a BRIEF ACCOUNT ON Class Cyclostomata

Cyclostomes (Greek: cyclos — circle; stoma — mouth) are primitive, jawless vertebrates commonly called lampreys. The salient features of Cyclostomata are:

• ·         Body is elongated, rounded and eel-like
• ·         Skin is soft and smooth
• ·         Exoskeleton is absent
• ·         Jaws are absent.
• ·         Mouth is circular and suctorial.
• ·         Nasal opening is single and median
• ·         Cartilaginous skeleton is present
• ·         Notochord is persistent
• ·         Heart has two chambers (auricle and ventricle).
• ·         Many aortic arches are present.
• ·         Gonad is single. Gonoducts are absent.
• ·         Development is direct or indirect

e.g. Petromyzon