What Is The Difference Between An Angler Fish and a Viperfish?

I get a surprising amount of misdirected traffic to this blog (because Google is imperfect) from people searching for variations on the title. I’ve never actually posted about that, beyond a vaguely humorous post where I renamed a load of deep sea fish to help a friend remember which one was which.

There are the odd collection of search terms that lead people here which make me feel moderately bad for the searchers not getting what they want and ending up on my unhelpful blog, so in the interests of making life easier for people I thought I’d make a post about it anyway (I am less likely to fulfil people’s needs for a summary of Michelangelo’s Rebellious Slave, or a dissection of how the word “disinclination” is used in Neil Gaiman’s Neverwhere, because I find the idea of people copy-pasting their homework answers a bit distasteful).

From Wikipedia:

Anglerfishes are members of the teleostorder Lophiiformes (pron.:/ˌlɒfəˈfɔrmz/).[1] They are bony fishes named for their characteristic mode of predation, wherein a fleshy growth from the fish’s head (the esca or illicium) acts as a lure; this is considered analogous to angling.

Some anglerfishes are pelagic (live in the open water), while others are benthic (bottom-dwelling). Some live in the deep sea (e.g., Ceratiidae) and others on the continental shelf (e.g., the frogfishes Antennariidae and the monkfish/goosefish Lophiidae). They occur worldwide. Pelagic forms are most laterally (sideways) compressed whereas the benthic forms are often extremely dorsoventrally compressed (depressed) often with large upward pointing mouths.

In summary: “anglerfish” covers a number of species, and are generally quite lumpy-looking, squat things with dangling lures intended to attract prey, like an angler (or fisher, but I think we can agree that “fisherfish” would be confusing: apart from anything else if you say it out loud it sounds like “fissure fish” and that would be some sort of blind white thing scavenging in the ecosystem associated with a sea floor vent). To identify a fish as a potential anglerfish, it must be in possession of some sort of growth that acts as lure, whether bioluminescent or not.

Another characteristic associated with anglerfish in general, although it is characteristic of the Ceratioid group (Ceratiidae), is the unusual mating method of a diminutive male attaching himself to a passing female and becoming part of her body, nourished by her blood stream, rather like a parasite. In retain for literally becoming an appendage to his missus – who may have several other males attached – she has a ready supply of sperm for when she spawns, and her eggs can be immediately fertilised without her having to find a male somewhere in the vast darkness of the deep ocean.

From Wikipedia again:

viperfish is a saltwater fish in the genus Chauliodus, with long, needle-like teeth and hinged lower jaws. They grow to lengths of 30 to 60 cm (12 – 24 inches).[2] Viperfish stay near lower depths (250–5,000 feet) in the daytime and shallow at night. Viperfish mainly stay in tropical and temperate waters. It is one of the fiercest predators in the very deep part of the sea and is believed to attack its prey by luring the victim close to itself with a light producing organ. This organ is called a photophore and is located on the end of its dorsal spine. It flashes this natural light on and off while at the same time moving the dorsal spine around like a fishing rod and hanging completely still in the water, and also uses the voluntary natural light producing organ to communicate to its potential mates and rivals. Viperfish vary in color between green, silver and black. It uses its fang-like teeth to immobilize its prey, and would not be able to close its mouth because of their length if it were not able to curve them behind its head. The first vertebra behind the head of the viperfish is known to absorb the shock of its attacks, which are mainly targeted against dragonfish and other small creatures. They are able to undergo long periods with scarcely any food.

While anglerfish as a word covers an entire order of fish (ie, several genus and species), the term “viperfish” applies to a specific genus, and is much more narrowly applied. As this illustration of C. danae demonstrates, rather than being bulky and compressed like the majority of anglerfish species, the viperfish is typically elongated:

Chauliodus danae

Anglerfish and viperfish should be easy to distinguish between upon sight: to help keep them straight in your head, remember that a viper is a term used for some types of poisonous snake, and that the viperfish is long and thin, like a snake. Anglerfishes use lures, like anglers.

Taxonomic tree:

For the sake of not confusing people further by talking about “Genus” and “Order” and so on, I’m just going to take a moment to talk about how living things are classified. Dividing up the enormous variety of lifeforms on our planet requires a system of classification that determines which lifeforms are more closely related to each other and which are less alike, and this helps us to track potential evolutionary paths and to determine whether medications and poisons that work on some will work on others.

Taxonomy (the classification of life) is usually displayed as a tree, with “subspecies” as the smallest twigs and “Kingdom” as the largest branches. It can also be thought of as nesting boxes, with small “subspecies” boxes – the most specialised differentiation between genetic groups – nestling inside the overarching “species” definition, which in turn fits (with other species) inside the “genus” definition.

The order of classification officially begins with kingdom, which separates out plants from animals, and whatever the fuck fungus is from plants and animals, and three separate domains of micro-organisms/single-celled life forms. The next most specialised taxonomic rank is phylum (plural: phyla), which is confusing as balls but separates out a lot of weird shit like round worms and slightly less weird shit like molluscs (snails and squid and so on) from each other, and from arthropoda (crabs, spiders, insects, etc), and from chordata, which is the phylum which interests us here. Chordata contains the subphylum (kind of like a smaller phylum but not specialised enough for the next step down) vertebrata which as the similarity to “vertebrae” should suggest, contains all backboned animals including people (mammals) and birds and fish and so on. The next step down is class, which in the case of this post would be the superclass (contains several classes) “Osteichthyes“, or “bony fish”. Within a class there are ordersC. danae above, for example, belongs to the order Stomiiformes, whereas “anglerfish” comprise an order of their own, Lophiiformes. After order comes family, which contains a number of genii (plural of genus) that are similar, and each genus contains one or more species: the genus Chauliodus, or “viperfish”, contains nine species of viperfish.

Both the order of anglerfish and the order Stomiiformes, which contains the family Stomiidae, which contains the genus Chauliodus, commonly known as “viperfish” are members of the class Osteichthyes, or bony fish, but they are not similar enough to be grouped together at more intimate levels than that. For comparison, the class “Aves” contains all birds, making the viperfish and any given anglerfish genus about as closely connected as an ostrich and a hummingbird or a penguin and a chicken.

For ease of visualisation, have this handy chart from Wikipedia:

taxonomic ranks

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