Do the variations which exist in modern groups of fish support evolution, creation, or intelligent design?



If evolution has occurred, then it could be expected significant variations could occur in groups of closely related fish.


If the creationism model is correct, fish which share a common ancestor are not expected to vary significantly. The complex aspects of the natural world would have resulted from the divine creation of a kind of fish rather than the variations which accumulated in lineages subsequently.


If intelligent design is correct, then natural processes should not be able to produce complex variations. Any complex structures should show evidence of a supernatural design.

Among closely related fish, size can vary considerably. Among the most primitive fish, the hagfish, Eptatretus is 16 times the weight of Myxine (Davie, 1987).
The length, width, and structure of the face can vary considerably in closely related teleost fish. In the related families Eupharyngidae and Monogathidae, the jaws extend far beyond the cranium. In the Monogathidae the length of the mouth is about 1/10 the length of the body while in the Eupharyngidae it is about 1/5 the length of the body.



Lungfish, especially fossil forms, have a number of small, highly variable bones of the face (Kemp, 1999a). Lungfish skulls vary in the fusion of small bones, division of bones into smaller parts, the absence of bones normally present, doubling of bones, abnormal processes. Some skeletal abnormalities, such as bone fusions, divisions, and asymmetry also known in fossil forms (Kemp, 1999b). Many closely related fish vary significantly in their facial bones.



The pectoral fins of the flying fish allow them to glide for 100 meters at about 1 m from the water surface (Moyle, p. 269). Some of the air breathing fish can actually move across land using modified fins. These include some catfish of the family Clariidae, some of the fish of the family Gobiidae (mudsuckers and mudskippers), and some of the family Synbranchidae (Moyle, 252, 304, 311). Many angler fish have muscular pectoral fins which allow them to walk along the bottom or cling to substrates (Moyle, p. 267). Some the fish of Dactylopteridae also use their fins to walk along the bottom (Moyle, p.289).

fish fish

Bony fish vary considerably with regards to their mode of reproduction. Some lay eggs in the open water, the bottom surface, or on plants; others hide them in rocks or even on invertebrates. Some fish guard their eggs after they have been laid on rocks, plants, or in the open water. Some make nests. Some bear live young by keeping them in an external pouch, the gill chamber, or in their mouth. Others bear live young utilizing fetal tissues which exchange materials with maternal tissues in a placenta-like fashion. These fetal tissues range from neck straps to long pectoral fins to projections from the anus. The diversity of tissues which may serve a placental function is depicted in a frog (left) and three fish below (Moyle, p. 111). In viviparous animals, the yolk sac may be reduced. The viviparous teleost fish Heterandria produces so little yolk that its yolk sac approaches the condition found in placental mammals (Mossman, p. 12).

Some species of Careproctus have a long ovipositor to place their eggs in the peribranchial cavity of stone crabs (it's an aerated environment). (Eastman, 1993, p. 64) Some bony fish of the families Scorpaenidae and Clinidae reproduce through live birth; some males in the family Clinidae possess an intromittent organ (Moyle, p. 284, 301).
While the fertilization of eggs typically occurs outside the body of the female (external fertilization), some frogs reproduce through internal fertilization and the male's cloaca can be modified to form an intermittent organ. The North American tailed frog Ascaphus reproduces through internal fertilization (Behler, 1989).

Lampreys are the most primitive known vertebrates. Their "vertebrae" (which consist only of neural arches), develop with blocks of muscle tissue called somites which form along the long axis of the body. Three species of lamprey (Lethernteron alaskense, L. lamottenii, and L. japonicum) have 66 to 72 trunk myomeres while another (L. meridionale) has 50 to 58 (Valdykov, 1978).

Vertebrae vary in among teleost fish. In ratfishes, the vertebrae are composed of cartilage which is only partially ossified. In minnows and catfish, the upper portions of the anterior vertebrae are not connected to the centra and form a chain of bones from the swim bladder to the ear (called the Weberian apparatus) (Moyle, p. 21). In the notothenioid fish Pleurogramma, its vertebrae are reduced and it relies on its continuous notochord for axial support In Discotrichus, cartilage replaces the bone of the skull, pectoral girdle, and caudal skeleton. Aethotaxis has a partially persistent notochord (Eastman, 1993).
There are a number of variations in teeth in modern groups of organisms. Actinopterygians may have homodont or heterodont teeth or lack teeth altogether. In many fish teeth are attached to bone by collagen fibers while in others they are located in deep sockets (Webster, 1974).

fish jaws

The long- and short-nosed gar differ in the length of their snout. The alligator gar has an additional row of teeth that other gars lack.

Some bony fish have expanded olfactory lobes and an enhanced olfactory perception; while other fish which depend on taste have expanded facial or vagal lobes (Moyle, p. 134).

Many cave dwelling and deep sea fishes have small or absent eyes and there can be variation in the presence of eyes within a family. Below, the genus Bathypterois has small eyes compared to some members of its genus but compensates with pectoral fins which function in touch.

Most deep sea fishes have very sensitive eyes; only one fish (Ipnops murrayi) has lost eyes altogether, the only vertebrate in which this is true. (Weichert, 1970, p.687). The fish Anableps, or four-eyed fish, has two pupils per eye. (Weichert, 1970, p.688). The optic cup induces the formation of the lens vessicle (Hall, p. 112) although the lenses of congeneric amphibians can develop with or without induction by the optic cup (Hall, p. 186). Different members of the genus Trematomus can possess single cones in the retina, twin cones, twin and single cones, or single cones and rods (Eastman, 1993, p. 258). The number of lateral lines in the family Bathydraconidae can be 1,2,3, or 4 (Eastman, 1993). Seahorses have binocular vision, unlike most fish (Moyle, p. 283). Many fish possess a tapetum layer in the eye which reflects light and improves vision in dark conditions but the substance which reflects light can vary considerably (Moyle, p. 146).

Some anglers possess a lure on their head which may be a dorsal spine and may possess a luminescent organ which attracts other fish. Some anglers produce their own luminescent materials; others employ symbiotic bacteria (Moyle, p. 267). Many possess fleshy outgrowths and additional spines as well.

There are two families in the fish order Miripinniformes, one of which (Miripinnidae) possesses a "hair cover" over the surface of its body (Lindbergh, 20).


Lungfish can vary in the robustness of their fins. The South American lungfish has the smallest fins.




The marble goby can survive in air for a week (Saha, 2007).Air breathing fish have evolved a variety of mechanisms to tolerate or eliminate nitrogenous wastes (which cannot be lost at the gills) (Saha, 2007).