Monday, February 29, 2016

Distressed Damselfish

Blue Damselfish

We’ve all heard the term ‘damsel in distress’ when describing some poor, helpless person who is screaming in the grips of a villain and is in need of the help of a heroic stranger to save their life.  That role has been played out in Hollywood countless times.  But what if it this scenario actually happened?  As it turns out, Damselfish (appropriately named) seem to do this type of thing when they are caught by predators.  These coral reef dwelling fish send out a chemical signal when injured that actually increases their chance for survival.
Scientists have known that Damselfish release chemicals from their skin when they are injured which causes other nearby fish to flee, but they recently have found that these chemicals also attract more predators to the scene of the crime.  Attracting more predators doesn’t sound like a good strategy for the Damselfish at first (MORE predators, are they nuts?!) but having more predators around causes interference with the initial predation event, giving the Damselfish a greater chance for escape.  The other predators are likely to try to steal the Damselfish from the initial attacker.  The commotion of competition gives the prey a greater chance to wiggle free and escape with its life.  A study found that when there is another predator at the capture site, the prey is up to 40% more likely to escape.

This is the first evidence scientists have found of the chemical signals released by captured prey actually increasing the prey’s chances for survival instead of just the other fish’s chances for survival by causing them to run away from the area.  Scientists have known for a long time that many organisms send out alarm cues but they didn’t know what advantage it served the sender until recent experiments.  It is thought that alarm cue cells originally evolved to protect fish from bacterial infection when there was tissue damage and they later developed secondary predator attracting qualities to help them escape from attackers.  They also think that the secondary predators have evolved to become sensitive to the chemical distress signals so they can gather important information from them, helping them decide whether or not it is worth trying to steal the potential meal.

If you’re a fish, being a damsel in distress can have its advantages.  In the case of the Damselfish, it may even be lifesaving. 


Sunday, February 28, 2016

Osteoporosis of the Ocean

This is a before and after picture due to Ocean Acidification. 

Ocean Acidification is a chemical process that denatures organisms like the corals. In chemistry, we learn that chemical processes are happening everywhere! In the ocean, higher pH near coral reefs help create chemical processes that form a calcium carbonate which is the process that coral grows and is built in such beautiful ways. Just as our body depends on calcium in our bones to hold us together for support, corals also need this calcification to become hard, stable, and sturdy. 

Now that we know why calcium carbonate is so important to corals, we can now discuss what ocean acidifcation is and why it is harming coral reefs. Ocean acidification denatures organisms like coral by decreasing the pH and basically dissolves the carbonate on corals by chemical processes irreversible because the water is too acidic to have a calcium carbonate coral. How can acidification occur in the ocean? What changes the pH to make it more acidic?

Increase in carbon dioxide in the atmosphere

An increase in carbon dioxide is all over the news in reference to climate change. Humans are burning fossil fuels and it is increasing the greenhouse gases in our atmosphere. A lot of those gases end up swallowed by the ocean and begins to change the chemistry in aquatic ecosystems. For example, the coral reefs are having a negative effect from increased carbon dioxide and increased acidity. 

In this study, they engineered a habitat replica of a coral reef (the Great Barrier to be specific) and mimicked the same alkalinity to test the results of increased or decreased alkalinity. One question they have been struggling to find a conclusion on is...

How much of an impact is ocean acidification having on coral reefs compared to warming of the ocean, pollution, or over-fishing?

They sought to decrease the alkalinity to a level that may have been present in coral reefs in the pre-industrial period. As they performed this test they found that a decrease in alkalinity in the manipulated reef was having a directly positive affect on the calcification rates in the corals. This study shows that acidification is having a direct affect on coral reefs quality of life and calcification rates. 

Many people argue about whether climate change is real, if carbon dioxide levels in the atmosphere are increasing, if it is caused by humans, or if it has potential to affect future generations. It is hard to see pictures like the one above and think that the earth just goes through cycles. The only way to help coral reefs increase in their calcification rates is by decreasing carbon dioxide levels in the atmosphere and in the ocean. Coral reefs no longer have the potential of dying, they are dying. Not only do coral reefs support a very bio-diverse marine ecosystem but they also prohibit waves swallowing islands, economic success from tourism and fishing. 

Below is a youtube video that touches on a lot of human related impacts on ocean biodiversity.


Carnegie Institution. "Ocean acidification already slowing coral reef growth." ScienceDaily. 24 February 2016.

