Sea toad

The sea toads and coffinfishes are a family of deep-sea anglerfishes known as the Chaunacidae.

These are bottom-dwelling fishes found on the continental slopes of the Atlantic, Indian, and Pacific Oceans, at depths to at least 2,460 m (8,070 ft). There have also been findings of deep-sea anglerfishes off the coasts of Australia and New Caledonia. Other findings suggest some genera of Chaunacidae are found near volcanic slopes encrusted with manganese. Of the two genera in the family, Chaunacops typically occurs at deeper depths than Chaunax, but with considerable overlap.

They have large, globose bodies and short, compressed tails, and are covered with small, spiny scales. The largest are about 30 cm (12 in) in length. During their gill ventilatory cycle, Chaunacidae are able to take in high volumes of water, increasing their total body volume by 30%. The first dorsal fin ray is modified into a short bioluminescent lure which dangles forward over the mouth, which is turned upwards so as to be nearly vertical. The sensory canals of the lateral lines are especially conspicuous. Chaunax have modified fins which resemble legs. It was also found that they use these modified pelvic fins to assist with maneuvering their swimming, especially when as an escape response.

Sea toads are mostly sedentary fish, and rely on a more opportunistic way of hunting where they prey on anything within reach. The sensory canals of the lateral lines are especially conspicuous, and confers advantages in avoidance of predators and consumption of prey.

Sexual Dimorphism
A species from Chau­naci­dae, Chau­na­cops melanostomus, ex­hibits a sin­gle trait show­ing sex­ual di­mor­phism. Sam­ple col­lec­tion shows that males tend to have larger nos­trils than fe­males, and even in the small­est males, nos­trils tend to be very apparent.

Distribution and Habitat
We cur­rently know of 3 species of Chauno­cops that live in the Indo-west Pa­cific Ocean, which are C. coloratus, C. melanostomus and C. spinosus. How­ever, mem­bers of the fam­ily Chau­naci­dae have been col­lected from the East­ern In­dian Ocean, the East­ern Pa­cific Ocean, and the West­ern At­lantic Ocean, show­ing that this fam­ily is rel­a­tively widely dis­trib­uted. Namely, in 1989 a study was done by John H. Caruso in which 21 spec­i­mens of Chau­nacid fish were col­lected off the west­ern coast of Aus­tralia, many of which were col­lected at ap­prox­i­mately -30° lat­i­tude, and ap­prox­i­mately 90° lon­gi­tude. These spec­i­men were from the genus Ba­thy­chau­nax, which be­fore this study only con­tained 2 other species: B. coloratus of the East­ern Pa­cific, and B. roseus from the West­ern At­lantic. The new species of Ba­thy­chau­nax was found at depths be­tween 1320m and 1760 m. Fur­ther­more, in 2015 an ar­ti­cle was pub­lished in­di­cat­ing that new specemins from the genus Chau­na­cops were found off the coasts of Aus­tralia and New Caledonia.

In ad­di­tion, it was found that the Chau­na­cops coloratus are also often found near "man­ganese-en­crusted vol­canic talus slopes". The fish were ob­served to often have one of their pec­toral fins in sed­i­ment and an­other one on a rock in order to make it seem as though they were wedged be­tween two sub­strates. The av­er­age oxy­gen con­cen­tra­tion was found to be about 1.59 ml/L at the depths they were found and the av­er­age tem­per­a­ture was about 1.68 °C. Salin­ity in their habi­tats did not change much and was found to be an av­er­age of 34.64 psu.

Chaunocops spinosis
Upon col­lec­tion and ex­am­i­na­tion of this species, it is ob­served to have sev­eral dis­tinct phys­i­cal at­trib­utes. One trait is the fine der­mal spin­ules, along with sim­ple and bi­fur­cate der­mal spin­ules, cov­er­ing the body. It also has four pec­toral lat­eral-line neu­ro­masts, which are sen­sory or­gans char­ac­ter­is­tic to fish and aquatic or­gan­isms. It has a grey­ish mouth, and semi-trans­par­ent, light-grey­ish skin. In­side the mouth are sev­eral rows of teeth. There are three or four rows of small ca­nine teeth on the upper jaw, and three rows of the same on the lower jaw. The skin of the head, belly, and most of gill cham­ber is dark blue, and it has a rel­a­tively short tail. As for the over­all body struc­ture, body is re­sem­blant of a ta­do­ple, with a more glob­u­lar shape in the an­te­rior which ta­pers in the pos­te­rior. The eyes are cov­ered by trans­par­ent skin and are very small.

Chaunacops melanostomus
An­other species in the same genus was col­lected with sim­i­lar traits to the above species, but some no­tice­able dif­fer­ences. The spin­ules are dis­trib­uted widely through­out the body, sim­i­lar to C. spinosis, but are sim­ple with a large base (dif­fer­ent from that of C. spinosis which has sim­ple as well as bi­fur­cate der­mal spin­dles). They also dif­fer slightly in color. The in­side of the mouth, the head, the gill cham­ber, and the an­te­rior por­tion of the body are dark brown to black. The dor­sal side of the body, and the cau­dal fin are light brown, and be­comes more lightly col­ored going to­wards the pos­te­rior end. Also, in­stead of hav­ing three or four rows of teeth, C. melanostomus has two rows on both jaws. The gen­eral body plan, how­ever, is vir­tu­ally the same, re­sem­bling a tad­pole, with a more glob­u­lar shape in the an­te­rior which ta­pers in the posterior.

