Pisces Agnatha dan Gnathostomata

Summary

This educational lecture covers the taxonomy of fish (Pisces), focusing on two main classes: Agnatha (jawless fish) and Gnathostomata (jawed fish). Agnatha includes primitive species like lampreys and hagfish, while Gnathostomata is divided into Chondrichthyes (cartilaginous fish like sharks and rays) and Osteichthyes (bony fish like goldfish and salmon). The lecture explores their anatomical features, ecological roles, and reproductive strategies, providing insights into the diversity of fish species found in various aquatic environments worldwide.

Takeaways

• 😀 Agnatha (Cyclostomata) is a group of jawless fish with cylindrical bodies, lacking scales, and soft, slimy skin.
• 😀 The main species in Agnatha include lampreys and hagfish, which are parasitic or scavengers.
• 😀 Gnathostomata is a group of jawed fish that includes Chondrichthyes (cartilaginous fish) and Osteichthyes (bony fish).
• 😀 Chondrichthyes, like sharks and rays, have cartilage instead of bones and are primarily marine predators.
• 😀 Cartilaginous fish like sharks and rays have placoid scales and internal fertilization, with some species being oviparous (egg-laying).
• 😀 Osteichthyes (bony fish) are characterized by a skeleton made of bone, paired fins, and a swim bladder for buoyancy.
• 😀 The subclass Actinopterygii consists of fish with fins supported by bony rays and includes most of the world's fish species.
• 😀 Sarcopterygii, the subclass of bony fish, includes the coelacanth, a 'living fossil' believed to have been extinct but rediscovered in the 20th century.
• 😀 Lampreys have a parasitic lifestyle, attaching to other fish to feed by using their circular mouths with sharp teeth.
• 😀 The lamprey life cycle includes two stages: a larval stage living in freshwater and an adult stage, which migrates to the ocean or freshwater for reproduction.

Q & A

What are the two main classes of fish in the Pisces group discussed in the script?

The two main classes of fish in the Pisces group discussed are Agnatha (Cyclostomata) and Gnathostomata. Gnathostomata is further divided into Chondrichthyes and Osteichthyes.

What is the primary difference between Agnatha and Gnathostomata?

The primary difference is that Agnatha lacks jaws, whereas Gnathostomata possesses jaws. This distinction is fundamental in classifying fish within these two categories.

What does the name 'Agnatha' mean, and what is its significance?

'Agnatha' comes from the Greek words 'a' (without) and 'gnathos' (jaw), indicating that these fish lack jaws, which is a key characteristic of this class.

What are some characteristics of fish in the Agnatha class?

Fish in the Agnatha class have cylindrical, elongated bodies, lack paired fins, have a circular mouth without jaws, and produce mucus. They also have a cartilaginous skeleton, a heart with one atrium and one ventricle, and a single gonad.

Can you give examples of fish from the Agnatha class mentioned in the script?

Examples of fish from the Agnatha class include the lamprey (Petromyzon marinus) and the hagfish (Myxine).

How does the lamprey's life cycle differ from other fish species?

The lamprey's life cycle includes both parasitic and non-parasitic stages. It begins as a larva in freshwater, migrates to the sea as a parasitic adult, and then returns to freshwater to spawn before dying, similar to the life cycle of salmon.

What is unique about the reproduction of Agnatha fish?

Agnatha fish have external fertilization, and they are hermaphroditic, meaning each individual has both male and female reproductive organs.

What are the distinguishing features of fish in the Chondrichthyes class?

Fish in the Chondrichthyes class, such as sharks and rays, have cartilaginous skeletons, five to seven gill slits, placoid scales, and internal fertilization. They do not have swim bladders like Osteichthyes.

What are the two subclasses of Chondrichthyes mentioned, and what distinguishes them?

The two subclasses of Chondrichthyes are Elasmobranchii (which includes sharks and rays) and Holocephali (which includes chimaeras). Elasmobranchii species have exposed gill slits, while Holocephali species have a single gill slit covered by an operculum.

How does the Osteichthyes class differ from Chondrichthyes?

Osteichthyes, or bony fish, have a skeleton made of bone rather than cartilage, unlike Chondrichthyes. They also have a swim bladder to maintain buoyancy, which Chondrichthyes lack. Osteichthyes reproduce externally and have paired gonads.

What are the two subclasses of Osteichthyes, and how do they differ?

The two subclasses of Osteichthyes are Actinopterygii (ray-finned fish) and Sarcopterygii (lobe-finned fish). Actinopterygii includes the majority of fish species, with fin structures supported by bony rays. Sarcopterygii has more robust, fleshy fins and includes species like the coelacanth, considered a living fossil.

What is the significance of the Sarcopterygii subclass mentioned in the script?

Sarcopterygii is notable because it includes the coelacanth, a fish once thought to be extinct. This subclass is crucial for understanding the evolution of vertebrates, as its characteristics are closer to those of early land vertebrates.

What ecological role do Chondrichthyes species like sharks and rays play in marine ecosystems?

Sharks and rays are top predators in marine ecosystems. They help regulate populations of other marine species, contributing to the balance and health of the ecosystem by controlling the numbers of prey species.