Is a cartilaginous fish filter-feeder?

Yes, some species of cartilaginous fish, such as rays and some sharks, are filter-feeders. For instance, the Manta ray (Manta birostris) has a specialized filtering system formed by its gills and gill rakers. These structures allow them to filter small organisms, such as plankton, from the water column.

The Manta ray swims with its mouth wide open, allowing water to enter. As water passes through the gills, the gill rakers act as a sieve, trapping small particles of food. These particles are then swallowed by the Manta ray, which has a specialized pharyngeal mill that helps crush the food.

Some species of sharks, like the whale shark (Rhincodon typus), are also filter-feeders. The whale shark is the largest fish species and has a similar filter-feeding mechanism. It swims slowly with its large mouth open, allowing water to enter its gill cavity, where the gill rakers trap small organisms, such as plankton, fish eggs, and small crustaceans.

Filter-feeding is a common adaptation in various marine animals, including some species of cartilaginous fish, allowing them to efficiently obtain food from the water column without actively pursuing prey.