Good Example Of The Anglerfish Essay

The Anglerfish, also known by its Latin or scientific name, Lophius piscatorius, is one of the more unique marine animals, both in anatomy and predatory habits. With this carnivorous predatory nature, an ugly countenance and extremely clever bioluminescent rod and bait anatomy designed for luring and catching various types of prey, it manages to avoid much work in hunting or capture of prey; it essentially is designed to bring prey right to its mouth, earning it the nickname of the fish that fishes (Murphy 4). Extreme sexual dimorphism and reproductive characteristics dependent upon parasitic relationships between male and female also contribute to the unique characteristics of this fish. Conversely, it is also an extremely diverse marine animal. With over 200 species of Anglerfish, it has variable habitats and can be found worldwide in deep or shallow water; its variation among species means it can display an extremely wide variety of sizes, colors, and opportunistic feeding preferences, while belonging to diverse taxonomic classifications.

Taxonomic Classification

All species of Anglerfish belong to the animal kingdom, chordata phylum, and vertebrata subphylum (Pietsch, “Lophiiformes” 1). The major order to which all Anglerfish belong is that of Lophiiformes, which contains a diverse blend of marine animals that are both benthic shallow water dwellers and deep shelf and slope inhabitants (Pietsch, “Lophiiformes” 1). One of the most prominent features of fish belonging to this order are prominent dorsal-fin spinal structures used as lures ((Pietsch, “Lophiiformes” 1). This order has approximately 322 species, which are spread across 65 genera and 18 families (Pietsch, “Lophiiformes” 1). These families have five subdivisions, or suborders. Antennariodei, with has four families, 15 genera, and 54 species, includes those known as frogfish, sea mice, sea toads, and warty anglerfish (Pietsch, “Lophiiformes” 1). Lophioidei, with one family, 4 genera, and 25 species includes goosefish, monkfish, and anglerfish (Pietsch, “Lophiiformes” 1). Chaunacoidei have only one family, two genra, and 4 species, and are known as coffinfishes (Pietsch, “Lophiiformes” 1). Ogcocephalioidei includes batfishes, with one family, ten genera, and 67 species (Pietsch, “Lophiiformes” 1). Finally, the last group, Ceratoioidei, consists of 11 families, 35 genera, and 162 species and is strictly confined to deep-sea anglerfish (Pietsch, “Lophiiformes” 1). Physical appearance can vary slightly throughout these species, although certain physical characteristics – including its characteristic bait and lure structure – are consistent throughout all species of female Anglerfish.

Physical Characteristics

Physically, the female Anglerfish is considered by many to be particularly ugly or angry looking, with its angled head and protruding sharp teeth (National Geographic 1). Its head is relatively large and mouth is very wide, compared to the small size of its body, which contributes further to its very unique physical appearance and earned it the nickname “allmouth” in many marine biology circles (Colidron 8). This characteristic face and body shape is shared by all species, although size can vary greatly. These fish may be as small as only ¼ of an inch, or 0.64cm, while the largest females may reach six feet (2 meters) and well over 110 pounds (National Geographic 1; Colidron 6). However, this physical appearance – from the size and shape of their body and head to the color – is entirely functional. Because they are predatory carnivores, their physical features are specifically designed to assist in capturing prey (National Geographic 1).
The color, which varies and can include black, brown, and grey, serves to keep the female Anglerfish well camouflaged, especially when resting on the sea floor (Colidron 10). Long rows of teeth that form a sharp, needle-like fang shape are designed to easily pierce and kill prey, with an inward curve that makes it more difficult for prey to escape (Lynette 6). However, one of its most characteristic and unique structural features designed specifically for the capture of prey, which can be seen throughout all species, is the piece attached to its head that resembles a fishing rod and lure (Colidron 10). The rod structure is made up of a piece of dorsal spine, and is called an illicium (Colidron 10; National Geographic 1). The lure, the most functional piece of this structure, functions as bait for various prey, and is called an escra (Colidron 10; National Geographic 1). Typically, the escra appear to be in the shape of shrimp, worms, small fish, or other appealing types of bait for the female Anglerfish’s prey (Colidron 10). One of the most unique aspects of the escra is its bioluminescence and the symbiotic relationship with the bacteria that are responsible for this characteristic.
During development, the escra requires the help of millions of bioluminescent bacteria to form properly (National Geographic 1). However, these bacteria do not disappear once the escra has matured; they remain in the escra for life, receiving their habitat and nutrition from the host Anglerfish (Lynette 8). In turn, they provide bioluminescence, which allows the escra to emit a light that draws prey toward it and emits a calming radiation (Lynette 4). This is considered a completely symbiotic relationship between the two (Lynette 8). However, it is important to note that all of these physical characteristics – including the size, shape, escra, and presence of bioluminescent bacteria, are limited to female Anglerfish.
One particularly unique aspect of its physical characteristics is the extreme sexual dimorphism exhibited by all Anglerfish species (Pietsch 3 “Oceanic”). While the females possess the typical, aforementioned Anglerfish structure, the males are extremely small, and lack an escra, although they do have extremely large, well-developed eyes and nostrils, with highly developed sight and smell (Pietsch, “Oceanic” 3). The purpose of the enlarged eyes is strictly to locate a female Anglerfish, to which the male attaches himself with extremely small teeth that are not intended for capturing prey; they are intended for the sole purpose of attaching to a female (Pietsch, “Oceanic” 3). The male fuses to the female, and becomes permanently dependent on her for food (Pietsch, “Oceanic” 3). The males are actually considered to be parasites, and may reach only 6-10mm in size, considered to be some of the world’s smallest vertebrates (Pietsch, “Oceanic” 3).

