Themes of Parasitology: Relaxing in the Rectum
Symbiosis is typically associated with one meaning; a mutually beneficial An example of Commensalism is the Pearlfish and Sea Cucumber. Pearlfish are marine fish in the Carapidae family of ray-finned fishes. Pearlfishes inhabit the However, some species are known to be parasitic on sea cucumbers, eating their gonads and living in their anal pores. Pearlfish The genera are divided into three major groupings based on their level of symbiosis: Echiodon. The symbiotic relationship between Sea cucumbers (Holothuriidae) and Pearlfish (Carapidae) Brooke Luciano, Ashleigh Lyman, Selena McMillan, Abby Nickels.
Both species of carapids either entered the first host that they came across or hosts other than their own. In 12 trials there were only 2 cases in which the fish did find its original host. We performed these trials with 2 adult C.
Each fish appeared to smell the length of the body of its potential host, doing lengthy surveys a number of times before actually entering the anus. Both species of carapids demonstrated this behavior. It was also observed that both species of carapids seemed to listen along the body of the host almost as if trying to detect the presence of another occupant inside.
A type of knocking around the anus area was initiated by the fish as a means of encouraging its entrance into the cavity. Nocturnal activity of two species of carapids After one all night survey of a B.
Discussion Many exciting observations were made throughout this venture and several of the statements made in our references were disproved with our findings. Many reported pearlfish as entering tail first, but we found headfirst entry prominent among our many specimens Myers Homei was reported as living independently from other species, while out of four cases of hosts containing multiple carapids, we found this species living with E.
Boraborensis three of those instances Trott and Trott It was stated in Micronesian Reef Fishes among other places that the pearlfish come out to forage at night, but our observations presented different information Myers No foraging occurred during our tests, but these observations were done in aquaria and could be construed do to stress of the specimens.
Evidence of competition was prominent among our observations. Initially, we expected to observe competition interspecifically, but not intraspecifically. However, 6 during out trials it was discovered that in fact aggression was both interspecific and intraspecific. Though our experiments had a more elevated competitive environment than what was seen in the wild and this provided accurate tests to show that competition was in fact present both interspecifically and intraspecifically.
During our trials, tail biting was the most common form of aggression seen, as were few instances of cannibalism. Before our trials began we expected to find to host fidelity among the carapids and their hosts.
However, after twelve trials we found that host preference was in fact not significant and most of the carapids chose to reside in the cucumber that was nearest them. We also expected that a carapid would be able to locate its original host during the trials, but that was not found to be true. Initially we believed that association cues were present for the entry of the Carapid into its Holothurian host.
After numerous observations, it was determined that this was true. The Carapidae was observed to perform several knocking and pecking motions at the cloaca of the Holothurian in order to communicate its entry.
During our assessment of distributions we found a significant difference between location sites of the two carapidae host species with B. There were two cases at PB in which both species were found in one host as well as one instance at WHW.
Looking at the pattern of age distributions among fish specimens collected, a two- way ANOVA test revealed a p-value of 0.
Pearlfish and Sea Cucumber Symbiosis
A large population of adult carapids was found at WHW and was prevalent to the population of juveniles. Color morphology of B.
For example, it would be interesting to conduct further research on the life history of the Carapidae and more specifically, activity within the Holothurian. During dissections of Holothurian hosts, we found carapidae specimens lodged within the respiratory trees and, in once instance inside the gut. We also observed the Carapid entering the Holothurian headfirst and exiting headfirst. Using such devices such as a sonogram or a hydrophone would be useful in further investigation of the orientation and observation of the Carapid.
During the housing of our specimens we observed carapidae eating through its host in order to exit its host.
This behavior was observed but has not been addressed in any other literature. In the literature it suggests that due to specialized morphology, E.
biosystems: Pearlfish and Sea Cucumber
This Carapidae species has well developed jaws and fang-like teeth. Their small eyes and behavior indicate that they would not need to leave their hosts. In contrast, the C. Due to the nature of the behavior observed, this appears to be true. 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. 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. So, these fish basically LIVE in the cloaca i.
Pearlfish and Sea Cucumber Symbiosis
Sometimes they're just too big and so, they stick the big forward part of their body OUT of the anal opening! Bear in mind though, that it doesn't take much for these fish to get into the body coelom or other parts of the sea cucumber host!!
For additional reasons outlined below, its thought that living within sea cucumbers is adaptive because it confers protection for the pearlfish.
One or sometimes two animals male and female when that is the case will geneally live in a single host sea cucumber.
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