Sunday, April 13, 2014

The California Sea Lion

Who among us has ever been to SeaWorld? I know when I was younger that it was one of my favorite places to go; I loved seeing all of the aquatic life and enjoyed the cheesy shows. One of those shows was similar to what is now called "Clyde and Seamore take Pirate Island," a show that can currently be seen at Orlando's SeaWorld. But when I was little, I confused seals for sea lions and just thought they were the same animals. Obviously  I now know the difference and after discussing them in class it is much easier to decipher between the two.
                                          Cheesy Pirate Show Picture!

Like we talked about in class, sea lions, seals, and walruses are classified in the scientific group called Pinnipeds, meaning "wing foot." Although walruses are easy to distinguish due to their larger body and long tusks, many people tend to confuse seals and sea lions. The main difference is that sea lions have an outer ear flap whereas seals just have a small opening. Sea lions can also use their flippers to stand and to scoot along beaches (refer to the SeaWorld picture above) but seals cannot do this.

The picture above shows a sea lion (left) compared to a seal (right)

To get into more specifics, I found a couple articles which discussed issues the California sea lions are facing today. The California sea lion (Zalophus californianus) are known for their intelligence, playfulness, and noisy barking. Their color ranges from chocolate brown to light golden brown; males are typically darker. Males also tend to be larger and can reach up to a whopping 850 pounds and seven feet in length whereas females grow to 220 pounds and up to six feet in length. The trained sea lions in zoos and aquariums are usually California sea lions. 

They can be found from Vancouver Island, British Columbia to the southern tip of Baja California in Mexico. California sea lions are very social animals and groups often rest closely packed together on land or float together on the ocean's surface. They are opportunistic eaters meaning they can feed on a variety of organisms, some of which include squid, octopus, herring, rockfish, mackerel, and small sharks! Sea lions are preyed upon by orcas and great white sharks.

Although their population is growing steadily, many sea lions have become injured due to malnutrition, domoic acid toxicosis, leptospirosis, cancer, pneumonia, entanglement in debris or fishing gear, etc. In 1998, the Marine Mammal Center diagnosed the first case of domoic acid toxicosis in marine mammals. This is a condition caused by harmful algal blooms which causes the animals to have seizures (like the article Dr. Posner posted in Piazza a couple weeks ago). Although the Center has conducted extensive studies to better understand this specific disease, hundreds of sea lions are affected annually.  

Other articles that I found looked specifically at DA (domoic acid) and its effects on the sea lion. In the first one I looked at, they carried out the study by using adult females and divided them into three different groups which were made up of: acute DA toxicosis, chronic DA toxicosis, and no DA present. It was found that the sea lions exposed to DA had higher eosinophil counts. Basically, what this study showed is that eosinophil counts may be a cost-effective biomarker for DA exposure and may reflect alternations in the hypothalamic and pituitary gland function. This means that DA may have subtle health effects on marine animals and as mentioned by the article Dr. Posner posted, can possibly aid in the study of how human brains work. 

In another study, the unusual occurrence of sea lion mortality was looked at. This was done by looking at both anchovies (which sea lions eat) as well as sea lions feces; this was done by using HPLC-UV. From the data collected, the study provides corroborating evidence that this toxic algal species was involved in this unusual sea lion mortality event. Finally, a third study looked at domoic acid and its effects on the sea lions reproductive success by looking at 209 intoxicated females. The data found indicates that DA can cause reproductive failure in California sea lions through mortality of pregnant females, abortion and premature parturition of pups. Whether the effects of DA on the fetus are direct or indirect was still unclear, though.

So in conclusion, besides being cute and fun to watch, sea lions can be quite helpful to us and should be studied more closely. Hopefully, in the future the effects of DA will become clear and scientists will be able to use the information to help aid humans as well. 

References:

Brodie, E. C., Gulland, F., Greig, D. J., Hunter, M., Jaakola, J., Leger, J. S., & Van Dolah, F. M. (2006). Domoic acid causes reproductive failure in California sea lions (Zalophus californianus). Marine Mammal Science, 22(3), 700-707. 

Gulland, F. M., Hall, A. J., Greig, D. J., Frame, E. R., Colegrove, K. M., Booth, R.K., & Scott-Moncrieff, J. R. (2012). Evaluation of circulating eosinophil count and adrenal gland function in California sea lions naturally exposed to domoic acid. Journal of the American Veterinary Medical Association, 241(7), 943-949.

Lefebvre, K. A., Powell, C. L., Busman, M., Doucette, G. J., Moeller, P. D., Silver, J. B., & Tjeerdema, R. S. (1999). Detection of domoic acid in northern anchovies and California sea lions associated with an unusual mortality event. Natural toxins, 7(3), 85-92. 


1 comment:

  1. This comment has been removed by a blog administrator.

    ReplyDelete