Anglerfish


The anglerfish are ray-finned fish in the order Lophiiformes. Both the order's common and scientific name comes from the characteristic mode of predation, in which a modified dorsal fin ray acts as a lure for prey. The modified fin ray, with the very tip being the esca and the length of the structure the illicium, is adapted to attract specific prey items across the families of anglerfish by using different luring methods.
Anglerfish occur worldwide. The majority are bottom-dwellers, being demersal fish, while the aberrant deep-sea anglerfish are pelagic, living high in the water column. Some live in the deep sea, while others live in shallower waters, such as the frogfishes and some batfishes.
Anglerfish are notable for their sexual dimorphism, which is sometimes extremely pronounced; the females may be several orders of magnitude larger in mass than males. This dimorphism has enabled a unique reproductive method in the deep-sea anglerfish; sexual parasitism is the attachment of male to the much larger female, sometimes fusing together as an example of natural parabiosis.

Taxonomy

Anglerfish were first grouped in the family of Acanthopterygians with "pediculate pectoral s" by Cuvier in the 1829 edition of Le Règne Animal; being characterized by possessing "a sort of arm supporting their pectorals, formed by an elongated carpal bone". Cuvier placed the genera Lophius, Chironectes/''Antennarius, Malthe, and Batrachus'' within this family. Translations of this work into English and Latin renderred the family name as "Pectorales Pediculati"; which was eventually truncated into Pediculati or Pediculata, these names being used to classify anglerfish through 1926. Though this term saw use in publications as late as the 1970s, Pediculati has fallen out of use.
The group Lophidia was conceived by Samuel Garman in 1899; this group was subdivided into the Lophioids and the Halieutoids based on the orientation of the ilicium's base. By 1905, Lophiiformes came into use, at that time being a suborder of Pediculati.

Classification

The following classification is based on Eschmeyer's Catalog of Fishes :
Alternatively, Lophiiformes may be treated as clade within Acanthuriformes; a 2025 paper defines Lophioidei as equivalent to the prior conception of Lophiiformes and converts the suborders into infraorders. Below are two phylogenetic trees; the left phylogeny elaborates on the relationships of the suborders within Lophiiformes as set out in Pietsch and Grobecker's 1987 Frogfishes of the World: Systematics, Zoogeography, and Behavioral Ecology, while the right phylogeny is based on the 2025 study, where Maile et al combines the analysis of Ultra-Conserved Elements s, mitochondrial DNA, and morphological evidence;
Phylogenetic studies have consistently recovered the Lophiiformes as sister-group to the Tetraodontiformes, with both within the larger clade Acanthuriformes as of 2025. The Lophiiformes and Tetraodontiformes are united by several derived morphological features separating them from other Acanthuriformes, including restricted gill openings, along with the absence of multiple skeletal elements, such as spines supporting the anal fin, ribs, nasals, and basisphenoid.

Evolution

The earliest fossils of anglerfish are from the Eocene, excavated from the Monte Bolca formation of Italy, and these already show evidence of diversification into the modern families that make up the order. Given this, and their close relationship to the Tetraodontiformes which are known from Cretaceous fossils, they likely originated during the Cretaceous.
A 2010 mitochondrial genome phylogenetic study suggested the anglerfishes diversified in a short period during the early to mid-Cretaceous, between 130 and 100 million years ago. A 2023 preprint reduces this time to the Late Cretaceous, between 92 and 61 million years ago. Other studies indicate that anglerfish only originated shortly after the Cretaceous-Paleogene extinction event as part of a massive adaptive radiation of percomorphs, although this clashes with the extensive diversity already known from the group by the Eocene. A 2024 study found that all anglerfish suborders most likely diverged from one another during the Late Cretaceous and Paleocene, but the multiple families of deep-sea anglerfishes, as well as their trademark sexual parasitism, originated during the Eocene in a rapid radiation following the Paleocene-Eocene thermal maximum. Adaptations to different ranges of depths may have driven the evolution of anglerfish species and families in prehistory.
Anglerfish appear in the fossil record as follows:

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Anatomy

Anglerfish are defined by gills that open behind the pectoral fins, depressible teeth that can hinge back, joints of the epiotic bone, the form of the pectoral fin radials, and the luring apparatus.
Anglerfish lengths can vary from, with a few larger species than. The largest members are the European monkfish Lophius piscatorius, the deep-sea warty anglerfish Ceratias holboelli, the giant frogfish Antennarius commerson, and the giant triangular batfish Malthopsis gigas.
Many suborders are sexually dimorphic, with the deep-sea anglerfish being the most extreme example; male C. holboelli can reach up to long, while females are commonly around TL, potentially weighing an order of magnitude more than her mate. Male Photocorynus spiniceps were measured to be at maturity, and were at one time claimed to be the smallest vertebrate known. However, due to not being free-living and the females being, they are now often excluded from the records. Sexual dimorphism is not as pronounced in other suborders; the Lophiid monkfish genus Lophiodes are quite similar in size between the genders, and the same is true for Lophius itself.
Anglerfish are generally ambush predators, with shallow-water species such as frogfish often camouflaging as rocks, sponges or seaweed. To blend in with the featureless dark depths they inhabit, deep-sea anglerfish are dark colored, with tints ranging from grey to brown.
In most species, a wide mouth extends all around the anterior circumference of the head, and bands of inwardly inclined teeth line both jaws. The teeth can be depressed so as to offer no impediment to prey gliding towards the stomach, but to still prevent its escape. Anglerfish are able to distend both their jaw and stomach to enormous size, since their bones are thin and flexible, which allows them to swallow prey up to twice as large as their entire bodies.