Escape by Inking and Secreting: Marine Molluscs Avoid Predators Through a Rich Array of Chemicals and Mechanisms

Abstract

Inking by marine molluscs such as sea hares, cuttlefish, squid, and octopuses is a striking behavior that is ideal for neuroecological explorations. While inking is generally thought to be used in active defense against predators, experimental evidence for this view is either scant or lacks mechanistic explanations. Does ink act through the visual or chemical modality? If inking is a chemical defense, how does it function and how does it affect the chemosensory systems of predators? Does it facilitate escape not only by acting directly on predators but also by being an alarm signal for conspecifics? This review examines these issues, within a broader context of passive and active chemical defensive secretions. It focuses on recent work on mechanisms of defense by inking in sea hares (Aplysia) and extends what we have learned about sea hares to other molluscs including the cephalopods.

Chemical Defenses: From Compounds to Communities

“…Alternatively, storage of secondary metabolites in skin or ink may deter feeding without the sea hares being consumed (Pennings and Paul, 1993). However, inking is not only for defense and probably has multiple ecological roles in sea hares (Derby, 2007). Other L. majuscula secondary metabolites, such as malyngamides and majusculamides, are also sequestered to the sea hare digestive gland, where they are transformed to less harmful acetates (Pennings et al, 1996(Pennings et al, , 1999.…”

“…Some marine natural products have been studied for their toxicity to nervous systems, but few of these investigations have determined how marine consumers sense and respond to these natural products (Derby, 2007). Even less understood is how these natural products affect a consumer's ability to learn and remember in predator-prey interactions (Lindquist and Hay, 1995;Long and Hay, 2006), and ultimately how resultant behavioral changes can impact the ecology of the organism.…”

“…A rarely considered aspect of chemical defenses is how predators detect and then respond to toxic compounds (Derby, 2007). Natural predators such as fish have an olfactory organ and are capable of smelling prey items (Hara, 1993;Laberge and Hara, 2001).…”

Freezing behaviour facilitates bioelectric crypsis in cuttlefish faced with predation risk

“…Cephalopods have long been of interest to researchers due to their ability to modify their appearance under changing conditions [1][2][3]. Within this group, behavioural mechanisms that either prevent detection by predators (camouflage) or that avoid attack after detection has occurred (visual displays, fleeing and inking) have been frequently studied in the common cuttlefish Sepia officinalis [4][5][6][7][8][9][10][11].…”

Ink From Longfin Inshore Squid, Doryteuthis pealeii, as a Chemical and Visual Defense Against Two Predatory Fishes, Summer Flounder, Paralichthys dentatus, and Sea Catfish, Ariopsis felis

“…Some molluscs use ink as a chemical defense against predators. Previous work on slow-moving inking molluscs-sea hares, Aplysia spp.-revealed a variety of molecules acting as chemical defenses through a variety of mechanisms (Derby, 2007;Derby and Aggio, 2011). One mechanism is the use of deterrent chemicals, either dietderived or synthesized de novo, that are aversive or unpalatable to predators (Aggio and Derby, 2008;Kamio et al, 2010Kamio et al, , 2011Nusnbaum and Derby, 2010a, b;Nusnbaum et al, 2012;Aggio et al, 2012).…”