Lepidophagy is a specialised feeding behaviour in fish that involves eating the scales of other fish. [1] Lepidophagy is widespread, having evolved independently in at least five freshwater families and seven marine families. [2] A related feeding behavior among fish is pterygophagy: feeding on the fins of other fish. [3]
Lepidophagy, or scale-eating, has been reported in a range of fish, including: Chanda nama (family Ambassidae), [4] Plagiotremus (family Blenniidae), [5] Terapon jarbua (family Terapontidae), [1] a few Ariopsis and Neoarius species (family Ariidae), [6] Pachypterus khavalchor (family Pachypteridae), Macrorhamphoides uradoi (family Triacanthodidae), several pencil catfish (family Trichomycteridae), [5] some piranha, Exodon paradoxus , Probolodus , Roeboides and Roeboexodon species (order Characiformes), [2] [7] [8] [9] Cyprinodon desquamator (family Cyprinodontidae), along with both Perissodus species, all four Plecodus species, Xenochromis , Haplochromis welcommei , Docimodus , Corematodus and Genyochromis mento (family Cichlidae from the African Great Lakes). [10] [11] [12]
Several of these scale-eaters also feed on fins of other fish, and many omnivorous or predatory fish may on occasion nip the fins of other fish. Only a few species are specialized fin-eaters, or pterygophagous; these include Belonophago , Eugnathichthys and Phago (family Distichodontidae), Aspidontus (family Blenniidae), and Smilosicyopus (family Gobiidae). [3] [13] A somewhat related behavior is found in Magosternarchus , which feed on the tails (both fin and connective tissue) of other gymnotiform knifefish. [14]
Many species of cichlid fish have evolved specialized teeth and mouth structures that make them better able to feed on the scales of other fish. [15] Other species of fish also have a morphology that is better adapted to scale-eating. Many such species’ oral structures closely resemble each other even though they live in different habitats, and many also have specialized jaw structures. [16] One species of fish in particular, called Roeboides prognathous, has a jaw structure that is extremely specialized for lepidophagy. [16] Certain species of lepidophagous catfish, Pachypterus khavalchor, have digestive enzymes which help them to more readily break down the fins, eyes, scales of other fish. [16] There are other morphological structures that are important in scale-eating habitats. There are six lepidophagous cichlid species who employ mimicry strategies to deceive their prey: the colors of the cichlid fish closely resemble the colors of some of their prey. However they not only eat the scales of the fish they resemble, but also prey on a wide range of other species. [15]
There are many different behaviours associated within lepidophagous fish. Aggression and attack behaviours like chasing and striking prey are common among Pachypterus khavalchor catfish, who then eat the fallen scales of their prey. [16] The attack behaviour of the wimple piranha Catoprion mento , whose diet consists mainly of scales, is described as a “high-speed” attack. They ram into their prey with their mouth open, biting the prey to obtain their scales. [17] Perissodus microlepis cichlid fish tear off the scales of their prey as they swim past. [18] This is very different from other lepidophagous species, who merely knock the scales loose by striking the prey. [17]
There are differences and similarities in lepidophagous behaviours across species. For example, the siluroid catfish’s attacking behaviour is similar to that of the Probolodus heterostomus : they both follow their prey and attack their prey from behind. This is different from the behaviour of Roeboides prognatus and Exodon paradoxus , who remove scales more easily by attacking a specific part of their prey’s body called the caudal area. [16] Many studies have examined the hunting behaviours of scale-eating fish and how those behaviours have evolved over time. Certain species of cichlid aggressively mimic the behaviours of their prey, [15] a tactic rarely used by other scale-eating fish species. [15]
The differences in the niche of certain species may play a role in their behaviours. Lepidophagous behaviours only exist in some species. [19] Adaptive radiation has been mentioned in many articles as having a role in the evolution of lepidophagy. [19] There is some evidence to support this but much is also unclear. Some behaviours in certain species of fish support the theory that extreme environments could be potential causes of scale eating behaviours. Some of those species are named below.
