Wednesday, September 23, 2015

El NIÑO AND THE XANTHIDS: A difficult relationship

Hi again, it's Nerea Nieto. It’s been a long time since the last time I posted here. Today I’d like to share with you something about my research and the relationship with an event that’s happening in Panama, El Niño. 

My research project is on the seasonal differences in egg size in three tropical intertidal crabs, Xanthodius sternberghii, Petrolisthes armatus and Clibanarius albidigitus. One of these, the Xanthid, has a lunar breeding cycle. They usually release larvae 1-4 days before the quarter moon (Christy, 1986); but I noticed that these animals stop laying eggs during some of the upwelling season (this is during Panama's dry season which lasts from December until May).

I have been sampling these crabs since November 2013.  I noticed they stopped having broods in February 2014 at the beginning of the dry season, and this year they also stopped reproducing again in February. This year I expected that they would start reproducing again when the dry season ended.  But we are in September, the dry season finished months ago, and my crabs haven’t started reproducing yet!

El Niño Southern Oscillation (ENSO) events suppress upwelling in the Bay of Panama, but it also reduces rainfall in the wet season.  This years' event is likely to be especially severe in Panama. Data from the Smithsonian Tropical Research Institute's long-term monitoring program shows that 2015 through July is the driest year on record.

What do you think? Could this event be the reason why my poor crabs are not laying eggs? My fieldwork is continuing until next year at least!

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