternsharks are bioluminescent, using hormone controlled mechanisms to emit light through ventral photogenic organs called photophores^[5][6] and are presumed to be ovoviviparous.^[2] The blackbelly lanternshark has been classified as "Not Threatened" within the New Zealand Threat Classification System.^[7]

Etmopterus lucifer is prevalent in New Zealand’s deep waters, most commonly found on the south Chatham Rise, with the greatest occurrence recorded at around 500 meters in depth.^[3] E. lucifer is categorized as a mesopelagic fish, preferring shallower and more southern habitats.^[3] Between 1992 and 2010, a significant increase in E. lucifer biomass was observed along the east coast of the North Island.^[3] In New Zealand’s deep-sea trawl fisheries, Etmopterus lucifer, alongside the Etmopterus granulosus, constitutes the predominant by-catch species.^[6]  

Etmopterus lucifer was first discovered and scientifically documented by David Starr Jordan & John Otterbein Snyder in 1902 off the east coast of Honshu, Japan.^[8] It is a member of the family Etmopteridae which is in the order Squaliformes.^[9]

• Additional phylogenetic information can be found here ^[10]

Etmopterus lucifer has a slender body with brown coloration on the top and black coloration on the bottom.^[11] E. lucifer is shown to have a higher amount pores on its ventral side than dorsal side, meaning the species likely closes in on prey from above.^[12] 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,^[9] the second of which is larger, and a caudal, or tail, fin, which is relatively long.^[11] The interdorsal space is short.^[13] E. lucifer has relatively long gills, as well as five branchial arches.^[12] Along the side of the body, from its snout to its tail fin, are rows of hook-shaped denticles.^[11][12] The lower jaw contains between 29 to 39 teeth that have one cusp, while the upper jaw contains between 21 and 26 teeth that have up to three cusps.^[13][14] Teeth are around 2 mm in length.^[13]

The maximum length of E. lucifer is about 47 cm.^[13] Males range from 29 to 42 cm, while females are 34 cm or more in length.^[13][14]

Etmopterus lucifer has a wide and protruding rostrum, with large nasal capsules and rostral fenestrae.^[12] As a deep-sea species, E. lucifer has a large eye diameter, which can result in higher sensitivity to penetrating light and bioluminescence.^[12] A translucent region in the upper eye orbit of E. lucifer can potentially help the species detect camouflage.^[15] E. lucifer has high rod density in the nasal area of the eye, that allow the species to detect bioluminescent markings of other individuals and adjust to low-light conditions.^[15]

Blackbelly lanternsharks are presumed to be ovoviviparous.^[2]

The diet of Etmopterus lucifer is generally characterized as consisting of squids and myctophids^[17] (lanternfishes) with slight regional differences. Populations found near Australia have been found to consume a variety of teleost, with the most common being myctophids, while also being known to feed on crustaceans and squids.^[3] Populations in Japan have been found to consume euphausiids as part of their regular diet instead of crustaceans, though they still retain squids, albeit mesopelagic squids, and myctophids as part of their feeding regime.^[3] In Southern Africa, E. lucifer has maintained myctophids in their diet, however, studies have found that they prefer to also hunt pelagic cephalopods in contrast to their regional counterparts that typically prefer squids in specific.^[3]

Etmopterus lucifer is thought to attract its prey through the use of the photophores primarily found concentrated on its body that contribute to its cryptic coloration that provides both camouflage from predators and prey alike.^[5][6] Etmopterus lucifer prey detection can be attributed to its theorized electro-sensory sensitivity.^[12] Blackbelly lanternsharks have been found to have a substantial number of Ampullae of Lorenzini, which contribute to the detection of electrical fields (and resultantly prey), and through the use of ducts and pores, blackbelly lanternsharks can reduce the hindrance experienced as the signal moves along by having the destination be a synapse with a large diameter.^[12] Through this reduction it is thought that the blackbelly lanternshark increases its overall sensitivity, allowing it to better detect faster prey.^[12] Once the prey is within distance, the blackbelly lanternshark then utilizes its jaw to consume its prey entirely. It is thought that the separation of the suborbital muscle from the mandibular adductor muscle observed within this species of lanternsharks is thought to aid in the further extension of the mouth and thus permit the lanternshark to consume larger prey.^[12] Labial cartilage present in E. lucifer has also been studied and found to aid in minor suction force which possibly assist with its feeding.^[18] 

In June 2018, the New Zealand Department of Conservation classified the blackbelly lanternshark as "Not Threatened" with the qualifiers "Data Poor" and "Secure Overseas" under the New Zealand Threat Classification System.^[7] The species has low fishing mortality, as its small size may allow evasion of nets and trawls.^[19]