Fishes I

Transcription

Fishes I

1/14/2011
Fishes I
Chordate characteristics
Chordate taxonomy
Hagfishes
Lampreys
Sharks, skates and rays
Chimaeras
Sturgeon
Gars and Bowfins
Scales
What are the defining characteristics
of chordates?
Segmentation
a segmented chordate
Body symmetry
Radial symmetry. The
parts of a radial animal,
such as a sea anemone
(phylum Cnidaria),
radiate from the center.
Any imaginary slice
through the central axis
divides the animal into
mirror images.
Complete digestive system
Bilateral symmetry. A
bilateral animal, such as
a lobster (phylum
Arthropoda), has a left
side and a right side.
Only one imaginary cut
divides the animal into
mirror-image halves.
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Body plans of the Bilateria
Anatomy of a trout, a representative ray-finned fish
Acoelomate
Pseudocoelomate
Coelomate
(true body cavity)
The cooperation of muscles and skeletons in movement
Closed circulatory system & ventral heart
Summary of chordate characteristics
1. Notochord present at some stage
2. Single, dorsal, hollow nerve chord
3. Pharyngeal slits present at some stage
4. Post-anal tail present at some stage
5. Segmented body and muscles
6. Complete digestive system
7. Bilateral symmetry
8. Coelom
9. Closed circulatory system & ventral heart
10. Cartilaginous or bony endoskeleton in most
Subphylum Cephalochordata: the lancelet Branchiostoma
Chordate Taxonomy
Phylum Chordata
Subphylum Cephalochordata (lancelets)
Subphylum Urochordata (tunicates)
Subphylum Vertebrata
Superclass Agnatha
Class Myxini (hagfish)
Class Petromyzontida (lampreys)
Dorsal nerve cord
Notochord
Brain
Gill slits
Superclass Gnathostomata
Class Chondrichthyes - cartilaginous fish
Class Actinopterygii - ray finned fishes
Class Amphibia - amphibians
Class Reptilia - reptiles
Class Aves - birds
Class Mammalia - mammals
Tail
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Subphylum Cephalochordata: the lancelet Branchiostoma
Chordate Taxonomy
Muscle segments
Phylum Chordata
Superclass Agnatha
Class Aves - birds
Subphylum Urochordata: tunicates
Chordate Taxonomy
Phylum Chordata
Superclass Agnatha
Adult “sea squirts” are
sessile filter feeders
Characteristics of Subphylum Vertebrata
1. Chordate characteristics - notochord, dorsal nerve
cord, pharyngeal pouches, post-anal tail.
2. Cartilaginous or bony endoskeleton with a backbone
and vertebrae (except hagfish).
3. Well-developed nervous system with anterior brain
and specialized receptors (nose, eyes, ears).
4. Closed circulatory system with 2 to 4 chambered
heart and blood with hemoglobin.
5. Excretory system of paired kidneys
6. Endocrine system of ductless glands
Class Aves - birds
Fish Taxonomy
Superclass Agnatha
Class Chondrichthyes - cartilaginous fishes
Subclass Elasmobranchii – sharks and rays
Subclass Holocephali – chimaeras (ratfish)
Class Actinopterygii – ray-finned fishes
Subclass Chrondrostei – sturgeons, paddlefish
Subclass Neopterygii – modern bony fishes
(Class Sarcopterygii – lobe-finned fishes)
Actinopterygii and Sarcopterygii are sometimes referred
to collectively as Osteichthyes – bony fishes
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Fish Taxonomy
(850 species)
Fin types
1st dorsal
2nd dorsal
adipose
(24,600 species)
pectoral
Class Sarcopterygii – lobe-finned fishes
(7 species – 0 in BC)
anal
caudal
pelvic
Types of
caudal fins
Fishes I
Diphycercal (coelocanth)
Homocercal (perch)
Heterocercal (shark)
Chordate taxonomy
Hagfishes
Lampreys
Chimaeras
Sturgeon
Gars and Bowfins
Scales
Hagfish
ENVR 242 Taxonomy for BC
Superclass Agnatha - fish without jaws
Order Myxiniformes
Family Myxinidae (1 genus, 2 species)
Pacific hagfish
Eptatretus stouti
no paired fins
caudal fin only
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Hagfish
slime glands
Hagfish
Cartilaginous skeleton:
notochord persists in
adult as cartilage rod no vertebrae
no eyes
Hagfish
Hagfish mouth
barbels
two rows of
teeth on
tongue
Hagfish
Class Myxini
• 30 species (2 sp. in BC:
Pacific Hagfish and Black Hagfish)
• all marine
• mouth modified for sucking – jawless with two
rows of teeth and barbels
• no eyes
• no paired fins (caudal fin only)
