Evolution: Survival: Coral Reef Connections
Feb 28, Barnacles on some types of whales have a commensal relationship. While hitching a ride, these crustaceans munch on algae and whale skin. The mutually beneficial symbiotic relationship between sea otters and kelp is Red rock shrimp cluster in groups on the rocky bottom of the kelp forest and provide have endosymbiotic zooxanthellae, or internal dinoflagellate algae. Apr 18, Tiny Crustaceans Play Big Role In Marine Ecosystems set out to crack the relationship between algae-chomping crustaceans and eelgrass.
Whatever morsels escape might be wasted, but are frequently caught and eaten by hitchhiking remoras. Fast-swimming predators, like the manta ray, are messy eaters who leave behind a trail of food scraps.
Remoras, or "suckerfish," have evolved a highly specialized body that allows them to exploit that resource.
Fast swimmers, they easily catch up with a host and attach from below, using a powerful suction disc -- which evolved from an ordinary dorsal fin -- on top of their heads. The remoras' streamlined shape allows them to hitchhike without slowing down their hosts. It takes a lot of energy to secrete the calcium carbonate exoskeletons hard outer structures that make up coral reefs.
Reef waters are typically very low in nutrients, so most coral animals can't filter out enough food to provide the extra energy they need. To make up for this deficiency, hermatypic corals shelter microscopic algae zooxanthellae within their tissues; in exchange, the algae supply the corals with carbohydrates so the corals have enough energy to build reefs.
Zooxanthellae pronounced "zoe-zan-thelly" are microscopic algae that live within the tissues of host animals, including hermatypic coral animals. Like all plants, zooxanthellae make their own food by a process called photosynthesis.
Using solar energy absorbed by special pigments, they transform carbon dioxide into carbohydrates and oxygen.
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What they don't need themselves passes directly into the coral's gut cavity, providing the extra energy the coral needs to produce a calcium carbonate exoskeleton.
Some multicellular algae on the reef produce calcium carbonate limestone skeletons very similar to those made by hard corals. These calcareous algae play a major role in barrier reef construction, acting as a sort of living mortar that holds together individual coral colonies. Growing between corals and wrapping around the bases of branching corals, calcareous algae protect the corals from erosion, especially in high-energy areas.
Individual coral colonies, especially branching corals, can easily be toppled in high-energy reef zones, such as the reef front and rock rim. Waves can easily scour away sediments from a colony's base, uprooting it and pushing it along like tumbleweed.
So how do branching corals ever get a solid foothold in such zones? Calcareous algae grow between corals and around their bases, preventing erosion and stabilizing the reef structure.
On the reef, carnivores have diversified into many more species than have herbivores. Competition among carnivores has produced a treacherous environment for prey, in which hungry jaws lurk around every corner, during all hours of the day.
To escape predation, some relatively defenseless herbivores, such as parrotfish Scarus spp. Goldlined rabbitfish Siganus lineatuslocally called spine-feet fish, are so named for the defensive venomous spines at the ends of each of their pelvic fins. But spines are a last-ditch defense. To avoid being thrust into a risky spine-to-fang battle, rabbitfish employ their expert color-changing talents to avoid predator detection in the first place.
Schools of rabbitfish thus provide an excellent refuge for their poorly defended relatives, the parrotfish. Nestling among the venomous stinging tentacles of a sea anemone seems like a very bad survival strategy -- unless you and the anemone have some kind of an arrangement. Clown anemonefish Amphiprion akindynos and sea anemones have evolved just such a relationship. As juveniles, clownfish perform a ritual of "anemone rubbing. From then on, they defend each other, and clownfish have even been seen dragging food to their host anemone.
The fish tend to wiggle through the burrows with force and no hesitation toward their crustacean partners. Due to the action, parts of the burrow system would often collapse. A fish buried under sand stays there without panic the shrimp can smell it and waits until the shrimp digs it out and begins to repair the burrow. The main way into the burrow can be up to 2 feet long during the first days of excavation.
