Box Jellyfish

December 7, 2019 Uncategorized

A great article from National Geographic:

About Box Jellyfish

The infamous box jellyfish developed its frighteningly powerful venom to instantly stun or kill prey, like fish and shrimp, so their struggle to escape wouldn’t damage its delicate tentacles.


Their venom is considered to be among the most deadly in the world, containing toxins that attack the heart, nervous system, and skin cells. It is so overpoweringly painful, human victims have been known to go into shock and drown or die of heart failure before even reaching shore. Survivors can experience considerable pain for weeks and often have significant scarring where the tentacles made contact.

Range and Appearance

Box jellies, also called sea wasps and marine stingers, live primarily in coastal waters off Northern Australia and throughout the Indo-Pacific. They are pale blue and transparent in color and get their name from the cube-like shape of their bell.


Up to 15 tentacles grow from each corner of the bell and can reach 10 feet in length. Each tentacle has about 5,000 stinging cells, which are triggered not by touch but by the presence of a chemical on the outer layer of its prey.

Highly-Advanced Adaptations

Box jellies are highly advanced among jellyfish. They have developed the ability to move rather than just drift, jetting at up to four knots through the water. They also have eyes grouped in clusters of six on the four sides of their bell. Each cluster includes a pair of eyes with a sophisticated lens, retina, iris and cornea, although without a central nervous system, scientists aren’t sure how they process what they see.

Blue-Bottles what exactly are they?

The Portuguese man o’ war (Blue Bottle) is composed of three types of medusoids (gonophores, siphosomal nectophores, and vestigial siphosomal nectophores) and four types of polypoids (free gastrozooids, gastrozooids with tentacles, gonozooids, and gonopalpons), grouped into cormidia beneath the pneumatophore, a sail shaped structure filled with gas.The pneumatophore should probably not be considered a polyp, as it develops from the planula, unlike the other polyps. This sail is bilaterally symmetrical, with the tentacles at one end. It is translucent, and is tinged blue, purple, pink, or mauve. It may be 9 to 30 cm (3.5 to 11.8 in) long and may extend as much as 15 cm (5.9 in) above the water. The sail is equipped with a siphon. In the event of a surface attack, the sail can be deflated, allowing the organism to briefly submerge.

The other three polyp types are known as dactylozooid (defense), gonozooid (reproduction), and gastrozooid (feeding). These polyps are clustered. The dactylzooids make up the tentacles that are typically 10 m (33 ft) in length, but can reach over 30 m (98 ft). The long tentacles “fish” continuously through the water, and each tentacle bears stinging, venom-filled nematocysts (coiled, thread-like structures), which sting and kill adult or larval squids and fishes. Large groups of Portuguese man o’ war, sometimes over 1,000 individuals, may deplete fisheries. Contractile cells in each tentacle drag the prey into range of the digestive polyps, the gastrozooids, which surround and digest the food by secreting enzymes that break down proteins, carbohydrates, and fats, while the gonozooids are responsible for reproduction.