Lab 1 Flashcards
Define allometric growth
Changes in body proportions during maturation
Total length
Straight-line distance from most anterior point of the fish to the tip of the caudal fin
Standard length
Most anterior tip of fish to end of vertebral column at base of caudal fin
Hypural plate
Internal structure in teleosts marking the end of the vertebral column
How to find hypural plate
Bend caudal fin laterally near the base - crease marks end of vertebral column
Snout-vent length
Distance from tip of snout to opening of anus
Fork length
Distance from most anterior tip of fish to middle of the fork of the caudal fin
Can only be measured where the caudal fin has a distinct fork or indentation
Head length
Distance from most anterior point of fish to the most posterior extension of operculum
Includes any membranous flap on operculum
In skates, rays and sharks goes to base of the most posterior gill slit
Maximum depth of body
Maximum vertical height of body not including fins
Located about 1/3 of the length from snout in active swimmers, such as the perch
Minimum depth of caudal peduncle
Minimum vertical height of trunk region between posterior insertion of anal fin and caudal fin
Three types of fin rays
Spiny
Heavy spinous
Soft
Features of spiny rays
Usually stiff and sharp (but not always)
Unsegmented + unbranched
Features of spinous rays
Stiff + often have sharp barbs on posterior edge (eg in catfish)
Not true spiny rays but thickened, hardened soft rays
Features of soft rays
Usually branched and clearly segmented
Usually occur on posterior portion of a fin behind spinous rays
Cleithrum
Shoulder girdle
External nares
Nostrils
Not connected to oral cavity - blind-ended sacs
Sensory organs ONLY
Protective layer on outside of eye
Cornea
Specialised cells in the retina
Rods + cones
Caniniform
Pointed, elongated teeth
Incisoriform
Blade-like teeth
Sharp, cutting edge with broad base
Molaiform
Blunt, flattened teeth
For grinding + crushing
Cirri
Small, fleshy projections from fish head
Chemosensory (taste) or mechanosensry function
Not present in all fishes
Branchiostegal rays
Parallel, bony struts arranged like ribs of bellow or a fan
Connect membrane of skin below and between the two sides of the lower jaw or mandible
Stretch -> expand buccal cavity -> draw in water
Support gill membranes
Isthmus
Skin connecting two sides of lower jaw on ventral side of head
Classification of gill membranes
Free or separate - not joined to isthmus or to each other
United - joined to each other across, but not to, the isthmus
Joined to the isthmus
Barbels
Fleshy, hair-like projections on the chin or around the mouth
Chemosensory or mechanosensory function
Cods, catfishes + sturgeons
Finlets
Numerous small, flag-like projections between main dorsal fins and caudal fin or anal fin
Present in fast swimming fish such as tuna
Function of anal fin
Stabiliser to prevent roll
Usually absent from bottom dwelling species
Heterocercal tail
Upper lobe of caudal fin is larger
Posterior end of vertebral column extends into upper lobe of caudal fin
Homocercal tail
Symmetrical
Neuromasts
Specialised sense organs in lateral line system
Nerve endings are sensitive to subtle changes in pressure in the water
Usually more concentrated at head end of lateral line
Ctenoid scales
Common in fishes with at least one spiny ray in the dorsal fin
Common in flatfishes such as halibut and flounders on their uppermost surface
Comb-like projections (ctenii) on exposed edge of scales
Placoid scales
Sometimes called dermal denticles
Characteristic of Chondrichthyes
Unlayered, tooth-like scales
Ganoid scales
Heavy + plate-like
Form a bony armour
Cycloid scales
Thin + round
Flat overlapping scales
In most soft-rayed fishes
Ctenii
Comb-like projections on exposed edge of ctenoid scales
Circuli
Growth rings in fish that have seasonal variations in growth
Faster growth -> rings further apart
Axial muscles
