New Freshwater Fishes Highlight Species’ Evolution and Unique Adaptations

Fish that swam with dinosaurs, fish that can teach us about evolution, and fish that “speak” using electric pulse signals are just some of the remarkable species you’ll find at the New England Aquarium. Get a look at the Ancestral Fishes and African Rivers exhibits—open now—and some of the incredible fish you’ll find there.

Ancestral Fishes Exhibit

Fish have been evolving for about 500 million years. The Aquarium’s Ancestral Fishes exhibit highlights unique characteristics that have allowed ancient species to overcome extreme changes in that time. It also shows how understanding fish evolution helps us understand the evolution of other species, too, including humans.

That’s right! If you trace our species’ lineage back far enough—hundreds of millions of years—you’ll find fish in our family tree. Unlike most fish, those in the subclass Sarcopterygii had lobed fins with bones and muscles. This distinctive feature led to the evolution of tetrapods, vertebrates capable of living on land.

Most sarcopterygian fishes are extinct, but eight known species remain. You can find two of them in our Ancestral Fishes exhibit, along with several other species representing some of the earliest families of fish still alive today. 

Australian lungfish (Neoceratodus forsteri)

This endangered sarcopterygian species is the closest living fish relative to tetrapods, including humans. They still have lobed fins, the evolutionary precursor to the limbs that allow us to live on land. While Australian lungfish primarily use gills for breathing, they also have a single lung—hence their name—that helps supplement oxygen intake during periods of low water oxygen, such as during seasonal changes. 

They are an impressive ancestor to have. Their genome, 14 times larger than the human genome, is the largest of any animal ever sequenced. They can live to be over 100 years old and use electroreception to detect electric fields generated by other organisms to sense and locate prey or predators that are hidden behind objects or under sediment.

Shovelnose sturgeon (Scaphirhynchus platorynchus)

Some species of sturgeon date back to the early Jurassic period, 175 to 200 million years ago. They literally swam with dinosaurs! Shortnose sturgeon and Atlantic sturgeon are endangered species native to New England. Shovelnose sturgeon, displayed at the Aquarium’s Ancestral Fishes exhibit, are the smallest sturgeons in the United States. They are a vulnerable species native to certain freshwater wetlands from Montana to western Pennsylvania.

Longnose gar (Lepisosteus osseus) and spotted gar (Lepisosteus oculatus)

Gars also date back to the Jurassic period, more than 150 million years ago. Gars have ganoid scales, which are thick, diamond-shaped, and interlocking, creating a protective layer that has helped the characteristic get passed from generation to generation. Their body structure and genome have not changed much compared to more modern fish species. 

Studying spotted gar, native to North American freshwater, has helped scientists uncover how teeth enamel evolved from ganoid scales and limbs evolved from fins. Scientists are even studying spotted gars to better understand human diseases and potential treatments.

Asian arowana (Scleropages formosus)

A member of the Osteoglossidae family, Asian arowana may be among the most primitive fish species still living. Also known as dragonfish due to their resemblance to a Chinese dragon, they are thought to be symbols of good luck and prosperity. This may have contributed to overfishing of this species, which is now endangered and protected in the US under the Endangered Species Act. 

Asian arowana also exhibit intriguing biological behaviors. They are a paternal mouthbrooder species, meaning males collect and incubate fertilized eggs in their mouths for about a month before they hatch. The males continue to carry the baby fish in their mouths for about another two to three months, until they are big enough to emerge.

African Rivers Exhibit

Freshwater ecosystems account for less than 1% of the water on Earth, but the fish that live in them make up 41% of all species. Freshwater habitats are diverse, including rivers, lakes, marshes, swamps, rainforests, and more. They range in depth, and the water in them moves at different speeds, so the fish species that live in these habitats need physical attributes and behaviors that allow them to adapt to their varied surroundings.

Ropefish (Erpetoichthys calabaricus)

One of these freshwater inhabitants is the ropefish, found in Benin, Cameroon, and Nigeria. Their eel-like body allows them to hide or rest in tight spaces, and they can not only breathe air but also, like humans, use paired lungs to do so! These amazing fish are considered near-threatened due to habitat loss. 

African freshwater butterflyfish (Pantodon buchholzi)

Freshwater butterflyfish have big, wing-like pectoral fins and are excellent jumpers. They use their specialized fins to propel themselves out of swampy waters and their trapdoor-like mouths to catch and eat small insects above the surface.

Elephantnose fishes 

There are eight species of elephantnose fishes in the African Rivers exhibit. They get their common name from the elongated snouts and chins, similar to an elephant’s trunk, that some species have—but that’s just the beginning of what makes them fascinating. Living in murky habitats, these nocturnal fish rely on an impressive adaptation to navigate and communicate. Elephantnose fish “speak” using a special organ at the base of their tails to send out electric pulses and “hear” through electro-receptor pores along their bodies. 

Each species produces a unique pulse wave and the wave frequency shifts depending on what they are trying to convey. Pulses may speed up when the fish feel aggressive or nervous, slow down when they’re calm, or take on a specific pattern while trying to attract a mate. 

Their specialized form of communication has led to another standout feature: big brains. Relative to their body size, elephantnose fish have the largest brains of any fish.

Visit the Aquarium to see these and more fascinating fishes in the Ancestral Fishes and African Rivers exhibits, open now!