In the case of Cyprinodon pupfish, almost all have a diet of algae and detritus but the species Cyprinodon desquamator (only scientifically described in 2013; previously known as Cyprinodon sp. "lepidophage" or Cyprinodon sp. "scale-eater") is different. There are only two known cases where several Cyprinodon species live together: lakes in San Salvador Island, the Bahamas, and Lake Chichancanab, Mexico. In both cases, the co-occurring Cyprinodon species have diverged into feeding on different things and in lakes on San Salvador Island, this includes the scale-eating C. desquamator (there are no scale-eaters in Lake Chichancanab, although C. maya has become a fish-eater). [20]
There is a diverse range of cichilds in Lake Tanganyika in East Africa but the Tanganyikan cichlid tribes, Perissodini and Plecodus, feed on the scales of cichlids and other fishes. [21] The species of cichilds that exhibit scale eating behaviours live in deep water with very low levels of oxygen and have had to rapidly evolve to keep up with a changing environment and lack of food. [19]
Fish scales are a nutritional food source, containing layers of keratin and enamel, as well as a dermal portion and a layer of protein-rich mucus. They are a rich source of calcium phosphate. [2] However, the energy expended to make a strike versus the amount of scales consumed per strike puts a limit on the size of the lepidophage; such fish seldom exceed 20 cm (8 in) and most are under 12 cm (5 in). [2] Because of this lepidophagous fish usually are much smaller than their prey. Though scales are nutritious, the average amount of scales dislodged and eaten may not be sufficient to make up for the energy lost during the attack. [17] The attack behaviours and strikes that are employed to remove and eat scales have an energy cost and risk of harm to the predator. [22] In light of this, there are also a number of advantages to consuming scales: scales are common, covering the body of most fish species, can be regrown relatively quickly by "prey" fish, are abundant and seasonally reliable, and their removal requires specific behaviours or morphological structures. [2] Scale eating behaviour usually evolves because of lack of food and extreme environmental conditions. The eating of scales and the skin surrounding the scales provides protein-rich nutrients that may not be available elsewhere in the niche. [20]
In evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, alters biotic interactions or opens new environmental niches. Starting with a single ancestor, this process results in the speciation and phenotypic adaptation of an array of species exhibiting different morphological and physiological traits. The prototypical example of adaptive radiation is finch speciation on the Galapagos, but examples are known from around the world.
Cichlids are fish from the family Cichlidae in the order Cichliformes. Cichlids were traditionally classed in a suborder, the Labroidei, along with the wrasses (Labridae), in the order Perciformes, but molecular studies have contradicted this grouping. On the basis of fossil evidence, it first appeared in Tanzania during the Eocene epoch, about 46–45 million years ago. The closest living relative of cichlids is probably the convict blenny, and both families are classified in the 5th edition of Fishes of the World as the two families in the Cichliformes, part of the subseries Ovalentaria. This family is both large and diverse. At least 1,650 species have been scientifically described, making it one of the largest vertebrate families. New species are discovered annually, and many species remain undescribed. The actual number of species is therefore unknown, with estimates varying between 2,000 and 3,000.
Lake Tanganyika is an African Great Lake. It is the second-oldest freshwater lake in the world, the second-largest by volume, and the second-deepest, in all cases after Lake Baikal in Siberia. It is the world's longest freshwater lake. The lake is shared among four countries—Tanzania, the Democratic Republic of the Congo (DRC), Burundi, and Zambia, with Tanzania (46%) and DRC (40%) possessing the majority of the lake. It drains into the Congo River system and ultimately into the Atlantic Ocean.
Pupfish are a group of small killifish belonging to ten genera of the family Cyprinodontidae of ray-finned fish. Pupfish are especially noted for being found in extreme and isolated situations. They are primarily found in North America, South America, and the Caribbean region, but Aphanius species are from southwestern Asia, northern Africa, and southern Europe. As of August 2006, 120 nominal species and 9 subspecies were known. Several pupfish species are extinct and most extant species are listed. In the U.S., the most well-known pupfish species may be the Devil's Hole Desert Pupfish, native to Devil's Hole on the Nevada side of Death Valley National Park. Since 1995 the Devil's Hole Pupfish has been in a nearly steady decline, where it was close to extinction at 35–68 fish in 2013.
Variabilichromis moorii has no common name and is a species of freshwater cichlid endemic to Lake Tanganyika in eastern Africa. It is a small ovate bodied fish named for an early collector of fish from the lake, John Edmund Sharrock Moore (1870-1947) who was a cytologist, zoologist and led an expedition to Lake Tanganyika and who discovered this species. Juveniles are usually yellow, and adults are dark brown to black in color. It reaches a total length (TL) of 10.3 centimetres (4.1 in). Currently it is the only member of its genus. V. moorii feeds on algae, zooplankton, and benthic invertebrates. It is also found in the aquarium trade.
