Catfish

Most catfish are bottom feeders. In general, they are negatively buoyant, which means that they usually sink rather than float due to a reduced gas bladder and a heavy, bony head. Juvenile catfish, like other fish, have relatively large heads, eyes, and posterior median fins in comparison to larger, more mature individuals. These juveniles can be readily placed in their families, particularly those with highly derived fin or body shapes; in some cases, identification of the genus is possible. As far as known for most catfish, features that are often characteristic of species, such as mouth and fin positions, fin shapes, and barbel lengths, show little difference between juveniles and adults. For many species, pigmentation pattern is also similar in juveniles and adults. Thus, juvenile catfish generally resemble and develop smoothly into their adult form without distinct juvenile specializations. Exceptions to this are the ariid catfish, where the young retain yolk sacs late into juvenile stages, and many pimelodids, which may have elongated barbels and fin filaments or coloration patterns. Sensory organs The maxilla is a tooth-bearing bone in vertebrates, and modified in neopterygian fish to facilitate the protrusion of the mouth and enable suction feeding. Catfish, despite being a group of neopterygians, reduced the maxilla into a support for the maxillary barbels; Because barbels and chemoreception are more important in detecting food, their eyes are generally small, and many species lost them entirely as they adapted to underground environments, becoming cavefish. Like other ostariophysans, they are characterized by the presence of a Weberian apparatus. as many as half of all catfish species may be venomous in this fashion, making the Siluriformes overwhelmingly the vertebrate order with the largest number of venomous species. This venom is produced by glandular cells in the epidermal tissue covering the spines. Despite the widespread use of the spines for taxonomic and phylogenetic studies the fields have struggled to effectively use the information due to a lack of consistency in the nomenclature, with a general standard for the descriptive anatomy of catfish spines proposed in 2022 to try and resolve this problem. The retinae of catfish are composed of single cones and large rods. Many catfish have a tapetum lucidum, which may help enhance photon capture and increase low-light sensitivity. Double cones, though present in most teleosts, are absent from catfish. Sexual characters Sexual dimorphism is reported in about half of all families of catfish. The modification of the anal fin into an intromittent organ (in internal fertilizers) as well as accessory structures of the reproductive apparatus (in both internal and external fertilizers) have been described in species belonging to 11 different families. The anatomical organization of the testis in catfish is variable among the families of catfish, but the majority of them present fringed testis: Ictaluridae, Claridae, Auchenipteridae, Doradidae, Pimelodidae, and Pseudopimelodidae. Fringes of the caudal region may present tubules, in which the lumen is filled by secretion and spermatozoa. Size '' (goonch) caught in India. Some goonch in the Kali River grow large enough to supposedly attack humans and water buffalo Catfish have one of the largest ranges in size within a single order of bony fish. In North America, the largest Ictalurus furcatus (blue catfish) caught in the Missouri River on 20 July 2010, weighed . The largest flathead catfish, Pylodictis olivaris, ever caught was in Independence, Kansas, weighing . The biggest flathead catfish caught was by Ken Paulie in the Elk City Reservoir in Kansas, US on 19 May 1998 weighing , which was certified by the International Game Fish Association IGFA. A Mekong giant catfish caught in northern Thailand on 1 May 2005, and reported to the press almost 2 months later weighed . This is the largest giant Mekong catfish caught since Thai officials started keeping records in 1981. Also in Asia, Jeremy Wade caught a goonch following three fatal attacks on humans in the Kali River on the India-Nepal border. Wade was of the opinion that the offending fish must have been significantly larger than this to have taken an 18-year-old boy, as well as a water buffalo. Piraíba (Brachyplatystoma filamentosum), a goliath catfish, can grow exceptionally large and are native to the Amazon Basin. They can occasionally grow to , as evidenced by numerous catches. Deaths from being swallowed by these fish have been reported in the region. ==Classification==

