Transcript Fishes Phylum Chordata - T.R. Robinson High School

Fishes
Phylum Chordata
Chapter 24
Class Myxini
• Common name:
Hagfish
• Lack jaws
• Entirely marine
• Scavenger & Predatorsfeed on annelids,
mollusks, crustaceans,
and dead/dying fish
• About 65 species
• Best known in North
America
Hagfish
• Most are completely
blind
• Attracted to food by
keen sense of smell
and touch
• Enters a dead or
dying animal an
orifice or by digging
inside
Hagfish feeding
• Using 2 toothed
plates on its tongue
that fold together in
a pincer-like action,
the hagfish rasps
ways bits of flesh
from its prey
Hagfish feeding
• For extra leverage,
the hagfish often
ties a knot in its tail,
then passes the
knot forward along
its body until it is
pressed securely
against the side of
its prey
Hagfish defense
• Renowned for their ability to generate
enormous amounts of slime
• Exudes a milky fluid from special glands
along its body
• On contact with seawater, the fluid
forms a slime so slippery that its almost
impossible to grasp
Class Cephalaspidomorphi
• Common name: lampreys
• Has a habit of grasping a stone with its mouth
to hold position in a current
• Some are parasitic
• All lampreys ascend freshwater streams to
breed
• Marine forms are anadromous-they leave the
sea where they spend their adult lives to
swim up streams to spawn
Lampreys
• Sea lamprey,
feeding on body
fluids of a dying fish
Lamprey reproduction
• In NA, spawning is in winter or spring
• Males begin nest building and are joined by
females later
• Using their oral discs to lift stones and
pebbles and body vibrations to sweep debris
away to form a depression
• At spawning, with the female attached to a
rock to maintain her position over the nest,
the male attaches to the dorsal side of her
head
• As eggs are shed into the nest, they are
fertilized by the male
• The sticky eggs adhere to pebbles in the nest
and quickly become covered with sand
• The adults die soon after spawning
Lamprey reproduction
• Eggs hatch
in about 2
weeks,
releasing
small larvae
called
ammocoetes
• Larvae looks
very similar
to
amphioxus
Parasitic Lampreys
• Attach themselves to a fish
by their sucker-like mouth to
a fish, and with teeth, rasp
away the flesh and suck out
body fluids
• To promote blood flow, the
lamprey injects an
anticoagulant into the
wound
• When gorged, the lamprey
releases its hold but leaves
the fish with a large, gaping
wound which is sometimes
fatal
Questions?
1. What is the freshwater larval stage of
a lamprey?
2. Hagfishes
A. An entirely freshwater animals
B. Are parasitic
C. Generate enormous quantities of slime if
disturbed
D. Have massive jaws
Class Chondrichthyes
(Cartilaginous Fish)
Subclass Elasmobranchii
• Sharks, Skates, and Rays
Form and Function
• Median anal fin is present (clasper) used for
copulation
• Lateral eyes are lidless, and behind each eye a
spiracle (remnant of the first gill slit) is usually present
• 5 gill slits are found anterior to each pectoral fin
Shark body
• Tough, leathery skin is
covered with tooth-like,
dermal placoid scales
arranged to reduce the
turbulence of water flowing
along the body surface
during swimming
• Can detect prey from a
kilometer or more away with
large olfactory organs
capable of detecting
chemicals as low as I part
per 10 billion
Shark body
• Prey are also detected by sensing low frequency
vibrations with receptors in the lateral-line system
• In final stage of attack, sharks are guided to prey by
the bioelectric fields that surround all animals with
ampullae of Lorenzini
Shark body
• Front row of functional teeth on the edge of
the jaw is backed by rows of developing teeth
that replace worn teeth throughout their life
• All have internal fertilization, but maternal
support varies
• Oviparous sharks (lay eggs immediately after
fetilization) deposit eggs in a horny capsule called
a “mermaid’s purse”
• Many retain embryos in reproductive tract for a
loing time (ovoviviparous)
• Some have true viviparous reproduction (like
humans)
Rays
Clearnose skate
• Include skates, electric
rays, stingrays, manta rays
• Specialized for bottom
dwelling and greatly
enlarged pectoral fins
fused to head used like
wings in swimming
• Gill openings are on the
underside of the head, but
have large spiracles on top
• Water for breathing is taken
in through spiracles to
prevent clogging the gills,
for the mouth is often
buried in the sand
• Teeth are adapted for
crushing mollusks,
crustaceans, and some
small fish
Rays
Southern stingray
• Stingrays have a
slender, whip-like tail
armed with one or more
saw-edged spines with
venom glands at the
base
• Electric rays are
sluggish fish with large
electric organs on each
side of their head
• High-amp current is
produced that flows out
into the surrounding
water (almost 1
kilowatt) stunning prey
or discouraging
predators
Electric ray
anatomy
Questions?
•
•
•
Sharks, skates, and rays belong to what
class?
Which organism have lateral expansion of
the pectoral fins that resemble wing-like
appendages?
Sharks are unique in all of the following
EXCEPT
a)
b)
c)
d)
Being able to detect bioelectric fields
Having a cartilaginous skeleton
Having external fertilization
Having placoid scales
Questions?
•
What is the function of the large
spiracles on top of the head of skates
and rays?
Class Osteichthyes (Bony Fish)
• Class Actinopterygii- ray-finned fish
• Class Sarcopterygii- lobe-finned fish
• Adaptations:
• Operculum: gill cover
• Swim bladder: buoyancy
Class Actinopterygii
• More than 23,600
species
• Represented by
freshwater and
anadromous
sturgeons,
paddlefishes, and
bichirs
Teleosts (modern bony fish)
A. Bowfin
B. Longnose Gar
Class Sarcopterygii
• Includes lungfish
Adaptations
• Myomeres: locomotory musculature in
zigzag bands
Most fish can swim about 10 body lengths
per second
Adaptations
• Lateral Line: senses vibrations and water
currents for schooling
• Buoyancy
• All fish are slightly heavier than water because of
skeleton
• Squalene: fatty hydrocarbon allowing sharks to
stay buoyant (produced by liver)
• Swim bladder: gas filled organ that expands with
gas when in shallower water because of reduced
pressure (and vice versa)
Swim Bladder
Osmoregulation
• Saltwater fish- Hypoosmotic regulators:
have much lower blood salt
concentration than seawater around
them
• Risk is drying out- loss of water and
taking on of salt
• Freshwater fish-hyperosmotic regulators
• Risk taking on too much water