• Today
– Critter of the day
– Notes on types of marine fish (jawless fish and sharks)
– Zap
– Finish review packet and make note cards for test
• Tomorrow
– Test
– Start the “Design a fish” project
Based on what you know, what phylum does this organism
belong to? What evidence can you provide to support this?
Helmet Urchin (Colobocentrotus atratus)
Marine Fishes
Types of Fishes
• Jawless Fishes (aganatha)
– Feed via suction
– Lack paired fins but have a brain protected by
skull, but lack true vertebrae
Hagfish (slime eels)
• Feed on dead and dying fish. Sometimes burrow into body
and eat from inside out. Burrow into muddy bottoms in
cold water
Lamprey
• Found in most temperate regions, are primarily
freshwater fishes. They breed in rivers and lakes but
some move to the sea as adults. The attach to other
fishes and suck their blood or feed on bottom
invertebrates.
Cartilaginous Fishes
•
•
•
•
Sharks, rays, skates and rat fish
Skeleton made of cartilage
Movable jaws and developed teeth
Paired lateral fins for efficient swimming
• Have rough sandpaper like skin because of their
Placoid scales, these consist of a pointed tip that is
directed backwards and have the same composition
as teeth.
Sharks
• Many species are little changed over past 100
million years
• Have a fusiform of spindle shaped body rounded
middle taper toward each end.
• Caudal fin- tail is usually heterocercal meaning that
the upper lobe is longer than the lower lobe.
• Upper surface of the body typically features two
dorsal fins. First is larger and nearly triangular
• Paired pectoral fins are large and pointed in most
species
• 5-7 gill slits
• Variations of body plan exist
– Hammer head
– Sawshark
Today
• Critter of the day
• Warm-Up
• Notes:
– Rays
– Bony fish – scales, fins, and body shapes
• Share the fish you’ve designed
• Independent research into fishing practices
and aquaculture.
Leatherback sea turtle (Dermochelys coriacea)
Warm-Up 5/4/15
1. What is the “Tragedy of the commons?”
2. Who is responsible for the collapse of shared
resources?
3. What can be done to prevent the “tragedy of
the commons”?
• Wide variety in sizes
– Pygmy shark- 25cm
Whale shark- 12m (but up to 18m have
been seen)
Fishing practices threaten many shark species
Rays and Skates
• Flattened bodies
• Mainly live on bottom, Often burry themselves in
sediment
Rays and Skates
• Gill slits on underside of the body rather than sides
• Pectoral fins are flat and greatly expanded looking
like wings and typically fuse with the head
Rays and Skates
• Feed on organism in the
sediment such as clams,
crabs, small fishes and
other small animals.
• Their teeth are modified
into grinding plates that
crush their prey
• Some species such as the
manta ray are filter
feeders
Bony Fishes
• Most fish are bony fish (Osteichthyes)
• Have skeletons made at least partially of bone.
• ~23,000 species
• Have cycloid or ctenoid scales- thin flexible and
overlapping
– Cycloid scales are smooth
– Ctenoid scales have many tiny spines along their
exposed boarders
– Scales are made of bone and are covered by a thin layer
of skin as well as protective mucus.
– Some lack scales entirely
•Have an operculum or gill
cover- a flap of bony plates
and tissue that protects
the gills
•Upper and lower loves of
the tail of the caudal fin
are generally the same
(Homocercal)
• Fins typically thin membranes supported by bony
spines known as finrays. (cartilaginous fish have stiff
fleshy fins)
• Fin rays can extend and contain venom
• Mouth typically terminal- located at the anterior
end and are protrusible (can be projected outward
from the mouth)
• Many bony fish have a swim bladder- a gas filled sac
just above the stomach and intestine that allows a
fish to adjust it buoyancy to keep from rising or
sinking
Today
• Critter of the day
• Discuss fishing and aquaculture techniques
– Collect papers after discussion
• Notes on bony fish body structures
• Perch Dissection Pre-Lab
• Tomorrow:
– Perch Dissection
• Friday:
– Notes on bony fish respiration and reproduction
– Time to work on Perch dissection write up (Due Monday)
Alligator Gar (Atractosteus spatula)
Biology of Fishes
• Directly related to its lifestyle
• The fastest swimmers have streamlined bodies
• Laterally compressed bodies are good for slow
swimming around reefs and kelp beds but are still
capable of speed burst
• Eel-like fishes often live in narrow spaces in rocks or
among vegetation.
