Range: Northern Europe and North America, Asia, and more

Habitat: Cold, turbid temperature marine shorelines, hydrothermal vents, some in tropical waters

Size: 1-6 inches (2.5-15cm)

Diet: Copepods and other planktonic prey

Threats: Rising sea temperatures (and exposure to more light), pollution, and more

Lifespan: Unknown

Transcript:

Today on Animal Fact Files we’re discussing stalked jellyfish. These animals have had a confusing past in terms of classification. Originally, they were believed to be sea cucumbers. Later on, they were classified as sea anemones. Then they were moved to be part of the jellyfish class, but today they're classified in a class all their own. Of course, new information could change this once again. They are relatively understudied and not well known even in the scientific community, so who knows what the future might hold!

Though they share the common name "jellyfish" these animals are only distantly related to true jellyfish. They spend most of their lives attached to substrate with a sticky disc. Like some anemones, some stalked jellyfish can move around their environment, but most remain in the same spot their entire life. There are currently 50 classified stalked jellyfish species. These invertebrates live in shallow, coastal water. They’re known from undisturbed shores of northern Europe, North America, and Asia. They’ve also been observed in temperate regions of the southern hemisphere. Some species also live in tropical places. Stalked jellyfish prefer cold, turbid, or cloudy, water which essentially acts as sunscreen. They’re common in the intertidal and subtidal zones where they attach to hard surfaces like rocks as well as soft surfaces like seagrass and seaweed. They require flowing water which propels food towards them. These animals have also been observed living on deepsea hydrothermal vents which suggests there's more to learn about them!

The stalked jellyfish has eight arms ending in bunches of tentacles. These come equipped with stinging cells like those seen in other cnidarians. When prey is near, the stinging cells activate and trap an organism which is then moved to the stalked jellyfish's mouth much like a sea apple eating a meal.

Threats to stalked jellyfish are believed to include pollution caused by humans as well as rising sea temperatures. Stalked jellyfish live in fragile habitats that are easily influenced by changes around the world. Longer warm days exposing them to more light could be leading to a decrease in populations, however, so little information exists it's unknown how impacted their numbers truly are.

Stalked jellyfish larvae hatch from eggs and crawl around on the seafloor until they find a suitable place to attach. Some larvae go into a dormant state, like the eggs of tadpole shrimp, until they reach optimal conditions and continue developing. Typically there is only one generation produced each year. Stalked jellyfish can also reproduce asexually by spilling themselves and growing a new individual from the split pieces. It's unknown how long they live.

These animals are rarely observed though they are considered somewhat common in the places they inhabit. Their lack of observation can partially be attributed to their small size. In length, these invertebrates only reach about an inch (2.5cm) long, though some, such as those living in the deep sea, are known to reach more than half a foot (15cm) in length. They also blend in with their surroundings making them nearly undetectable to the untrained eye. Perhaps next time you’re around their habitat you can try and spot one!

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