Anglerfish, with their distinctive appearance and glowing lures, are creatures of the deep ocean. These elusive fish inhabit some of the planet’s most mysterious environments. Their unique adaptations, particularly the bioluminescent “fishing rod” used to attract prey, highlight a fascinating existence in perpetual darkness. These diverse forms hint at a complex biology shaped by their extreme surroundings.
Diverse Sizes Across Anglerfish Species
Anglerfish exhibit a remarkable range in size, from millimeters to over a meter in length. Most species are relatively small, often less than 30 centimeters (one foot) long. Dimensions vary significantly across the more than 200 species in the order Lophiiformes.
Deep-sea anglerfish, such as the humpback blackdevil (Melanocetus johnsonii), females grow up to 18 centimeters (7.1 inches), while their male counterparts are considerably smaller, under 3 centimeters (1.2 inches). An extreme example is the male Photocorynus spiniceps, measuring 6.2–7.3 millimeters (0.24–0.29 inches), making it one of the smallest known vertebrates. The female of this species reaches 50.5 millimeters (2 inches).
In shallower waters, anglerfish species are much larger sizes. Frogfish, part of the anglerfish order, range from as small as 0.3 centimeters (1/8 inch) to 56 centimeters (22 inches). The European monkfish (Lophius piscatorius), a type of goosefish, grows to 200 centimeters (6.6 feet) and weighs 57.7 kilograms (127 pounds). Similarly, the American goosefish (Lophius americanus) reaches 61 to 122 centimeters (2 to 4 feet) and weighs up to 22.7 kilograms (50 pounds).
Influences on Anglerfish Size
The varied sizes observed among anglerfish species are influenced by sexual dimorphism, particularly in deep-sea inhabitants. Females are much larger than males, sometimes by several orders of magnitude in mass. This extreme size difference is linked to their reproductive strategy, known as sexual parasitism.
In many deep-sea anglerfish, the male seeks out a female and permanently attaches to her body. He fuses his tissues with hers, becoming dependent on her for nutrients, while providing sperm. This adaptation ensures reproduction in the vast, sparsely populated deep-sea where finding a mate is challenging. The male’s small size conserves resources and minimizes impact on the female’s ability to move and hunt.
The deep-sea habitat plays a role in shaping anglerfish size. Conditions such as food scarcity, immense pressure, and cold temperatures necessitate adaptations. Deep-sea anglerfish have evolved large mouths and expandable stomachs, allowing them to consume prey up to twice their own size, crucial where meals are infrequent. Their sit-and-wait predation strategy and low metabolic rates are energy-efficient adaptations suited to the limited resources of their dark, cold environment. Anglerfish at greater depths tend to be larger, possibly gaining an advantage in capturing prey and withstanding high pressures.
The Largest Anglerfish On Record
While many anglerfish are small, some species and individuals achieve considerable sizes. The largest anglerfish ever recorded was an individual weighing 57.2 kilograms (126 pounds and 6 ounces), caught by Gunnar Thorsteinsen on July 4, 1994, which holds the all-tackle world record. This record highlights the potential for exceptional growth within the anglerfish order, particularly among species like the goosefish, which inhabit more accessible waters.
Among the deep-sea anglerfish, Krøyer’s deep-sea anglerfish (Ceratias holboelli) is the largest, with females reaching 1.2 meters (3.9 feet). The males of this species are smaller, with free-living individuals rarely exceeding 1.3 centimeters (0.5 inches), and parasitic males reaching 16 centimeters (6.3 inches). This vast difference means a female Ceratias holboelli can be 60 times longer and 500,000 times heavier than her male counterpart. Despite these larger specimens, encountering massive anglerfish remains rare due to their deep-sea habitats.