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Cnidarians of Zihuatanejo

PHYLUM CNIDARIA

-Animals (Kingdom Animalia)

-Cnidarians (Phylum Cnidaria)

-Sea Anemones and Corals (Class Anthozoa)​

-Subclass Hydroidolina

-Athecate Hydroids (Order Anthoathecata)

-Suborder Capitata

-Family Porpitidae

-Genus Porpita

-Blue Button (Porpita porpita)


The Blue Button, scientifically known as Porpita porpita, is a small, floating colonial hydrozoan commonly found in warm tropical and subtropical oceans. Although it resembles a single jellyfish, it is actually a colony of specialized polyps working together as one organism. The most distinctive feature is its circular, flat, bright blue central disc—often 1–3 cm across—surrounded by radiating, tentacle-like feeding structures that may be blue, turquoise, or yellowish. Unlike the Portuguese man o’ war, it lacks a sail and instead floats at the sea surface using a gas-filled float embedded in the disc. Blue Buttons drift with currents and winds in open ocean waters and often wash ashore in large numbers. Their tentacles contain nematocysts (stinging cells) used to capture tiny plankton and small marine organisms. While they can cause mild skin irritation if handled, their sting is generally not dangerous to humans.

Diet

  • Porpita porpita is a carnivorous colonial hydrozoan that feeds mainly on zooplankton and other small organisms near the ocean surface.

  • Its prey includes copepods, crustacean larvae and other small planktonic animals.

  • The specialized dactylozooids bear numerous nematocysts that capture and immobilize prey, which is then transported towards the mouth beneath the float.

Range

  • Porpita porpita has a very broad distribution in warm tropical and subtropical seas.

  • In the eastern Pacific it occurs along tropical and subtropical Pacific coasts, including the Pacific coast of Mexico.

  • It can occur in the waters of the Zihua region, particularly when wind and currents bring surface-dwelling colonies close to shore.

Habitat

  • Porpita porpita is a pleustonic organism that lives at or immediately below the ocean surface rather than attached to the seafloor.

  • It is a passive drifter, relying primarily on wind, waves and surface currents for movement.

  • Colonies may occur offshore but are frequently carried into coastal waters and can accumulate along beaches, especially during favourable wind and current conditions.

  • It forms part of the neustonic community, living among other organisms associated with the air–sea interface.

Description

  • Porpita porpita, commonly called the blue button, is not a true jellyfish but a colonial hydrozoan composed of numerous specialized polyps.

  • The colony consists of a small, flattened, circular float that is generally blue to turquoise around the margin, with a darker central area.

  • The float is typically a few centimetres across, with specimens reaching approximately 5 cm in diameter.

  • Numerous branching blue, turquoise or yellow hydroid structures extend beneath the float, giving the colony a superficial resemblance to a tiny jellyfish.

  • The branching dactylozooids terminate in clusters of nematocysts used for prey capture and defence.

  • A single mouth occurs on the underside of the float and serves both for ingestion and the expulsion of waste.

  • The combination of a rounded blue disc and radiating, branching hydroid polyps makes P. porpita readily recognizable among surface-dwelling hydrozoans.

Blue Button

Porpita porpita

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