Yep, but do not get to alarmed just yet… it is not the same species as the famous one from Australia. That said… who is this new invader to our waters and is it of concern?
According to NOAA and the University of California at Berkeley there are between 20-50 species of box jellies from around the world. Their distinct shape, often called “cubomedua”, places them in their own family. Most of the “medusa” jellyfish we know are in a group called “scyphozoans” but box jellies differ in several ways.
- Their shape – the “box” shaped and their tentacles are clustered into four groups on the corners of the “box”.
- They are very good swimmers – most medusa can undulate their “bells” and move but they are planktonic (drifters) in the ocean currents. Box jellies are very strong swimmers. They can move against currents, tend to swim below the surface more (often collected in shrimp trawls), and have been clocked at top speeds of 4 knots! (This is very fast for a jellyfish).
- They do have eyes. They know where they want to go, can avoid colliding with piers, and have been known to even swim away from collectors trying to catch them. Not typical of our locals jellyfish. Lacking a central nervous system like ours, science is not sure how they see, or what they see, but they do.
Box jellies are found in all tropical seas, including the south Atlantic and Gulf of Mexico. They range in size from less than an inch to about 8 inches, with tentacles extending as far as 10 feet behind. Breeding in this group is interesting. Males will place their tentacles inside the bell of the female and deposit sperm. The female will then fertilize her eggs and release planktonic larva called planula. These planula will drift in the currents for a short period before metamorphosing into a flower-like creature called a polyp. Polyps are sessile (non-swimming) and attach to hard structures on the ocean floor. Here they can move and adjust to feed with their extended tentacles and can actually produce more polyps by budding. After a period of time each polyp will metamorphose into a swimming medusa, the box jelly we know and love. As already mentioned, they swim with purpose hunting small fish and invertebrates. They do have their predators. Certain fish and sea turtles are known to consume with no ill effects.
They all possess a very strong toxin which is quite painful. The most toxic of the group is Chironex fleckeri, the famous one from Australia. This jellyfish has been listed by many, including NOAA, as the most venomous marine animal in our oceans. It has certainly caused death in their waters. The majority of the lethal box jellies live in the Indo-Pacific. So what about Florida?
I am aware of two species that have been found here. The “Four-handed Box Jelly” (Chiropsalmus quadrumanus) and the “Mangrove Box Jelly” (Tripedalia cystophora). The Four-handed box jelly is the larger of the two, and the one pictured here. The Mangrove Box Jelly typically lives in the Caribbean. The first reported in south Florida was in 2009 near Boca Raton but they have since been reported in the Keys and along the Southwest coast of Florida. This is a small box jelly (about 0.25” in diameter) and seems to prefer the prop roots of mangrove trees.
The Four-handed box jelly can reach almost 5” in length with up to 10’ of tentacles attached. It is more widespread in Florida, though more common on the Atlantic coast then our own. One was brought to me about 6 years ago. The person found it next to pier at Quietwater Boardwalk, in the evening, swimming around the lights shining in the water, it was near Thanksgiving also. The one pictured here was seen by a local surfer and by Robert Turpin (Escambia County Division of Marine Resources) last week. Both sightings were near NAS Pensacola and may have been the same animal. This box jelly has the same characteristics as others – box shape, clustered tentacles, and very painful sting. The surfer who brought me the one from 6 years ago was stung by it. He said the pain brought him to his knees… so do not handle this animal if you see one. There was a report of a small child who died after being stung by one in 1991. However there are reports of young kids dying from the Portuguese man-of-war as well. Lesson here… treat it with caution.
These box jellyfish are not the deadly ones known from Australia, and it is certainly not common here – preferring to stay in the open ocean more than nearshore, but it is an animal all should know about and avoid handling if encountered.
More resources on this animal:
- 50 Years of the Endangered Species Act Part 1 - June 2, 2023
- A Sea of Grass Part 9 The Rays - June 2, 2023
- A Sea of Grass Part 8 Echinoderms - May 26, 2023