Classification

 
As described by Albert Günther, Melanocetus johnsonii means large black sea creature.  The root 
words of  Melanocetus are the greek words melano and ketos.  Melano describes the distinct black color
of the fish.  Ketos refers to a large sea creature, often describing a whale.  Other common names 
include the humpback anglerfish, the deep-sea anglerfish, and the black sea-devil (Miya et. al. 2010).

source:  Wikimedia commons, Natural History Museum London 

The taxonomical classification of Melanocetus johnsonii is as follows...

Kingdom:  Animalia
M. johnsonii is a multicellular eukaryotic organism that is motile and thrives as a heterotroph.

Eukaryotic Cell, source:  wikimedia, Mariana Ruiz

Phylum:  Chordata
The black sea devil has a notochord, a dorsal nerve cord, pharangeal slits, as well as a post anal tail and
is thus classified as a chordate.  Examples of other chordates include other fish like the Yellow Perch, 
amphibians likethe Panamanian Golden Frog, reptiles such as the American Toad, birds such as the 
American Pelican, and mammals like the Common Muskrat.

Primative Chordate Ancestor, source:  wikimedia by user vojtech.dostal

Class:  Actinopterygii
As a part of its morphology, the humpback anglerfish is classified as a member of the class
because it has fins that are built with a web of skin supported by bony spines.  This class is also
 known as the ray-finned fishes. A few representatives of this class include the Common Shiner and
 the Smallmouth Bass.

 
Ray-finned fish example, source:  wikimedia by user marrabbio

Order:  Teleosti 

This species of anglerfish has the ability to protrude its jaw forward from the mouth, among other 
characteristics and therefore is aparttofftheeorderrteleosti.. Thissorderrincludessmembersssuchhassthethe 
Atlantic Cod.

Family:  Lophiiformes
As a heterotroph, the humpback anglerfish has a fleshy, often bioluminescent growth upon its head as
a mechanism to lure prey closer to its position.  Lophiiformes possess this structure and are informally called
the anglerfish family.

Source:  Orlov, Alexei Fishbase.org

Genus:  Melanocetus

This genus was originally established by Günther (1864) when he described Melanocetus johnsonii.
He recognized this important species based on a single female specimen that he collected in the Atlantic Ocean. 
Since that time, 13 additional species based on females have been described.  This genus of anglerfish have dark, 
almost black skin and intense jaws.

Species– Melanocetus johnsonii
Melanocetus johnsonii has a globular shape with jaws that point almost directly upward.  Its bioluminescent lure 
is short in comparison to its body size and has rounded spine (Shedlock et. al. 2004).

Source:  Ho, Hsuan-Ching and the National Museum of Marine Biology & Aquarium, Taiwan

In order to understand this fascinating species of fish, it is important to look at the evolutionary history of fish and tetrapods as shown in Figure 1.

source: BiologyForums.com

Figure 1. Phylogenetic tree of all fish and tetrapods.  Notice the Ray finned fishes which include M. johnsonni.

To seperate Melanocetus johnsonii from other fish and tetrapods, we look to the ray-finned fishes (Actinopterygians) for further descriptive power.

(Miya et. al. 2010)

Figure 2. Phylogenetic tree of fish

Melanocetus johnsonii can be located within the clade called actinopterygians which includes all ray-finned fish species. Within this clade, the teleosts branch off from other ray finned fish because of their unique jaw structure that allows them to protrude their jaws outward from their mouths.  From within the Teleosts, the anglerfish or lophiformes break off into their own group.

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