Questions and Answers
What are the characteristics of Class Agnatha (Jawless Fish)?
The lamprey and hagfish are the only living representatives of Class Agnatha.
True
What are the characteristics of Lamprey?
They migrate to reproduce in freshwater, can grow up to 2-3 ft long, and have a rasper.
What are the characteristics of Hagfish?
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Earliest known organisms were found in ___________ __________ times?
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What is the difference between Hagfish and Lampreys?
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Study Notes
Class Agnatha Characteristics
- Class Agnatha comprises jawless fish, characterized by the absence of jaws and paired fins.
- Skeletons are made of cartilage, featuring a round eel-like body and a compressed caudal fin.
- Soft skin is devoid of scales and they lack a swim bladder and gill covers (operculum).
- Possess 7 gill slits on each side of the head; these gills are essential for respiration.
- Include species that are parasitic, like lampreys, and scavengers, like hagfish.
- Ectothermic nature means they cannot regulate their body temperature.
- Reproductive strategy involves external fertilization and being oviparous (egg-laying).
- Species can be found in both marine and freshwater environments with a lateral line for sensory perception.
- Have a two-chambered heart, no external ears, and no eyelids.
- Instead of jaws, possess an oral sucker; some species are highly predatory.
- Anadromous lifestyle indicates they live in both fresh and marine waters at different life stages.
Living Representatives of Class Agnatha
- The only living representatives of Class Agnatha are lampreys and hagfish.
Lamprey Characteristics
- Found in both fresh and marine waters; they migrate to freshwater for reproduction.
- Notorious for devastating fisheries in areas like the Great Lakes.
- Can grow up to 2-3 feet long and exhibit an anadromous lifecycle.
- Complete their life cycle in environments such as Greenlake, CA.
- Possess a pair of eyes and a rasping mouth; approximately 70% of the breeding population dies post-breeding.
Hagfish Characteristics
- Exclusive to marine environments and equipped with three eyes.
- Known for their unique adaptation of gnawing at food using specialized teeth.
- Gills operate at depths of 600 feet or deeper along coastlines.
- Act as scavengers, approximately 2 feet long, and have a unique feeding method where they enter the gill chambers of fish to secrete mucus that obstructs breathing.
Historical Context
- The earliest known organisms of the Agnatha class were discovered in Upper Ordovician times.
Differences Between Hagfish and Lampreys
- The hagfish is characterized by a lack of eyes, whereas lampreys possess well-developed eyes.
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Description
Test your knowledge of Class Agnatha, the jawless fish! This quiz covers their key characteristics, anatomy, and ecological roles. From lampreys to hagfish, explore the diverse traits that define these unique organisms.
