Courtesy of: http://dels-old.nas.edu/oceans/oceans_and_human_health_part_2.shtml
Introduction: This blog examines the relationship between the Hawaiian Bobtail Squid and a bioluminescent bacterium. The Hawaiian Bobtail squid acquires an enhanced ability to capture prey and avoid predators, while the bacterium receives key nutrients from residing within the squid . Distribution of this aquatic relationship is limited by the habitat of the squid (Hawaii). Several bioluminescent bacteria cycle through a single squid daily.
Description of Relationship: The type of relationship observed between Euprymna scolope(Hawaiian Bobtail squid) and Vibrio fischeri(bioluminescent bacterium) is unique to organisms with specialized structures called light organs. These light organs are specialized structures that have evolved to allow the organisms that house them to create light. While the evolutionary reason for this structure is unknown, many individuals hypothesize that certain marine organisms form these light organs through adaptation from dark environments in order to increase vision. By using Combes’ logic, this is a textbook example of a symbiosis (when individuals of two species whose evolution has previously been independent associate with one another so that each benefits) . Justification for this statement will be discussed in the cost/benefit analysis section. The life cycle or interaction between these two partners is interesting. Each morning, a squid will eject the bacteria from the previous day and take in new/infant bacteria of that same species. Over the course of the day, the bacteria will multiply and be utilized by the squid at night. The next day the squid repeats this peculiar behavior of ejecting old bacteria and absorbing new bacteria .
Cost/Benefit Analysis: In this relationship, both organisms seem to benefit one another. By properly utilizing the bacteria to reduce its shadow from the moonlight, the Euprymna scolope is able to become a better predator to the prey below and evade its own predators through camouflage. Vibrio fischeri receive a special source of nutrition in the form of amino acids and other essential compounds that are provided to them via the Euprymna scolope’s light organ and bacteria are provided with shelter . The extra weight the squid obtains from housing these bacteria, thus reducing their speed and more likely to be eaten by a predator, is a questionable cost. This cost seems to be outweighed by the beneficial ability the bacteria provide to squid. The squid does not appear to exert any recognizable cost on the bacteria.
 Art of Being a Parasite, Claude Combs
Apparently the bacteria (Vibrio fischeri) does not need the squid to survive. If the bacteria is flushed out the next morning, it has to find other methods of obtaining the food outside the squid if the bacteria wants to survive and pass on their genes. Does the Vibrio fischeri have any special adaptations that allow it to survive outside the host and obtain nutrients? Also, are the light organs only specific to the squid (Euprymna scolopes) or are there other organisms that have them? If there are other organisms that have them, does Vibrio fischeri have adaptations that allow it to survive in any other host that have the light organs other than the Euprymna scolopes?ReplyDelete
when the bacteria get their nutrients from the squid do they harm the squid in anyway? In other words, are the amino acids the bacteria is taking causing a lack of amino acids in the squid? To add to what Kunjal was saying,the squid also does not need the bacteria to survive since it can live while it obtains new bacteria, so would this truly count as a mutualistic relationship?ReplyDelete
Out of curiosity, why is it that the squid gets a new batch if bacteria every morning, and how does it find the bacteria?
Even if the bacteria do not absolutely need the squid to survive, it would seem logical that they would benefit from the energy supply that the squid would give them, so it would also be beneficial for the bacteria to develop traits that would make them more prone to be taken up by a squid. Did you find any characteristics of the bacteria that helped them compete for placement inside a squid?ReplyDelete
In response to Kunjal Patel:ReplyDelete
Given that this is a mutualistic relationship, I would assume that while it is in the best interest of the Vibrio fischeri to live inside the squid it must have adaptations to obtain nutrients while outside the squid. Vibrio fischeri uses its flagella to feed on decaying organic material. Light organs are not unique to Euprymna scolopes but are found in marine organisms that have adapted to dark environments. Vibrio fischeri can and in fact does inhabit other organisms possessing light organs.
In response to Prerana Patel:
There is no observable cost presented to Euprymna scolopes from Vibrio fischeri. I would guess if any cost was present, would be reduced speed on the squid when escaping predators from the weight gained from taking in the bacteria. I looked at this relationship as one between two species and not just between two organisms. The bacteria must be flushed out and replaced because they multiply quite rapidly and the squid does not have the space to house all of them.
In response to Kacie Niemann:
The Euprymna species produces a mucus that attracts bacteria, however no one knows what allows Vibrio fischeri to outcompete other bacteria.