Column SFF Bestiary Marine Life Weirder Than Space Aliens Colonial animals like the Portuguese Man o’ War push the boundaries on life as we know it… By Judith Tarr | Published on December 8, 2025 Photo by Sebastian Schuster [via Unsplash] Comment 0 Share New Share Photo by Sebastian Schuster [via Unsplash] I have learned so much while researching and writing this chapter of the SFF Bestiary. I’m endlessly intrigued by the sheer range and variety of creatures that live in the ocean. Some, like cetaceans, are alien but still relatable to our mammalian brains. Others are as weird and truly other as anything we can imagine on another planet. When I started researching this topic, I was surprised to discover that the Portuguese man o’ war is not a jellyfish. It looks like one, with its shimmering, clear-plastic-like inflatable bladder and its trailing tentacles, not to mention its notorious stingers, but it’s something else. It’s a siphonophore. Jellyfish and siphonophores are related. They’re both classified as Cnidarians. They share a gelatinous body, stinging tentacles, and no blood or brain. But structurally they’re very different. A jellyfish has a bell or hood, tentacles, arms, and a mouth. Sometimes it has eyes or eye-like structures. It’s an animal in the way we are, a collection of specialized organs that add up to a single creature. A siphonophore is what’s known as a colonial animal, a community of tiny creatures called zooids. Every member of the colony has a specific and separate function. Some feed, some swim, some reproduce. They’re joined together along a central stem, through which they share energy and nutrition. Individual zooids can’t survive apart from the colony, but if some are separated, the rest of the colony can survive and generate new zooids. All the zooids in a siphonophore are clones of a single fertilized egg. The egg develops into a polyp, which buds off copies of itself, specialized according to its location in the colony. The ones that eat can’t swim, the ones that swim can’t eat, and so on. Siphonophores of the same species grow their zooids in the same order, but different species have different arrangements. Many have swimming zooids called nectophores that propel them through the water. Some species, including the man o’ war, have a gas-filled bladder or pneumatophore at or near the front. Some have pneumatophores but not nectophores. They all have feeding polyps with long tentacles that capture and usually sting prey and then consume it, and reproductive zooids that can be either all male or all female or both. A man o’ war’s balloon or float is fairly small, around six inches (15cm) high, but the stinging tentacles can extend as far as 100 feet (30 meters). Hundreds of man o’ wars can congregate in a single area, just like a jellyfish bloom, with similar effects on swimmers and beachgoers. What you see on the beach or above the water is a tiny fraction of the whole animal. The man o’ war is far from the largest or longest of its kind, and it’s one of the few that lives on or near the surface of the ocean. Most siphonophores live in the twilight zone, down 2000 feet (700 meters) and more. That’s where the giants are. The giant siphonophore, the praya dubia (doesn’t that sound like an alien species?), is one of the longest creatures in the ocean, longer than the blue whale. Supposedly it can reach 50 meters (160 feet). It’s an apparently endless ribbon, glowing with bioluminescence, transcribing enormous spirals in the darkness of the deep sea. Seeing it and its fellow siphonophores on video, it’s hard to comprehend the scale. What looks like a hollow sea cucumber or a textured wind sock moves into the frame with human divers, and dwarfs them. We’ve seen something like it on Star Trek, in “The Doomsday Machine”. The way it’s constructed, as a colony of individual organisms rather than a single entity, is about as far from our experience as it can be. Its body is toxic to us, and it lives in an environment that cannot support human life. It’s beautiful and weird, and proves yet again that nature is stranger than we humans can imagine. If we find living creatures on other planets, we might encounter a being, or colony of beings, remarkably like this. Or it might even appear in space. The question then might be, is it sentient? Will we communicate with it? Can we? Or will it be as mysterious as our own terrestrial alien?[end-mark] The post Marine Life Weirder Than Space Aliens appeared first on Reactor.