external anatomy Flashcards
anterior (placement)
towards the top or head end of the body
posterior (placement)
towards the back or tail end of the body
cranial (placement)
head region
caudal (placement)
tail region
dorsal (placement)
towards the top (back / spinal) area of the body
ventral (placement)
towards the underside of the body
tall, narrow body shape
adapted to live in slow moving water
torpedo-shaped body
adapted to live in fast moving water
superior mouth
- top swimmers
- straight dorsal surface
- upturned, scoop like mouth
terminal mouth
- mid water swimmers
- mouths at the tip of the snout
inferior mouth
- bottom-dwellers
- flattened ventral surface
- downturned / underslung mouth
larger eyes
generally seen in deep-water fish
smaller eyes
generally seen in shallow-water fish
dilating pupils
- seen in some species (e.e. shark and eels)
- not seen in bony fish usually
nostrils
- not used for breathing
- water will pass through
- detects chemical traces at the base of the nostril
- essential in low visibility
- may have one pair, two pairs or a single nostril
skin
- defence against pathogens through mucous layer that entraps and immobilises pathogens
scales
- bony material
- placoid scales, ganoid scales, ctenoid scales, cycloid scales
- scutes (on catfish)
placoid scales
- found in rays and sharks
- resemble teeth-like projections
- do not increase in size, but in numbers as the fish grows
ganoid scales
- mosaic in arrangement with overlaps
- seen on sturgeons and gar fish
ctenoid scales
- have a spiny comb or teeth-like extensions to the outer edge
- perch fish have ctenoid scales
cycloid scales
- are round or oval shaped
- grow with the fish → creates growth rings which determines a fish’s age
scutes
- in place of scales on armoured catfish
- their bodies are covered with two or three overlapping bony plates
fin functions
- stability
- propulsion
- steering
- balance
dorsal fin
- located along the back of the fish (between tail fin and head)
- provides lateral stability to allow swimming in a straight line and prevents it from rolling over
caudal fin
- aka tail fin
- located at the rear of the fish
- responsible for propulsion + fast swimming patterns
- can be used to slow forward movements and for turning
anal fin
- located on the underside of the body between the pelvic and caudal fin
- helps with stability + steering
- prevents fish from rolling over
pectoral fins
- paired and located near the bottom of the fish, directly beneath the gill openings
- used in navigation and stability
- provide the upward lift that helps fish maintain depth + enables the flight go flying fish
- can be adapted for “walking” above or below water on some fish
- can have defensive spines
pelvic fins
- located in front of the anal fin, on the abdomen of the fish (underside)
- used for braking, stabilising + changing direction
adipose fin
some fish (e.e. tetras) have an additional fin located between the dorsal and caudal fins
lateral line
- helps detect vibrations and currents while underwater
- senses water movement and pressure
- pressure around objects are distorted which is detected by the lateral line; allowing a fish to change direction
- enables fish to escape predators, catch prey and take part in a shoal
