User:Madelinefinnegan/Humpback anglerfish

= Humpback Anglerfish = From Wikipedia, the free encyclopedia

Melanocetus johnsonii is a species of black seadevils in the family of Melanocetidae, which means 'black large sea creature' in Greek. The species is named after James Yate Johnson, the English naturalist who discovered the first specimen in Madeira in 1863. The common names include humpback anglerfish, humpback blackdevil, and Johnson's anglerfish.

Historical Background
The first specimen of M. johnsonii was discovered by English naturalist James Yates Johnson near Madeira, an archipelago off the coast of northwestern Africa, on December 24th, 1863. It was then brought to Albert Carl Ludwig Gotthilf Günther, keeper of zoology at the Natural History Museum in London, who described it as “a fish which proves to be the type of a new genus, not only on account of its extraordinary form, but also on account of the absence of pelvic fins.” Günther was the first to record the unique morphology of the species and named it after Johnson, the initial collector. Early hypotheses about anglerfish behavior posited that their illicium and esca, the extended dorsal fin spine and bulbous apparatus that protrude from the snout, are used for luring prey, with Danish naturalist Christian Frederik Lütken being the first to state the idea that this feature was central in feeding behavior. Until the 1920s, male specimens without a luring apparatus had been thought to be distinct, and were placed in separate taxonomic categories than their female counterparts. In 1924, British ichthyologist Charles Tate Regan realized that a small fish attached to a larger anglerfish was actually a male in the process of reproduction, leading to the discovery of the sexual dimorphism that characterizes anglerfish. Several specimens that were previously categorized as separate species, including M. ferox and M. krechi, have since been recognized as synonyms of M. johnsonii.

Habitat[edit]
((picture)) A real humpback anglerfish M. johnsonii inhabits the mesopelagic and bathypelagic zones, and is found most commonly at depths between 100 and 1500 meters. Compared to other species in the genus, M. johnsonii is more likely to be found at shallower depths; 65% of recorded specimens were collected at depths at or above 1000 m. At these depths, there is little to no light penetrating from the surface photic zone. Because of this, the humpback anglerfish has evolved means of predation using bioluminescence based on the constraints of their habitat.

M. johnsonii has the widest geographic distribution of all the species within the Melanocetus genus. The species had been known to be widely distributed in the temperate and tropical ranges of all oceans, as well as in the South China Sea and the East China Sea. Its southern geographic distribution was expanded in 2014 when the first specimen of M. johnsonii in Antarctic waters was obtained from the stomach of an Antarctic tooth fish in the Ross Sea on Jan 6, 2014. The specimen was identified by morphologic methods and further genetic analysis using the fish's pectoral fin clip which verified that the specimen belonged to M. johnsonii. An individual specimen of M. johnsonii was found near Father Charles Canyon in British Columbia, extending its known northern distribution in the East Pacific and solidifying it as one of the most widely distributed anglerfish.

Morphology[edit]
M. johnsonii is a soft-bodied anglerfish that is dark brown or black in color. Female humpback anglerfish have short, globular bodies, large heads with a widened mouth that is nearly vertical, and long pointed teeth capable of eating prey larger than themselves. Numerous small skin spines are found under the dorsal fin. Compared to other species within the genus, M. johnsonii has a longer illicium and fewer jaw teeth, but these teeth are relatively longer than those of other species. Like all other anglerfish, females have a short dorsal fin spine (illicium) with a bulbous luring apparatus (esca) on the snout. The esca has compressed posterior and anterior crests, noted when distinguishing it from other anglerfish. Unlike other species in the genus, females of the species have a nearly straightened anterior margin of vomer. Female M. johnsonii have small, subcutaneous eyes that may suggest their lack of dependency on visual sight for feeding and reproduction.

Humpback anglerfish exhibit extreme sexual dimorphism, with larger sized females and dwarfed males. Females have been found to grow up to 153 mm, while males only grow between 15.5 to 28 mm. Males lack a luring apparatus, but have large eyes and nostrils which may be helpful for locating far dispersed mates. While distinguishing characteristics of males in the genus are not well defined, M. johnsonii males usually have a relatively larger number of denticular teeth and dorsal and pectoral fin rays.

Also, as there are many similarities in morphological characteristics of M. johnsonii and M. rossi, one distinguishing feature is that M. johnsonii has black pigmentation on its upper body exterior while M. rossi does not. Because of the numerous similarities between the two, it has been suggested that M. rossi may be a synonym of the M. johnsonii species.

Feeding behavior[edit]
M. johnsonii females have large mouths filled with sharp teeth and huge stomachs that make them capable of eating nearly everything they encounter. Their stomachs are highly distensable and expand easily, allowing them to consume meals weighing more than themselves. One M. johnsonii individual weighing 8.8 grams was retrieved using a trawl, and the specimen was found to have three snipe eels totaling 12.3 grams in its stomach.

Since only 5% of nutrition produced by the photic zone in the open passes down to the deep ocean, there is not much food available in the deep sea. M. johnsonii are ambush predators, meaning that they use a sit-and-wait predation strategy. Individuals of M. johnsonii have a low metabolic rate, even compared to organisms living at similar depths. To test this, experimenters used a trawl to retrieve eight M. johnsonii individuals, all with empty stomachs. The fish were kept alive in a laboratory and their aerobic metabolisms were measured. Researchers found that M. johnsonii is able to regulate its aerobic metabolism by adjusting its oxygen consumption, allowing it to live in hypoxic or anaerobic conditions for long periods of time.

