1. Chondrichthyes

2. Chondrichthyes General characteristics
cartilagenous skeleton
Jaws
Skin covered with placoid scales also called dermal denticles

3. Chondrichthyes General characteristics
a.) lack of lung, swim bladder –
use oil in liver to regulate buoyancy
b.) teeth not fused to jaws;
replaced when lost
many sharks can replace every tooth in 7-8 days!!
c.) gills not covered by operculum
d.) reproduction
- leathery egg case (in oviparous species)
- males have claspers on pelvic fins for internal fertilization
- insert claspers into female’s cloaca
- groove carries sperm to female

4. Method of rearing varies...
oviparous
eggs with leathery sheaths develop, hatch outside female’s body

5. Chondrichthyes - Reproduction
Method of rearing varies...
b. ovoviviparous-
eggs retained within female’s body, but still nourished by yolk
c. viviparous –
embryos nourished continuously by mother throughout development; several forms possible
Several species of shark exhibit intrauterine cannibalism

7. Chondrichthyes General characteristics
Senses
Vision -
most have excellent vision probably have color vision
Smell -
very acute
Vibration -
Lateral Line system senses vibration

9. Chondrichthyes General characteristics
Senses (continued)
Hearing -
The shark middle ear senses sound waves, especially low frequency
Electrical impulses -
Ampullae of Lorenzini sense electrical impulses
- detect weak magnetic fields
- locate prey buried in the sand
- detect changes in water temperature

11. Chondrichthyes General characteristics
Internal skeleton is well developed and includes...
robust skull, jaws
“u-shaped” pectoral girdle supporting strong fins
laterally flexible vertebral column,- permits swimming by lateral undulation
shark swimming

13. Chondrichthyes Systematics & taxonomy
Class Chondrichthyes
1) Subclass Holocephali (chimaeras)
- 56 species of deep-water fish; very poorly known
Characteristics of Holocephali: chimaeras
a. single gill slit on each side
b. teeth are grinding plates
lack enamel and have slow replacement
c. males with claspers on the head in some species
d. no scales,
except for small denticles on back and on claspers
e. jaw not protrusible

18. Chondrichthyes Systematics & taxonomy
2) Subclass Elasmobranchii (sharks, skates, rays)
i) Galeomorph orders (“classic” sharks)
ii) Squalomorph orders (deep water sharks)
iii) Squatinomorph order (angel sharks)
iv) Batoid fishes (skates and rays)

19. Chondrichthyes - Elasmobranchii
Characteristics of Elasmobranchii (sharks, skates, rays)
a. 5-7 gill slits on each side of head

20. Chondrichthyes - Elasmobranchii
b. protrusible jaw
- gives very wide gape during biting, with streamlined shape when not feeding also permits strong suction feeding

21. shark eating

23. Chondrichthyes - Elasmobranchii
c. numerous teeth with serial replacement
“conveyer belt” of replacement teeth

25. Shark Teeth

26. Chondrichthyes - Batoid orders
Characteristics of skates and rays
Most are Benthic (bottom-dwelling)
A few are Pelagic (live in water column)
Most are Durophagous (“hard-eating”)
teeth generally hard, flattened plates for crushing shells of invertebrates)
protrusible jaws give suction to pick food out of sediments
body dorsoventrally flattened
pectoral fins enlarged
swim by undulation of pectoral fins

28. Chondrichthyes - Batoid orders
Skates and Rays
Placoid scales mostly absent,
modified in some into venomous spines at base of tail
eyes large, dorsally placed
dorsal spiracles take in water to go past gills and out gill slits
largest forms are filter feeders
Some can generate electric fields

29. Chondrichthyes - Batoid orders
Differences between skates and rays:
skates generally have elongate, thick tail with dorsal fins;
all oviparous
“mermaid’s purses” are skate egg cases

30. b. rays have long, whip-like tail with one or more venomous barbs;
b. rays have long, whip-like tail with one or more venomous barbs; all viviparous