Do jawless fish have operculum?

No, modern jawless fish such as lampreys and hagfish do not have an operculum; they breathe through multiple round gill openings instead of a single gill cover.

What is an operculum?

The operculum is a hard bony flap that covers and protects the gills of most bony fish like salmon, goldfish, and tilapia. It swings open and shut to pump water over delicate gill filaments. Jawless fish belong to class Agnatha. Living examples are lampreys (Petromyzontida) and hagfish (Myxini). They lack true jaws and paired fins and show many primitive features that date back to early vertebrates.

Respiratory openings

Instead of one gill slit per side, lampreys show seven round gill pores, while hagfish can have up to fifteen. Water enters either through the mouth or specially through a nasal tube, then exits the pores, supplying oxygen.

Evolutionary significance

The operculum evolved later with jawed fish (Gnathostomata). Its absence in agnathans tells us about ancestral vertebrate anatomy. Researchers study these fish to understand the transition from simple gill pores to complex gill covers.