jmalloldiaz's blog

•In your summary reflect on one aspect that you find important to your interests (eg a new model for fat metabolism, or a unique system for conservation biology etc):

My interest in this paper: parasite infection setting conditions for a possible speciation event

Long distance migratory species like monarch butterflies (Danaus plexippus) are an interesting subject of study, because if they are exposed to selective pressures like parasitic protozoans such as Ophryocystis elektroscirrha during their migratory journeys, there are chances of fragmenting the population and setting the conditions for an speciation event to occur.

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Overview:

Migration is triggered by cues of habitat deterioration such as the photoperiod that instill an animal to travel to another location where resources and living conditions will be more favorable. It can also have indirect benefits, like reducing the predominance of parasites among a population by removing the infected individuals, a phenomenon known as "migratory culling". Such is the case for long-distance migratory monarch butterflies (Danaus plexippus) and parasitic protozoans like Ophryocystis elektroscirrha in North America.

Objective:

It is known that parasitic infection rates are higher southwards in eastern North America, supporting the evidence that infected monarchs are slower and have less endurance, thus performing poorly in migration. The objective of this study was to determine the effect of parasite infection in the flight performance of monarchs migrating towards their wintering grounds in Mexico. The researchers hypothesized that infected individuals would travel shorter distances, and that among infected individuals shorter distances are correlated with higher parasite loads.

Regarding the Emlen funnel tests, 40.9% were discarded for being either inactive (7.4%) or disoriented (33.5%). There is no further information about which birds had their tests discarded, which could be an interesting fact to consider because it could change sample sizes and induce bias. In order to support the discarding of such tests, the researchers could refer to the variables that may have influenced the results, such as the weather or the age of the bird. It is possible that some of the discarded results belonged to juvenile birds on their first migration, which would use vector navigation since they still lack part of the map component of navigation that is gained through experience. Since birds may rely on multiple cues for navigation, this study does not provide the whole picture of bird migration because it was performed at fixed locations. An interesting follow-up study could track the same birds with satellite tagging to determine if they reached their breeding grounds despite having a sectioned V-1.

One cue for determining position is using magnetic parameters. Birds may process such information using the ophthalmic branch of the trigeminal nerve (V1). The goal of this study was to test if V1 plays a role in the navigation of migratory Eurasian reed warblers after being displaced 1,000 km toward the east from their breeding ranges during spring migration. The hypothesis was that V1-sectioned birds would use vector navigation and behave like intact birds in Rybachy, while sham-sectioned birds would readjust their orientation because an intact V1 plays a role in true navigation.

Evidence for V1 in true nav. -> map info

V1: magnetosensory (long distance) + olfaction (?) at local scale?

RY -> ZV: magnetic parameter differences (intensity, inclination, and declination)

The results support the hypothesis that V1-sectioned birds would behave as if they had not been displaced and thus use vector navigation, while the sham-sectioned birds would use true navigation and readjust their orientation towards their final destination to compensate for their relocation. This experiment gives evidence for the role of V1 in providing magnetic-related map information to the avian brain during navigation. It is possible that V1 may be involved in olfaction as well, but olfactory cues are reliable on a local scale, whereas magnetic cues can be useful over large distances with changing magnetic parameters. That is the reason why the birds were displaced 1,000 km east from Rybachy (intensity 50,688 nT, inclination 70.3°, declination 5.6°) to Zvenigorod (52,175 nT, inclination 71.2°, declinnation 10.1°), where all the geomagnetic parameters differ.

The Emlen funnel tests at Rybachy of previous studies indicate that the mean orientation of intact Eurasian reed warblers is 42° towards the Northeast (43° when combined with actual data of this study), while the same intact birds after being displaced to Zvenigorod had a mean orientation of 334° towards the Northwest. Regarding the displaced birds of this study, the sham-sectioned group in Zvenigorod had a mean orientation of 354° towards the Northwest, while the V1-sectioned had a mean orientation of 40° towards the Northeast.

All the mean values of the orientation tests were highly significant (P<0.001), except the V1-sectioned data which had P=0.04, good enough to be considered significant but close to the cut value for significance (0.05).

Look at Results section in the text and add supporting comments like: sham-sectioned corrected their displacement... look at significance values to support those claims.

Navigation requires a compass, which indicates where is the North, and a map, for knowing your position relative to your destination. If a migratory bird follows a bearing for a determinate amount of distance and time it is using vector navigation. Meanwhile, if it uses a map, reliable cues, and a bi-coordinate system, it is using true navigation and can adjust its orientation to reach a determined destination in case of being displaced. There is evidence for true navigation in seasoned migratory songbirds, but the cues and sensory systems on which they rely are still unclear.

One possible cue for determining position is using magnetic parameters, and it is thought that birds may process such information using sensory sytems like the ophthalmic branch of the trigeminal nerve (V1). The goal of this study was to test if V1 plays a role in the navigation of migratory Eurasian reed warblers after being displaced 1,000 km toward the east from their breeding ranges during spring migration. With this purpose, the researchers performed a series of orientation tests with Emlen funnels at the capture site in Rybachy on intact birds, then sectioned the V1 of one group and performed sham-surgery on another as a control. Both groups were displaced to Zvenigorod where they were subjected to further orientation tests. The hypothesis was that V1-sectioned birds would use vector navigation and behave like intact birds in Rybachy, while sham-sectioned birds would readjust their orientation because an intact V1 plays a role in true navigation.

Also talk about the differences in magnetic field parameters between the two areas (done in discussion)

and talk about how the compass part of navigation is better understood than the map info, which is why they are doing this experiment

"Sea star wasting syndrome" (SSWS) is a disease that affects many species of sea stars, causing them to lose turgor pressure until they eventually rip apart and turn into white puddles of goo. The origins of this disease are still uncertain, and while most researchers suspect that it is caused by a virus, other scientists like Melissa Pespeni from the University of Vermont think that SSWS is caused by a combination of environmental and genetic circumstances. Pespeni and her team studied the genome of the microbiota present in healthy and sick sea stars, and exposed a group of 37 healthy sea stars to SSWS in order to record the progression of the disease. Only 8 sea stars remained healthy after the experiment, and the results showed that their microbiomes change as the disease settles in, decreasing the numbers of beneficial bacteria in the Pseudoalteromonas genus and leading the way for opportunistic pathogens to cause more damage in the tissues. Pespeni argues that SSWS is most likely caused by pollution particles that disrupt the microbiome of healthy sea stars, allowing for the virus to attack their weakened immune systems.

When I was at Bunker Hill Community College I took Population Ecology, where I carried out a field project based on using transects for documenting the presence of squirrels in Boston Common. As part of my individual project I recorded other data as well, including temperature and whether the squirrels were on the ground or on trees. Using this data I studied squirrel behavior depending on temperature to find on which temperature ranges they were more likely of being active (foraging on the ground) or inactive (resting on trees). In this course I received an A.