lecture12

Ichthyology
Spring 1999
T. Turner

Lecture 12 - Chondrostei and Basal Neopterygiins

lecture12 Subclass Actinopterygii

Infraclass Chondrostei

Order Polypteriformes - bichirs, reedfish (1 family, 11 spp., African, freshwater)

Body Form

Pectoral fin is lobed!
Dorsal fin is numerous finlets supported by a single spine
Ganoid scales, paired lung, external gills when young, however internal structure suggest analogy rather than homology with lungfishes
Use dorsally placed spiracle to exhale! (not inhale like skates and rays); also use recoil aspiration (early tetrapods thought to use this method of respiration)

Life history and ecology

Order Acipenseriformes

Family Acipenseridae - 1 family, 24 spp. anadromous or freshwater, North America, Europe, Asia, Acipenser, Scaphirhynchus

Body Form

Four barbels in front of ventral mouth (sturgeons) long paddle-like snout (paddlefish)
Sturgeon -- four or five rows of bony scutes, minimal bony armor otherwise, no bony armor in paddlefish (patches of minute scales)

Life history and Ecology

Long-lived (70 - 120 years), large bodied (up to 8.5 m, 1300 kg), highly fecund, spawn every 2-5 years, mature late
Spawn over gravel beds with flowing fresh water, probably the rarest habitat on the Mississippi R.
Make large spawning migrations, hampered by dams

Infraclass Neopterygii

Order Lepisosteiformes - 1 family, 7 spp., freshwater North America fossil forms suggest widespread pangeal distribution

Body form

Life history and ecology

Order Amiiformes - 1 family, 1 sp., freshwater North America

Body form

Life History and Ecology

Slides

Family Acipenseridae

Acipenser medirostrus - Western distribution, disjunct; N. California, N. British Columbia, Alaska

Family Polyodontidae

Family Lepisosteidae

Lepisosteus osseus- backwaters, medium and large rivers of the Mississippi Drainage

Family Amiidae

Updated 08 March 1999, T. Turner