Fish Anatomy and Adaptations

In this lesson, we will explore the external anatomy of the gizzard shad (Dorosoma cepedianum). We will also define and discuss adaptations through an evolutionary lens.

What is anatomy?

Anatomy is the study of the bodily structure of living organisms. Fish anatomy is the study of the bodily structure of fish.

Understanding anatomy allows us to better understand adaptations and how they might be beneficial to a species. We will discuss adaptations in further depth at the end of this lesson.

Species Profile: Gizzard Shad

The gizzard shad (Dorosoma cepedianum) is a member of the herring family (Clupeidae) regularly found in the tidal Potomac and Anacostia Rivers. It is an important forage fish for a number of predatory fish species like largemouth bass, blue catfish, and striped bass, among others. Follow along as we explore its external anatomy!

Mouth

The gizzard shad's unique mouth allows it to feed on plankton and detritus.

Eyes

The eyes serve as the gizzard shad's sight organs.

Nares

Nares, or nostrils, allow the fish to detect various odors underwater.

Operculum

The operculum, or gill plate, protects the gizzard shad's sensitive gills.

Gills

The gills allow the gizzard shad to breathe oxygen underwater.

Lateral Line

The lateral line is a series of sensory pores that runs along the side of the fish. The lateral line helps the fish detect vibration.

Dorsal Fin

The dorsal fin helps stabilize the gizzard shad while swimming.

Dorsal Filament

The dorsal filament is the elongated final ray of the dorsal fin. It is found on mature fish.

Pectoral Fins

The pectoral fins help the gizzard shad with lateral (side to side) movement.

Pelvic Fins

The pelvic fins help stabilize and balance the gizzard shad, thus preventing it from rolling while swimming.

Anal Fin

The anal fin provides additional stability to the gizzard shad while swimming.

Caudal Fin

The caudal fin, or tail fin, assists the gizzard shad with propulsion (forward movement).

Northern snakehead (Channa argus), pictured above

Adaptations

In the field of evolutionary biology, adaptations are characteristics that better allow an organism to survive and reproduce in its natural environment. Adaptations can be structural, behavioral, or physiological.

Take the example of the northern snakehead (Channa argus) , a non-native invasive species now found in the waters of the District of Columbia. Snakeheads have long, torpedo-like bodies that allow them to swim at high speeds through open water to chase down prey. Snakeheads are fry guarders, meaning they actively guard their offspring from potential predators. Snakeheads are also capable of breathing atmospheric oxygen (air) directly.

These three characteristics are examples of structural, behavioral, and physiological adaptations, respectively.

Adaptation Activities

Test your adaptation knowledge by reading this article on the longnose gar (Lepisosteus osseus) from our friends at the Chesapeake Bay Program.

Once you've completed the article, brainstorm three advantageous adaptations that might help the longnose gar survive in our local waters.

Longnose gar (Lepisosteus osseus), pictured above

To learn more about the adaptations of fish found in District waters, check out our Fashion a Fish Activity on Google Jamboard!

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