Thursday, February 25, 2016

Fish controlling microbes through their gills

When fish are in facilities such as aquacultural ones, risk of exposure to diseases affecting skin, gills, and the digestive tract, increases. All of these areas of a fish have something in common; they are mucosal surfaces, or have a mucus-like layer to aid in protection. In order to come up with some form of a vaccine for these types of fish, researchers set out to discover how fish can respond and detect to different pathogens through these various mucosal surfaces.

It was found that fish induce production of a specific antibody in their gills when they sense there is a pathogen they have been exposed to. It was also discovered that the gills’ microbiota is covered with the same antibody. This is an immunoglobulin and is referred to as IgT. Up until this point, it was widely believed that mammals alone had this specific immune response involving mucosal surfaces.

Through earlier research it was found that IgT coats the commensal bacteria that are living on the skin and guts of fish. It is believed that this is done to help keep the microbes under control and to prevent them from causing illness.

Researchers examined the gills of these fish, since they are also considered to be a surface that is mucosal. The goal was to see if the same immune defense strategies were used there. To do this, they examined rainbow trout and found IgT to be present. Other immunoglobulins like IgD and IgM were also present, however the IgT was by far the most abundant.

To see why there was an abundance of the IgT immunoglobulin, the researchers exposed the fish to a parasite that is responsible for white spot disease. This is a very common disease in fish that are wild, farmed, or are pets.

A while after they had been initially infected, the fish were examined and found they were coated with a large majority of IgT. Only a few were coated with IgM, but there were none with IgD. If a fish survived, it was found that it had an increased amount of IgT-producing B cells in their gill areas. This indicates that the response associated with IgT was crucial to helping fight these types of parasites.

These findings help connect, with an evolutionary outlook in mind, that since both fish and mammals have these very well developed immune defense mechanisms, it must have developed very early on through the process of evolution.


Thursday, February 18, 2016

Dolphin DNA

Photo credit:
          I read a book one time about a girl who fell overboard during a tropical boating expedition.  Somehow the crew didn’t notice her absence and left her, stranded, in the middle of the ocean.  Worried, alone, and exhausted, the girl was rescued by a friendly dolphin, who gave her a ride back to the boat.

Regardless of how unrealistic this story is, I can’t help being captivated by the majestic beauty of these marine mammals.  When I think of Marine Biology, my mind quickly creates this heroic rescue by the dolphin pod.  So without further ado, we can proceed to the science surrounding these beautiful creatures.

Although microorganisms can be useful indicators for various aspects of marine ecology, dolphins and other large marine organisms are important to study because of their large size.  Contaminants to the marine environment can actually be identified and estimated using samples from dolphins.  Along the same lines, the health of a marine habitat can be evaluated by assessing the health of animals farther up the food chain such as dolphins.  It was with these aspects in mind that a team of nine researchers joined forces to sequence and assess the DNA of five Tursiops truncatus (bottlenose dolphin) populations.  They published their multidisciplinary results in 2015.

DNA was collected from blood samples from dolphins in the following locations:
  • Beaufort, NC
  • Sarasota Bay, FL
  • Saint Joseph Bay, FL
  • Sapelo Island, GA
  • Brunswick, GA

Samples were collected from 69 dolphins total, 30 males and 39 females collectively from these five locations between 2005 and 2010.  The team evaluated 30 control genes to verify the species.  Additionally, blubber samples were examined for the presence of polychlorinated biphenyls (PCB), which are persistent organic pollutants that are banned in many countries including the US.

Photo credit:

Since this was a new technique, the capabilities of the microassay was evaluated through the completion of this project.  It identified seven genes that correctly differentiated the dolphins by sex as well as 153 genes that were expressed differently depending on whether dolphins were part of Gulf or Atlantic populations.  The researchers found that the genomes of the dolphins from the two locations in Georgia – Sapelo Island and Brunswick – did not contain significant differences, so they were regarded as one population.  Specific differences were noted between the genomes when gender was consistent and population was assessed, such as specific genomic differences between a male Gulf dolphin and a male Atlantic dolphin.  The researchers expressed concern about drawing many conclusions about the sexes individually due to low sample sizes, so statistical analysis was focused on the group of both sexes together.

Georgia dolphins were found to be significantly different than the other dolphins in 69 of the 153 genes that were assessed.  The differences among both male and female members of the respective populations each fell into four categories, as you can see in the table below.

