Symbiotic Relationships: in it for the long-term

When viewing symbiotic relationships, the ocean has many #relationshipgoals, and just as many #relationshipfails. Symbiotic relationships are interactions between two different species that don’t directly involve one species eating the other. There are three main types, mutualism, commensalism, and parasitism.  These relationships give us insight into how ocean animals interact, how different organisms have evolved together, and why protecting one organism can often protect multiple. Let’s dive in to explore how chondrichthyes get caught up in these different relationships.

hawaiiactivities.com

Mutualism is when two animals interact in a way that is positive for both. Imagine driving a buddy somewhere where they will buy you food: you provided transport and they provided good noms (this is still mutualism even though your buddy is the same species, unless your dog can drive OR afford to treat you to dinner). An awesome cartilaginous example of this is Manta Rays and cleaner fish. Manta Rays and shark species can carry parasitic copepods (don’t worry we’ll discuss those too) that various cleaner fish love to have as food.  Cleaner Wrasses win MVP of the cleaning station, not only eating parasites but cleansing other animals of dead scales and mucus as well. The chondrichthyes get a nice clean, and the cleaner fish get a readily available meal brought to them.
​
Commensalism is an interaction that is positive for one species, but has no influence on the other. Just like you dropping your friend off while you were already on your way, it added no time for you but benefitted your friend. Remoras are often thought of as representing commensalism. They don’t harm sharks in any way, but can suction to them for a free ride, even picking up scraps from the sharks meal. HOWEVER they sometimes feed on shark parasites, which can make them mutualistic. Imagine your friend taking all the trash out of your car every time you drop them off (which is a really nice gesture for any ride moochers reading). It isn’t the main reason they’re there, but it is still helpful.  A lesser known example of commensalism can be found in Eagle Rays and Jack fish. The fish follow the rays, waiting for them to hunt in the sand. As rays look for food they startle and stir up smaller fish that the jacks can then chomp down on.  The Eagle Ray is minding its business hunting its own food, but the jack is benefiting by creeping behind and waiting for the ray to feed first.  
​

Parasitism is when one species survives due to the harm of another species, often called the host.  Imagine your car riding friend makes you buy them dinner every time: you’re losing time, energy, and money while they benefit. The Greenland shark has a parasitic copepod that latches onto its eye. These copepods aren’t just catching a ride, they cause the individual shark to go blind (Greenland sharks from certain waters are more likely than others to carry this parasite WHOA)! Now, as with every science term or rule, weird critters and exceptions swim our way.  The cookie cutter shark (yes, it is real) is considered a facultative parasite. A fun slightly confusing twist that means the cookie cutter doesn’t need a host to survive, but can still cause damage to other species. Obligate parasites must have a host in order to survive.
 
Symbiotic relationships give us insight into the full details of an ecosystem, not just who eats who.  Even though some of these relationships are not healthy for all parties involved, they have withstood time and extra salt the ocean threw at them in ways not even The Bachelor could do. Many species rely on each other in ways scientists have yet to understand! Our ocean is an intricate web of interactions, protecting one species could protect the whole network of relationship movies. 

GLOSSARY

• Symbiotic relationship: a long-term interaction between two species.
• Mutualism: a relationship between two species of organisms in which both benefit from the association.
• Commensalism: a relationship between two species of organisms in which one lives with, on, or in another without damage to either.
• Parasitism: a relationship between organisms in which one is damaging to the other

               Facultative: An organism that may either lead an independent existence or live as a parasite.
               Obligate: An organism that cannot lead an independent nonparasitic existence.

• Evolved: changed over time
• Copepod: any of numerous tiny marine or freshwater crustaceans 

GUEST BLOGGER AND TFUI OFFICER CARISSA THIEL

Carissa Thiel graduated with a BS in marine biology and then spent a few years working in environmental education. She now works as a Guest Engagement Educator, spreading conservation messages to locals and visitors alike!

Carissa loves exploring, reading, talking to people, and awkward get to know you questions. If she could be any bird she would want to be an osprey, because they have wonderful adaptations to hunt fish and are always found by water. However, she would probably be an emu because they have long legs, make awkward faces, and only watch other birds fly.