Cooperative Defense by Non-Kin Related Caribbean Spiny Lobsters Under Attack by Cooperating Predators Kari Lavalli CGS, Division of Natural Science, Boston University William F. Herrnkind Dept. of Biological Science, Florida State University
Natural Selection is a “Selfish” Process in Many Respects It acts on individuals to maximize their own reproductive output Paradox? We see LOTS of animals living in cohesive social groups, cooperating, and appearing to behave “altruistically”
Behaviors that Seem to Violate Natural Selection Principles
Darwin recognized one behavioral trait that was not compatible with Natural Selection
It posed, “one special difficulty, which at first appeared to me insuperable, and actually fatal to my whole theory.”
Evolution of sterile castes in social insects
termites, ants, bees, wasps
sterile individuals forego reproduction to raise queen’s offspring
Darwin suggested that natural selection might operate on the level of the family here, rather than on the individual
Possession of weapons allows for cooperative defense above and beyond a simple dilution or confusion effect
Grouping in Panulirus spp. Codenning and emerging en masse is common in some spiny lobster species Herrnkind, Childress, & Lavalli, 2001. Mar. Freshwat. Res. 52 : 1113-1124.
Panulirus argus Lobsters Queue to Move Across Featureless Terrain Most (95%) queues have 5-20 members Few solitary lobsters or small groups (5%) Herrnkind, Childress, & Lavalli, 2001. Mar. Freshwat. Res. 52 : 1113-1124.
Queues Coil into “Rosettes” If Disturbed Antennae directed outward Herrnkind, Childress, & Lavalli, 2001. Mar. Freshwat. Res. 52 : 1113-1124.
Description of Fish Behaviors APPROACH (APR): Triggerfish swims to between one and two lobster antenna lengths ATTACK (AT): Triggerfish moves to within one lobster antennae length BITE (B): Triggerfish makes contact with the lobster by either smashing the shell with its mouth or by using the mouth to remove antennal tips or eyes SWIM OVER (SO): Triggerfish turns on side while swimming over lobsters at a distance of approximately 2 antennal lengths Lavalli & Herrnkind, 2008. N.Z. Mar. Freshwat. Res. 42 : (in press).
Description of Lobster Behaviors ANTENNA POINT (AP): Antennae moved and directed at approaching triggerfish ANTENNA WHIP (AW): Lobster uses one or both antennae to lash at fish LUNGE (L): Lobster rapidly thrusts antennae against fish TAIL FLIP (TF): Rapid abdominal flexion causing backward movement PIROUETTE (P): Animal spins rapidly, pointing antennae towards fish that are approaching in all directions Lavalli & Herrnkind, 2008. N.Z. Mar. Freshwat. Res. 42 : (in press).
No difference in size among intact, injured, or victims
Solitary Lobsters have Greater per Capita Death Risk, but No Difference for Grouped Lobsters Regardless of # of Fish N=13 N=13 * * ANOVA, p < 0.001 Actual death risk close to risk predicted by dilution
Time to Kill Not Affected by # Lobsters or # of Predators N=13 ANOVA, p = 0.55
Removal of Stridulating Organ Has an Effect on Attacks/Kills by Naïve Fish N =15 fish per lobster treatment Pearson’s 2 , p < 0.01