Actinopterygii
| Ray-finned fish | |
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Scientific classification 
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| Kingdom: | Animalia |
| Phylum: | Chordata |
| Superclass: | Osteichthyes |
| Class: | Actinopterygii Klein, 1885 |
| Subclasses | |
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Actinopterygii (
The ray-finned fishes are so called because their fins are webs of skin supported by bony or horny spines (rays), as opposed to the fleshy, lobed fins that characterize the class Sarcopterygii (lobe-finned fish). These actinopterygian fin rays attach directly to the proximal or basal skeletal elements, the radials, which represent the link or connection between these fins and the internal skeleton (e.g., pelvic and pectoral girdles).
By species count, actinopterygians dominate the
Characteristics
Ray-finned fishes occur in many variant forms. The main features of typical ray-finned fish are shown in the adjacent diagram. The swim bladder is a more derived structure than the lung.[5]
Ray-finned fishes have many different types of scales; but all
Ray-finned and lobe-finned fishes sometimes possesses lungs used for aerial respiration. Only bichirs retain ventrally budding lungs.[5]
Body shapes and fin arrangements
Ray-finned fish vary in size and shape, in their feeding specializations, and in the number and arrangement of their ray-fins.
deeply forked tail
The swordfish is even faster and more streamlined than the tuna
tail finto jump obstacles during river migrations
anal fins, which give them great maneuverability
Flatfish have developed partially symmetric dorsal and pelvic fins
The four-eyed fish Anableps anableps can see both below and above the water surface
Fangtooth are indifferent swimmers who try to ambush their prey
The first spine of the dorsal fin of anglerfish is modified like a fishing rod with a lure
basalliving ray-fins; they possess lungs
European conger are ray-finned fish
Hawaiian turkeyfish
The
benthic batfish Ogcocephalus notatus
The
cartilaginous endoskeleton
The
Belone belone
Seahorses are in the extended pipefish family
The "
pectoral finsfor gliding
The hoodwinker sunfish
caudal fin
The
filter-feederand the largest ray-finned fish to have ever lived
boxfish
Reproduction
In nearly all ray-finned fish, the sexes are separate, and in most species the females spawn eggs that are fertilized externally, typically with the male inseminating the eggs after they are laid. Development then proceeds with a free-swimming larval stage.
Most families use external rather than internal fertilization.[9] Of the oviparous teleosts, most (79%) do not provide parental care.[10] Viviparity, ovoviviparity, or some form of parental care for eggs, whether by the male, the female, or both parents is seen in a significant fraction (21%) of the 422 teleost families; no care is likely the ancestral condition.[10] The oldest case of viviparity in ray-finned fish is found in Middle Triassic species of †Saurichthys.[11] Viviparity is relatively rare and is found in about 6% of living teleost species; male care is far more common than female care.[10][12] Male territoriality "preadapts" a species for evolving male parental care.[13][14]
There are a few examples of fish that self-fertilise. The mangrove rivulus is an amphibious, simultaneous hermaphrodite, producing both eggs and spawn and having internal fertilisation. This mode of reproduction may be related to the fish's habit of spending long periods out of water in the mangrove forests it inhabits. Males are occasionally produced at temperatures below 19 °C (66 °F) and can fertilise eggs that are then spawned by the female. This maintains genetic variability in a species that is otherwise highly inbred.[15]
Classification and fossil record
Actinopterygii is divided into the classes
The classification of ray-finned fishes can be summarized as follows:
- Cladistia, which include bichirs and reedfish
- Actinopteri, which include:
- Chondrostei, which include Acipenseriformes (paddlefishes and sturgeons)
- Neopterygii, which include:
- Teleostei (most living fishes)
- Holostei, which include:
- Lepisosteiformes (gars)
- Amiiformes (bowfin)
The
Vertebrates
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The polypterids (bichirs and reedfish) are the sister lineage of all other actinopterygians, the Acipenseriformes (sturgeons and paddlefishes) are the sister lineage of Neopterygii, and Holostei (bowfin and gars) are the sister lineage of teleosts. The Elopomorpha (eels and tarpons) appear to be the most basal teleosts.[17]
The earliest known
| Chondrostei | Teleostei than their external appearance might suggest.[24]
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|---|---|---|
| Neopterygii | electroreception and the ampullae of Lorenzini is present in all other groups of fish, with the exception of hagfish, neopterygians have lost this sense, though it later re-evolved within Gymnotiformes and catfishes, who possess nonhomologous teleost ampullae.[25]
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