Females use their bulbous esca as a bioluminescent lure to attract prey. The bioluminescence of M. johnsonii is caused by E. escacola bacteria living in symbiosis with the hook of the fish. It was originally thought that E. escacola was obligately dependent on its host because its genome was reduced about 50% compared to free-living bacteria. Through genetic analysis and experimentations, it was determined that E. escacola and M. johnsonii are facultatively symbiotic, meaning that they can survive without each other but still choose to live in symbiosis. Furthermore, E.escacola are acquired from the environment and therefore do not evolve with the host.

Reproduction[edit]
Searching for a mate for M. johnsonii is difficult because they live solitarily and far apart from each other in the deep sea. Males have highly developed sensory organs that allow them to trace the scent of a female as it is minimally disrupted in the still waters of the deep sea. Unlike other species of anglerfish, males of M. johnsonii are non-parasitic. This means that M. johnsonii males only temporarily attach onto the larger M. johnsonii female using a unique denticular apparatus before releasing their sperm. Once this process is complete, males detach from the females to find other mates. Two cases of this phenomenon have been captured, one on the RRS Discovery in Ireland and the other on the R/V Tansei-Maru. In both instances, there was no evidence of tissue fusion between the male and female anglerfish. Inspection of the morphology of male M. johnsonii supports this non-parasitic mating strategy. Most importantly, both M. johnsonii males and females are able to reach sexual maturity without the presence of the other sex. In parasitic ceratioids, metamorphosed males usually attach to the female before they reach sexual maturity. M. johnsonii males also have a well-developed jaw with many highly functional teeth that allow them to consume prey after metamorphosis. Additionally, the stomachs of metamorphosed males have been dissected and found to contain food items.

Conservation[edit]
M. johnsonii was classified as a "Least Concern" species on IUCN Red List of Threatened Species. It is not a food source for humans and, therefore, is not actively fished by humans. However, individuals may be collected as bycatch with trawling, and as commercial fisheries shift more toward deep sea resources, the species may become more affected by this bycatch. The relatively small number of individuals currently recorded may be due to the scarcity of the species in the deep sea environment and the constraints of collecting such widely dispersed deep sea organisms.

In the Media
Suprisingly, M. johnsonii appears in the media quite frequently. One of the most notable instances of this was in Finding Nemo. While Marlin and Dory search for the notorious P. Sherman diving mask, they are distracted by the bioluminescence of the esca of a M. johnsonii female. As they swim towards the light, the anglerfish appears and attempts to make them her next meal. Because of the feedback they got from this scene, Disney decided to add several of these anglerfish characters into their Finding Nemo Submarine Voyage attraction at Epcot.

In 2014, the first footage of M. johnsonii was captured off of the coast of California by the Monterey Bay Aquarium Research Institute using their remotely operated submersible Doc Ricketts. The video shows a female M. johnsonii, estimated to be around nine centimeters long, slowly swimming at a depth of about 1,900 feet in the Monterey Canyon. The high-tech camera was able to capture all the details of the specimen, including a broken tooth dangling from her mouth and the spots on the side of her body that she uses to sense prey. Most notably, the footage shows the bioluminescent esca of M. johnsonii.

References[edit]

 * 1) Froese, R., Pauly D., Eds. (2015) Melanocetus johnsonii. FishBase.
 * 2) ^ Jump up to: a b Fitch, J.E., Lavenberg R.J. (1968). Deep-water teleostean fishes of California.University of California Press, 115.
 * 3) ^ Jump up to: a b c d e Humpback Blackdevil, Melanocetus johnsonii Gunther, 1864. Australian Museum.
 * 4) ^ Jump up to: a b c d e Arnold, R. (2015). Melanocetus johnsonii. The IUCN Red List of Threatened Species 2015. Retrieved from https://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T18127840A21911455.en.
 * 5) ^ Jump up to: a b c Ryan, P. (2006). Deep-sea creatures - The bathypelagic zone. Te Ara - the Encyclopedia of New Zealand. Retrieved from http://www.TeAra.govt.nz/en/deep-sea-creatures/page-3
 * 6) ^ Jump up to: a b c Orlov, A. M., et al. (2015). First record of humpback anglerfish (Melanocetus johnsonii) (Melanocetidae) in Antarctic waters. Polar Research, 34(1),1-5. doi:10.3402/polar.v34.25356
 * 7) ^ Jump up to: a b c Quigley, D.T. (2014). Ceratioid Anglerfishes. Sherkin Comment, 1(58), 7. http://www.sherkinmarine.ie/SherkinComment58.pdf
 * 8) ^ Jump up to: a b c d Humpback anglerfish. Ocean Animal Encyclopedia. [1] Oceana.
 * 9) ^ Szakmány, C. (2013). Luminescence in Nature and in the Education. Physics Competitions, 15(1), 58-64. http://wettbewerbe.ipn.uni-kiel.de/ipho/wfphc/data/journal/PhysicsCompetitions_Vol_15_No_1u2_2013_09.pdf
 * 10) ^ Pietsch, T. W. (2009). Oceanic Anglerfishes: Extraordinary Diversity in the Deep Sea (1 ed.). University of California Press. p. 365. doi:10.1525/j.ctt1ppb32. ISBN  978-0-520-25542-5.

External links[edit]

 * Melanocetus johnsonii. Marine Species Identification Portal.
 * Melanocetus johnsonii specimen. Museum of New Zealand Te Papa Tongarewa.

Categories:


 * IUCN Red List least concern species
 * Melanocetidae
 * Deep sea fish
 * Fish described in 1864