Ocean drifters: The intricate world of the Portuguese man-of-war

The first story is not about just one natural oddity, but actually many.

The Portuguese man-o-war is not a single organism; rather, it is a floating colony of specialized individual organisms called zooids or polyps that are so intricately entwined that they cannot exist independently. These zooids are linked together and carry out several tasks necessary for the colony to survive. The Portuguese man-of-war includes:

· Pneumatophore: The man-of-war’s gas-filled bladder, which allows it to float and catch wind and appears in shades of pink, blue, or violet, acts as a sail and a warning flag to onlookers and potential predators.

· Dactylozooids: Long, tentacle-like structures extending below the float; these structures are equipped with poisonous nematocysts that allow them to paralyze and capture prey, showcasing the predatory abilities of man-of-war.

· Gastrozooids: Specialized zooids that digest their captured prey and absorb nutrients to keep the colony alive.

· Gonozooids: Reproductive zooids responsible for laying eggs or sperm, which aid in spreading the species.

“In general, the [Portuguese man-of-war] is comprised of several types of zooids with specific functions,” Paul Bologna of Montclair State University in Montclair, New Jersey, told How Stuff Works in a 2022 article. Depending on the size of the man-of-war, “Hundreds to thousands of individual zooids might comprise the whole colony.”

The Portuguese man-of-war reproductive process, which releases gametes into the water column for external fertilization, is a marvel of nature. The resultant planula larvae establish themselves and grow into new colonies, with each zooid differentiating to fulfill a distinct function. This process ensures genetic diversity and population resilience.

What and how do they eat?

The man-of-war is continually “fishing” for prey with its tentacles as the colony floats along.

Many specialized stinging capsules, or nematocysts, encase the food within the tentacles (dactylozooids). When the cells within a nematocyst are disturbed in any way — for example, by a brush against them or by changes in the osmotic pressure of the water — tiny coiled stinging barbs shoot out.

Because of the potent neurotoxin they contain, these stinging cells paralyze potential food items like plankton, tiny fish, and crustaceans. After the meal is rendered motionless, the feeding tentacles (gastrozooids) cling to it and bring it close to the man-of-war’s mouths.

“Siphonophores are abundant, diverse, and widespread predators in all oceans of the world yet their role in marine food webs has been long overlooked,” said Yale doctoral candidate Alejandro Damian-Serrano. “They are an ideal system to study the evolution of prey capture tools, as they have tentacles that are exclusively used to capture prey with a wide range of shapes and sizes.”

Do they have predators?

Despite being a strong predator itself, the Portuguese man-of-war has natural enemies of its own. The powerful venom of the man-of-war’s tentacles is intended to render fish and other small aquatic animals helpless. However, some animals have evolved to live alongside or even feed on man-of-war:

· Loggerhead turtles: These turtles eat siphonophores because their skin is thick enough to withstand the stings of man-o-war.

· The man-of-war’s tentacles are consumed by blue sea slugs (Glaucus atlanticus), which are pelagic nudibranchs that absorb and concentrate venom for self-defense.

· Ocean sunfish: These cnidarians are occasionally eaten by ocean sunfish, illustrating how interconnected marine food webs are.

Beachgoers should exercise caution in areas where man-of-war is common because even washed-up specimens can still sting severely. By lowering unfavorable interactions, education and awareness can encourage a safer coexistence with these marine species.