Agnatha and Hagfish Overview

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Questions and Answers

What is Class Agnatha known for?

Bony skeleton

Hard scales

Jawless fish (correct)

Cartilaginous skeleton

How many species are there in Class Agnatha?

What are hagfish known for?

Small eyes and pinkish, gray bodies

Where do Class Agnatha fish live?

Bottom dwellers in cold marine waters Signup and view all the answers

How do Class Agnatha eat?

They pinch off chunks of flesh using movable plates and a rough tongue Signup and view all the answers

What do hagfish do after burrowing into the bodies of a dead fish?

Eat the internal organs Signup and view all the answers

How many hearts do hagfish have?

6 Signup and view all the answers

What type of circulatory system do hagfish have?

Open Signup and view all the answers

How do hagfish evade capture?

They tie their bodies into knots or secrete a bad-tasting slime Signup and view all the answers

What are lampreys characterized by?

Having large eyes Signup and view all the answers

What do lampreys do after finding a suitable host?

Attach to the host and scrape a hole with their rough tongue Signup and view all the answers

Where do all lampreys breed?

In fresh water Signup and view all the answers

What happens after lamprey eggs hatch?

They hatch into small larva that become filter feeders Signup and view all the answers

What is Class Chondrichthyes known for?

Cartilaginous skeletons Signup and view all the answers

What type of scales cover animals in Class Chondrichthyes?

Placoid scales Signup and view all the answers

How many species of sharks, skates, and rays exist?

Approximately 800 Signup and view all the answers

What kind of diet do animals in Class Chondrichthyes have?

Carnivorous Signup and view all the answers

How do sharks locate prey?

By using their sense of smell and lateral line system Signup and view all the answers

What do sharks have the largest of for any fish?

Brain Signup and view all the answers

What are rays and skates characterized by?

Flattened bodies and paired wing-like pectoral fins Signup and view all the answers

How many teeth do animals in Chondrichthyes have and what happens when a tooth breaks?

6-20 rows of teeth that point inward, replacement teeth move forward Signup and view all the answers

How many teeth may an animal in Chondrichthyes have in their lifetime?

2,000 teeth Signup and view all the answers

Study Notes

Class Agnatha

Comprises approximately 80 species, including hagfish and lampreys.
Characterized by jawless structure, smooth skin without plates or scales.
Features an eel-like body and a cartilaginous skeleton with unpaired fins.
Notochord remains present throughout their lifespan.

Hagfish

Possess small, subdermal eyes that act as light detectors.
Lack vertebrae which differentiates them from other fish.
Body fluids share nearly the same ion concentration as seawater, allowing them to adapt to their environment.
Exhibit pinkish-gray coloration with 4-6 short tentacles around the mouth.

Habitat and Feeding

Found as bottom dwellers in cold marine waters, feeding on small invertebrates or decaying fish.
Lack biting capability; utilize two movable plates and a rough tongue-like structure for feeding by pinching off flesh chunks.

Feeding Behavior of Hagfish

Burrow into dead fish through gills, skin, or anus to consume internal organs after entering.

Hagfish Physiology

Have a total of six hearts.
Function with an open circulatory system.
Evade predators by tying bodies into knots or secreting bad-tasting slime, primarily staying hidden in mud burrows.

Lampreys

Have large eyes and primarily inhabit freshwater, reproducing in these environments.
Approximately half of all lamprey species are free-living and do not feed as adults; the other half are parasitic, feeding on the blood and fluids of other fish.

Lamprey Feeding Technique

Attach to hosts using a disk-shaped mouth, scrape a hole with a rough tongue, and secrete an anticoagulant to prevent blood clotting during feeding.

Reproductive Behavior of Lampreys

Breed exclusively in freshwater, choosing gravel-bottomed shallow streams for spawning.
Female releases eggs while male fertilizes externally; eggs hatch into larval forms resembling lancelets.

Class Chondrichthyes

Composed of fish with cartilaginous skeletons, including sharks, skates, and rays, totaling around 800 species.
Movable jaws and paired fins are characteristic features.

Cartilage

A flexible, lightweight material consisting of cells embedded within tough fibers of protein, providing structural support in Chondrichthyes.

Feeding and Adaptations in Chondrichthyes

All species are carnivorous, with some scavenging; diet can include fish, seals, aquatic invertebrates, and plankton.
Covered in placoid scales, which are tooth-like spines that reduce water turbulence, enhancing swimming efficiency.

Sharks

Exhibit large, curved tails and torpedo-shaped bodies, swimming with a side-to-side motion from an asymmetrical tail fin.
Pectoral fins are located behind the head, resembling wing structures of an airplane.

Teeth and Sensory Systems

Have 6-20 rows of inward-pointing teeth that are self-replacing; can possess up to 2,000 teeth in their lifetime.
Utilize heightened senses to locate prey: keen sense of smell, developed lateral line system, excellent vision in low light, and sensitivity to electrical fields from other animals.

Brain Size

Sharks possess the largest brain relative to body size of any fish.

Rays and Skates

Flat bodies with paired wing-like pectoral fins; some have whip-like tails.
Rays typically have diamond or disc-shaped bodies, while skates have triangular shapes; sizes generally do not exceed 3.3 feet in length.
Primarily bottom dwellers, with their flat shape aiding in camouflage and movement along the ocean floor.

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Description

Explore the unique characteristics and behaviors of Agnatha, including hagfish and lampreys. This quiz covers their anatomy, habitats, and feeding methods, revealing the adaptations that make these jawless fish distinct in the marine environment.