Dive in Flower Garden Banks National Marine Sanctuary and sometimes you’ll be treated to the beautiful view of an Atlantic sea nettle. (Just don’t get too close – those tentacles sting!) 

Sea jellies like these are classified as cnidarians, a group of animals that also include corals and sea anemones. 

(Photo: G.P. Schmahl/NOAA)

Summer is a great time to enjoy all things strawberry — including strawberry anemones!

At Cordell Bank National Marine Sanctuary, these inch-wide anemones carpet the sea floor. They use their tentacles to capture food and to defend themselves. As plentiful as they are, we doubt they’d taste great in a strawberry shortcake.

(Photo: NOAA)


Scyphozoan Life Cycle

1. Planula : The free-swimming medusa is either female or male and produces eggs or sperm which combine to produce a larva, called a planula. The planula is planktonic and will float around until it finds a substrate to bind to.

2. Scyphistoma : Once the planula binds to a substrate it develops into a scyphistoma. Scyphistoma is a feeding polyp with protruding tentacles on top used to catch food particles.

3. Strobila : The polyp soon turns into a reproductive polyp with stacks of strobilae. The strobilae are immature medusa that are being asexually reproduced by the polyp.

4. Ephyra : When a strobila is mature it breaks away from the reproductive polyp as a planktonic ephyra.

5. Medusa : The ephyra matures into a full grown medusa.



The lobby outside my lab room at USYD is filled with a collection of preserved animals, I thought you guys might like to take a look at some of the marine-related displays.

Phylum CNIDARIA! Defined by radially symmetrical bodies which either take the medusa (jellyfish) or polyp (corals and sea anemones) form, and contain stinging cells called cnidocytes.

Note the anemones attached to a hermit crab’s shell (image 2), and the Box Jellyfish (image 4)!

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Coral reefs and crevices create complex underwater structures. When turbulence is generated by these hard structures, it creates eddies that catch the coral larvae. Because coral larvae are poor swimmer, and are not able to suitable settlement sites on their own, depend on the structures that help shape these eddies, otherwise they are basically lost at sea, with no chance to settle and grow up. 

Nowadays, coral reefs around the globe suffer from repeated environmental disturbances, which are only compounded with climate change. According to coral reef experts, maintaining structural complexity of scales on reefs is vitally important in terms of aiding reef recovery. Relevant management actions include limiting factors that reduce complexity, such as destructive fishing practices, and promoting factors that enhance complexity, as algae-eating fish to the area to prevent algae from growing and smothering corals. 

Today the weather here in Scotland was better than yesterday, so my boyfriend and I took the chance to spend it at the beach on the west coast. As the high tide started retreating in the afternoon, two massive Rizhostoma pulmo, the barrell jellyfish, sadly got stranded ashore, they were the biggest I have ever seen!

Take my footprint as a reference, it’s about 27 cm, or about 10.5 in. This is the largest jellyfish species in British waters, but it is more commonly found in the Mediterranean, Black Sea, Sea of Azov and is also present in the Southern Atlantic, around South Africa.

On average they measure about 40 cm (16 in) in diameter, but I roughly estimated these two to be both above 50 cm (c. 20 in). They were big, but they can reach almost double this size!

They possess eight short and fleshy tentacles, but they are unable to cause any harm to humans as they feed on plankton, which they strain using the orange frills you see in photo, so they don’t need the urticating toxins found in other species. 

The second one was still moving, I tried my best but couldn’t pull it back to the water…it was slippery, and so much heavier than you might think!

There’s a whole world to discover in Olympic Coast National Marine Sanctuary tidepools! 

These are giant green anemones, which can often be spotted in the rocky tidepools lining the sanctuary. Their brilliant green color comes from symbiotic algae that live within their tissues! 

(Photo: Shawn Sheltren/NPS)

Have you ever seen coral under the microscope?

Well now you have! This is a coral called Frogspawn coral. One of its tentacles had to be removed because it was attacking another coral! See the bleached edges of the red plate coral?

This is a common behavior among corals and sea anemones. They can send out those extended tentacles filled with stinging nematocysts, which are basically poisonous harpoons. Some of you might have had some personal experience with nematocysts- if you’ve ever had close contact with a jellyfish, that’s what caused the stinging! Makes sense, since jellyfish and corals are actually closely related

And that’s what they look like at high magnification. The arrow on the left is pointing to the spiny string that can penetrate like a hypodermic needle. The arrow on the right is the empty cell were the nematocyst was previously coiled up. Overlaying the cell is a cell with a nematocyst that has not yet been released. Note all the strings in the background- those are more nematocysts! 

You’ll notice that the tentacle is chock-full of little red-brown dots. Those are actually symbiotic algae called zooxanthellae (don’t ask me to pronounce that) that live in coral by the millions and help the coral gain energy. To be more specific, those algae are dinoflagellates, which I’ve featured on my blog before

Check out these yellow zoanthids! Zoanthids are invertebrates related to reef-building corals and sea anemones. 

These were spotted colonizing the base of a dead golden octocoral in the deep waters of National Marine Sanctuary of American Samoa! 

(Photo courtesy of the NOAA Office of Ocean Exploration and Research, 2017 American Samoa) 

Plerogyra sinuosa

Commonly known as the grape, bladder, pearl or branching bubble coral Plerogyra sinuosa is a species of “bubble coral” that is distributed throughout the Indian and Pacific Oceans, ranging from the Red Sea to the West and Central Pacific Ocean. P. sinuosa’s bubbles will vary in size and will increase/decrease depending on the amount of light available. With them being larger during the day and smaller at night, as it will make room for its tentacles to reach out to capture food.


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Image: RevolverOcelot