Primary and secondary defences of squid to cruising and ambush fish predators: variable tactics and their survival value

Abstract

Longfin squid (Loligo pealeii) were exposed to two predators, bluefish (Pomatomus saltatrix) and summer flounder (Paralichthys dentatus), representing cruising and ambush foraging tactics, respectively. During 35 trials, 86 predator-prey interactions were evaluated between bluefish and squid, and in 29 trials, 92 interactions were assessed between flounder and squid. With bluefish, squid predominantly used stay tactics (68.6%, 59/86) as initial responses.The most common stay response was to drop to the bottom, while showing a disruptive body pattern, and remain motionless. In 37.0% (34/92) of interactions with flounder, squid did not detect predators camouflaging on the bottom and showed no reaction prior to being attacked.Squid that did react, used flee tactics more often as initial responses (43.5%, 40/92), including flight with or without inking. When all defence behaviours were considered concurrently, flight was identified as the strongest predictor of squid survival during interactions with each predator.Squid that used flight at any time during an attack sequence had high probabilities of survival with bluefish (65%, 20/31) and flounder (51%, 18/35). The most important deimatic/protean behaviour used by squid was inking. Inking caused bluefish to startle (deimatic) and abandon attacks (probability of survival = 61%, 11/18) and caused flounder to misdirect (protean) attacks towards ink plumes rather than towards squid (probability of survival = 56%, 14/25). These are the first published laboratory experiments to evaluate the survival value of antipredator behaviours in a cephalopod. Results demonstrate that squid vary their defence tactics in response to different predators and that the effectiveness of antipredator behaviours is contingent upon the behavioural characteristics of the predator encountered.

Defensive Responses of Cuttlefish to Different Teleost Predators

“…Erratic and unpredictable behaviors, known as "protean defense," increase the potential for escape by confusing predators and retarding their ability to predict the location of fleeing prey (Driver and Humphries, 1988;Domenici et al, 2008). Protean behaviors in cephalopods are often used in conjunction with locomotion (Hanlon and Messenger, 1996;Staudinger et al, 2011). For example, the ink-blanch-jet maneuver, which is used by many cephalopods, combines rapid color change, inking, and irregular swimming or jetting to confound the escape trajectory as the animal moves away from a threat Messenger, 1988, 1996).…”

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

“…However, there was no significant difference in approach time for a cloud of ink compared with a cloud of dye, suggesting that the protective effect of ink is visual. This is further supported by the fact that predatory strikes of summer flounder on squid are quick and visually guided (Staudinger et al, 2011;Derby, pers. obs.).…”

“…Inking by longfin inshore squid is associated with increased survival during staged encounters in laboratory aquaria (Staudinger et al, 2011). In addition, summer flounder are highly visual predators in encounters with squid (Staudinger et al, 2011). Thus, we chose the summer flounder as a natural and proven predator of longfin inshore squid and one for which vision plays a dominant role.…”

“…Summer flounder are voracious, sympatric predators of longfin inshore squid in their natural environment (Staudinger and Juanes, 2010). Inking by longfin inshore squid is associated with increased survival during staged encounters in laboratory aquaria (Staudinger et al, 2011). In addition, summer flounder are highly visual predators in encounters with squid (Staudinger et al, 2011).…”

“…Summer flounder are sympatric with and voracious predators of longfin inshore squid (Staudinger and Juanes, 2010), making inking a behavior critical to higher survival rates (Staudinger et al, 2011). Sea catfish are active predators (Muncy and Wingo, 1983) with well-categorized olfactory and gustatory pathways (Michel and Caprio, 1991;Michel et al, 1993;Kohbara and Caprio, 1996;reviewed in Caprio and Derby, 2008) and are already used as an electrophysiological model of neural processing of sea hare inking chemical defenses (Sheybani et al, 2009;Nusnbaum et al, 2012).…”