Cyclostomata refers to a taxonomic group of jawless vertebrates commonly known as cyclostomes or the cyclostome fish. The term is derived from the Greek words "kyklos," meaning circle or ring, and "stoma," meaning mouth, highlighting the unique circular shape of their mouths.
Cyclostomata is comprised of two extant orders: Myxini, which includes hagfishes, and Petromyzontida, which includes lampreys. These organisms possess several distinguishing features which set them apart from other vertebrates. Most notably, their mouths lack jaws and instead present a round sucker-like opening encircled by prominent oral discs.
Cyclostomata are fish-like in appearance, but they exhibit primitive characteristics that provide insights into the evolutionary history of vertebrates. These jawless fishes are often referred to as living fossils, as they have retained many ancient traits, including a cartilaginous skeleton, a notochord that serves as a flexible supportive structure, and a lack of paired fins.
Members of Cyclostomata also possess unique and specialized adaptations. For instance, hagfishes secrete copious amounts of slime as a defense mechanism, allowing them to escape from predators. Lampreys, on the other hand, are known for their parasitic lifestyle, attaching themselves to the body of other fishes and feeding on their bodily fluids.
Due to their anatomical and physiological diversity, cyclostomes have considerable ecological importance and serve as valuable models for the study of vertebrate evolution and development. Cyclostomata's ancient lineage, peculiar morphology, and intriguing lifestyle make them a fascinating group within the animal kingdom.
