One can’t live without the other – this is the nature of a truly symbiotic relationship, and in the wilds of nature it is often a very delicately balanced situation. Evolution is an amazing thing – but species that evolve together can be all the more spectacular, protecting, feeding and cleaning one another in incredible ways.
In the oceans, sharks pair with fish, fish with shrimp and shrimp with sea cucumbers and much much more. From boxing crabs that wield poisonous anemones as weapons to shrimp that scour the mouths of electric eels, here are seven of the most radical symbiotic relationships from the shallowest to the deepest waters of our world. And of course this is only the life that we know about; it is most likely that even more bizarre creatures exist at the depths we have not yet begun to understand. So this list will present what we do know about symbiotic life-buddies in the oceans.
The two most obvious symbiotic relationships involve food associations (commensalism) and associations in which both host and symbiont benefit (mutualism). These two are very close, but in commensalism, the issue is only food and it’s usually only the symbiont that benefits directly.
10. Carrier Crab and Sea Urchin
Some animals like the Carrier Crab are highly creative in locating their defenses. The urchin being carried by this crab would likely prefer a solitary existence. This is an example of leveraging other animals in their habitat for protection – the crab is much safer with these spiky needles surrounding it – that leads to the symbiotic relationship.
9. Decorator Crabs and Sponges
Some creatures use others as camouflage. Decorator crabs snip pieces off of sponges and other nearby organisms and embed them into their shells, sometimes even carving the sponge into a cap that neatly fits on their carapace. Other crabs plant sea anemones onto their shells devising a built-in self-maintaining shield of stinging cells – or hold one in each claw, and like a boxer, attempt to punch the offender with its borrowed battery. Scientists believe these types of relationships merely evolved from creatures living in close proximity with one another.
8. Cleaner Shrimp – Eels
The cleaner shrimp seems foolhardy, climbing into the open mouths of sharp-fanged eels to dig around for food. These photos seem to depict daring shrimp shortly before their demise, but actually show an ancient tradition of cleaning. Moreover, these shrimp have evolved beyond merely finding eels and fish in order to eat their mouth parasites: they congregate at ‘cleaning stations’ in vast numbers. And yes, if you are looking for an alternative dental hygienist, they will even clean your mouth.
7. Crabs and Sea Anemones
Boxing, hermit and other crabs have found that they make friends with strange benefits in various species of stinging sea anemones. Boxing crabs (above, top) hold on to anemones and wield them like deadly pom-poms, warding off potential predators with their poisonous pals. Some hermit crabs (above, bottom) lift anemones and attach them to their shells in order to dissuade attackers. These relationships go both ways: the anemones are able to pick up more food as they move through the water with their shelled allies.
6. Shrimp-Goby Friendship
A happy-looking spotted fish living with a hard-nosed shelled shrimp: it sounds like something from made-for-kids animated movie. However, the goby and their shrimp buddies are truly contented cohabitants. They occupy holes together dug by the shrimp and protected by the goby. The relatively blind shrimp rely on their strong-sighted goby door guards to signal them about when it is safe to move. The gobies, in turn, rely on the burrowing shrimp to have a safe place to hide and sleep.
5. Sharks and Remora
Sharks seem like the most unlikely allies of the ocean: huge, speedy, vicious and ruthless predators – so why are they so tolerant of remora fish using strange stickers on their heads to attach to attach to the shark’s underbelly. This was initially thought to be a case of commensalism – a relationship in which one species benefits and the other gains nothing – but it is now widely thought that the remora not only picks up the scraps after a shark has a meal but also cleans the parasites from its underside, much like insects do with elephants and rhinos on land.
4. Angler Fish and Its Bacteria Bait
The angler fish is one of the most infamously ugly and unbelievable deep-sea swimmer, luring unsuspecting victims into is gaping toothed mouth. How does it accomplish this feat? With the promise of a small glowing prey that is, in fact, millions of glowing bacteria attached to a fishing-pole-like protrusion from its forehead.
3. Emperor Shrimp and Its Ride
The Emperor Shrimp is the ultimate hitchhiker and a prime example of mutualism. The appropriately named emperor shrimp, however, is one that benefits more than its partners from its relationships with them. While it is not a parasite, its rides gain no real advantage from having a shrimp cruising around on their backs. These hitchhikers of the sea can be found on top of much larger and faster-moving creatures including nudibranchs and sea cucumbers. They hang off the sites and pick up scraps from the dirt as their mounts move about the sea floor.
2. Clown Fish and Sea Anemone
Made popular by Nemo: The clown fish is virtually the only species of fish that seems able to resist the toxic effects of sea anemone poison, moving through them unharmed. The anemones protect them and they eat the leftovers from fish on the anemone including copepods, isopods and zooplankton. They also fiercely protect their territory, keeping individual anemones to themselves in small gender-switching self-sufficient groups. Remember Finding Nemo? In real life, Marlin would have turned female after Nemo’s mother died.
1. Coleman Shrimp and the Fire Urchin
Coleman shrimp are normally found in pairs on the toxic sea urchin, Asthenosoma varium, also called a fire urchin, with the female being the larger of the two. Coleman shrimp move amongst the poisonous spines and pedicellaria without incurring harm but they usually clear an area of these obstructions where they perch. They have every confidence that they are secure on their poisonous perch and do not move about as other shrimp often do. The white and dark brown striped Urchin crab is another guest of the fire urchin often occurring on the same animal as the Coleman Shrimp. Whereas the Coleman Shrimp only lives on the fire urchin, Urchin crabs live in association with a variety of urchins. The last segment of its leg forms a hook to hold onto the spines of the sea urchin. It can be found singly or in pairs.
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