While keeping marine organisms is interesting to us all or we would not be reading this board, it can be made even more interesting if we try and understand some of the terms and relationships that we see and hear about.
Certainly the enjoyment we derive from our aquaria will be enhanced by understanding relationships within the marine environment. This includes knowing the habitat of marine animals, knowing what they eat, and knowing about relationships that occur with other animals. In grade school biology, you may have heard of the term ââ"šÂ¬Ã…"œsymbiosis,ââ"šÂ¬Ã‚ referring to a give-and-take relationship between two organisms. But, in fact, symbiosis refers to any number of different kinds of partnerships ââ"šÂ¬Ã¢â‚¬Å“ some are mutually beneficial and some are not. Partnerships in which the host is harmed are termed ââ"šÂ¬Ã…"œparasiticââ"šÂ¬Ã‚ and include diseases as well as mere symbiont exploitation until the host dies such as an isopod on a Squirrelfish. Nevertheless, in the tropical marine world, almost every creature lives in symbiosis with another in some way. Itââ"šÂ¬Ã¢"žÂ¢s simply an easier way to live given the scarcity of resources and the competition for them.
A symbiotic relationship can take on many forms, which are classified depending on how the creatures share their living space or use each other. Understanding what sorts of relationships may exist in the natural world between species will help us better understand how to create environments for the animals we enjoy. The specialized defenses of certain species are often used by those that have little or none of their own, and is called inquilinism. A defenseless little reef fish would want to take advantage of the natural protection provided by a sea-urchin neighborââ"šÂ¬Ã¢"žÂ¢s razor-sharp, and sometimes venomous, spines. Clownfish, having covered themselves in mucus that makes them invisible to their host anemone are able to dance among the battery of the anemoneââ"šÂ¬Ã¢"žÂ¢s stinging cells without harm. The clownfish associates with the anemone while the anemone hosts the clownfish.
Likewise, schooling behavior is a stochastic form of defense mechanism. As some recently mentioned, it is a mathematical form of protection since the odds of a single fish being subject to predation is very low. That is the reason that schooling behavior involves a large number of animals; it is why the group moves together appearing from a distance as if it were a larger animal than the individual members.
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 ââ"šÂ¬Ã¢â‚¬Å“ or hold one in each claw, and like a boxer, attempt to punch the offender with its borrowed battery. Scientists believe inquilinistic relationships merely evolved from creatures living in close proximity with one another.
Endoecism refers to animals that live in the shelters created by their host, most typically burrows. Proximity is also a likely reason for such a relationship to grow over the millennia, combined with a frequent hunt for shelter by what eventually becomes the symbiont. The arrow goby of North America is commonly found in the burrows of various invertebrates, favoring crab holes. The symbiont usually benefits the most in this relationship; however having a little visitor has its advantages. Should the goby find a chunk of food too large for it to handle, it will give it to the crab. The crab chops it up as it devours its free snack, allowing the goby to take a few shredded pieces back. Sometimes the live-in symbionts feed on the hostsââ"šÂ¬Ã¢"žÂ¢ waste products, earning their space as housekeepers. In the goby and blind shrimp relationship, the goby is unable to dig a burrow and the blind shrimp is unable to see potential predators.
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 itââ"šÂ¬Ã¢"žÂ¢s usually only the symbiont that benefits directly. Many shrimp, crabs and copepods, for example, live on the surface of corals and other cnidarians, eating their mucus coating, dead skin or any adhering organic particles. The crustaceans usually cause no harm to their coral hosts ââ"šÂ¬Ã¢â‚¬Å“ and may even pluck off an occasional parasite.
Mutualism is the most well-known type of symbiosis, and is marked by an interdependence of host and symbiont. In most mutualistic relationships, one could not survive without the other, which makes these sorts of relationships among the most fascinating. Hermatypic (reef-building) corals and their algal symbionts, zooxanthellae, are a common example of such crucial interdependence. The zooxanthellae live inside the coralââ"šÂ¬Ã¢"žÂ¢s tissue, taking advantage of its waste products and transforming them into substances the coral can use to grow and maintain its calcium carbonate home. During times of high stress, such as prolonged high temperatures, the coral will eject zooxanthellae into the water column. Although the coral can live with a small amount of algal symbionts over short periods of time, a long absence of their usual population of symbionts spells certain death.
Cleaning symbiosis is similar, but the symbionts donââ"šÂ¬Ã¢"žÂ¢t live within their hostsââ"šÂ¬Ã¢"žÂ¢ tissues. A large fish will literally pull into a ââ"šÂ¬Ã…"œcleaning station,ââ"šÂ¬Ã‚ which is nothing more than an area where cleaner shrimp and fish live. Like Indy 500 pit mechanics, the cleaners scramble from their crevasses and overhangs, picking off parasites, algae, and detritus for the fish, while scoring an easy meal. Often times the fish signals it willingness to be cleaned by its sidewise positioning.
Hopefully this discussion of relationships, relationship types, and especially hitchhikers on the reef will give you an idea for creating interesting aquarium environments.
