Title: Chondrichthyes
1Chondrichthyes
2Defining Characteristic of Chondrichthyes
- Cartilaginous skeleton
- Tough, flexible and lightweight
- Increases efficiency of swimming
3Class Chondrichthyes
- Split into 2 subclasses
- Elasmobranchisharks and rays
- 800 species
- Very diverse
- Holocephalichimeras
- 30 species
- All very similar
4Characteristics of Subclass Elasmobranchi
- Multiple gill slits (usually 5-7)
5Subclass Elasmobranchi
- 3 Superorders
- GaleomorphiGaleomorph sharks
- SqualimorphiSqualomorph sharks
- BatoideaSkates and rays
6Galeomorph sharks
- Sharky-looking sharks
- Anal fin
- Dominant predators of shallow warm ocean waters
7Gaelomorph Sharks
ANAL FIN
8Squalomorph sharks
- Not so sharky-looking
- No anal fin
- Deep-sea sharks
- Dogfish sharks, angel sharks and saw sharks
- Relationships within this group are uncertain
9ANGEL SHARKS
M Harris
DOGFISH SHARKS
SAW SHARKS
10Megamouth shark(Megachasma pelagios)
- Filter feeder
- Discovered in 1976
- Has been seen fewer than 20 times
11Skates, Rays, and Guitarfish
- Bottom-dwelling
- Flat
- Large pectoral fins attached to head
- No anal fin
- Eyes and spiracles on top of head
- Pavement-like teeth for crushing inverts
- Gills on ventral (tummy) side
12Skate or Ray?
- Skates
- Long, thick tail stalk supporting 2 dorsal fins
and a caudal fin - Oviparous
- Rays
- Whip-like tail stalk with a venomous dorsal barb
instead of fins - Ovoviviparous
13Skate or Ray?
H Carvalho
LO Duarte
RAY
SKATE
14Skate or Ray?
RAY EMBRYO
SKATE EGG CASE MERMAIDS PURSE
15Guitarfish
- Intermediate between sharks and rays
- Harmless
- Ovoviviparous
16Subclass Holocephali
- 1 OrderChimaeriformes
- 3 families
- No spiracle
- Only 1 gill opening each side of head (sharks
and rays have 5-7) - Tail is symmetrical (sharks and rays are
asymmetrical)
17Chimaeras (ratfish)
- Bottom dweller
- Eat crustaceans and molluscs
- Spine in front of dorsal fin with a venom gland
for defense
18- Produce only 2 eggs at a time
- Claspers on head and pelvic finsunknown use
- Oviparous
egg cases
19Obtaining Oxygen
- RAM ventilation
- Must swim or die
- Great white shark, mako shark, great hammerhead
and others
20Obtaining Oxygen
- Buccal pumping
- Skates and rays, most species of sharks
- Steady flow of oxygen across gills
- Same as most bony fish
21Obtaining Oxygen
- SPIRACLES
- An opening behind eyes
- Bring water to gills
- Can sit on the bottom and still breathe
- In some pelagic sharks, these operate
independently of gill, instead bring oxygen to
the eye muscles
22Buoyancy
- No swim bladder
- Many dont need to floatstay on bottom
- Big oily liver
- Tail provides lift in sharks
23(No Transcript)
24Heterocercal tail helps stay near the bottom
while swimming
More homocercal tail helps provide thrust for
swimming fast
25Sensory SystemsVision
- Rely less on vision than other fish used at
close range - Can see color
- See well during the day and in low light
26Nictitating membranes cover eyes when about to
seize prey
27Sensory systemselectroreception, smell and
hearing
- How sharks locate prey
- Smell
- Reception of electrical currents emitted from
muscle contractions of prey - Vision
28Sensory Systemstaste
- Sharks will spit out the Moses sole
- Secretes toxic substance from bases of dorsal and
anal fin rays - Substance could be used as shark repellent?