Development and Differentiation
Transcription and Translation
Wound Healing and Tumor Prevention
Immune Response
Inflammatory Response
Cell Development and Growth
Metabolism of Foreign Chemicals
Metabolism of Foreign Chemicals

The differences between Georgia dolphins and other dolphins generally center around immune response, so blubber was analyzed.  The research team found that Georgia dolphins deal with more PCBs than the other populations, most likely due to their proximity to the Linden Chemicals and Plastics plant on the Georgia coast.  Not only is it clear that the Atlantic habitat off the coast of Georgia is contaminated with PCBs, we can see that these toxins are genetically – and thus, physiologically – affecting the marine organisms there.  A quick search online shows that PCBs have been linked to decreased lymphocyteresponses and negative reproductive effects in dolphins, not to mention their prey and consumers.  After identifying the PCB level in the Georgia dolphin population, the researchers were able to identify specific genes that reflect this differing level of contaminants, which will make future assessments easier.

Overall, this method of genetically analyzing Tursiops truncates is quite informative about the marine environments that were studied.  I appreciate the interdisciplinary nature of this paper, as it integrates genetics so flawlessly into the field of marine biology.  Who knows if I’ll ever befriend a dolphin, but they are fascinating to study and beautiful to see!


Tuesday, February 9, 2016

Do Fish Have Feelings?

Fish are typically viewed as simple organisms that don’t think and just go off of instinct because of their small brains, but a study published in November of 2015 suggests that zebrafish may be conscious beings that are aware of their own suffering.  The researchers went off of other recent studies that discovered that the dorsomedial and dorsolateral telencephalic pallium in the forebrain of fish are functionally the same as the amygdala and hippocampus in mammal brains, which are responsible for emotional responses to stimuli.  There are physiological changes in mammals when they experience emotions so the researchers measured physiological changes in the fish when they were put under stress to see if happened in them as well.  Stress-induced hyperthermia (SIH) is shown in mammals and birds when they are under stressful situations, so the researchers wanted to see if zebrafish showed SIH when put in a stressful environment.  SIH is thought to be a survival adaptation for fish because stressors can be precursors to a life-threatening event so increasing their body temperature can increase their chances for survival.  Evidence of SIH would mean that the fish have a physiological response to a stressor, indicating that they are conscious beings and have an emotional response to stressful situations.

They divided a fish tank into 6 sections with Plexiglas with a hole in it so the fish could switch from section to section and kept each section at a different temperature.  The temperatures were 17.92, 24.83, 26.92, 28.75, 32 and 35˚C.  The ideal temperature for the zebrafish was 28˚C. To get rid of confounding factors, the oxygen levels in all the chambers were kept high and equal to each other.  They studied 6 groups that had 12 fish in them.  All of the fish were put into chamber 4, the ideal temperature chamber.  But 3 of the 6 groups were experimental groups and were confined in a small fishing net in the chamber for 15 minutes before being released.  Being confined in a fishing net is a known stressor for zebrafish.  Every 30 minutes for the next 8 hours, the sections of the tank that the fish chose to stay in were recorded.

The results showed that...

  • For the first 4 hours after confinement, the stressed zebrafish had a greater percentage in sections above 28˚C than the control fish

  • After 4 hours, the stressed zebrafish slowly started to migrate back to the 28˚C chamber

The graph shows the chamber preferences for the control fish in blue and the confinement fish in red for the first 4 hours after being kept in the net.  The confinement fish showed a greater preference for the warmer chambers than the control fish.

Their results showed that the stressor of being confined changes the water temperature choices of the zebrafish because the confined fish spent more time in the warmer water which raised their body temperatures by 2-4˚C.  This measurable change in behavior and body temperatures of the confined fish is evidence of SIH which led researchers to conclude that fish have emotional responses to stressful stimuli, an indicator (but not proof) that fish are conscious beings.  The zebrafish that were confined showed a change in behavior for 4 to 8 hours after the 15 minute confinement stressor, showing that brief stressors can have an impact on the behavior of zebrafish long after the stressor is removed.  Based off of their data, they also concluded that the water temperature that fish prefer can be an indicator of their health because the stressed fish chose to be in warmer chambers than the non-stressed fish chose to be in.

So next time you’re tormenting your beta fish in your dorm by tapping on the glass or trying to catch your goldfish in a net, keep in mind that it may be emotionally impacted and you could be inducing SIH in your fishy little friend.