Back after an adventurous month!

Last month, I visited McDonald Observatory, a research unit of The University of Texas at Austin. The observatory of situated in West Texas, an area that experiences some of the darkest night skies in the continent. The location thus makes it perfect for astronomical research and star gazing during night times (along with experiencing the least white pollution due to its location). I attended three events at the observatory – solar viewing, twilight program and star party. The solar viewing program in the afternoon consisted of watching the majestic sun on a huge screen in real time. It was an informatory session that introduced the audience to the concepts of sunspot formation and solar flares. The session concluded with a tour of the 107 inch and the 82 inch telescopes. The twilight program in the evening was about “Modelling the Night Sky”, and was followed by a star party in the night. Many telescopes were set up for the public to view saturn, binary star systems, nebula, moon craters, and other celestial objects up close. It was magical treat for the eyes.

From the wild desert of the south, I travelled up north to the land of the midnight sun – Alaska! For the first time in my life, I saw – caribou, a wolf, moose, grizzly bears, dall sheep, orcas, humpback whales, puffins, murres, sea otters, bald eagles and many other animal species. The abundant and diverse wildlife of Alaska has left me stunned and speechless. Also, during the journey, I developed a deep admiration for the field of Geology. It was interesting to witness all the geographical occurrences that I once briefly learnt back in high school (and so easily forgot). Walking on glaciers and observing braided rivers triggered a sense of appreciation for all the geologists who battle extreme weather conditions to understand our planet better and discover its glorious history.

The last month has been a roller coaster ride across amateur astronomy, ecology, geography and surely lots of biology. I’m now back at school and ready to do some awesome science in the lab with a whole new perspective on the world. Photographs from my Alaskan adventure can be viewed on my photoblog, here.

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How Genetics can help rescue endangered species – Case of the whale sharks

Whale sharks are the largest fish in the ocean and are about eighteen to twenty meters long. They weigh around twenty tons and can live up to a hundred years. Though normally pelagic animals, whale sharks are seen in large feeding aggregations in certain parts of the tropical and warm temperate zones around the world, like the Gulf of Mexico and the Indian Ocean. They are known to consume twenty kilograms of food per day that mainly includes plankton, small fish, crustaceans, and coral spawn1.

Source: Wikiemedia Commons
Credit: Courtesy of Wikimedia Commons

The decreasing number and size of whale sharks at some aggregations suggests the species may be declining2. While they are protected in many parts of their range, whale sharks are fished legally and illegally for food (especially for their fins in the Asian markets) and medicinal purposes. Their slow growth and late maturation (when they are 25-30 years old) prevents them from being recovered from over-fishing or habitat disruption.

Whale Shark Habitat Around the Globe. Source: Wikimedia Commons
Whale Shark Habitat Around the Globe. Credit: Courtesy of Wikimedia Commons

Genetic analysis can tell us about whale shark migratory behaviour, social structure and breeding habits. The genetic drift between their populations can help us study the gene flow and interbreeding.  A key question for whale shark conservation is whether the fish aggregations represent isolated populations, or whether whale sharks are migratory and comprise a single global population.

The highly polymorphic microsatellite DNA sequences undergo frequent mutations over time and aid in understanding the population genetics of the species. These mutations are passed on to the offspring and thus provide great resolution for studying the variation and differentiation between populations. The degree of relatedness between different whale shark groups tells us about their migration and breeding patterns (closely related species have similar genetic sequences). For their research, Dr. Schmidt and her colleagues at UIC tagged the satellite sequences to pool the whale shark samples geographically into Pacific Ocean animals, Atlantic Ocean animals and Indian Ocean animals for analysis3. Polymerase Chain Reaction (PCR) was used to amplify and analyse DNA sequences and Principle Components Analysis (PCA) was done to examine the population differentiation. Through DNA analysis of 68 whale sharks from 11 locations, it was shown that the species found in different locations were in fact, quite similar. The little genetic variation among populations confirmed the migratory behaviour and interbreeding among populations. These results further calls for more stringent conservation plans to protect the big fish of the ocean.

As to this day, whale sharks mating has never been observed. The location of their mating is not known either. None of them have been observed giving birth and very young whale sharks are rarely seen. These facts pose a lot of questions regarding the whale shark reproduction. In 1995, a litter of more than 300 whale shark embryos were found inside of a captured female animal at Taiwan5 (the only pregnant female whale shark ever studied scientifically) which suggested that whale sharks are ovoviviparous animals i.e., they give birth to live young that hatch from eggs within the uterus. Paternity analysis through DNA fingerprinting suggested that a single male fathered all the embryos4. Since multiple paternities is common in many shark species, genetics could be used to determine whether the embryos were sired by a single male or multiple males.

The ability to use genetic analysis to study the whale shark behaviour, population and breeding patterns can help us design appropriate tools for their conservation across the oceans. Conservation genetics is an important tool and should lead the way for rescuing many other endangered species around the globe.

Sources:

  1. World Wildlife Org –  http://worldwildlife.org/species/whale-shark
  2. Whale Shark (Rhincodon typus) Issues Paper by The Department of the Environment and Heritage, May 2005, Australian Government – http://www.environment.gov.au/node/15909
  3. Schmidt J.V., Schmidt C.L., Ozer F., Ernst R.E., Feldheim K.A., Ashley M.V., Levine M. (2009) Low genetic differentiation across three major ocean populations of the whale shark, Rhincodon typus. PLoS One, 4:e4988.
  4. Schmidt J.V., Chien C.C., Sheikh S.I., Meekan M.G., Norman B.M. and Joung S.J. (2010) Paternity analysis in a litter of whale shark embryos. Endangered Species Research, Vol 12: 117-124.
  5. Over 300 embryos found in pregnant whale shark – http://www.theepochtimes.com/n2/science/over-300-embryos-found-in-pregnant-whale-shark-41759.html