• Color has several functions
– Warning coloration – advertise that the animal is
poisonous or bad tasting
– Cryptic coloration- blending in with the environment
some can change color to better fit in
– Disruptive coloration- stripes or spots that break up the
outline of the animal
– Counter shading- seen mainly in open water fish, dark
back, with a silver or white belly. Form of disguise in
open water.
– Additionally many deep fish are red or black
Nervous System and Sensory Organs
– Olfactory sacs detect “smell” each has an opening known
as a nares (nostrils)
• Sharks have renown ability to detect blood in the water down
to 1 part per million
• Salmon use smell to find the stream they were born in
• Lateral line- Unique sense organ that enables them
to detect vibrations in the water.
• System of small canals that run along the body and
contain sensory cells that are sensitive to vibration.
Circulatory System
• Irrigation of the gills
– Fish extract oxygen and release carbon dioxide via their
gills
– To do this they must make sure that water flows over the
gills (known as irrigating or ventilating)
– Most sharks must swim continuously with their mouth
open, this forces water over the gills (ram irrigation)
– When caught in nets they cannot ventilate their gills and
will “drown”
– Some sharks such as the Nurse shark can pump water
over their gills by opening and closing their mouths
(buccal pumping)
• The first pair of gill slits on cartilaginous fish is modified
into structures known as spiracles, which allow them to
continue breathing even if their mouth is buried in
sediment.
• Gill structure
– Gills are supported by cartilaginous or bones structures
known as gill arches
– Each gill arch bears two rows of slender fleshy
projections call gill filaments
• Gill rakers project along the inner surface of the gill
are.
• They prevent food particles from entering and
injuring the gill filaments or may be specialized for
filter feeding
END.
Agenda
• Today:
– Finish notes on marine fish (respiration and
reproduction)
– Time to work on perch dissection write up
• Monday:
– Notes on marine communities
– Assign groups and ecosystems
– Begin projects (presentation on May 20th)
Hogfish (Lachnolaimus maximus)
• Gill filaments have a rich blood supply which makes
them bright red
• Each gill filament contains many rows of thin plates
or disks called lamellae which contain capillaries
(tiny vessels that allow nutrient and gas exchange
• Gas exchange
– Oxygen diffuses into the capillaries and c02 diffuses out
– Diffusion is the movement of molecules from an area of
high concentration to an area of low concentration.
• Diffusion will only take place if oxygen is more
concentrated in the water than in the blood. This is
usually true because the blood is coming from the
body and is depleted of oxygen
• To maximize efficiency fish will
utilize a counter current system of
flow
• Blood in the gills flows in the
opposite direction to the water
passing over them.
• This ensures that the environment
will have a higher concentration of
oxygen the blood in the gills
Reproduction and Early Development
• Urogenital opening- exit port for urine and gametes
in bony and jawless fish
• Cartilaginous fish have a cloaca
• Sex hormones- Timing of reproduction is critical.
Both sexes must be ready and environmental
conditions need to be good. Especially if you’ve just
made a long trip.
• Timing of reproduction is controlled by sex
hormones. Stimulate maturation which can cause
changes in color, shapes and behavior.
• Release of sex hormones is triggered by environmental
factors such as day length, temperature and the availability
of food. (some of these can be mimicked to improve
productivity in aquaculture.)
Hermaphrodites
• Simultaneous hermaphrodites some fish can
produce both sperm and eggs at the same time.
• While they can fertilize themselves, they typically
mate with one or more other individuals. Typically
role reversal is involved. One will release its eggs
while the other the sperm, they will then switch
roles.
• Sex reversal/Sequential hermaphroditism occurs in
some species in which individuals begin life as one
sex but then become another.
• Controlled by sex hormones but trigged by social
cues such as the absence of a dominant
male/female.
• Protogyny- Start as a female and change to male
– Examples: Moon Wrasse
Protandry- Start as a male and change to female
– Examples: Clownfish
Early development
• Oviparous- Spawn eggs
– Oviparous cartilaginous fishes the embryo is encased in
a leathery egg case (mermaid’s purse of skates)
– Eggs are relatively large and have a large yolk sac
containing nutrients for the fishes development
• Ovoviviparous- Eggs develop inside mother’s
reproductive tract
– Sandtiger shark
• Viviparous- Embryos absorbed nutrients from walls
of mother’s reproductive tract
– Example: Lemon Shark
END.