Cyclostomata: Definition, Meaning, Characteristics, Classifications, Examples

Cyclostomata, or cyclostomes, is a unique class of jawless vertebrates characterised by their elongated, eel-like bodies, absence of paired fins, and round, sucker-like mouths adapted for parasitic or filter-feeding lifestyles. Members of this class Cyclostomata also include living species such as Petromyzon (lampreys) and hagfish. These serve as primary examples of this group. Cyclostomes are classified under Agnatha, the superclass of jawless fish, and have a primitive skeletal structure composed of cartilage instead of bone. Cyclostomata is part of the animal kingdom Biology chapter class 11th and has important weightage in the exam.

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This Story also Contains

1. What are Cyclostomata?
2. Taxonomy and Classification of Cyclostomata
3. General Characteristics of Cyclostomata
4. Anatomy and Physiology of Cyclostomata
5. Diagram of the Structure of Cyclostomata
6. Habitat and Ecology
7. Tips, Tricks, and Strategies for Cyclostomata

What are Cyclostomata?

The class Cyclostomata represents the jawless fish and consists of two basic divisions. These are hagfishes (Myxini), and lampreys (Petromyzontida). These animals are the absence of jaws and paired fins, which allow their study to be of central importance in understanding vertebrate evolution. Cyclostomes are among the most primitive living vertebrates, which help us to understand vertebrate development at an early stage.

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Taxonomy and Classification of Cyclostomata

• Kingdom: Animalia

• Phylum: Chordata

• Subphylum: Vertebrata

• Class: Cyclostomata

• Order: Myxiniformes (Hagfishes)

• Order: Petromyzontiformes (Lampreys)

Myxini (Hagfishes)

• Characterised by slime on their bodies and their scavenging lifestyle.

• Mostly marine species on dead or dying fish.

Petromyzontida (Lampreys)

• They are known to be parasites of some species, attaching themselves to other fish to suck their blood.

• It occurs in both marine and freshwater environments.

General Characteristics of Cyclostomata

Some general characteristics of Cyclostomata are discussed below:

• Body Structure: The cyclostomes are characterised by their elongated bodies, eel-like in shape, with no paired fins, and no jaws. The mouth is sucker-like and circular.

• Skeleton: They have cartilaginous skeletons that is, they are made of cartilage rather than bone. In addition to this, they do not have true vertebrae, only a notochord. The notochord is a long, flexible, rod-like structure that tends to help in supporting the animal.

• Sensory Organs: The cyclostomes have rather poorly developed eyes and a lateral line system that detects vibrations and movements in the water. This enables one to steer through the medium of water and to search for food.

Anatomy and Physiology of Cyclostomata

The general anatomy and physiology of Cyclostomata are discussed below:

• Mouth: Circular, sucker-like structure with keratinised teeth (particularly in lampreys).

• Gill Slits: Multiple external openings along the sides of the body used for respiration.

• Nostril: Single median nostril located on the top of the head, used for olfaction.

• Eyes: Simple, lacking the complexity of higher vertebrates.

• Fins (if present): Some species may have caudal fins for stabilisation during swimming.

• Segmented Body: Cyclostomes have elongated, cylindrical bodies that are segmented.

• Setae are absent in cyclostomes, differentiating them from other segmented animals like annelids.

• Clitellum: Not present in cyclostomes, unlike in annelids such as earthworms.

Diagram of the Structure of Cyclostomata

The diagram below shows the different body parts of a Cyclostomata.

Habitat and Ecology

These cyclostomes inhabit a variety of habitats. Hagfishes are mostly deep-sea marine, while lampreys are both in marine and freshwater systems. Lampreys also make very long migrations from one habitat to the other.

Ecological Roles:

• Some of the species, like the hagfish, act as scavengers, devouring dead and decaying remains.

• The impact that lampreys, particularly their parasitic forms, have on fish populations involves sucking their blood and feeding on tissues.

• Lampreys can significantly affect fish populations, both through predation and parasitism.

Tips, Tricks, and Strategies for Cyclostomata

It takes effort to remember everything in a single go. We made the entire problem easy. Some of the tricks regarding cyclostomata are given below which you can use to memorise the important points.

Classification and Characteristics of Cyclostomata

"JS-SLS: Jawless, Sucker-like mouth, Scaleless, Lateral line system, Simple skeleton"

• J: Jawless vertebrates (lack jaws, unlike other fish classes)

• S: Sucker-like mouth (adapted for attachment to host or substrate)

• S: Scaleless (absence of scales on their bodies)

• L: Lateral line system (used to detect vibrations in water)

• S: Simple skeleton (cartilaginous, with no bones)

Examples of Cyclostomata

"HL: Hagfish, Lamprey"

• H: Hagfish (known for producing slime as a defence mechanism)

• L: Lamprey (parasitic, attaching to other fish for feeding)

Evolutionary Traits and Habitat

"AP-GF: Ancestral, Parasitic, Gills, Freshwater/Marine"

• A: Ancestral traits (considered among the earliest vertebrates)

• P: Parasitic feeding in some species (such as lampreys)

• G: Gills for respiration

• F: Found in freshwater and marine environments

Cyclostomata Anatomy

"NSO-LS: Notochord, Single nostril, Open circulatory system, Lateral line System"

• N: Notochord (flexible rod supporting the body)

• S: Single nostril (a distinctive feature of cyclostomes)

• O: Open circulatory system (simple cardiovascular system)

• L: Lateral line system for detecting movements in water

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