29Thermoregulation
- Some sharks (family Lamnidae) can generate heat
30Scales
- All have placoid scales
- Sharks have tiny, overlapping scales that feel
like sandpaper - Increase hydrodynamic efficiency
- In some fast-swimming sharks, channels between
scales to decrease turbulence - Some slow-moving sharks have stouter scales for
defense
31PLACOID SCALES
32Scales
- Placoid scales modified into
- Barb of stingray
- Dorsal spines of dogfish sharks
- Defensive spines on skates
- Teeth of sharks and rays
33BARB OF STINGRAY
DEFENSIVE SPINE
34Teeth
- Rows of teeth are shed and replaced
- Can lose up to 30,000 teeth in a lifetime
- Each shark and ray species has distinctive teeth
that reflect how it makes a living
35(No Transcript)
36DietLarge fish and mammals
- Predatory sharks
- Serrated teeth for tearing off chunks of big prey
37Dietsmall fish
- Teeth that come to long thin points
- Can hold onto prey until it can be swallowed
38DietSmall fish and invertebrates
- Rows of small sharp teeth
- Filter feeders like whale shark
39DietInvertebrates
- Flat, pavement-like teeth
- Crush hard-shelled invertebrates (like clams)
- Skates and rays,
40How a shark bites
- Large bladelike teeth for grabbing and sawing or
snapping off large chunks - Jaws have pressure up to 2800 kg/cm3
- Jaws loosely attached to head
- Lower jaw moves first, then upper
- Cant move jaws back and forth so must shake head
back and forth
41Reproductive Strategy
K
- K-selected
- Long-lived, slow to sexual maturity
- Long gestation periods (6-22 months)
- Produce a small number of large, active young
- Offspring have a good chance of survival
42Sharks are Sexually Dimorphic
MALE
FEMALE
43Females have thicker skin, to withstand bites
from males while mating
44John Stevens
45Oviparity (egg-laying)
- All skates and chimaeras, many sharks
- Large eggs covered with tough leathery cases and
tendrils at corners - May take up to 15 months to hatch
- Female horn sharks carry eggs and nudge into
crevices
46Ovoviviparity
- Produce thin-shelled eggs
- Eggs are retained in female uterus
- Shell disappears and young stay in uterus until
fully developed - Obtain nutrition from a yolk sac
- Rays and some sharks
47YOLK SAC
48Viviparity (live bearing)
- Some sharks
- Eggs retained in uterus
- Mother secretes a nutrient-rich fluid
- Young ingest or take up fluid through skin
- Membrane covers embryos teeth
Eve Bunting
49Cannibal Viviparity
- Some sharks
- Eggs retained in uterus
- Hatchlings have teeth
- Those that hatch first eat the other embryos
- Mother continues to produce eggs for them to eat
50Young
- Females move into shallow protected area to give
birth - Females do not eat during birthing period
- 2-60 pups per litter
- Young are miniature adults
- Quickly disperse and hide
- No parental care
51Shark Attacks
- Most US attacks occur in Florida
- 75-11 bites each year
- lt20 are fatal
- You are more likely to be killed by a pig than a
shark!
52Why do sharks attack humans?
- Interpret swimmers behavior as threatening
- Think small submersible vehicles are predators
- Male whale sharks think large boats are
competitors and will ram them - Prefer prey with high fat content, will spit out
skinny humans
53Man-eaters
- Of 350 species, 32 have attacked humans,
especially - White shark (Carcharodon carcharias)
- Oceanic whitetip shark (Carcharinus longimanus)
- Bull shark (Carcharinus leucas)
- Tiger shark (Galeocerdo cuvieri)
- BUT almost any shark will attack if provoked
54Conservation Issues
Shark fin soup
55Conservation Issues
- Shark Cartilage Pills
- No evidence ingesting it combats cancer
- More than 200,000 sharks killed every month to
make these products
http//healthwatcher.net/Quackerywatch/Shark-carti
lage/
56Conservation Issues
- Why no shark-safe tuna?
- Sharks also caught in nets along with dolphins
57Conservation Issues
- Sport Fishing
- Some species are not sexually mature until age 30
- Takes a long time for a population to bounce back
if over-fished
58Conservation Issues
- Harassment?
- Adventure sports
59(No Transcript)