Soon after, side ways are constructed, which can be as short as 2 inches. They can be driven forward and later form an exit to the surface, or they are extended to form a subterranean chamber.
Repeatedly, I could observe the shrimp molting in these chambers.
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This happens during the night every two to four weeks. The next morning, I would find exuviae close to them, and the female was carrying eggs on her abdominal legs if the shrimp are in good condition, molting and egglaying coincide. The shrimp cut the exuviae into pieces and transported them out of the burrow as soon as their new test hardened.
Hatching of the zoea larvae seems to happen overnight, which makes sense to avoid predators as long as possible. The currents caused by the beating of the pleopods must pump the eggs out of the burrows, where they become a part of the plankton. The shrimp are omnivorous and collect large pieces of frozen fish positioned close to the entrance of the burrow.
They collect the food and transport it immediately into the burrow, where they feed on it. However, outside they can also be observed eating algae growing on rocks.
The shrimp directly gnaw with their mouth pieces on rock where algae is growing. Even more fascinating was that I found parts of the algae Caulerpa racemosa inside the burrow system, though it grew more in another edge of the tank. It took some time until I could observe that the shrimp cut these algae with their claws if they get access to it. However, that can only happen when fish and shrimp are on a coexcursion outside the burrow.
In one instance, after cutting, the shrimp lost the algae due to the currents in the tank. But the unexpected happened: The goby immediately took action and grabbed the Caulerpa with its mouth. That moment, the shrimp lost antenna contact with the fish and quickly rushed backward to the entrance. The goby transported the lost food to the entrance and spit it out into the entrance of the burrow where the shrimp was waiting.
The fish was actively feeding the shrimp! I tested this observation and pulled algae off the rocks. When the fish was in the entrance of the burrow, I threw a 1. The goby directly approached it while it was still floating in the water column, collected it and brought it to the burrow.
That collecting behavior could be induced up to five times repeatedly. The shrimp handled the algae inside the burrow in the meantime. I could never observe that the shrimp were keeping algae in certain parts of the burrow. There was not a special storage chamber for algae pieces. Instead the algae pieces were pushed around, and the shrimp fed on them here and there. After some days, the algae disappeared completely. Breeding in the Burrow While the reproduction of the shrimp is not spectacular, that of the gobies bears some peculiar aspects.
Close to mating, the male and female gobies start a wild circular dance in an extended side corridor of the burrow. They stimulate each other head to tail, which causes sand and gravel to fall from the ceiling. The gobies can successfully mate only when the shrimp are healthy and have hard tests. The female does not go back to the breeding chamber—the male fish is the only one to care for the eggs. Usually, he moves the approximately 2, eggs which can easily be done, as the eggs are attached to each other and form a bundle by moving his pectoral fins backward and forward.
He swims around the eggs once in a while, which supplies oxygen to the eggs. Oxygen is low in chambers deep in the sand; only intensive care will keep them oxygenated.
The male goby protects the eggs against a potential predator in the burrow: In fact, the shrimp couple never gets access to the fish eggs. In the s, whalers noticed the small creatures and thought they looked and moved like human lice. They assumed they must be the same type of animal, only much larger, as they can grow up to 19mm in size. Many mysteries still surround whale lice, but we do know they are highly specialized.
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Many types of whale lice can only be found on one species of whale. Grey and humpback whales each have their own variety! While hitching a ride, these crustaceans munch on algae and whale skin. You may remember the juvenile humpback whale that fatally stranded on White Rock Beach last summer, its death attributed to the effects of fishing gear found entangled around its body.
Although it is certain that the whale would have had lice on it before becoming entangled, the larger than expected population indicates the whale had been suffering the negative effects of the fishing equipment for some time. Stories like this remind us that we are part of the complex community of oceanic animals, and it is not just parasites that can negatively affect them, our actions can too.
If you see any dead, injured, entangled or distressed marine mammal, report it to Fisheries and Oceans Canada at 1