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Aquatic Invertebrates


Photo Gallery

The head of a dragonfly nymph of the genus Erythemis. Hydra. Beetle larva of the genus Haliplus.
A dragonfly nymph of the genus Erythemis. All dragonfly and damselfly nymphs have a specialized "lip" that unfolds to reach out and capture prey.
This hydra belongs to a group called the Cnidaria, which also include jellyfish, corals, attached anemones and other polyps. Just like jellyfish, hydras have a specialized cell on the tentacles that contains a stinger that is fired on prey to sting or entwine them. The prey is then pulled in by the tentacles to the mouth.
Can you guess what this is? This is a larva of a beetle of the genus Haliplus. Both adults and larvae are herbivorous. The larvae are sluggish crawlers whereas the adults are good swimmers.
Damselfly nymph of the genus Enallagma catching a beetle. A leech (Helobdella stagnalis) eating a snail. Moth caterpillar of the genus Synclita.
This damselfly nymph of the genus Enallagma has caught a beetle for lunch. Damselflies and dragonflies feed on insects, molluscs, crustaceans, aquatic earthworms, and even small vertebrates. The larvae breathe through three external gills at the hind end of the body.
This leech (Helobdella stagnalis) has inserted its head into a snail's shell in order to feed on it. This leech also feeds on aquatic insects and worms. Other leeches are strictly parasitic on fish or crustaceans. Leeches can be found in warm shallow waters that are protected from currents.
Of all lepidopterans, only one family of moths (Pyralidae) has truly aquatic larvae. Aquatic caterpillars, like this one belonging to the genus Synclita, are herbivorous and pupate under water in silken cocoons.
Neoplea striola eating a hydra. The head of a damselfly nymph of the genus Enallagma. Caddisfly larva of the genus Oecetis in its case, side view.
Neoplea striola has specialized needle-like mouthparts for piercing and sucking out the liquids inside their prey, in this case a hydra. Hemipterans (the order of sucking insects) are predators that feed on insects and crustaceans. Larger Hemipterans can also feed on frogs and fish.
Odonates (dragonflies and damselflies), like this damselfly nymph of the genus Enallagma, are predators with eyes that are well developed for hunting. Some nymphs burrow in the sediment and ambush while others actively stalk their prey on submerged plants.
Caddisfly larvae, like this one belonging to the genus Oecetis, build cases by using silk to cement found materials together. They use these cases to aid respiration, as ballast to sink, as camouflage and as a pupal case.
  Caddisfly larva of the genus Oecetis in its case, front view.  
A front view of a caddisfly larva of the genus Oecetis in its case. The head and eyes of are visible here. This caddisfly is a swimming predator.


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A Project of the Canadian Museum of Nature
 Images: Chris Allaway, Ed Hendrycks