• cartilaginous skeleton
• notochord extends the length of the body
as cartilaginous rod (no vertebrae)
• slime glands
• predators and scavengers on invertebrates a
and dead and dying fish
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Fishes I
Chordate taxonomy
Hagfishes
Lampreys
Chimaeras
Sturgeon
Gars and Bowfins
Scales
Superclass Agnatha - fish without jaws
Order Petromyzoniformes
Family Petromyzontidae (1 genus, 2 species)
tooth at top of mouth with 3 points
prominent eyes
Pacific Lamprey (Lampetra tridentata)
Maximum size: 76 cm
Lampreys
Lamprey
dorsal fins
prominent eyes
gill pores
oral disc has numerous teeth (no jaws!)
dorsal fins
gill pores
no barbels
Cartilagineous skeleton: Notochord persists in
adult, surrounded by cartilage pipe with rudimentary
vertebrates
Sea lamprey
Lamprey - Life history
migrate to lakes
or ocean
adults reproduce
in streams and die
parasitic adult
anadromous - spend all or part of
their adult life in salt water and return to
freshwater streams and rivers to spawn.
(larvae)
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Lampreys
• 35 species (2 in BC: Pacific Lamprey and River Lamprey)
• notochord – surrounded by a cartilaginous pipe
with rudimentary vertebrae
• parasites on fish
• jawless, sucking disc with many teeth, no barbels
• prominent eyes
• dorsal fins (and caudal fins)
Fishes I
Chordate taxonomy
Hagfishes
Lampreys
Chimaeras
Sturgeon
Gars and Bowfins
Scales
Subclass Elasmobranchii (sharks, skates, rays)
Superclass Gnathostomata - jawed vertebrates
Order Lamniformes (regular sharks)
Order Squaliformes (dogfish & sleeper sharks)
Order Rajiformes (skates & rays)
shark
shark
ray
skate
Subclass Holocephali (ratfish=chimaeras)
Sharks
Sharks
460+ species (12 in B.C.)
Streamlined body
Cartilaginous skeleton
Paired pectoral and pelvic fins
Two dorsal fins
Oil in Liver
Must swim continuously
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caudal fin
caudal fin
water enters spiracles
Shark picture
Shark picture
heterocercal tail
heterocercal tail
… and exits through 5
to 7 pairs of gill slits
How sharks (almost) achieve
neutral buoyancy
Predators with teeth!
• Cartilaginous skeleton (bone is dense)
• Pectoral fins, surface of the head and heterocercal tail
provide lift
• Large livers with large quantities of lipids (sp. gr.= 0.90-0.92)
and squalene (sp. gr. = 0.86). (Specific gravity of seawater = 1.026.)
… but are still negatively buoyant and
must swim continuously
Shark picture
…embedded
in JAWS
teeth are shed and replaced
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Most sharks are predators with large teeth …
… but the largest sharks filter
plankton (free floating, mostly microscopic organisms)
maximum length: 15.2 m ...
Temperate zone oceans
of the world; In BC:
Strait of Georgia, Queen
Charlotte Sound, Prince
Rupert
but most <10 m
Basking shark
Cetorhinus maximus
The whale shark filters plankton
Sharks’ teeth are modified placoid scales
not in BC
The world’s largest fish – maximum length: 18 m
sensitive to water pressure
and vibration
Sharks have relatively short digestive tracts …
sensitive to weak electric fields
(and possibly temperature,
water pressure and salinity)
…but the spiral valve increases surface area.
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The blood of sharks is isosmotic to sea water and
contains high concentrations of urea and
trimethylamine oxide (TMAO – from ammonia) and low
concentrations of NaCl (about 1/3 that of seawater).
Internal fertilization !
kidney
rectal gland excretes NaCl
Claspers (in males)
= modified inner edges of pelvic fins:
inserted into female cloaca for sperm transfer
oviparous – eggs laid outside the
mother’s body
ovoviviparous – mother retains
eggs in uterus; embryo nourished
by egg yolk; young born alive
viviparous – embryos develop in
the uterus nourished by the
mother’s blood through a placenta
In viviparous sharks, the embryo receives nutrients
from its mother via a yolk sac placenta
Most sharks are viviparous!
embryo
yolk sac placenta
yolk stalk
uterus
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Shark egg case (“mermaid’s purse”)
embryo
Direct development:
