A Tale of Two Anemone Shrimps: Predation Pressure and Mimicry in a Marine Cleaning Mutualism

Abstract

For mutualistic relationships between different organisms, coloration and behavior can be used to indicate the ability to provide a service. These visual signals allow other organisms to mimic them to gain their benefits without providing the same negative or positive reinforcement for the signals as the model organism. This has been previously demonstrated for the fangblenny (Plagiotremus rhinorhynchos), an aggressive mimic of a major cleaner fish (Labroides dimidiatus). For my Master’s thesis I examined the possible mimicry of the Pederson cleaner shrimp Ancylomenes pedersoni by the spotted anemoneshrimp Periclimenes yucatanicus in the Caribbean. I first quantified the coloration of A. pedersoni, P. yucatanicus, and their host anemones Bartholomea annulata and Condylactis gigantea using spectrographic methods. Overall, A. pedersoni were significantly more contrasting against all anemone backgrounds than P. yucatanicus. Additionally, I measured the predation pressure of A. pedersoni, P. yucatanicus and a non-cleaner Alpheus armatus in-situ on a coral reef, and found that potential client fish were significantly more likely to orient towards and attack the non-cleaner more than the other treatments. I also measured the average distance A. pedersoni and P. yucatanicus reside away from their two host anemones species in a laboratory setting, and the propensity of the shrimps to physically signal to potential client fish in-situ on a coral reef. There was a significant effect for the duration of the trial on the distance from the anemone for all shrimp treatments, and overall A. pedersoni stayed significantly farther away from C. gigantea than P. yucatanicus, but not for B. annulata. Lastly, the distribution of responses to potential client fish were significantly different, with A. pedersoni more likely to signal, and P. yucatanicus more likely to retreat. These data indicate that P. yucatanicus is receiving some benefit (reduced predation) from physically looking like and behaviorally acting like A. pedersoni, but is not a perfect mimic.