Transcript Fig. 10-1 Fishes – Overview I. • • • Oldest group of vertebrates (530 mya) 27,000+ species (15,600+ marine spp.) Four major groups • Agnatha (Jawless fishes) • • Hagfishes, lampreys Chondrichthyes (Cartilaginous.

Fig. 10-1
Fishes – Overview
I.
•
•
•
Oldest group of vertebrates (530 mya)
27,000+ species (15,600+ marine spp.)
Four major groups
•
Agnatha (Jawless fishes)
•
•
Hagfishes, lampreys
Chondrichthyes (Cartilaginous fishes)
•
•
Sharks, rays, skates, ratfishes
Actinopterygii/Osteichthyes (Bony fishes)
•
•
Most familiar fish species
Sarcopterygii
•
Coelacanths, lungfishes
Fishes – Overview
I.
A.
Agnatha
•
Four chordate characteristics
•
Brain protected by skull made of bone or cartilage
Myxini (subphylum) – Hagfishes
1.
•
•
Unpaired fins
Lack jaws
•
Round, muscular mouth with dental plates
•
Predators and scavengers (max length ~80 cm)
How do they feed? video
•
Dig burrows in mud bottoms, usually cold water
•
Attack hooked or trapped fish
•
Capable of producing slime!!
•
Very flexible (can tie selves into knots) – Why?
•
Little known about reproduction
•
Exploited commercially – Eelskin wallets
Fig. 10-3
Fishes – Overview
I.
A.
Agnatha
•
Four chordate characteristics + vertebral
column
•
Spine encloses and protects nerve cord
Petromyzontida – Lampreys
Unpaired fins
Lack jaws
2.
•
•
•
•
•
•
Round, muscular mouth with dental plates
Most live in fresh water as adults
•
Marine species are anadromous, semelparous
(ammocoete larvae)
Attach to other fishes, rasp away sides and suck blood
Also feed on benthic invertebrates
Fig. 10-4
Fishes – Overview
I.
B.
Chondrichthyes (Cartilaginous fishes)
•
•
Skeleton of cartilage (more flexible than bone)
Movable jaws (upper & lower)
•
•
•
Paired and unpaired fins
•
•
•
Unpaired
•
Dorsal
•
Caudal
•
Anal
Paired
•
Pectoral
•
Pelvic
Placoid scales
•
•
Often contain well-developed teeth
Mouth usually ventral
Similar to teeth (pulp, dentine, vitrodentine)
Liver (lipid-rich) used for buoyancy
Fig. 10-5
Fishes – Overview
I.
B.
Chondrichthyes (Cartilaginous fishes)
1.
Sharks
•
•
•
•
•
•
•
•
Fusiform body
Heterocercal tail
Typically two dorsal fins
Pectoral fins usually large and pointed
Five to seven gill slits
•
Most sharks swim continuously to ventilate gills
Whale shark = Largest fish species (to 14+ m)
•
Planktivorous (zooplanktivorous) – How?
Most prevalent in tropical coastal waters
Reproduction
•
Internal fertilization (claspers)
•
Viviparous
•
Ovoviviparous
•
Oviparous