Chaunacops coloratus
The Chau­na­cops coloratus are an­other species that were dis­cov­ered and are known for their bright red and blue col­ors. It was found that the blue C. coloratus often had an av­er­age length of about 110 mm, whereas the red spec­i­men had an av­er­age length of 184 mm. It was ob­served that the spec­i­men begin in a trans­par­ent lar­val form, then be­come blue, and even­tu­ally reach their adult red color. As for pre­da­tion, it is hy­poth­e­sized that the spec­i­men turn­ing red is ad­van­ta­geous for am­bush­ing preda­tors that use bi­o­lu­mi­nes­cent light to at­tract pos­si­ble prey, since the red col­oration of this spec­i­men would con­ceal the preda­tor and make it invisible.

C. coloratus
Through ob­ser­va­tions made by an ROV, it was found that the C. coloratus swim ver­ti­cally with their head ori­ented up­wards. While in rapid as­cent, the spec­i­men will use their dor­sal, cau­dal, and anal fins to pro­pel them­selves up­wards and tuck the rest of their fins in close to their body. The ob­ser­va­tion col­lected found that the spec­i­men had av­er­age ve­loc­i­ties of 0.036 m/s and 0.021 m/s while as­cend­ing. As for ma­neu­ver­ing across the ocean floor, ob­ser­va­tions found that the spec­i­men use their pec­toral and pelvic fins. In order to per­form this "walk­ing," they use their dor­sal fin from one side to side, then thrust their cau­dal fin re­peat­edly, and then ma­neu­ver using their pec­toral and pelvic fins. It was also ob­served that these spec­i­men are ca­pa­ble of walk­ing back­wards using their pec­toral and pelvic fins.

Breathing
Fish of the fam­ily Chau­naci­dae have been shown to have slow ven­ti­la­tory cy­cles in which the fish ex­hales 20-30% of their body vol­ume of water. Upon in­hala­tion, Chau­naci­dae can en­dure long pe­ri­ods of time main­tain­ing a fully in­flated gill cham­ber, some­times up to 245 sec­onds which con­fers many po­ten­tial ad­van­tages for fish of this fam­ily. Chau­naci­dae have been found to con­tain a spe­cial­ized ap­pa­ra­tus con­tain­ing ad­duc­tor mus­cles that can main­tain its ven­ti­la­tory cycle, and con­trol the vol­ume of water en­ter­ing and ex­it­ing. These mus­cles are cross-hatched, and func­tion to not only in­hale and ex­hale, but to pre­vent any leak­age out of the gills.

Due to the high-vol­ume and slow ven­ti­la­tory cycle, Chau­naci­dae are able to be ma­jorly en­ergy ef­fi­cient as it re­quires less en­ergy to push water across the sur­face of their gills. Be­cause of this, Chau­naci­dae are able to go with­out prey for long pe­ri­ods of time, and re­main mostly sedentary.

There are many other hy­pothe­ses of ad­van­tages con­ferred by the breath­ing cycle of Chau­naci­dae. Due to the long pe­ri­ods of high-vol­ume in­hala­tion, Chau­naci­dae makes lit­tle dis­tur­bance of lat­eral line sys­tems, al­low­ing for bet­ter hunt­ing and avoid­ance of preda­tors. In ad­di­tion, the max­i­mally filled mouth of the Chau­naci­dae is often in­tim­i­dat­ing to preda­tors, mak­ing it a de­fense mech­a­nism that the fish can use much like the Pufferfish.

Diet
Chau­naci­dae are known to be mostly seden­tary fish, and spend most of their time dor­mant on the seafloor. Be­cause of their en­ergy ef­fi­cient way of ven­ti­la­tion, Chau­naci­dae are able to go long pe­ri­ods of time with lit­tle food. In a diet study, Chau­nax fimbriatus was found to con­tain a stom­ach that con­tained many dif­fer­ent prey, show­ing that Chau­naci­dae are op­por­tunis­tic hunters that will eat most any­thing it can on the seafloor.

Chau­naci­dae are also steady hunters, as they are able to main­tain rel­a­tively low move­ment. Due to their gill cham­bers, Chau­naci­dae are able to re­main still enough until their prey is within distance.

Taxonomy
Chau­naci­dae are a fam­ily of fish that arise from the order Lophi­iformes and of the class Actinoptery­gii. Chau­naci­dae con­tain the gen­era of both Chau­na­cops and Chau­nax.

In popular culture
As of re­cent years, sea toads have be­come the tar­get of a viral meme, par­tic­u­larly pop­u­lar on Twit­ter and Red­dit. The meme is a pun on the word 'de­spacito', which was brought to the lime­light after the re­lease of a song with the same name by Luis Fonsi.