Cyprinodon is a genus of pupfishes found in waters that range from fresh to hypersaline. The genus is primarily found in Mexico, the Caribbean Islands and southern United States, but C. variegatus occurs as far north as Massachusetts and along the entire Gulf of Mexico coastline, and C. dearborni and C. variegatus are found in northern South America. Many species have tiny ranges and are highly threatened, in some cases already extinct. Cyprinodon are small; the largest reaches 10 cm (3.9 in) in length and most other species only reach about half that size.
Paedophagy in its general form is the feeding behaviour of fish or other animals whose diet is partially, or primarily the eggs or larvae of other animals. However, P. H. Greenwood, who was the first to describe paedophagia, defines it to be a feeding behaviour evolved among cichlid fishes.
The wimple piranha, Catoprion mento, is a specialized, South American species of piranha that feeds on fish scales. There is debates over whether or not this species is considered a true piranha. If it was considered a true piranha, then it would be the smallest species in the world
Catoprion is a genus of serrasalmids from tropical South America, including the basins of the Amazon, Essequibo, Orinoco and Paraguay rivers. It was believed to be a monotypic genus until the 2020 description of C. absconditus.
The Maya pupfish, known in Spanish as cachorrito gigante, is a highly threatened species of fish in the family Cyprinodontidae. It is endemic to Lake Chichancanab in Quintana Roo, Mexico. In almost all places, different Cyprinodon species do not overlap in their range, but there are two notable exceptions and one of these is Lake Chichancanab, which is inhabited by C. maya, C. beltrani, C. esconditus, C. labiosus, C. simus, C. suavium and C. verecundus. Living together, the Cyprinodon species in Lake Chichancanab have diverged into different niches. Pupfish typically feed on algae and detritus. In Lake Chichancanab, however, C. maya has become not only the largest species in the genus Cyprinodon, up to 10 cm (3.9 in) long, but also the only that catches and eats whole fish. In smaller quantities it eats ostracods and freshwater snails.
The largefin pupfish, also known as cachorrito de dorsal larga, is a small species of pupfish in the family Cyprinodontidae. It is endemic to Lake Chichancanab in Quintana Roo, Mexico. In almost all places, different Cyprinodon species do not overlap in their range, but there are two notable exceptions and one of these is Lake Chichancanab, which is inhabited by C. verecundus, C. beltrani, C. esconditus, C. labiosus, C. maya, C. simus and C. suavium. Living together, the Cyprinodon species in Lake Chichancanab have diverged into different niches. Pupfish typically feed on algae and detritus. In Lake Chichancanab, however, C. verecundus has become an amphipod- and bivalve-eater.
Perissodus microlepis is a species of cichlid endemic to Lake Tanganyika. This species reaches a length of 11 centimetres (4.3 in) TL. This species can also be found in the aquarium trade. It is a scale-eating 'parasite' on other fish species. It occurs in two distinct morphological forms. One morph has mouth parts twisted to the left, enabling it to eat scales off its victim's right flank. In contrast, the other morph, whose mouth is twisted to the right, eats scales off its victim's left flank. The relative abundance of the two morphs in populations is regulated by frequency-dependent selection.
Plecodus elaviae is a species of cichlid endemic to Lake Tanganyika. This schooling species is a scale-eater, plucking scales from other fishes. Both parents care for the offspring in this mouthbrooder. This fish can reach a length of 32 centimetres (13 in) TL.
Plecodus is a genus of cichlids endemic to Lake Tanganyika in Africa. They feed on scales.
Plecodus paradoxus is a species of cichlid endemic to Lake Tanganyika. This fish is a scale-eater, gathering in large schools exceeding 500 individuals and eating the scales of other fish. This species can reach a length of 30 centimetres (12 in) TL.
Plecodus straeleni is a species of cichlid fish that is endemic to Lake Tanganyika in East Africa. This species can reach a total length of 16 centimetres (6.3 in).
A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as well as possible hydrodynamic advantages. The term scale derives from the Old French escale, meaning a shell pod or husk.
Cyprinodon desquamator is a scale-eating species of pupfish in the genus Cyprinodon. It is endemic to hypersaline interior lakes on San Salvador Island, Bahamas. It coexists alongside two other closely related Cyprinodon species C. brontotheroides and C. variegatus. Together, these three species represent a recent adaptive radiation, each having moved into a difference niche within their specialized environment. Each of these species are defined by distinct trophic adaptations that have affected various aspects of their functional morphology, behavior, strike kinematics, and reproductive coloration.
Cyprinodon brontotheroides is a species of pupfish in the genus Cyprinodon.
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