Water is about 800 times thicker than air and an aquatic life has its own difficulties, such as buoyancy, drag and the amount of effort needed to move through such a dense medium.Like all animals, the fish’s body is a result of specialization in its environment.
They come in all shapes and sizes, from the expected, to the bizarre. Form and function work together and examination of basic body shapes gives us insight to fish lifestyles.There are majorly six body forms of fish wich include the following
- Rover predator
- Lie in wait predator
- Surface oriented
- Bottom oriented fish
- Deep bodied fish
- Eel-like fish
The rover predator is one of the commonest body forms wich fish take on.It is generally A streamlined body, pointed head, narrow caudal peduncle and a forked tail are the characteristics of this typical fish. In fact, this is the shape most people think of when they think of a fish! Their evenly distributed fins provide stability and manoeuverability, which is important for endurance swimming and actively seeking prey. This body type is typical of stream dwellers, which forage in fast water. Common examples of this body form are the trouts (family Salmonidae), some minnows (family Cyprinidae), tuna (family Scombridae) and swordfish (family Xiphiidae).
Minow Rainbow trout
LIE IN WAIT PREDATOR
This type of fish are generally suited for surprise attacks on fellow fish (piscivorous) or passing small aquatic animals. Their bodies are streamlined and elongate, with a flattened head and a mouth full of pointy teeth. In some families with this body plan, such as the pikes, the dorsal and anal fins are inserted far toward the rear, very near the caudal fin. This fin arrangement allows the normally still fish to generate rapid acceleration when the large muscle mass of the cylindrical body pushes against the water with the combined area of the dorsal, caudal and anal fins. In this way, they are able to thrust forward at high speeds to attack a passing fish. Their cryptic colouration and secretive behaviour helps to conceal them from suspecting prey. The pikes (family Esocidae), gars (family Lepisosteidae) and the marine barracudas (family Sphyraenidae) have this body plan.
Just as its name this is generally a surface dweller and it is suited for this enviroment and obtaining of food from the surface.it has an upward turned mouths of these fish allow them to exploit plankton and small fish at the surface of the water. These fish are typically small in size, with a dorsoventrally flattened head, large eyes, streamlined body and a dorsal fin that occurs far back on the body. In stagnant water, this body design is ideal for taking advantage of the rich oxygen supply at the air-water interface. The Arctic cod (family Gadidae) and many killifishes (family Fundulidae) have this body form.
Killi fish Arctic cod
BOTTOM ORIENTED FISH
These have a body plan suited for living in benthic habitats. Many body shapes accomplish this goal, but generally fish with this body plan have a reduced or absent swim bladder and are flattened. Bottom fishes can be further classified into five categories: bottom rovers, bottom clingers, bottom hiders, flatfish and rattails.
Bottom rovers have a shape similar to the rover-predator, but have a flattened head, humped back and enlarged pectoral fins. These fish often possess barbels or “whiskers” with taste buds to locate prey in muddy water. The mouth shapes of these fish vary to exploit different food sources found on the bottom. Catfishes (family Ictaluridae) have large, terminal mouths, while sturgeons (family Acipenseridae) have fleshy, protrusible lips to suck plant and animal material off the bottom.
African cat fish
Bottom clingers, such as the sculpins (family Cottidae), have enlarged, closely spaced pelvic fins and specialized pectoral fins which help to anchor them to the bottom. The pectoral fins of gobies (family Gobiidae) and clingfishes (family Gobiesocidae) are actually modified into suction cups.
Bottom hiders are typically found under rocks, in crevices or remain still at the bottom. Darters (family Percidae) and blennies (family Blennidae) have this strategy.
Flatfish are also specially designed for benthic habitats. Flounders (family Pleuronectidae) are unusual looking, deep-bodied fish with both eyes on one side of their head. Their mouth is twisted for feeding on the bottom. Skates (family Rajidae) and rays (family Dasyatidae) are also flattened, but have a completely ventral mouth.
DEEP BODIED FISH
These type of fish has a deepened body form is adapted for maneuverability in spatially complex habitats. The pelvic fins are moved far forward, so that the pectorals and pelvics together form a single control surface for turning, stopping and holding position. The mouth is generally small, the eyes large and the snout short, adaptations for feeding on small invertebrates at the bottom or in the water column. These fish are not designed for speed and instead rely on their maneuvering ability and spiny fins for protection from predators. The butterflyfish (family Chaetodontidae), which live in coral reefs, and the sunfish (family Centrarchidae) have this body form.
Butterfly fish Sun fish
Finally we have this type of body form wich is generally has elongate bodies, rounded heads and rounded tails allow these fish to explore a diversity of habitats including crevices and holes in rocky and reefed areas, soft muddy bottoms and densely vegetated areas. Long dorsal and anal fins allow these fish to exploit open water habitats as well. Eels (family Anguillidae), loaches (family Balitoridae) and gunnels (family Pholidae) have this body plan.
Loaches An eel