Science Articles

Marine Animal Interdependencies

The population of marine life is very important. Study how one species has lasted longer than others.

Marine Animal Interdependencies

Evolution is a spectacular thing in itself, but for species to co-exist with one another in complete harmony is even more amazing. Deep into the oceans or even in the shallow waters, the marine ecosystems that exist showcase some incredible relationships amongst the inhabitants of such water bodies that depend on each other for protection, cleaning, feeding, and many other reasons. A lot of factors are responsible for the lifespans of each such individual species in the oceans right from food available to feed on for their growth to the presence of predators that can prey upon them. Let’s look into the symbiosis in the sea and try to understand the functioning of the aquatic ecosystems.

Symbiosis in the Sea

In symbiosis, different organisms belonging to different species live in close association with each other and form different relationships based on feeding strategies.


  • Mutualism: Mutualism, as the name suggests, is a form of symbiotic relationship where both the different species are able to benefit off each other. A perfect example of mutualism is the relationship between sea anemones and hermit crabs. Hermit crabs are known to stick sea anemones to their shells as they can then be protected from predators’ attack. The sea anemone spread their stinging tentacles are alert the hermit crabs as soon as they sense the proximity of a predator. The sea anemone also benefits from the hermit crab in terms of mobility. The sea anemones are not too mobile on their own and by sticking to the shells of hermit crabs they can cover longer distances to look for food. They can also eat the leftovers of food by the hermit crabs.


Another example of mutualism is between the sea anemone and clownfish. While the sea anemone protects the clownfish from predators with its poisonous tentacles and also leaves tidbits for the clownfish to feed on, the clownfish as a return favor rids the anemone of harmful parasites and provides nutrients by way of its excrement.


  • Commensalism: In this type of symbiotic relationship, one of the two species tends to gain or benefit from the relationship whereas the other species remain unaffected by the association. This type of association is mostly seen in species that are restricted in their locomotion skills and cannot move away from their predators’ paths in time so they need other species to protect them. An example would be a small group of pilotfish that can be found swimming below or ahead of the huge sharks in the ocean. As these sharks move around, the small pilotfishes can feed on their leftovers as they cruise along with them. The shark, on the other hand, is neither helped nor harmed by the presence of the small group of fishes and so this relationship comes to fall under commensalism.


Another example of commensalism is the sea cucumber and the imperial shrimp. The imperial shrimp uses the sea cucumber for moving faster within the ocean by hanging on to it tightly. It can thus forage through longer distances for food in the water and disembark only to eat, after which it climbs back on the sea cucumber to transport itself to the next feeding destination. The sea cucumber derives no benefit from the imperial shrimp in this relationship.


  • Parasitism: The third type of symbiotic relationship is called parasitism which involves one species that benefits from the other as the latter gets harmed i.e. one thrives at the cost of the other. An organism that lives in or on another creature is called a parasite whereas the species that is infected with such a parasite is known as the host. An example of parasitism would be the ocean sunfish and its numerous parasites. The ocean sunfish is host to about 40 parasitic species that can be found in the ocean including the flatworms, roundworms, and shark tapeworms. Some of these parasites are placed on its body surface while some others can be found inside its body.


Another example is the sea lamprey and lake trout. The sea lamprey sticks to the body of the lake trout create a hole in its skin and feed on the body fluids of the trout. This had also resulted in a rapid decline of the lake trout in the Great Lakes.


It is evidently clear that the lifespan of a species in the marine environment may depend on the relationship it is in. Also, the food web chain is a critical aspect that links all these species in an ecosystem. Any gaps or disruptions can affect the entire chain and the repercussions can be felt on all the levels of the food pyramid. When the chemical and physical conditions in the marine environment become unsuitable for the existing aquatic populations, a new community slowly begins to take over.