Abstract
The symbiosis of anemonefish and sea anemones is a mystery that has perplexed many over the years. Cnidarians are incredible complex invertebrates that have evolved a system to not only deter their predators but to also become lethal hunters themselves. Anemonefish have somehow managed to sidestep the defenses of sea anemones and become beneficial caregivers to their hosts while also increasing their own fitness. Together each participant gains protection, nutrients, and increased fitness. The caveat with this friendship stems from the specialized stinging cells that can hurt and/or kill the anemonefish if stimulated. Many studies have attempted to determine the biology of cnidocyte discharge in sea anemones and how anemonefish are protected. The ultimate conclusions include that their mucus coat is either not stimulating to the receptors of the sea anemones, or that the fish somehow produces a protective entity found in its mucus following acclimation. We hypothesized that anemonefish use acclimation to regulate the mucous proteome to suit diverse host species that differ widely in toxicity and adhesiveness. To test this hypothesis, we used LC-MS/MS to compare the mucous proteomes of naïve Clark’s anemonefish (Amphiprion clarkii) to fish associating with one of two natural hosts: the bubble tip sea anemone (Entacmaea quadricolor, Family Actiniidae) or the more venomous and adhesive carpet anemone (Stichodactyla sp., Family Stichodactylidae). Peptide content and quantity was not significantly different between naïve and associating anemonefish, or between fish associating with different species. Oxidation, acetylation, and deamidation of glutamine post-translational modifications also were not significantly different. We therefore conclude that this symbiosis does not depend upon changes in the quantities of peptides in the mucus but instead likely involves some other aspects of mucus such as mucins or changes in protein function.