1. Fish
Ho Suet Ying
6S (8)

2. General features
any gill-bearing aquatic vertebrate (or craniate) animal which lacks limbs with digits
most fish are ectothermic (Tuna, swordfish, and some species of shark are homoiothermic)
has a streamlined body
has gills or an accessory breathing organ
has two sets of paired fins
has skin that is usually covered with scales
Fishes are divided into two main classes: chondrichthyes(fishes with cartilaginous skeletons) and osteichthyes(bony fishes)

3. Fish Chondrichthyes Osteichthyes Elasmobranchii Sarcopterygii
Holocephali
Actinopterygii

4. Chondrichthyes (Cartilaginous fishes)
jawed fish with paired fins
paired nares
scales
two-chambered hearts
skeletons made of cartilage rather than bone
large, oily liver for buoyancy
swim bladder and lungs are absent
forward swimming only
2 subclasses -Elasmobranchii (includes sharks , rays and skates)
-Holocephali.

5. (A) Skeleton cartilaginous (cartilage is often partly calcified )
notochord
lack ribs
do not have bone marrow (red blood cells -> spleen , epigonal organ , Leydig’s organ

6. (B) Scales (placoid scales or dermal denticles)
covered with dermal teeth
toothlike ( feel like sandpaper)
protection
in most cases streamlining
(C) Respiration
breathe through 5-7 gills (D)Excretion
excrete urea as nitrogen waste (they are ureotelic,
like adult amphibians and mammals).
Tuna gills

7. (E) Reproduction (Three types)
OVIPAROUS like fish-- external fertilization of egg
OVOVIVIPAROUS -embryos develop inside eggs - no placental connection
VIVIPAROUS - oppose to laying eggs

8. Bullhead and its egg
Catfish and its egg

10. Osteichthyes (Bony fish)
head and pectoral girdles are covered with large dermal bone
eyeball is supported by a sclerotic ring of four small bones
a lung or swim bladder
Gas-filled swim bladder for buoyancy
no fin spines (has lepidotrichia)
an operculum
bones are much heavier and less flexible than cartilage
both forward and backward swimming
2 subclasses -Sarcopterygii
-Actinopterygii

11. (A) Scales ( 2 types ) 1 . Ganoid scales
covered by enamel like substance called ganoin
found in primitive bony fishes such as gars
diamond-shaped
thick
non-overlapping

12. 2 . Leptoid scales
found on higher-order bony fish
overlap in a head-to-tail direction
2 sub-groups
- Cycloid scales Ctenoid scales
*scaleless fish -sacrifice protection of scales presumably for added flexibility

13. (A) Sarcopterygii (fleshy-finned fish)
2 subclasses : Sarcopterygii & Actinopterygii
(A) Sarcopterygii (fleshy-finned fish)
a clade (traditionally a class or subclass) of fleshy-finned or lobe-finned vertebrates.
only eight living species
lobed paired fins, joined to the body by a single bone
two dorsal fins with separate bases.
3 subclasses - Coelacanthimorpha — Coelacanths
- Dipnoi — Lungfishes
- Tetrapodomorpha — Tetrapods and their extinct relatives

14. A specimen of Latimeria Chalumnae
Queensland Lungfishes

15. (B) Actinopterygii ( ray-finned fish )
possess lepidotrichia or "fin rays"
Considered more “advanced” than (A)Sarcopterygii
– increased caudal symmetry - trend toward homocercal tail
– fin membranes with fewer rays
– reduction in dermal armor
– loosening of maxillary and premaxillary bones,
leading to a rounded mouth
2 subclasses - Chondrostei
- Neopterygii

16. Gar Fish
(Neopterygii)
Nile Bichir
(Chondrostei)

17. Excretion Reproduction
excrete nitrogen as ammonia, NH3, (they are ammoniotelic)
Reproduction
generally is external
gametes are released in the water, where they can fecundate their counterpart and
form the zygote.

18. Osteichthyes VS Chondrichthyes
Chondrychthyes Osteichthyes

19. Sources http://en.wikipedia.org/wiki/Osteichthyes