Molecular evidence suggests that in spite of the great morphological diversity in the order, all catfish form a monophyletic group, originating from a common ancestor. Catfish belong to a superorder called the Ostariophysi, which also includes the Cypriniformes (carps and minnows), Characiformes (characins and tetras), Gonorynchiformes (milkfish and beaked salmons) and Gymnotiformes (South American knifefish), a superorder characterized by the Weberian apparatus. Some place Gymnotiformes as a sub-order of Siluriformes; however, this is not as widely accepted. Currently, the Siluriformes are said to be the sister group to the Gymnotiformes, though this has been debated due to more recent molecular evidence. there were about thirty-six extant catfish families, and about 3,093 extant species have been described. This makes the catfish order the second or third most diverse vertebrate order; in fact, one out of every twenty vertebrate species is a catfish. The taxonomy of catfish is quickly changing. In a 2007 and 2008 paper, Horabagrus, Phreatobius, and Conorhynchos were not classified under any current catfish families. Many sources do not list the recently revised family Anchariidae. The family Horabagridae, including Horabagrus, Pseudeutropius, and Platytropius, is not shown by some authors but presented by others as a true group. In June 2005, researchers named the newest family of catfish, Lacantuniidae, only the third new family of fish distinguished in the last seventy years, the others being the coelacanth in 1938 and the megamouth shark in 1983. The new species in Lacantuniidae, Lacantunia enigmatica, was found in the Lacantun river in the Mexican state of Chiapas. The higher-level phylogeny of Siluriformes has gone through several recent changes, mainly due to molecular phylogenetic studies. While most studies, both morphological and molecular, agree that catfishes are arranged into three main lineages, the relationship among these lineages has been a contentious point in which these studies, performed for example by Rui Diogo, differ. The three main lineages in Siluriformes are the family Diplomystidae, the denticulate catfish suborder Loricarioidei (containing the Neotropical "suckermouth" catfishes), and the suborder Siluroidei, which contains the remaining families of the order. According to morphological data, Diplomystidae is usually considered to be the earliest branching catfish lineage and the sister group to the other two lineages, Loricarioidei and Siluroidei. Molecular evidence usually contrasts with this hypothesis, and shows the suborder Loricarioidei as the earliest branching catfish lineage, and sister to a clade that includes the Diplomystidae and Siluroidei; this phylogeny has been obtained in numerous studies based on genetic data. However, it has been suggested that these molecular results are errors as a result of long branch attraction, incorrectly placing Loricarioidei as the earliest-branching catfish lineage. was used to reduce lineage rate heterogeneity (the potential source of bias) on their dataset, a final phylogeny was recovered which showed the Diplomystidae are the earliest-branching catfish, followed by Loricarioidei and Siluroidei as sister lineages, providing both morphological and molecular support for Diplomystidae being the earliest branching catfish. • Order Siluriformes • Suborder Diplomystoidei • Family Diplomystidae Eigenmann, 1890 (diplomystid catfishes) • Suborder Cetopsoidei • Family Cetopsidae Bleeker, 1858 (cetopsid catfishes) • Suborder Loricarioidei • Family Nematogenyidae Bleeker, 1862 (mountain catfishes) • Family Trichomycteridae Bleeker, 1858 (pencil catfishes) • Family Callichthyidae Bonaparte, 1835 (callichthyid armored catfishes) • Family Loricariidae Rafinesque, 1815 (suckermouth armored catfishes) • Family Scoloplacidae Bailey & Baskin, 1976 (spiny dwarf catfishes) • Family Astroblepidae Bleeker, 1862 (climbing catfishes) • Suborder Siluroidei • Genus Conorhynchos Bleeker, 1858 (incertae sedis) • Family Chacidae Bleeker, 1858 (squarehead or angler catfishes) • Family Plotosidae Bleeker, 1858 (eeltail catfishes) • Family Ritidae Bleeker, 1862 (velvet catfishes) • Family Ailiidae Bleeker, 1858 (Asian schilbeids) • Family Horabagridae Jayaram, 2006 (imperial catfishes) • Family Bagridae Bleeker, 1858 (bagrid catfishes) • Family Akysidae Gill, 1861 (stream catfishes) • Family Amblycipitidae Day, 1873 (torrent catfishes) • Family Sisoridae Bleeker, 1858 (sisorid catfishes) • Family Pangasiidae Bleeker, 1858 (pangasid catfishes) • Family Siluridae Rafinesque, 1815 (sheatfishes) • Family Kryptoglanidae Britz, Kakkassery & Raghavan, 2014 (Indian cave catfishes) • Family Aspredinidae Adams, 