Mary Allen
Which Animals Breathe Through Gills?
Gills are respiratory organs that enable animals to breathe underwater. They are specialized structures that extract oxygen from water and release carbon dioxide, allowing aquatic animals to survive in their watery habitats. Many different types of animals have evolved gills, including fish, sharks, crustaceans, mollusks, amphibians, aquatic insects, echinoderms, marine reptiles, cephalopods, tunicates, and lampreys. Each of these groups has its own unique adaptations for gill respiration, which reflect their diverse evolutionary histories and ecological niches.
Fish: The Most Common Gill-Breathing Animals
Fish are by far the most common group of animals that breathe through gills. There are over 30,000 species of fish, ranging from tiny minnows to massive whale sharks, and they all share the same basic respiratory anatomy. Fish gills are located on either side of the head and consist of thin, finger-like structures called filaments. These filaments are covered in tiny projections called lamellae, which increase their surface area and maximize gas exchange. As water flows over the gills, oxygen diffuses across the thin walls of the lamellae and into the bloodstream, while carbon dioxide diffuses out in the opposite direction. Fish are highly efficient at extracting oxygen from water, which allows them to thrive in a wide range of aquatic environments, from shallow streams to deep oceans.