Jellyfish Facts: Jellyfish Pictures and Identification

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picture of a Portuguese man-of-war jellyfish (Physalia physalis)

A day at the beach without meeting up with a jellyfish normally gets counted as a good beach day.

Jellyfish facts starts by defining Jellyfish as marine animals without backbones (invertebrates), that live in oceans around the world.

Jellyfish facts two: We know them as the stinging ocean animals.

The name jellyfish refers to the animal’s jelly-like bell, or box shaped body. The accompanying tentacles suit their carnivorous diet bu paralyzing prey with toxic substances.

While most jellyfish sting, not all jellyfish stings are deadly to humans. The Portuguese man-of-war (Physalia physalis), pictured above, and various box jellyfish are probably the two most dangerous jellyfish found along the coastal waters of the United States.

Types of Jellyfish

picture of a sea nettle jellyfish
Prevention is worth an ounce of cure, and knowing which jellyfish to avoid is the best way to prevent jellyfish stings.

Other native jellyfish such as sea nettles and purple-striped jellyfish are also known to cause painful stings. The picture shows the rust colored marks of the Sea Nettle Jellyfish (Chrysaora quinquecirrha), and East Coast species.

picture of a Cannonball Jellyfish
Cannonball Jellyfish are one of the most common jellyfish species along the Mid-Atlantic and Southeast Atlantic Coast.

The bell grows about a foot in diameter. Their sting is fairly mild.

picture of a Lion's Mane Jellyfish, jellyfish facts
Reputed to be the world largest Jellyfish, Lion’s Mane jellyfish swim in all the world’s oceans. Sometimes they wash ashore, and when the larger ones, with caps up to eight feet in diameter, they cause quite the scene.

The tentacles reach even longer. The national aquarium says the world record is over one hundred feet.

The sting from the tentacles can cause severe pain. Just a friendly reminder that it’s always a good idea to wear some type of foot covering while walking on a beach with washed up jellyfish.

picture of a Pacific Sea Nettle Jellyfish
Pacific Sea Nettles are found all along the West Coast of the United States. The bell can reach over a foot in diameter and is typically tinted red.

Like their East Coast counterpart, their sting hurts.

picture of an Egg Yolk Jellyfish
The yellow color in the middle of the bell explains the name of another fairly common West Coast species, the Egg Yolk Jellyfish.

Their bell can grow two feet in diameter and the sting of the tentacles is reported to be more annoying rather than dangerous.

picture of a Moon Jellyfish
A few species of Moon Jellyfish live in all the waters of the United States. The clear bell with four almost circular spots in the middle, plus the lack of long tentacles are the defining characteristics of the species.

They tend to swim close to the top of the water. Their sting is considered fairly mild.

Avoiding jellyfish stings can also be as simple as checking local beach reports about areas where large numbers of jellyfish (often called blooms) have been cited. Avoiding any jellyfish that wash up on the beach also helps.

Jellyfish Facts: Jellyfish Stings


One of the most practical jellyfish facts deals with jellyfish stings.

As mentioned previously, all jellyfish sting. In most instances of jellyfish stings, the pain can be dealt with by rubbing sand and/or splashing salt water on the affected area to remove any remaining tentacles, and them applying vinegar on the area to reduce the pain.

Of course, since all jellyfish stings differ, jellyfish remedies differ, depending on the species. A 2013 research review, Jellyfish Stings and Their Management: A Review, published in Marine Drugs. Feb 2013; 11(2): 523–550 , concludes,

With some differences between species, there seems to be evidence and consensus on oral/topical analgesics, hot water and ice packs as effective painkillers and on 30 s application of domestic vinegar (4%–6% acetic acid) to prevent further discharge of unfired nematocysts remaining on the skin.

Jellyfish Blooms

In the past decade increasing numbers of jellyfish blooms have been reported, and scientists are testing a variety of hypotheses related to their cause. One such hypothesis assumes that increases in jellyfish populations results from declining fish populations. The reasoning starts with the assumption that many jellyfish species share a similar diet with fish.

As an area becomes over fished, the jellyfish move in to feed on the smaller fish and plankton still remaining.

Results of ongoing jellyfish population studies continue to be mixed. For example, a recent study, Recurrent jellyfish blooms are a consequence of global oscillations published in the Proceedings of the National Academy of Sciences (2013), evaluated the changing population hypothesis using longer term statistical data and concluded the evidence was inconclusive

Rather, the strongest nonrandom trend indicated jellyfish populations undergo larger, worldwide oscillations with an approximate 20-y periodicity, including a rising phase during the 1990s that contributed to the perception of a global increase in jellyfish abundance. Sustained monitoring is required over the next decade to elucidate with statistical confidence whether the weak increasing linear trend in jellyfish after 1970 is an actual shift in the baseline or part of an oscillation.

Meet the Jellyfish Relatives: Sea Anemones

picture of a green anemone
Sea Anemones share similar feeding habits with jellyfish, their tentacles contain a toxin that can paralyze small fish and other creatures that come into contact with it.

Sea anemone habitat varies. Many species around the world live along the rocks in coastal tide pools. When the tide goes out it is often easy to walk around the area in search of them. They come in a variety of colors and sizes, with approximately one thousand species documented world wide. Of those, about ten species live in harmony with fish, specifically clownfishes.

Look, but don’t touch, represents a rule of thumb for anyone who crosses paths with them. Many species have stings that produce ill effects on humans.