Living fishes • The living fishes (not a monophyletic group) include: • the jawless fishes (e.g. lampeys), • cartilaginous fishes (e.g. sharks and rays), • bony, ray-finned fishes (most of the bony fishes such as trout, perch, pike, carp, etc) and • the bony, lobe-finned fishes (e.g. lungfishes, coelacanth).
Bony fishes: Osteichthyes • The term osteichthyes does not describe a monophyletic group, but is a term of convenience to describe the fishes whose skeletons are made of bone that replaces cartilage during embryonic development. • There are two classes the Actinopterygii (the ray-finned fishes) and the Sarcopterygii (the lobe-finned fishes)
General characteristics of bony fish • Skeleton made of bone of endochondral origin (derived from cartilage). • Paired and median fins supported by dermal rays. • Respiration mainly by gills. Gills covered with operculum. • Swim bladder often present. • Complex nervous, circulatory and excretory systems present
Class Actinopterygii (ray-finned fishes) • This is by far the larger of the two living classes of fishes with more than 27,000 species. • Includes probably every fish you can think of. E.g. salmon, cod, herring, tuna, marlin, pike, sardine, clownfish, goldfish.
Divisions of Actinopterygii • The Actinopterygii are divided into two groups • Palaeonisciformes (formerly known as the “chondrosteans”), which includes the relic species just mentioned. • Neopterygii, which includes the most derived and most recent group of ray-finned fishes the Teleostei and a number of primitive species including the gars and bowfins. These primitive Neopterygii were once grouped as the “holosteans.”
Ancestral ray finned fishes in the Devonian were small and heavily armored with ganoid scales (thick, bony, non-overlapping, relatively inflexible scales) and heterocercal tails (shaped like that of modern sharks).
Palaeonisciformes “Chondrosteans” • A few relic species still possess such characteristics. • These include sturgeon and paddlefish which are included in the Acipenseriformes and the bichirs (Polypteriformes).
Palaeonisciformes • The relatively few surviving Palaeonisciformes are the remnant of what was once a much more diverse group. • Palaeonisciformes were the first bony fishes and were most diverse in the Carboniferous and Permian.
Palaeonisciformes • Extinct palaeoniscids were mostly small < 0.5m with a fusiform shape which suggests they were active foragers. • They were covered with small diamond-shaped scales. • The base of each scale was made of bone, the middle of dentin and the surface with an enamel-like substance called ganoine. Hence the name ganoid scales.
Sturgeons and Paddlefish • These lack ganoid scales except for in sturgeons the rows of enlarged scales that run along the sides of the body. • The skeleton is almost entirely cartilaginous, which has resulted from the loss of mineralization.
Paddlefish • The two species of Paddlefish are found in fresh water in North America and China. The Chinese species is nearly extinct. • About 2m long paddlefish possess an elongated flattened rostrum, which is believed to be used to detect tiny, electric fields. • The North American paddlefish is a planktivore.
Sturgeons • There are 24 species of sturgeons and all are large fish that reach up to 6m in length. • They have a protrusible jaw (evolved independently of the teleosts) which they use for suction feeding. • They are commercially important for their meat, but especially their eggs (caviar).
Bichirs • There are 11 species of bichir and they are considered the most primitive surviving group of the ray-finned fishes. • They are heavily armored with dermal bone and a thick layer of ganoid scales. • Occur in swamps and streams in Africa and have a swim bladder that acts like a paired ventral lung. They will drown if unable to gulp air at the surface.
Armored Bichir http://www.aquarticles.com/images/Gallo/Armoured%20bichir%202.gif http://www.fbas.co.uk/Bichir.jpg
Bichirs • Because bichirs have paired fleshy pectoral fins and lungs they were formerly classified with the lungfishes, but are now considered to have evolved these traits independently.
Neopterygii: “holosteans” • There are two genera of primitive Neopterygians that were previously grouped together as holosteans. • Both have more flexible jaws than Palaoniscids, but less flexible than those of more advanced Neopterygians. • These are the seven species of gars (Lepisosteiformes) and the single species of bowfin (Amiiformes).
Gars • Gars are medium to large (1-4m) predatory fish with a distinctive elongated body and long jaws. • They have hard, interlocking, multilayered ganoid scales which provide excellent protection and are similar to the scales of many extinct Paleozoic and Mesozic actinoptrygians.
http://animals.nationalgeographic.com/staticfiles/NGS/ Shared/StaticFiles/animals/images/primary/gar.jpg Longnose gar http://www.biokids.umich.edu/files/12296/gar_large.jpg
Bowfin • There is only one species of bowfin. • Its scales are of a single layer of bone as in teleosts, but the caudal fin is asymmetric and similar to that of more primitive fishes.
Teleosts • The vast majority of modern fishes are “teleosts.” • They have replaced the heavy armored scales of their ancestors with much lighter more flexible scales that overlap each other and also have evolved homocercal symmetrical tails.