Make up most of the mass of the trunk
Myomeres
Form W-shaped blocks in axial muscles
Electroplaques
Arrangement of axial muscles in fish that are able to produce electric current
Insulating layers between muscles + skin -> act like a storage battery to accumulate electrical charge
Physostomous condition
Fish that have a duct connecting the swim bladder to the mouth in bony fish
Ancestral
Used to breathe atmospheric air during periods of drought
Physoclistous condition
Fish that do not have a duct connecting the swim bladder to the mouth
More advanced bony fish
Pyloric ceca
Blunt-ended finger-like projections extending into the stomach
Over 100 in salmonids
Increase absorptive surface area of stomach
Mesentery
Surrounds the intestine
May contain yellow-orange fat deposits
Function of spleen
Produces new blood cells and destroys old ones
Function of reproductive ducts
Conduct gametes from gonads to outside for fertilisation
Function of cerebral hemispheres of forebrain
Sense of smell
Cerebellum
Hindbrain
Function of the cerebellum
Co-ordinates muscular movement and adjusts spatial equilibrium
Integrates info from lateral line + inner eat
Elongated body form
Fusiform
Anguilliform
Eel-like
Greatly elongated
Ovate body form
Truncated
Shortened
Compressiform
Thin, narrow, deep
Eg. angel fish
Depressiform
Flattened
Globiform
Subcircular
Hemispherical
Eg. pufferfish
Holobranch
Bony gill arch supporting gill filaments
Four on each side of gill cavity in most fish
Hemibranch
Reduced gill arch
Attached to underside of operculum
Gill rakers
Extensions of gill arches
Project inwards
Prevent food particles passing out with flow of respiratory water
Agnathans
Jawless fishes
Ostracoderms
500 million years ago (Cambrian period)
Jawless fishes
Successful for 100 million years
Surviving ostracoderms today
Lampreys + hagfishes
Differences between hagfish and lampreys
Hagfish have single nostril opening into the mouth, lampreys do not
Lampreys have well developed eyes, hagfishes do not
Lampreys have well-developed lateral line system, hagfish do not
Ammocoetes
Filter-feeding larval stage of lampreys
Lamprey teeth
Made of keratin
Derived from the skin
Which (hagfish or lampreys) have dorsal fins?
Lampreys
Which (hagfish or lampreys) have pre-anal fins?
Hagfish
Origin of the jaw
Hinged gill supports modified for improved feeding efficiency
Number of dorsal fins in sharks
Never more than two
Most sharks have ___ gill slits
5 but can have 6 or 7
Function of spiracles in sharks
Accessory water intake when mouth is feeding
Carchariniformes
Largest order of sharks
Hammerheads, requiem sharks, blue sharks and cat sharks
Rajiformes
Rays and skates
What order do rays and skates belong to?
Rajiformes
Position of gill openings on a skate
Ventral
The anterior edge of skate’s pectoral fin is attached to…
Side of the head
The sting on an electric ray is a modified…
Caudal muscle
Basking shark feeding method
Filter feeder
Traps plankton in gill rakers
Differences between skates and rays
Skates are oviparous (lay eggs), rays are viviparous (live births)
Skates have distinct dorsal fins, rays have lost or is vestigial
Skates pelvic fin is divided into two lobes, rays have just one
Skates have a fleshy tail, rays have a whip=like tail with 1-2 stinging spines
Skates are usually smaller
Rays usually inhabit shallower water (although not always)
Holocephali
Chimaeras + ratfish
First definitive fossils from Jurassic period 200 million years ago but could be much earlier
Cartilaginous skeleton + internal fertilisation
Autostylic jaw suspension
Upper jaw is connected directly to cranium, lower jaw is directly attached
Protection for gills in chimaeras
Calcified opercular plate
Not present in any other fish
Ampullae of Lorenzini
Sensing organs - jelly-filled pores
Electroreceptors
Common in sharks, rays + chimaeras
Function of head clasper in male ratfish
Stimulate female during courtship