1854 (banjo catfishes) • Family Auchenipteridae Bleeker, 1862 (intromittant catfishes) • Family Doradidae Bleeker, 1858 (thorny catfishes) • Family Heptapteridae Gill, 1861 (seven-finned catfishes) • Family Phreatobiidae Reichel, 1927 (cistern catfishes) • Family Pimelodidae Bonaparte, 1835 (long-whiskered catfishes) • Family Pseudopimelodidae Fernández-Yépez & Antón, 1966 (bumblebee catfishes) • Family Clariidae Bonaparte, 1845 (airbreathing or labyrinth catfishes) • Family Heteropneustidae Hora, 1936 (airsac catfishes) • Family Ariidae Bleeker, 1858 (sea catfishes) • Family Anchariidae Glaw & Vences, 1994 (Malagasy catfishes) • Family Austroglanididae Mo, 1991 (rock catlets) • Family Cranoglanididae Myers, 1931 (armorhead catfishes) • Family Ictaluridae Gill, 1861 (North American freshwater catfishes) • Family Lacantuniidae Rodiles-Hernández, Hendrickson & Lundberg, 2005 (Chiapas catfishes) • Family Amphiliidae Regan, 1911 (loach catfishes) • Family Malapteruridae Bleeker, 1858 (electric catfishes) • Family Mochokidae Regan, 1912 (squeakers and upside-down catfishes) • Family Auchenoglanididae Jayaram, 1966 (flatnose catfishes) • Family Claroteidae Bleeker, 1862 (grunter catfishes) • Family Schilbeidae Bleeker, 1858 (schilbeid catfishes) Phylogeny Phylogeny of living Siluriformes based on 2017 and extinct families based on Nelson, Grande & Wilson 2016. }} Evolution Catfish are believed to have a Gondwanan origin primarily centered around South America, as the most basal living catfish groups are known from there. The earliest known definitive members lived in the Americas from the Campanian to Maastrichtian stages of the Late Cretaceous, including the Andinichthyidae, Vorhisia vulpes and possibly Arius. though this has been considered unreliable, and the putative earliest armored catfish known from the fossil record, Afrocascudo, lived during the Cenomanian age of the Late Cretaceous in Morocco of North Africa (Kem Kem Group). The authors of the original study still stood by their original conclusion based on the absence of important holostean characters, and noted that it could not be a juvenile, since the bones were completely ossified. Fossil taxa • Order Siluriformes • Family †Andinichthyidae (Late Cretaceous to Paleogene of South America) • Suborder Diplomystoidei • Family †Bachmanniidae (Eocene of Argentina) • Suborder Siluroidei • Family †Astephidae (Paleocene to Oligocene of North America) • Family †Hypsidoridae (Eocene of North America) ==Distribution and habitat==

Catfish live inland or in coastal waters of every continent except Antarctica. Catfish have inhabited all continents at one time or another. They are found in fresh water/brackish water environments, with most inhabiting shallow, running water. One such species is Phreatobius cisternarum, known to live underground in phreatic habitats. Numerous species from the families Ariidae and Plotosidae, and a few from Aspredinidae and Bagridae, are found in salt water. ==Behavior==

Many catfish are nocturnal, but others (many Auchenipteridae) are crepuscular or diurnal (most Loricariidae or Callichthyidae, for example). Communication Catfish can produce different types of sounds and also have well-developed auditory reception used to discriminate between sounds with different pitches and velocities. They are also able to determine the distance of the sound's origin and from what direction it originated. This is a very important fish communication mechanism, especially during agonistic and distress behaviors. Catfish are able to produce a variety of sounds for communication that can be classified into two groups: drumming sounds and stridulation sounds. The variability in catfish sound signals differs due to a few factors: the mechanism by which the sound is produced, the function of the resulting sound, and physiological differences such as size, sex, and age. To create a drumming sound, catfish use an indirect vibration mechanism using the swimbladder as a resonating chamber. In these fishes, special sound-producing muscles (sonic muscles) insert on the ramus Mulleri, also known as the elastic spring. The sonic muscles pull the elastic spring forward and extend the swimbladder. When the muscles relax, the tension in the spring quickly returns the swimbladder to its original position, which produces the sound. In stridulators, the sound-generating mechanism is found in their pectoral fins; the first pectoral fin ray or spine can be moved by large abductor and adductor muscles. The base of the catfishes' spines has a sequence of ridges, and the spine normally slides within a groove on the fish's pelvic girdle during routine movement; but, pressing the ridges on the spine against the pelvic girdle groove creates a series of short pulses. Sound production in catfish may also be correlated with fighting and alarm calls. According to a study by Kaatz, sounds for disturbance (e.g. alarm) and agonistic behavior were not significantly different, which suggests distress sounds can be used to sample variation in agonistic sound production. ==Relation to humans==

