 An additional ectosymbiotic example of commensalism is the relationship between small sessile organisms and echinoids in the Southern ocean, where the echinoids provide substrate for the small organisms to grow and the echinoids remain unaffected.Mutualism is a form of ectosymbiosis where both the host and parasitic species benefit from the interaction.There are many examples of mutualistic ectosymbiosis that occur in nature.