All text copyright Steven N. Norvich 2001
Certainly the enjoyment we derive from our aquaria will be enhanced by understanding relationships within the marine environment. This includes knowing the habitat of marine animals, knowing what they eat, and knowing about relationships that occur with other animals. In grade school biology, you may have heard of the term ââ"šÂ¬Ã…"œsymbiosis,ââ"šÂ¬Ã‚ referring to a give-and-take relationship between two organisms. But, in fact, symbiosis refers to any number of different kinds of partnerships ââ"šÂ¬Ã¢â‚¬Å“ some are mutually beneficial and some are not. Partnerships in which the host is harmed are termed ââ"šÂ¬Ã…"œparasiticââ"šÂ¬Ã‚ and include diseases as well as mere symbiont exploitation until the host dies such as an isopod on a Squirrelfish. Nevertheless, in the tropical marine world, almost every creature lives in symbiosis with another in some way. Itââ"šÂ¬Ã¢"žÂ¢s simply an easier way to live given the scarcity of resources and the competition for them.
A symbiotic relationship can take on many forms, which are classified depending on how the creatures share their living space or use each other. Understanding what sorts of relationships may exist in the natural world between species will help us better understand how to create environments for the animals we enjoy. The specialized defenses of certain species are often used by those that have little or none of their own, and is called inquilinism. A defenseless little reef fish would want to take advantage of the natural protection provided by a sea-urchin neighborââ"šÂ¬Ã¢"žÂ¢s razor-sharp, and sometimes venomous, spines. Clownfish, having covered themselves in mucus that makes them invisible to their host anemone are able to dance among the battery of the anemoneââ"šÂ¬Ã¢"žÂ¢s stinging cells without harm. The clownfish associates with the anemone while the anemone hosts the clownfish.
Likewise, schooling behavior is a stochastic form of defense mechanism. As some recently mentioned, it is a mathematical form of protection since the odds of a single fish being subject to predation is very low. That is the reason that schooling behavior involves a large number of animals; it is why the group moves together appearing from a distance as if it were a larger animal than the individual members.
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 ââ"šÂ¬Ã¢â‚¬Å“ or hold one in each claw, and like a boxer, attempt to punch the offender with its borrowed battery. Scientists believe inquilinistic relationships merely evolved from creatures living in close proximity with one another.
Endoecism refers to animals that live in the shelters created by their host, most typically burrows. Proximity is also a likely reason for such a relationship to grow over the millennia, combined with a frequent hunt for shelter by what eventually becomes the symbiont. The arrow goby of North America is commonly found in the burrows of various invertebrates, favoring crab holes. The symbiont usually benefits the most in this relationship; however having a little visitor has its advantages. Should the goby find a chunk of food too large for it to handle, it will give it to the crab. The crab chops it up as it devours its free snack, allowing the goby to take a few shredded pieces back. Sometimes the live-in symbionts feed on the hostsââ"šÂ¬Ã¢"žÂ¢ waste products, earning their space as housekeepers. In the goby and blind shrimp relationship, the goby is unable to dig a burrow and the blind shrimp is unable to see potential predators.
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 itââ"šÂ¬Ã¢"žÂ¢s usually only the symbiont that benefits directly. Many shrimp, crabs and copepods, for example, live on the surface of corals and other cnidarians, eating their mucus coating, dead skin or any adhering organic particles. The crustaceans usually cause no harm to their coral hosts ââ"šÂ¬Ã¢â‚¬Å“ and may even pluck off an occasional parasite.
Mutualism is the most well-known type of symbiosis, and is marked by an interdependence of host and symbiont. In most mutualistic relationships, one could not survive without the other, which makes these sorts of relationships among the most fascinating. Hermatypic (reef-building) corals and their algal symbionts, zooxanthellae, are a common example of such crucial interdependence. The zooxanthellae live inside the coralââ"šÂ¬Ã¢"žÂ¢s tissue, taking advantage of its waste products and transforming them into substances the coral can use to grow and maintain its calcium carbonate home. During times of high stress, such as prolonged high temperatures, the coral will eject zooxanthellae into the water column. Although the coral can live with a small amount of algal symbionts over short periods of time, a long absence of their usual population of symbionts spells certain death.
Cleaning symbiosis is similar, but the symbionts donââ"šÂ¬Ã¢"žÂ¢t live within their hostsââ"šÂ¬Ã¢"žÂ¢ tissues. A large fish will literally pull into a ââ"šÂ¬Ã…"œcleaning station,ââ"šÂ¬Ã‚ which is nothing more than an area where cleaner shrimp and fish live. Like Indy 500 pit mechanics, the cleaners scramble from their crevasses and overhangs, picking off parasites, algae, and detritus for the fish, while scoring an easy meal. Often times the fish signals it willingness to be cleaned by its sidewise positioning.
Hopefully this discussion of relationships, relationship types, and especially hitchhikers on the reef will give you an idea for creating interesting aquarium environments.
All text copyright Steven N. Norvich 2001