Melanoma: Not Just a Human Problem

By January 11, 2013 Ocean News

As i’m sure you are all aware of the increase in the skin cancer melanoma, the deadliest of the skin cancers.  This has been thought to coincide with an increase in tanning, both in the summertime and throughout the year in tanning beds.  It also coincides with the depletion of our ozone which allows more UVA and UVB rays to pass through. 

In response people have adapted, wearing more sunscreen, hats, long-sleeves, limiting their time outside and religiously checking their bodies for any irregular and/or dark shapes.  If caught in time, this cancer will have only reached the skin and not made it’s way into the rest of the body, where it then becomes fatal.

It seems, however, that our depletion of the ozone due to our own emissions is not only effecting humans, it is effecting fishScreen-Shot-2012-07-31-at-8.57.01-AMThat’s right, 15% of coral trout species studied on Australia’s Great Barrier Reef were found to have dark skin lesions similar to the human melanoma. 

A team of researchers led by Michael Sweet from Newcastle University conducted the study after another research team noticed the lesions.  The team from the Australian Institute of Marine Sciences were catching the trout to study predator-prey dynamics in sharks and alerted them to their findings.  The two research teams joined forces, with every coral trout caught analyzed to determine the cause of these dark skin lesions.  After testing for bacteria and viruses to rule out the microbial world, the skin lesions were determined to be cancerous.  Not only were they cancerous, they were melanoma. The picture shows healthy skin (left) and melanoma diseased skin (right) from coral trout.

healthy-v-melanoma-troutMelanoma was found in three different species of coral trout including the common, bar-cheeked and blue spotted coral trout.  (The picture to the right shows a healthy coral trout on the top compared to various species of melanoma diseased trout below).  On top of these findings, Sweet believes this is a low-ball figure for the amount of coral trout actually effected by melanoma.  “Once the cancer spreads further you would expect the fish to become quite sick, becoming less active and possibly feeding less, hence less likely to be caught. This suggests the actual percentage affected by the cancer is likely to be higher than observed in this study.” 

They also believe that this is not the only species of fish effected by melanoma.  Cases have been documented for a wide variety of species including catfish and nurse sharks, but have never been seen at the population level.  Additionally, a study conducted in a laboratory determined the life span of the Platyfish/Swordtails can be reduced from four years to a mere six months when effected by melanoma.

What does this mean for our oceans? 
It means these animals have little natural protection against the increased amount of UV rays that reach them under the water.  Unlike us, they cannot put on hats or wear longer clothing, slather up with sunscreen or go to the doctor to have that odd looking mole removed.  Thanks to our own actions, these animals now have to deal with the consequences we seem to be cleverly avoiding.

Without addressing the underlying issues, sadly, there is likely no feasible or practical cure for skin cancer in wild fish populations.
-Michael Sweet

Do you think other fish populations are going through the same thing? Let us know in the comments below.

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