Cyclostomata – Characteristics and Classifications

Cyclostomatas are unique jawless fishes belonging to class Agantha. Cyclostomatas include lampreys and hagfishes and have a soft body. They get their name because of their round mouth. Cyclostomatas are found in different aquatic environments. They are also known as jawless fishes due to rudimentary jaw development.

Cyclostomatas have 6-14 pairs of gills and a cartilaginous skeleton. They can be found in both marine and freshwater and thus they are adaptable in many conditions. Cyclostomatas are different from fishes in many ways such as they do not have paired fins or true jaws.

What is Cyclostomata?

Cyclostomata are jawless fishes and they are known as cyclostomata due to their round mouth. The morphology of Cyclostomata is similar to that of eels. Their name, Agnatha comes from the fact that they are all vertebrates lacking actual jaws. Cyclostomata comprises lampreys and hagfishes.

Cyclostomata are only vertebrates without true jaws and because of their round mouth, they are known as Cyclostomata. They are in the superclass ‘Agantha’. When they fully develop they become parasitic and frequently feed on fish. Cyclostomatas resemble fish.

Examples of Cyclostomata

Examples of Cyclostomata are:

• Hagfish (Myxini)
• Japanese Lamprey
• Atlantic Hagfish
• European River Lamprey
• Pacific Lamprey

Cyclostomata Classification

The classification of Class Cyclostomata is shown below:

Kingdom	Animalia
Phylum	Chordata
Group	Craniata/Euchordata
Sub-Phylum	Vertebrata
Division	Agnatha
Class	Cyclostomata

Sub-Divisions of Cyclostomata

There are two subdivisions of Cyclostomata:

Petromyzontiformes

It includes eels or Lampreys:

• Found in both marine and freshwater.
• Indirect development.
• Ventral mouth and dorsal nostrils.
• Well developed dorsal fin is present.
• Examples are Lampetra and Petromyzon.

Myxiniformes

It includes hagfishes:

• Present in marine water.
• No buccal cavity.
• The dorsal fin is absent or weak.
• Few and large numbers of eggs.
• Examples are Paramyxine and Myxine.

Cyclostomata Characteristics

A few of the characteristics of Cyclostomata are:

1. The body is round and elongated like an eel.
2. The fins are not paired.
3. The median fins have cartilaginous fin rays.
4. Not paired appendages.
5. The skin is soft and smooth and it has no scales.
6. The sexes are different.
7. Some species of hagfish are believed to be hermaphrodites.
8. The spleen is not present.
9. Exoskeletons do not exist. The cartilaginous endoskeleton does not include any bones.
10. The notochord is present throughout their lives.
11. The nostril is single and median.
12. Five to sixteen pairs of gills are present.
13. The heart has two chambers. The brain is visible. The lateral line is a sensory organ.
14. Cranial nerves are found in around eleven pairs.
15. The two mesonephric kidneys are part of the excretory system.
16. The digestive system does not have a stomach.
17. Examples – Maxine and Petromyzon

Habitat of Cyclostomata

They are primitive in many respects but specialised in others because of their resilience and adaptability, they have survived in various habitats and adapted to a wide range of environmental conditions. They belong to the phylum chordata of the kingdom Animalia. They are believed to have originated in the Devonian period. Cyclostomata are extremely adaptable, they survive in a wide range of environments. These are found in a variety of conditions. They live in marine or freshwater habitat.

Difference between Cyclostomata and Fish

The following table lists the difference between cyclostomata and fish:

Cyclostomata	Fish
It has a rudimentary pancreas.	It has a well-developed pancreas that performs its functions
Cyclostomata has a small brain.	Fish have a developed brain.
Cyclostomata has an incomplete cranium.	Fish have a developed cranium.
Cyclostomata has a single nostril in the middle.	Fish have paired nostrils.

Function of the Cyclostomata

The following are the functions of cyclostomata:

• They are necessary for the nutrient cycle which maintains the balance of ecosystems.
• They act as indicators of environmental health.
• They also regulate the aquatic system by controlling the population of fish.

Conservation Concerns

One of the main issues is the degradation of habitat brought on by pollution and human-caused changes to waterways. Over-exploitation is a potential problem. Conservation efforts need to encourage eco-friendly behaviour and raise public awareness of the importance of freshwater lampreys and hagfish for the environment. By recognising and resolving these issues, we can contribute to the preservation of freshwater lampreys and hagfish.

Conclusion

In conclusion, Cyclostomata is warm-blooded vertebrates found in marine environments. They are essential to maintain the balance and well-being of ecosystems because of their distinctive features, long history of evolution and diversity of habitats. Cyclostomata’s role in the larger picture helps us better understand the interconnectedness of all living things.

FAQs on Cyclostomatas

1. What are the characteristics of Cyclostomata?

Cyclostomatas mostly consume fish and are parasitic. Their morphology is similar to that of eels. They live in both marine and freshwater conditions. Cyclostomatas lack scales and have cartilagenous structure which makes it flexible.

2. What is the difference between Cyclostomata and true fish?

Cyclostomata lacks biting jaws, hair, true teeth, non-paired fins, girdles, ribs, stomach and spleen. Fish have developed paired fins, stomachs, spleens, girdles and teeth. Cyclostomatas also lack scales and have circular mouths.

3. What class is Cyclostomata?

Cyclostomatas are in subclass Agnatha which includes jawless fish. Then two groups within Agnatha are Petromyzontida and Myxini.

4. Does Cyclostomata lay Eggs?

Yes, Cyclostomatas such as hagfish and lampreys lay eggs. Both groups reproduce through external fertilization. After fertilisation, the eggs develop into larvae and then into adult forms.

5. Are Cyclostomatas Extinct?

No, cyclostomatas are not extinct. It includes lampreys and hagfish is not extinct. Lampreys and Hagfish are found in both freshwater and marine all around the world. They are parasitic feeders and survived million years of evolution.