Larval fishes utilize Batesian mimicry as a survival strategy in the plankton

Abstract

Marine teleost fishes often experience over 99% mortality in the early life stages (eggs and larvae), yet larval survival is essential to population sustainability. Marine fish larvae from a wide range of families display elaborate, delicate features that bear little resemblance to adult forms and hinder their swimming escape ability by increasing drag. Here, we systematically examine the criteria needed for Batesian mimicry to evolve as a survival strategy and present new evidence from in situ imaging technology and simulation modelling to support the hypothesis that many larval morphological features (particularly long, delicate fin rays) and behaviors evolved at least in part through Batesian mimicry of less palatable or noxious gelatinous zooplankton. Many of these or- ganisms (e.g. hydromedusae, cteno phores, and siphon - o phores) are much more abundant than previously recognized. The high predation mortality during the larval phase provides strong potential for selection in favor of maintaining complex and metabolically costly features that mimic gelatinous zooplankton, provided that larger fishes, as selective visual predators, can occasionally be fooled. We conclude that recent ad- vances in our understanding of mimicry combined with information obtained from plankton imaging supports the hypothesis that Batesian mimicry is a widespread survival strategy for larval fishes, which could have broad implications for fish population dy- namics. However, further research is needed in the areas of predator cognition and larval fish behavior in the presence of different predators and models to elu- cidate the circumstan ces in which the larval fish mim- icry hypothesis may apply.