Blue Buttons

Blue Buttons
Captured in Bay of Bengal at Thotlakonda beach in Visakhapatnam, India. Photo by N. Aditya Madhav. Licensed under CC BY-SA 3.0.

As I sit down to write my final words for this magazine, my heart is filled with a myriad of emotions. It's hard to believe that this journey, which started over a decade ago with a short filler article on oil spills, has now come to an end. With each creature discovered and ecosystem mechanic explored, I hope you learned a little more about our amazing bays, as I did. To all of the readers, contributors, and supporters who reached out to me over the years, THANK YOU. Your enthusiasm has been the fuel that has driven me forward. Thank you for being a part of this journey. Until we meet again in the pages of a new story, be well, be inspired, and keep learning.

Porpita porpita, commonly called the blue button, is a hydrozoan that is superficially similar to a jellyfish. However, each apparent individual is actually another set of creatures altogether. Like other members of the class Hydrozoa, they are marine organisms composed of colonies of polyps, or zooids, each specializing in a different function, such as eating, defense, or reproduction. The most famous hydrozoan is probably the Portuguese man o' war, Physalia physalis. Luckily, the blue button is not nearly as treacherous as the man o' war. Though they have a mild sting, they're not particularly dangerous to humans. Blue buttons consist of two main parts: the float and the hydroid colony. The float is a golden-brown circular disk filled with concentric air chambers and reaches up to 2 inches in diameter. This styrofoam-like organ is responsible for the button’s buoyancy and also contains pores that are able to communicate with other blue buttons. The hydroid colony, which can range from bright blue/turquoise to yellow, resembles jellyfish tentacles, ringing the central disk. Each “tentacle” branches out about halfway down its length, and each branch ends in a node of stinging cells (nematocysts). The mouth is located directly beneath the float and is used for both the intake of prey and the expulsion of waste. The mouth is surrounded by a ring of gonozooids (polyps in charge of developing reproductive structures called gonophores) and dactylozooids (polyps heavily armed with nematocysts, primarily concerned with defense). Tentacles are only found on the dactylozooids, which exist furthest away from the mouth, towards the outer part of the hydroid colony. The air-filled disk keeps the button afloat on the ocean surface, where it spends most of its life, drifting, at the mercy of wind, tides, and currents.

Blue buttons are found in tropical and sub-tropical waters off Europe, New Zealand, in the Mediterranean Sea, the eastern part of the Arabian Sea, the Gulf of Mexico, and other parts of southern U.S. Though they live on the ocean surface, they are sometimes blown ashore in large numbers. North of Bob Hall Pier is one area they sometimes wash up in. The blue button is a part of the neustonic food web, which is comprised of organisms that inhabit the region on or near the surface of the ocean. They are carnivores and prey on many small organisms including copepods, crustacean larvae, plankton, and other small creatures that also float near the surface of the water. While not particularly dangerous to humans, the blue button’s sting is venomous enough to keep the creature well-fed, despite being highly dependent on ocean currents and winds for bringing food to them. They are typically eaten by blue dragons, Glaucus atlanticus, and purple storm snails of the genus Janthina. Young Malabar trevally, Carangoides malabaricus, sometimes take shelter underneath the floats of blue buttons. These juveniles also appear to have preferences for particular buttons. When two pairs of buttons and trevally are separated by species, then returned to the same tank, each fish will return to its respective partner.

As hermaphrodites, each blue button has both male and female reproductive organs. Specialized polyps release eggs and sperm into the water where fertilization takes place. Fertilized eggs go through a larval stage before developing into adult polyps. New hydroid colonies form by the union of emerging polyps, which divide into new specialized polyps. A comprehensive count of living blue buttons isn’t known. However, a sudden and rapid increase in their numbers has been reported – possibly due to rising temperatures from climate change. Colonies have begun appearing in larger numbers along coastlines in Japan, as well as in the Ionian and Adriatic seas. The expansion of habitat and increase in population means increased competition with other organisms that consume the same food. A new balance in the neuston will have to be struck.

Where I learned about blue buttons, and you can too!

World Register of Marine Species

Texas Marine Species



Research Gate

Springer Link

My Animals


Slightly Blue



Go Science Girls