Lecture 20 Flashcards
What was the skeletal structure of Placoderms like?
They had an endoskeleton of cartilage and an exoskeleton of dermal bone.
Who were the Placoderms?
The first jawed vertebrates, with armored bodies and jaws; they had separate head and trunk shields and mobile joints, but are now extinct.
What are paired fins and why are they important?
Pectoral and pelvic fins that allow fish to have greater control in water movement, aiding in yaw, pitch, and roll.
How did jaws in fish originate?
From two pairs of endochondral cartilaginous arches, the mandibular and hyoid arches, which evolved from gill arches.
Besides eating, what are some functions of jaws in fish?
Communication, breeding, defense, and respiration.
What does “Gnathostomata” mean?
“Jaw + mouth”; refers to vertebrates with jaws.
Why are lampreys considered a nuisance in the Great Lakes?
They significantly reduced populations of native fish species, and control efforts led to a 90% decline in lamprey populations.
What is the life cycle of lampreys?
They spawn upstream in freshwater, with some being anadromous (migrating from sea to freshwater to spawn), and adults die after spawning.
What are some unique features of lampreys?
They have a round mouth for suction, a protrusible tongue to scrape flesh, and are often parasitic on other fish.
How do hagfish feed without a jaw?
They are bottom scavengers with a protrusible tongue equipped with keratinized teeth, and use a tail-to-head knot to create suction for feeding.
Describe Ostracoderms.
Extinct jawless fishes from the Ordovician to Devonian periods, characterized by bony armor and found outside their bodies.
What are some features of jawless fishes like hagfish and lampreys?
Lack jaws, internal ossification, scales, and paired fins; have eel-like bodies and keratin “teeth.”
Which living group is a true monophyletic clade among jawless fishes?
Cyclostoma, which includes hagfish and lampreys.
What are jawless fishes also known as, and what does this term mean?
“Agnatha,” meaning “without a jaw.”
What is the lateral line system in fish?
A sensory system that allows fish to detect water movements and nearby objects.
