biosystems: Pearlfish and Sea Cucumber
Pearlfish and Sea Cucumber Symbiosis discussed by That Fish Place marine biologist Brandon Moyer on That Fish Blog. And then, inevitably, the pearlfish would find you. And there are few better shelters than sea cucumbers, little mobile homes that Depending on what species it is, the pearlfish initiates one of two relationships once inside: a commensal one, Hat tip to Oceans IQ for suggesting this week's critter. Browse . The Pearlfish-Sea Cucumber Relationship! So, How Does This uh relationship work??? First. AND as a personal bit of good advice?.
Pearlfish live in the cloaca but can also live in the actual body cavity i. Sea cucumbers use this structure to extract oxygen. Pearlfish seek out the cloacal opening of the host and then work their way INTO the anus sometimes head first or sometimes tail first, working themselves backwards into the anus of the sea cucumber.
Larger pearlfish are found in larger host sea cucumbers. Only SOME species of pearlfish are commensals in certain species of sea cucumbers. Some are free living and others are not Talk about a bad houseguest! Acanthaster planci Which as we've seen in prior posts Parasitic pearlfish species inside starfish will devour tube feet, stomach tissue, gonads, digestive organs, and etc Reproduction The commensal Carapus doesn't get food from the host-so what benefit comes??
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It turns out that that Carapus spp. The eggs are released via the water currents through the respiratory tree and anus into the water. The juveniles are carried by currents to the open ocean before hatching.
Protection It turns out that some pearlfish, such as Carapus actually have increased resistance to the sticky toxins produced by Culverian tubules, which many tropical sea cucumber species spurt out and use to defend themselves The intrusion of pearlfish into the cloaca of the sea cucumber? Is it possible that the sea cucumber hosts are chosen because of their built in defense systems against predators???
What fish wouldn't want to live in a giant sticky-guts shooting house?? The tail of the pearl fish is long and pointed, and the anus of this fish is located close to its neck. Pearl fish typically grow to be about 15 cm long 4. The female pearl fish releases clumps of eggs late in the summer to begin the life cycle.
Pearlfish and Sea Cucumber Symbiosis
These eggs rise to the surface and hatch, turning into a specific type of larvae called vexillifers. These larvae live among the plankton until reaching a length of about 7 to 8 cm. At this point, the larvae develop into tenuis. These forms descend to the ocean floor and begin their search for food and a host 5. The pearl fish will constantly be on the lookout for sea cucumbers to create a symbiotic relationship.
Once a pearl fish Onuxodon or Carapus finds a sea cucumber Holothuroideait immediately begins to smell around to distinguish between the head and the anus of the cucumber 6. Once it finds the anus, the pearl fish works its way into the rectum of the sea cucumber, eventually being completely engulfed in the digestive canal of its host.
There it will spend the day inside, using its host as a form of protection. After feeding, the pearl fish returns to its host and waits for the sea cucumber to take a breath.
Pearlfish and Sea Cucumber Symbiosis
When the anus opens for respiration, the pearl fish simply swims back inside, seeking shelter in the rectum of its host 8. The pearl fish and the sea cucumber have evolved a symbiotic relationship know as commensalism. Meanwhile, the sea cucumber appears to be unaffected by this relationship. As far as we know, the pearl fish is not taking anything from the sea cucumber. The reproductive success of the cucumber remains the same. Therefore, since the pearl fish benefits and the sea cucumber is neither helped nor harmed, one can argue that this relationship is one of commensalism.
Many other organisms have benefitted from relationships similar to that of the sea cucumber and the pearl fish.
The pearl fish have also learned to penetrate the bodies of other invertebrates such a starfish, sea squirts, and clams. A number of crabs and polychaete worms have also evolved to live inside sea cucumbers and have become specialized for gaining protection from the cloaca of that host 9.
The relationship between the pearl fish and the sea cucumber is not obligatory, but the pearl fish benefits from its symbiosis with the sea cucumber.