This paper will examine the benefits of having a symbiotic relationship between the bobtail squid, Euprymna scolopes and the bacteria, Vibrio fischeri. By analyzing, the specific characteristics found in V. fischeri and how it assist the bobtail squid defend itself against deep-sea predators.
The resulting defense mechanism
The horizontal transmission has proven to be highly important to maintain and develop
the defense mechanism this organism needs to survive. By storing Vibrio fischeri in the mantle cavity, E. scolopes are able to use light produced in counter-illumination as a way to deter
predators from attacking them (Nyholm and McFall-Ngai 2004). The use of light by the animal
is emitted from the ventral surface and when viewed from below it can cast a silhouette,
mimicking moonlight. In addition, Jones and Nishiguchi’s (2004) research also explains the
conditions for which enable or prevent the squid from effectively using the bioluminescence. As
stated in the data gathered, the light levels produced cannot be too high or too low such as where counter-illumination would be unuseful. From a study conducted, Jones and Nishiguchi (2004) were able to conclude that these cephalopods are able to modify their light intensity. During the experiment conducted by Jones and Nishiguchi (2004), the bobtail squid that was examined were able to change the intensity of the light they produced through each different trial they were put through. When they were exposed to more artificial light or less, the squid were able to increase or decrease the light they emitted. For example, when they were exposed to a high intensity of artificial light, squids produced only one-third of the natural amount of bioluminescence emitted. It was also made notice that the animals were sensitive to any disturbance during the trials conducted. If they were moved by the investigator, the squid would ink, reducing their luminescence. This research is also closely related to other research that was able to determine why the squid was nocturnal. After hosting the bacteria, each day at dawn, the squid discharges 95% of their light-organ symbionts into their surrounding areas as they bury themselves into the sand for dormancy. According to Lee and Ruby (1994), the organism will remain dormant throughout the day due to it being exposed to a lot of light. As examined in Jones and Nishiguchi’s (2004) study, with more light, the squid will produce less bioluminescence. Without being able to produce the bioluminescence that protects them from predators, the organism has to bury and camouflage themselves in the sand during the day to survive. As opposed to the night, when the squid is exposed to nearly no sunlight, it is then then the bioluminescence will shine the brightest protecting the squid and coming into full effect. This cycle that is maintained helps keep the horizontal transmission enabled throughout different generations and as a result maintaining the produced defense mechanism within the organism.
Research analyzed throughout this paper has been able to give depth into how bacteria is
transmitted within the bobtail squid, how the bacteria is used as a defense mechanism while also
acknowledging the problems and challenges faced when hosting bacteria. Recent findings
suggest that horizontal transmission of the bacteria, V. fischeri, has been successful in
maintaining the bacteria in many generations. Successful research also presented the requirements for a successful symbiotic relationship between the organism and microorganism.
However, while there were many interesting and fascinating discoveries made, scientists still left
questions unanswered that could use further work. For example, during the permissive and
restrictive process, the organism inevitably goes through, the answer to why the squid rejects
bacteria has not been found. In addition, during aggregation of the cells in the pores, the question
of why Vibrio fischeri has become the dominant cell also remains unanswered. If these areas
were to be studied, answers could help explain further questions and mysteries that surround the
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