The diversity of jawed vertebrates may indicate the evolutionary advantage of a jawed mouth. They lacked distinct teeth, having instead the oral surfaces of their jaw plates modified to serve the various purposes of teeth. The first jaws are found in Placodermi fossils. An extant clade, the lampreys may approximate ancient pre-jawed fish. Jawless fish lineages are mostly extinct. Lower jaw of the placoderm Eastmanosteus pustulosus, showing the shearing structures ("teeth") on its oral surface from the Devonian of WisconsinĮarly fish from the fossil record are represented by a group of small, jawless, armored fish known as ostracoderms. to sea star) is an attempt to retroactively apply the current meaning of fish to words that were coined when it had a different meaning. Names such as starfish, jellyfish, shellfish and cuttlefish attest to almost any fully aquatic animal (including whales) once being fish. The English word once had a much broader usage than its current biological meaning. The word for fish in English and the other Germanic languages ( German Fisch Gothic fisks) is inherited from Proto-Germanic, and is related to the Latin piscis and Old Irish īasc, though the exact root is unknown some authorities reconstruct an Proto-Indo-European root * peysk-, attested only in Italic, Celtic, and Germanic. Furthermore, cetaceans, although mammals, have often been considered fish by various cultures and timeperiods.
#FISHING IN THE DARK SONG MEANING PLUS#
However, traditionally fish ( pisces or ichthyes) are rendered paraphyletic by excluding the tetrapods, and are therefore not considered a formal taxonomic grouping in systematic biology, unless it is used in the cladistic sense, including tetrapods, although usually " vertebrate" is preferred and used for this purpose (fish plus tetrapods) instead. Tetrapods ( amphibians, reptiles, birds and mammals) emerged within lobe-finned fishes, so cladistically they are fish as well. Fish have had a role in culture through the ages, serving as deities, religious symbols, and as the subjects of art, books and movies. They are also caught by recreational fishers, kept as pets, raised by fishkeepers, and exhibited in public aquaria. Commercial and subsistence fishers hunt fish in wild fisheries or farm them in ponds or in cages in the ocean (in aquaculture). įish are an important resource for humans worldwide, especially as food. With 34,300 described species, fish exhibit greater species diversity than any other group of vertebrates. They can be found in nearly all aquatic environments, from high mountain streams (e.g., char and gudgeon) to the abyssal and even hadal depths of the deepest oceans (e.g., cusk-eels and snailfish), although no species has yet been documented in the deepest 25% of the ocean.
įish are abundant in most bodies of water. Fish can acoustically communicate with each other, most often in the context of feeding, aggression or courtship. Most fish are ectothermic ("cold-blooded"), allowing their body temperatures to vary as ambient temperatures change, though some of the large active swimmers like white shark and tuna can hold a higher core temperature. The first fish with jaws appeared in the Silurian period, after which many (such as sharks) became formidable marine predators rather than just the prey of arthropods. Many fish of the Paleozoic developed external armor that protected them from predators. Fish would continue to evolve through the Paleozoic era, diversifying into a wide variety of forms. Although they lacked a true spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts. The earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period.
Around 99% of living fish species are ray-finned fish, belonging to the class Actinopterygii, with over 95% belonging to the teleost subgrouping. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Jawless fish † Armoured fish † Spiny sharks Cartilaginous fish Bony fish Ray-finned fish Lobe-finned fishĬladistically included but traditionally excluded taxaįish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Giant grouper swimming among schools of other fish
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