Agnatha (Cyclostomata) Past Paper PDF

**Superclass: Agnatha (Cyclostomata)** Nadtrieda: bezčelustné ryby (kruhoústnice) **Classification** Proposed relations among living (black) and extinct (red) Agnatha\... \| Download Scientific Diagram Class: Cephalaspidomorphi - Hyperoartia - Lampreys (mihule) Class: Pteraspidomorphi - Hyperot...

**Superclass: Agnatha (Cyclostomata)** Nadtrieda: bezčelustné ryby (kruhoústnice) **Classification** Proposed relations among living (black) and extinct (red) Agnatha\... \| Download Scientific Diagram Class: Cephalaspidomorphi - Hyperoartia - Lampreys (mihule) Class: Pteraspidomorphi - Hyperotreti (Myxini) - Hagfish (sliznatky) **Characteristics of Cyclostomata (Agnatha)** **Cyclostomata (Agnatha)** (bezčelustnaté ryby) appeared on Earth **500 million** years ago. They were a large superclass in the past. Now many are extinct except of **lampreys** and **hagfish**. They live in deep marine waters in tropical seas and shallow waters in temperate zones. They are **parasitic**, usually **feeding on fish** in their adult stage. Morphologically, they resemble **eels**. They are known to be the only living vertebrates without true jaws, hence called Agnatha. The body is round and elongated like an eel. Mouth opening is **round** without jaws with **many rows of teeth** and **suckers.** The endoskeleton is **cartilaginous** with no bones. The **cartilaginous notochord** is present throughout all their lives. They have odd fins (dorsal and caudal), the paired fins are absent. The skin is soft and smooth without scales. **Breathing system:** They breathe by gills, they have gill openings (6-14 pairs). The nostril is single in the middle of the head.  **Circulatory system:** It is closed. The heart is two-chambered. **Digestive system:** Mouth with teeth and a sucker, pharynx, intestines , stomach is not visible, pancreas, liver, gall bladder as accesory digestive organs are opened into the intestines, anus. Cyclostomata -- Wikipedia **Excretory system:** A pair of **mesonephric kidneys** make up the [excretory system](https://byjus.com/biology/human-excretory-system/). **Nervous system:** They have a brain and about ten pairs of cranial nerves are present. The lateral line acts as a sense organ. **Reproductory system:** The sexes are separate. Some hagfish species are believed to be hermaphrodite. Development may be direct or indirect. **Class: Cephalaspidomorphi - Hyperoartia - Lampreys (mihule)** - They are found in both **marine** and **freshwater**. - They are **predators**, feed on fish blood and tissue. - They have a **ventral mouth** with many horny teeth. - The nostril is present dorsally. - They possess a **well-developed dorsal fin**. - The development is indirect, they **have a larval stage.** Fresh water lampreys living in Slovakia: - [mihuľa morská](https://sk.wikipedia.org/w/index.php?title=Mihu%C4%BEa_morsk%C3%A1&action=edit&redlink=1) - [mihuľa riečna](https://sk.wikipedia.org/w/index.php?title=Mihu%C4%BEa_rie%C4%8Dna&action=edit&redlink=1) - [mihuľa potočná](https://sk.wikipedia.org/wiki/Mihu%C4%BEa_poto%C4%8Dn%C3%A1) - [mihuľa potiská](https://sk.wikipedia.org/wiki/Mihu%C4%BEa_potisk%C3%A1) Some of these species are source of food. Many of lampreys live in marine waters but travel to fresh water to lay eggs and multiply. After laying eggs and fertilisation they stop eating and die. **Class: Pteraspidomorphi - Hyperotreti (Myxiniformes) - Hagfish (sliznatky)** - They are found exclusively in the **marine environment**. Hagfishes are found in **cold seawater**, to depths of about 1,300 m. They live on soft bottoms, in **burrows**, and habitually lie buried except for the tip of the head. - They have a **terminal mouth with few teeth**. Their diet includes marine **invertebrates** and **dead** or **crippled fishes**. Sometimes, hagfishes attack [fish](https://www.britannica.com/animal/fish) caught on lines or in nets, boring their way into the bodies and eating the **fish from the inside**. - They have no buccal cavity. - The nostril is **terminal**. - They possess **6-14 pairs of gill slits**. - Eggs are large and few in number. - The **dorsal fin is usually absent**, or weak. - They don´t have larval stage. Development is **direct.** - To deter predators,. For this reason, they are sometimes known as slime eels. They produce a **huge amount of slime** to protect themselves in danger against predators. They have special **pores** along the body to secrete geat amounts of slime.