Teleost characters • Homocercal tail • Circular scales without ganoine • Ossified vertebrae • Swim bladder • Skull with complex jaw mobility
Teleost classification • How the Neopterygii should be subdivided differs greatly from authority to authority. • We will use the text’s division of the teleosts into three large groups: • Teleostei • Euteleostei • Acanthopterygii
Diversity of bony fishes: Teleostei • There are three major clades of the Teleostei • Osteoglossomorpha: [greek bony tongue]. About 220 species of tropical freshwater fish. Includes from the Amazon Osteoglossum or Arawana, and Arapaima the largest purely freshwater fish (regularly 3m long, but up to 4.5 m). • Also includes the African elephant nose fish, which are bottom feeders and that use weak electric signals to communicate with each other
Elephant nose fish http://images.google.com/imgres?imgurl=http://www.bio.davidson.edu/people/ midorcas/animalphysiology/websites/2003/Wilson/cfunspics/ elephant_nose.jpg&imgrefurl=http://www.bio.davidson.edu/people/midorcas/ animalphysiology/websites/2003/Wilson/ GalONE.htm&usg=__yE31La06_D121J4Yga5NHWknr5Y=&h=467&w=1458&sz =57&hl=en&start=3&tbnid=xQ3Vx636CuW21M:&tbnh=48&tbnw=150&prev=/ images%3Fq%3Delephant%2Bfish%26gbv%3D2%26hl%3Den%26sa%3DG
Teleostei: Elopomorpha • Elopomorpha: includes tarpons, bonefishes, and eels. • Specialized leptocephalous [Greek small headed] larvae are a unique feature of the group. The larvae spend a long time adrift on the ocean being moved by ocean currents.
Bonefish http://www.islaculebra.com/puerto-rico/fishing.html Tarpon http://www.wildernessaccess.com/images/ fishn/Tarpon-FISH-Justin- S-America-Venezuela-Los-Rogos.jpg
Eels • Most elopomorphs are eel-like and marine, but some tolerate freshwater. • The American eel has a very unusual life-cycle. The eels grow to sexual maturity in rivers and streams (taking 10 years or more) and then migrate downriver into the ocean to breed. (They are catadramous.)
Eels • They swim to the Sargasso Sea (an area of the North Atlantic between the Azores and West Indies) where they apparently spawn and die, presumably at depth. • Eggs and larvae float to the surface and drift on the currents until they reach the near the coast. Then they transform into miniature eels and travel up rivers to mature.
American Eel http://www.peacefulparks.org/800x600/eels/ Anguilla-rostrata-2.jpg Eel larvae http://media-2.web.britannica.com/eb-media/17/54217-004-411C3896.gif
Eels • European eels also spawn in the Sargasso Sea. Their larvae travel on clockwise currents mainly of the Gulf Stream and are distributed to North Africa, Northern Europe, the Mediterranean and as far as the Black Sea. • Because they drift in cooler waters European eels grow more slowly than American eels. Development is slowed less than growth however, and as a result European eels have more vertebrae than American eels.
Teleostei: Clupeomorpha • Are a commercially very important group of about 360 species of marine schooling, silvery fishes. • They include herring, shad, anchovies and sardines. • They feed on plankton which they gather using a specialized mouth and gill-straining apparatus.
Euteleostei • The next major division of the teleosts contains about 10,000 species. • There are four major groups of the Euteleostei • Ostariophysi: carp, catfish, piranhas: about 7,900 species • Salmoniforms: trout, salmon and relatives: about 366 species • Paracanthopterygii: cod and anglerfishes about 1,300 species. • “Stem Neoteleosts” not a monophyletic group, but includes just over 900 species of lanternfishes and relatives.
Euteleostei: Ostariophysi • Ostariophysi (from Greek for bone and bladder). • Represent about 30% of all living fishes, about 6500 species. • Display very diverse traits, but many have protrusible jaws and pharyngeal teeth act as second jaws.
Euteleostei: Ostariophysi • The group possesses two unique derived features: alarm substances in the skin and the Weberian apparatus. • When the skin is damaged, pheromones are released into the water and these stimulate a fright reaction in other members of the species and other ostariophysians. In response, they may quickly seek cover or school together.
Weberian Apparatus • Weberian apparatus: The name ostariophysian (Greek bone and bladder) refers to a series of small bones that connect the swim bladder with the inner ear. • The Weberian apparatus greatly enhances hearing in these fish and as a result they are more sensitive to sounds and can hear a wider range of sounds than other fishes.
Weberian apparatus • When sound waves strike the swimbladder it vibrates. • A bone (the tripus) in contact with the swim bladder then conducts this vibration via ligaments to two other bones, the second of which moves and compresses a section of the inner ear against a fourth bone. • This fourth bone (the claustrum) then stimulates the auditory region of the inner ear.