Reproductive Characteristics

Mating, then, occurs when the attached male releases a long, ribbon-like gelatinous mass, which is called an egg raft, or veil. The eggs from the female are deposited into this substance, along with waterborne sperm. The canals within the structure facilitate egg fertilization. Because this egg raft is free floating outside of the body of the Anglerfish, the gelatinous mass also serves as protection against predators: most marine animals that would ingest it are unable to due to the structure and consistency of the mass (Pietsch, “Oceanic” 198). This egg raft floats to the surface after fertilization, ensuring the eggs are kept in a sunlight and nutrient-rich environment until they hatch (Pietsch, “Oceanic” 198). Mating habits may also influence habitat; while habitat is dependent on species, spawning may temporarily induce the same habitat preference among most (if not all) species of Anglerfish.

Habitat

Mainly, the habitat of the anglerfish varies by species. It is found worldwide, in both deep water and somewhat shallower conditions (Lynette 5). However, all species prefer to reside in the deep ocean where there is little to no sunlight, and the environmental temperature is extremely cold (Lynette 5). Deep sea species of Anglerfish live up to 13,000 feet or 4,000 meters below the surface, in what is considered to be a midnight zone (cold and completely devoid of sunlight) (Lynette 4). Among primarily all species, however, a two-way ontogenic vertical migration occurs from deep water to shallow depths (and back again), and it is believed that this migration to shallower depths occurs for purposes of mating, fertilization, and release of the egg raft; the Anglerfish then migrates back to its most comfortable depth (once again dependent upon the species) (Pietsch, “Oceanic” 198). Habitat and species were also originally thought to influence the hunting habits and diet of the Anglerfish, and some researchers believe they still may, to a certain degree; however, more similarities than differences were found among both hunting habits and dietary preferences across all species.

Hunting Behavior and Feeding

The Anglerfish hunts by hiding on the ocean floor and keeping its body completely still; only the glowing escra can be seen (Lynette 8). It moves the lure back and forth in front of its mouth for the purpose of attracting prey (Lynette 8). While it has been found that food preferences vary across the many species of Anglerfish, most are considered opportunistic feeders, who will consume nearly anything that is available to it: fish, crustaceans, and molluscs (Stagioni, Montanini, and Vallisneri 374). Studies that analyzed stomach contents of various Anglerfish found that fish was consumed most often, with favorite prey consisting of Merluccius merluccius, or European hake (preferred by medium to large Anglerfish of over 150mm), and Gaidropsarus biscayensis, the Mediterranean Bigeye Rockling (preferred by smaller Anglerfish under 150mm) (Stagioni, Montanini, and Vallisneri 374).
Although the Anglerfish shares a few of the very common characteristics of most fish species, such as seasonal migration, production of eggs, symbiosis with various bacteria or parasites, and large variety of both deep and shallow water species. However, this fish also appears to have a number of characteristics that make it extremely unique. With a physical structure resembling a fishing rod and lure, combined with camouflaging color, bioluminescent bacteria to attract prey, and an angled mouth to prevent it from escaping, this carnivorous predatory fish has an extremely unique way of hunting that involves very little (if any) physical activity on its part. Equally unique is its complete sexual dimorphism with parasitic male fish that spend their lives fused to, and dependent upon, the female for nutrition and habitat. While it may be thought of as one of the ugliest, angriest-looking fish in the sea, it is also one of the most biologically unique, diverse, and fascinating of the marine creatures.

Works Cited

Coldiron, Deborah. Anglerfish. Minneapolis: ABO Publishing, 2008. Print.
Lynette, Rachel. Deep-Sea Anglerfish and other Fearsome Fish. Chicago: Raintree, 2012. Print.
Murphy, Julie. Anglerfish. Ann Arbor: Cherry Lake Publishing, 2015. Print.
National Geographic. Anglerfish. National Geographic Online, 2015. Web. 13 March 2014. <http://animals.nationalgeographic.com/animals/fish/anglerfish/>
Pietsch, Theodore. Lophiiformes: Anglerfishes. Tree of Life Web Project, 18 October 2005. Web. 13 March 2015. <http://tolweb.org/Lophiiformes/21989/2005.10.18> 
Pietsch, Theodore. Oceanic Anglerfishes: Extraordinary Diversity in the Deep Sea. Berkeley: University of California Press, 2009. Print.
Stagioni, M., Montanini, S., and Vallisneri, M. “Feeding habits of anglerfish, Lophius budegassa (Spinola, 1807) in the Adriatic Sea, north-eastern Mediterranean”. Journal of Applied Ichthyology 29.2 (2013): 374-380. Print.