This Fish Lives Inside Sea Cucumber's Anus
The juvenile stage develops after settlement inside the body cavity of a sea thought to be parasitic and then gradually assume a commensal relationship with H2 When presented with different species of cucumbers, pearlfish will prefer its . A leopard sea cucumber excretes its organs for defense. . But the Encheliophis pearlfishes are full-blown parasites that devour their host's. Pearlfish and Sea Cucumber Symbiosis discussed by That Fish Place marine It is unclear whether this relationship is commensal or parasitic.
Observations were made of the twelve trials on the behavior and decisions of the tagged pearl fish as to what host it decided to enter. The presence of association cues between the Holothurians and Carapids H3 was investigated by the following method. The tagged pearl fish was introduced to a holothuriidae host and observations of association cues i. To test the idea that carapids were nocturnally active H4night observations were done to see if the fish really did exit its host for feeding purposes.
Results Intraspecific and interspecific competition between two carapid species for a Holothurian host Intraspecific and interspecific competition was found in both species of carapids.
It was found that competition occurred inside the body cavity of the cucumber between several carapids. In one trial, two male E. Dissection of the host cucumber took place finding one male, one female, and an adult C. Within the stomach of the surviving male E. This was verified in another replication as a juvenile C.
Pearlfish and Sea Cucumber Symbiosis
Other evidence of competition included bite marks on the specimens used in these trials and on other carapids extracted from collected cucumbers. In one such case, evidence of interspecific fighting between the two species of carapids was observed. Host specificity of Carapidae in relation to Holothurian hosts After monitoring 12 trials of host preference, the results indicated no selectivity of carapids for their original hosts.
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.
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.
This Fish Lives Inside Sea Cucumber’s Anus
In contrast, the C. Due to the nature of the behavior observed, this appears to be true. Although our data remained significant throughout the duration of the project, many problems could have been prevented with a more adequate sea water system. However, we strongly believe that the answers to our questions were strongly supported by our data. Alain, thank you for your bomb-biggity food and your awesome dance moves.
Thanks to Luke for his wonderful help with our seawater logistics. Thank you Lyndsey and Katie for you fabulous contribution to our cucumber night watch. Thanks to Rudy Raimondi for bringing out the kid in all of us and the great video contribution. Thank you to all of our classmates for such a memorable adventure.
And last but definitely not least, thank you so so much to our families for your financial and endless support…without you, this unforgettable experience would not have been possible!
- Smithsonian Institution
If we simplify that a bit to this drawn by Echinoblog Art Department! So, these fish basically LIVE in the cloaca i. 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 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?? It turns out that that Carapus spp.