Fish dissection Flashcards
What is considered the head of a fish?
the anterior end, posterior to the last gill slit
What are the major features of a fish head?
snout
eyes
mouth
tongue
operculum (gill cover)
branchiostegal rays
isthmus
gill membrane
gill cavity
What features does the snout have?
external nares (nostrils)
What kind of organs are the external nares (nostrils) of a fish?
olfactory only, no respiratory function
T or F: external nares of fish are both olfactory and respiratory organs
false. Only olfactory, they are blind-ended sacs and not connected to the oral cavity
T or F: fish sleep with their eyes open, why / why not?
true because fish don’t have movable eyelids
How does the vision of fish that live in shallow water compare to fish in deeper water?
shallow water: tend to have colour vision
deeper water: have reflective crystals to enhance vision in poor light conditions (reflective green)
What is the mouth margin of a fish called?
gape
Which two bones may contribute to the gape in a bony fish?
maxilla or premaxilla
Describe fish tongues
either cartilaginous or bony
immobile
not involved in food consumption
might have teeth
T or F: fish tongues are muscular
false - they are either cartilaginous or bony
What is unique about bony fish tongues?
they are cartilaginous or bony
some have teeth
not involved in eating
What is the function of the operculum?
it covers and protects the gill openings and controls water flow over gills
Which fish groups have operculums? which don’t?
operculum present:
bony fish
ratfish (cartilaginous)
operculum absent:
cartilaginous fish (shark, rays)
marine eels
What are branchiostegal rays?
fanned, parallel bony struts that connect skin membranes under and beside the mandible/lower jaw
What are branchiostegal rays used for?
allow for drawing in water into mouth
What is the isthmus?
the skin that runs underneath (ventral) and connects the sides of the lower jaw
What are the gill membranes?
membranes that cover the gill cavity and are supported by the branchiostegal rays
What is a holobranch?
another name for a gill
How many holobranchs do most bony fish have?
4
What is the gill cavity?
underneath the operculum where the gill arches (holobranchs) are located
What form the respiratory surface?
the gill filaments
What is the name of the body compartment behind the head?
the trunk
Describe the trunk
posterior to the last gill slit to the base of the tail
What are the two major components of the trunk?
Paired fins
unpaired fins
What are the most obvious features of the trunk?
fins
What are the two paired fins?
pectoral fins - anterior
pelvic fins - posterior
What are the pectoral fins attached to?
the pectoral girdle
In more advanced bony fishes, what are the pelvic fins attached to?
the pelvic girdle, but it in some it has migrated up and fused to the pectoral girdle
What are the 5 unpaired fins?
dorsal
finlets
anal fin
caudal fin
adipose fin
In what ways can the dorsal fin(s) be present?
always along the dorsal midline
can be single, paired, or in threes
can be a single continuous fin
In some fish, what are the dorsal fins used for?
propulsion
In more advanced bony fish, what else can be present with the dorsal fins?
spines - rigid, inflexible
rays - soft, flexible
What are finlets?
small
numerous
flag-like projections
Where are finlets located?
between dorsal and caudal fins or posterior to the anal fin
Which kind of fish would have finlets? why?
fast-swimming fish like tuna and mackerel because they likely function to reduce drag
Where is the anal fin located?
midventrally and posterior to the anus
How many anal fins can be present?
one or two
What is the function of the anal fins?
prevent rolling - acts as a vertical stabilizer
What type of fish will usually lack anal fins?
bottom-dwellers
How does the shape/size of the caudal fin vary?
it depends on the fish’s swimming style
describe the adipose fin? where is it located?
small
soft
located posterior to dorsal fin
What type of fish have adipose fins?
salmoniforms
What is the lateral line system?
a sensory system that runs laterally from the head to the tail
What is the lateral line system composed of?
jelly-filled canals with specialized sense organs (neuromasts)
What is the function of the lateral line system?
to feel pressure changes caused by vibrations from moving prey
What are the 4 types of fish scales?
placoid
ganoid
cycloid
ctenoid
What kind of scales do fish without spiny dorsal fins have?
cycloid scales
what kind of scales do fish with spiny rays in dorsal fins have?
ctenoid
Describe placoid scales - what type of fish have these?
aka dermal denticles
tiny, unlayered
tooth-like scales
characteristic Chondrichthyes
Describe ganoid scales - what type of fish have these?
heavy
plate-like
form a body armour
ancestral fish like bichirs, gar, stugeons
Describe cycloid scales - what type of fish have these?
thin
round
smooth
flat
overlapping
soft-rayed fish - salmon, trout
Describe ctenoid scales - what type of fish have these?
tiny, comb-like projections on exposed end
rough
mostly spiny-rayed fish - ex. perch
Describe the circulation circuit of fish hearts
single circuit - blood passes through the heart once per circuit
how many times does blood pass through the heart per circuit ?
once
What is the swim bladder?
a thin-walled sac in the dorsal body cavity to adjust buoyancy
T or F: jawless fish (lamprey and hagfish) lack a true stomach
true
