Who, What, When, Where, Why, and How of
Fish and Other Vertebrates
• Who studies FISH?
• What are: oviparous, viparous,
ovoviviparous? What are adaptations fish
possess to avoid predation?
• When do fish school?
• Where are fish located?
• Why is body shape important to fish?
• How do fish differ from other vertebrates?
Chapter 10
Marine Fishes
Karleskint
Turner
Small
• Vertebrate
– Jawless vertebrates – jawless fish
– Jawed vertebrates
– Fish
» Chondrichtyes
» Osteichtheyes
– Amphibians
– Reptiles
– Birds
– Mammals
• First we’ll talk about fish:
• Jawless fish
• Jawed fish
– Cartilaginous fish – Class Chondrichthyes
» Chimeras and ratfish
» Elasmobranchs – sharks, skates and rays
– Class Osteichthyes
» Lobed fin fish
» Ray finned fish
Fishes
• Fishes are vertebrates—animals that
possess vertebrae, a series of bones or
cartilages that surround the spinal cord
and help support the body
• Primitive fishes lacked paired fins and
jaws
• Adaptation of jaws and paired fins allowed
fish to more efficiently obtain food
ultimately replacing all but a few jawless
forms.
Jawless Fishes
•
•
•
•
Hagfish and Lampreys
Lack both jaws and paired appendages
Have skeletons of cartilage (no bone)
Lack scales
• Hagfish also lack vertebrae (some scientists
consider them invertebrates), recent DNA
evidence indicates that they are most closely
related to lampreys
Hagfishes
• Bottom dwelling “slime eels”
• Skins are used to make leather goods
• Hagfish feeding apparatus is composed of two
dental plates containing horny cusps, used to
grasp the prey’s flesh, fang above dental plates
keeps prey from escaping
– feed on live prey and scavenge
• Slime glands produce abundant milky, gelatinous
fluid for protection if hagfish is disturbed
Lampreys
• Have oral disk and rasping tongue covered with
horny dentacles to grasp prey, rasp hole in the
body and suck out tissue and fluid.
Cartilaginous Fishes
• Class Chondrichthyes
– e.g. sharks, skates, rays, chimaeras
•
•
•
•
Skeleton of cartilage
Possess jaws and paired fins
Placoid scales cover skin
2 major groups:
– holocephalans - chimaeras or ratfish
– elasmobranchs
• 2 body forms: streamlined, e.g., sharks or
dorsoventrally flattened, e.g., skates and rays)
Sharks
• Top predators of ocean’s food webs
• Excellent swimmers with streamlined
bodies
– swim with powerful, sideways sweeps of the
caudal fin (tail)
– heterocercal tail: caudal fin in which the dorsal
lobe is longer than the ventral
• Males have claspers—modified pelvic fins
which transfer sperm from the male to the
female
Dorsal fin
Kidney
Rectal
Spine
Stomach Testis Gill slits
gland Spleen
Caudal fin
Mouth
Clasper
Pelvic Intestine Pancreas
fin
Liver
Cloaca
Heart Pharynx
Pectoral
fin
Placoid
scales
Stepped Art
Fig. 10-3, p. 266
Sharks
• Ventral mouth with multiple rows of teeth
which are constantly replaced
• Found in all oceans with the greatest
numbers in temperate and tropical waters
• Humans exploit shark populations for fins,
meat, oil, leather, cartilage and sport
Skates and Rays
• Have flattened bodies adapted to a bottom
existence
• Greatly enlarged pectoral fins that attach to the
head
• Reduced dorsal and caudal fins
• Eyes and spiracles (openings for the passage of
water) on top of the head
• Gill slits on the ventral side
• Lack anal fin
• Specialized pavement-like teeth are used to crush
prey (e.g. benthic invertebrates)
Skates and Rays
• Electric rays have electric organs that can deliver
up to 220 V
• Stingrays have hollow barbs connected to poison
glands
– treatment for stingray wounds: submerge in hot water to
break down protein toxin
• Fished commercially for food, many are considered
threatened
Differences between Skates and Rays
Rays: swim by moving
fins up and down
streamlined tails with
venomous barbs or
spines
larger size
Ovoviviparous – young
born live but no
placental connection
Skates: create a wave
from the forward to
backward fin edges
fleshier tails with small
fins and no spines
smaller size
mostly oviparous – egg
laying
Chimaeras
• Subclass Holocephali
– e.g., ratfish, rabbitfish, spookfish
• Large pointed heads and long, slender tails
• Gills covered by operculum; water inhaled through
the nostrils rather than mouth
• Have flat plates for crushing prey instead of teeth
• Scales confined to a few dentacles
• No cloaca, i.e., have separate anal and urogenital
openongs
• Males have claspers on their heads and pelvic fins
Chimaeras
• Oviparous – produce large eggs in a
leathery case
• Generally bottom dwellers
• Little commercial value
– marketed as food in parts of China and New
Zealand
– their oils can be used as a lubricant
Lobefins
• Coelacanths – classified as lobefins due to
presence of rod-shaped bones surrounded
by thick muscle in the pelvic and pectoral
fins
• Now considered all to belong to
monophyletic group, the class Sarcopterygii
• Two extant species (Latimeria) of
coelacanths
• Only known as fossils until discovery of living
specimen in 1938
Lobefins
• Live in Indian Ocean at depths of 150 to 250
meters
• Skeleton made of bone and cartilage (vertebral
column is cartilage)
• Rostral organ in head detects weak electrical
currents, may aid in prey detection
• Life span is 60 years, reach sexual maturity at ~ 20
years, produce 5 to 26 live young
• Considered to be in danger of extinction
Ray-Finned Fishes
– Group we’ll be looking at:
– subclass Neopterygii – homocercal tails,
cycloid or ctenoid scales, more maneuverable
fins
• homocercal tails: tails with dorsal and ventral