a shark pup emerges from its egg.
yolk
egg case (keratin)
Class Chondrichthyes
What is the difference between skates and rays?
Skates and rays: cartilaginous fish
collectively known as “batoids”
Rays are kite-shaped with streamlined tails
Skates have fleshy tails with small fins
Clearnose Skate
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Sting ray with spine (modified placoid
scale) with venom gland at base.
thorns
skate
Manta ray: a plankton feeder
Mermaid’s purse (skates)
6m
All skates lay eggs;
rays are ovoviviparous!
Rays
• fewer species
• long, thin tail without fins
• stingray tail armed with spines
• ovoviviparous
Skates
• more species
• thicker tail with fins
• horns on tail
• oviparous
Class Chondrichthyes – cartilagenous fishes
Subclass Elasmobranchii - sharks, skates and rays
• cartilaginous endoskeleton
• placoid scales
• 5 to 7 pairs of gills and gill slits
• no swim bladder
• heterocercal tail (sharks)
• spiral valve in intestine
• urea in muscle tissue – blood isosmotic to seawater
• direct development
• internal fertilization
• oviparous, ovoviviparous, or viviparous
• senses of smell, vibration sensation (lateral line system) ,
and electroreception (ampullary organs of Lorenzini) welldeveloped
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Fishes I
Chordate taxonomy
Hagfishes
Lampreys
Chimaeras
Sturgeon
Gars and Bowfins
Scales
Spotted ratfish - Hydrolagus colliei
Superclass Gnathostomata - jawed vertebrates
Subclass Holocephali (ratfish)
Spotted ratfish
Hydrolagus colliei
= only ratfish sp. in B.C.
spine
long thin tail
large pectoral fins
Skeleton of cartilage
bottom feeders on mollusks and other invertebrates
upper jaw fused to the skull
teeth are large plates
male, identifiable by the paired pelvic
claspers and the cephalic clasper
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Spotted ratfish egg capsule - Hydrolagus colliei
Spotted ratfish
Hydrolagus colliei
male, identifiable by the paired pelvic
claspers and the cephalic clasper
Subclass Holocephali
• 30 species (1 species in BC)
• lack scales
• males possess pelvic and cephalic claspers
• upper jaw fused to skull, mouth ventral
ENVR 242 Taxonomy
Superclass Agnatha
Fishes I
Chordate taxonomy
Hagfishes
Lampreys
Chimaeras
Sturgeon
Gars and Bowfins
Scales
Subclass Chrondrostei – sturgeon
Sturgeon (Acipenser)
barbels
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Sturgeon
Sturgeon
2 species in BC:
• Green Sturgeon (Acipenser medirostris)
• White Sturgeon (Acipenser transmontanus)
marine
2 species in BC:
• Green Sturgeon (Acipenser medirostris)
• White Sturgeon (Acipenser transmontanus)
freshwater
Sturgeons are the largest fish found in
freshwater.
White Sturgeon (Acipenser transmontanus)
Columbia and Fraser Rivers
up to 6.1 m
and 816 kg
Sturgeon
• heterocercal tail
• head covered with bony plates
• 5 rows of bony scutes (remnant ganoid scales)
• no teeth and 4 barbels
• prey on benthic invertebrates and fish
ENVR 242 Taxonomy
Fishes I
Chordate taxonomy
Hagfishes
Lampreys
Chimaeras
Sturgeon
Gars and Bowfins (0 sp. in BC)
Scales
Superclass Agnatha
(Infraclass Holostei – gars and bowfin)
Infraclass Teleostei – 23,640 species
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Fishes I
 Bowfin (Amia)
Chordate taxonomy
Hagfishes
Lampreys
Chimaeras
Sturgeon
Gars and Bowfins
Scales
Gar Pike (Lepisosteus)
Types of fish scales
1. Placoid – sharks and rays
spine
2. Cosmoid – lung fish
pulp
basal plate
sharks
rays
Similar to placoid scales and probably evolved
from the fusion of placoid scales
3. Ganoid – sturgeon, bowfins, gars, etc.
4. Leptoid – most fish
- cycloid
trout
gar
Modified cosmoid
scales with pegs and
sockets
herring
Smooth posterior margin
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Most fishes have scales … but some lack scales
swordfish
4. Leptoid – most fish
- cycloid
- ctenoid
mackerel
ctenii on posterior margin
perch
eel
snapper
catfish
… and some that appear to lack scales have a
complete coating of deeply embedded scales
Blue-fin tuna
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Fishes I

Transcription

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