Fish morphology and anatomy Flashcards
Body shapes
Compressed: laterally compressed, v common in reef fish.
Depressed, benthic species by some rays.
Globiform: rounded, deep sea fish.
Anguilliform, eel-like, tubular. snake like movement.
Fusiform: bullet shaped, active predatory fish
Caudal fin shape
Aspect ratio fin height to SA.
Rounded fins have a low aspect ratio, fish that use pectoral fins, caudal won’t displace a lot of water.
Lunate, fast swimmers with v small SA, rigid muscular bodies and swim with powerful tail strokes.
Heterocercal tails in sharks where upper lobe is larger than lower.
Functional anatomy, movement
Body shape and fins are good predictors of lifestyle.
Water is 800x denser than air, 50x more viscous, gravity is not the same, locomotion is contrained by density of water.
Drag:
Viscous (frictional): between fish and water
Pressure (inertial): P differences from displacement of water by body of the fish.
Viscous not affected much by speed but smoothness of fish and SA.
Inertial drag increases with speed, reduced by body shape, width around 25% of length and fattest part 2/5 down body
Swimming form
Anguilliform: large headmovements
Subcarangiform: medium head movements
Carangiform: small
Thunniform: little to no
Functional anatomy, feeding
Must take bites or whole.
Active pursuit, tuna, sharks, salmon
Ambush, anglerfish, pike
filter feeding, whale sharks, mackerel
scavenging, benthic species
Sunction, lion fish
Herbivory, goatfish, parrotfish
Diversity in capture methods facilitated by flexibility offered by complex skull morphology.
Position and size of mouth variesm large mouths mean can eat bigger or more, small are for precision and specialisation while long mouths are better for pursuit predators.
Axial skeleton, vertebral column and notochord
The axial skeleton has 3 function
- protect dorsal nerve cord
- resists shortening when muscles contract
- allow flexibility
Vertebral column in fishes doesn’t provide support.
Functions of skin and scales
Many vital functions:
- maintain shape
- mechanical protection
- defence
- communication
- gas exchange
- ion regulation
- camouflage.
Vision
Most fish have functioning eyes, including abyssal fish.
Difference in refractive index between water and lens proteins is much lower than water so aquatic have larger spherical lenses to achieve the same focussing ability.
Sound
Main organ in sound to electrical impulses are the otoliths
inorganic calcium carbonate structures in the fish ear.
Most teleosts have three pairs of otoliths that float in a fluid matrix called the endolymph
Otoliths vibrate with sound waves, transmitted to brain
V wide diversity in hape, reflects requirements.
Otoliths of fast pelagic are small, for benthic they are large.
Important in fisheries science as they have growth lines.
Mechano
Need to perceive their movement with respect to the surrounding water.
Achieved by neuromasts in the lateral line system.
Superficial neuromasts are found in the skin and detect slow moving currents, while canal neuromasts are located below the scales in the trunk of the fish. better suiteed for perceiving fast moving water.
Electro
Emitted by muscular contractions of other animals.
Transmitted much more efficiently in saline water, perhaps explaining why electro-reception is common and well-developed in ancient lineages.
Impulses dectected by amullary receptors embedded in recesses in the skin and connected to the surface by a channel filled with conductive gel.
In elasmobranchs, the well-developed ampullae of lorenzini are easily seen in the nasal regions.
Skin structure
epidermis and the dermis, epi is upper layer in contact with water.
epidermis doesn’t have active bloody supply, but has cells for mucus and pheremones.
Active role in immune system, contains cells implicated in ion exchange, perceptain and altering colour.
Lower dermis, comprised of connective tissue and houses the scales.
Pigmentation is largely contained in the dermis.
