Final answer:
Spiracles are present in cartilaginous fish, such as sharks and rays, and serve as respiratory apertures allowing water intake for gill ventilation. This feature differentiates them from bony fish who often lack spiracles but have an operculum covering their gills.
Step-by-step explanation:
Spiracles are present in cartilaginous fish. Spiracles are small openings or respiratory apertures behind the eyes of certain cartilaginous fishes, such as sharks and rays. These openings allow water to intake and pass over the gills for respiration, even when the animal is stationary or eating, hence, optimizing their survival.
The clade Chondrichthyes includes these cartilaginous fishes, characterized by their paired fins and a skeleton made of cartilage rather than bone. Differentiating them from bony fish, also known as Osteichthyes which includes Actinopterygii (ray-finned fishes) and Sarcopterygii (lobe-finned fishes), wherein spiracles are usually not present. These bony fish often possess operculum, a muscular flap that covers and ventilates the gills.
Understanding the morphology and physiology of different fish species, including the presence of features like spiracles can aid in distinguishing different classes of fish and their unique survival strategies in a diverse array of habitats.
Learn more about Spiracles in Cartilaginous Fish