flanges nearly equal in size; vertebral column
usually does not continue into the tail
• cycloid & ctenoid scales: scales that are thinner
and more flexible; less cumbersome for active
swimmers
Ray-Finned Fishes
• Median fins consist of 1 or more dorsal
fins, caudal fin, and usually anal fin
– help maintain stability while swimming
• Paired fins consist of pectoral and pelvic
fins
– both used in steering
– pectoral fins also help to stabilize the fish
The Biology of Fishes: Body Shape
• Shape of body determined by characteristics
of habitat
• Fusiform body shape: streamlined shape
with a very high and narrow tail
– efficient movement for active swimmers
Body Shape
• Laterally
compressed
or deep body
– allows
navigation
through
complex
habitat, e.g.,
grass or
corals
Body Shape
• Depressed or flattened bodies
– bottom-dwelling fishes
Body Shape
• Globular bodies, enlarged pectoral fins
– appropriate for sedentary lifestyle
Body Shape
• Long, snake-like bodies, absent or
reduced pelvic and pectoral fins
– useful for burrowing, living in tight spaces
Fish Coloration and Patterning
• Countershading is seen in open ocean fish
– obliterative countershading—coloration in which the
back (dorsum) is dark colored, and graduates on the
sides to the belly’s pure white
– when viewed from above, dark color blends in with
surrounding water; when viewed from below, white
belly blends in with lit surface waters
• Disruptive coloration—background color of the
body is usually interrupted by vertical lines; may
be a dark dot (“eyespot”) present in tail area
– more difficult for predators to see the fish
Fish Coloration and Patterning
• Poster colors: bright, showy color patterns
– may advertise territorial ownership, aid
foraging individuals to keep in contact, or be
important in sexual displays
– aposematic (warning) coloration: bright
coloration to warn predators that the fish is
too venomous or spiny to eat
Fish Coloration and Patterning
• Cryptic coloration: coloration which blends
with the environment
– used for camouflage
Locomotion
• In swimming, the trunk muscles propel the
fish through the water
– trunk muscles are arranged in a series of
muscle bands
– muscles contract alternately from one side of
the body to the other
– contractions originate at the anterior end and
move toward the tail, flexing the body and
pushing against the water
Locomotion
• Fish with different body forms swim in
different ways
– elongate fish undulate the entire body
– swift swimmers flex only the posterior portion
of the body
– other fish are somewhere in between
– fish with a dermal skeleton can only flex the
area before the caudal fin
– some fish swim using their fins alone without
body flexure
The Biology of Fishes
Buoyancy Regulation
• Maintaining buoyancy
– sharks sink if they stop swimming
– large livers produce squalene—an oily material
with a density less than seawater
– squalene offsets the shark’s higher density to
help maintain buoyancy
Buoyancy Regulation
• Most fish use a swim bladder—a gas-filled
sac that helps offset the density of the
body and regulates buoyancy
– the fish can adjust the amount of gas in the
swim bladder to maintain depth
– gas is added as the fish descends and
removed as it ascends
The Biology of Fishes
Adaptations to Avoid Predation
• Many exhibit elaborate camouflage
• Pufferfishes and porcupinefish inflate their
bodies to deter predators
• Flying fishes use enlarged pectoral fins to
glide through the air and escape
• Pearlfish hide in other organisms
• Parrotfish secrete a mucus cocoon
• Surgeonfish are armed with razor-sharp
spines
Adaptations to Avoid Predation
• Clingfishes use a sucker to attach to rocks
so predators can’t dislodge it
• Triggerfish projects spines to deter
predators or wedge itself into cracks
• Scorpionfish and stonefish have venom
glands for self-protection
Reproduction
• Three reproductive modes:
• Oviparity – eggs are shed into the water column
and embryo develops outside the mother’s body
– common in ray-finned fishes
• Ovoviviparity – fertilization is internal and eggs
hatch within mother’s uterus, where they are
nourished by yolk stored in egg
– common in sharks
• Viviparity – young attach directly to mother’s
uterine wall or uterus produces “uterine milk” that is
absorbed by embryo
– occurs in some sharks and some ray-finned fishes
The Biology of Fishes
Reproductive Strategies
• Pelagic spawners (e.g. tuna, wrasses)
– release vast quantities of eggs into the water
for fertilization by males
– fertilized eggs drift with the currents
– no parental care
• Benthic spawners (e.g. smelt)
– non-buoyant eggs with large yolks
– no parental care
– pelagic or benthic embryos/larvae
Reproductive Strategies
• Brood hiders (e.g., grunion)
– species that hid their eggs in some way but exhibit no
parental care
• Guarders (e.g., damselfish)
– species that care for their offspring until they hatch and,
frequently, through their larval stages
• Bearers (e.g., jawfish, seahorses)
– species that incubate their eggs until they hatch (in the
mouth or a special pouch)
The Biology of Fishes: Schooling
• School of fish = group of individuals that
operates in a polarized, synchronized
fashion
• Reasons for schooling:
- more eyes increases food finding abilities and
predator avoidance
- predators can’t focus on an individual
Chapter 10 Concepts
• Describe the Biology of Fishes:
– Shapes
– Coloration
– Adaptations to avoid predation
– Reproductive strategies
• Table 10