Food Catfish are easy to farm in warm climates and are often sold cheaply by local grocers. About 60% of U.S. farm-raised catfish are grown within a 65-mile (100-km) radius of Belzoni, Mississippi. Channel catfish (Ictalurus punctatus) support a $450 million/yr aquaculture industry. Catfish raised in inland tanks or channels are usually considered safe for the environment, since their waste and disease should be contained and not spread to the wild. In Asia, many catfish species are important as food. Several airbreathing catfish (Clariidae) and shark catfish (Pangasiidae) species are heavily cultured in Africa and Asia. Exports of one particular shark catfish species from Vietnam, Pangasius bocourti, have met with pressures from the U.S. catfish industry. In 2003, the United States Congress passed a law preventing the imported fish from being labeled as catfish, this being the conclusion of the so-called Catfish Dispute. As a result, the Vietnamese exporters of this fish now label their products sold in the U.S. as "basa fish". Trader Joe's has labeled frozen fillets of Vietnamese Pangasius hypophthalmus as "striper". Catfish have widely been caught and farmed for food for thousands of years in Africa, Asia, Europe, and North America. Opinions of their quality and flavor vary, with some food critics considering catfish excellent and others dismissing them as watery and lacking in flavor. Catfish is high in vitamin D. Farm-raised catfish contains low levels of omega-3 fatty acids and a much higher proportion of omega-6 fatty acids. In Central Europe, catfish were often viewed as a delicacy to be enjoyed on feast days and holidays. Migrants from Europe and Africa to the United States brought along this tradition, and in the Southern United States, catfish is extremely popular. The most commonly eaten species in the United States are the channel catfish and the blue catfish, both common in the wild and increasingly widely farmed. Farm-raised catfish became such a staple of the U.S. diet that President Ronald Reagan proclaimed National Catfish Day on June 25, 1987, to recognize "the value of farm-raised catfish." Catfish is prepared in a variety of ways. In Europe, it is often cooked in similar ways to carp, but in the United States it is popularly crumbed with cornmeal and fried. Only fish of the family Ictaluridae may be marketed as catfish in the United States. In the UK, Vietnamese catfish is sometimes sold as "Vietnamese river cobbler", although more commonly as basa. In Nigeria, catfish is often cooked in a variety of stews. It is particularly cooked in a delicacy popularly known as "catfish pepper soup" which is enjoyed throughout the nation. In Jewish dietary law, known as kashrut, fish must have fins and scales to be kosher. Since catfish lack scales, they are not kosher. Mythology In the mythology of the Japanese Shinto religion, natural phenomena are caused by kami. Earthquakes are caused by a giant catfish called Namazu. There are other kami associated with earthquakes. In Kyoto it's usually an eel, but after the 1855 Edo earthquake, were printed, giving more popularity to the catfish kami that has been known since the 16th century Otsu-e. In one catfish print the divine white horse of Amaterasu is depicted knocking down the earthquake-causing catfish. In aquaria There is a large and growing ornamental fish trade, with hundreds of species of catfish, such as Corydoras and armored suckermouth catfish (often called plecos), being a popular component of many aquaria. Other catfish commonly found in the aquarium trade are banjo catfish, talking catfish, and long-whiskered catfish. As invasive species Representatives of the genus Ictalurus have been introduced into European waters in the hope of obtaining a sporting and food resource, but the European stock of American catfishes has not achieved the dimensions of these fish in their native waters and have only increased the ecological pressure on native European fauna. Walking catfish have also been introduced in the freshwater areas of Florida, with the voracious catfish becoming a major alien pest there. Flathead catfish, Pylodictis olivaris, is also a North American pest on Atlantic slope drainages. ==See also==