One More Odd Thing I Just Learned About Fish
When I’m not blogging for mental_floss, I can usually be found wearing bright orange rubber pants and gutting, cutting and selling fish at my local Whole Foods (and winning awards for it). Sometimes, my two worlds collide and I find some scientific research involving my ocean-dwelling friends that begs for a blog post. This is one of those times.
Take the Last Train to Lobsterville, I’ll Meet you at the Station
Panulirus argus, the Caribbean spiny lobster, spends most of its time in shallow waters among coral reefs and mangrove swamps in the western Atlantic Ocean and Caribbean Sea (as far south as Brazil and as far north as North Carolina). Every year in mid-Fall, much of their range gets hit with increased storm activity and the usually pleasant water conditions get disrupted by high winds, water turbulence, colder temperatures, and turbidity from kicked-up sediment.
After the first storm, many of the lobsters (especially those in southeast Florida, the Florida Keys, Bimini and Grand Bahama and eastern Yucatan, Mexico), which are normally nocturnal and solitary, become active in the day and gather in groups to form queues of up to 65 individuals. Once a queue is sorted out, the lobsters begin marching – single-file, with each individual maintaining antennae-to-cephalothorax contact with the lobster in front of them – into deeper, calmer water.
Researchers hypothesize that these mass migrations are a response to the autumn storms, which can make the shallows too cold and turbulent for normal lobster activity and can even kill molting individuals. The cue to begin lining up appears to be the sharp drop in water temperature; captive spiny lobsters in laboratories have been observed to remain active during the day and queue up when the temperature of their tanks are dropped.
All the lobsters seem to have an innate sense of the migratory bearing, as followers occasionally break rank and form separate queues that maintain the normal pace and direction and quick removal of a queue leader by researchers has resulted in the next lobster in line continuing to lead the train on the migratory.
A mass exodus from an unfriendly environment makes sense, but why would creatures who normally prefer to go out at night by themselves join into groups and travel during the day?
The conga line formation seems to serve two purposes. One, it reduces drag on the lobsters that aren’t leading and lets them conserve energy. Lobsters in a queue of 20+ individuals sustain only about half the drag of solo travelers. Two, if a predator happens upon the caravan, the queue formation allows the lobsters to quickly “circle the wagons” and go into a defensive formation that protects their vulnerable legs and presents their sharp antennae to predators.
Want to see the lobsters in action? With an epic musical score and the dulcet tones of Sir David Attenborough? Then you’ve come to the right place.
Reference: Kanciruk, P., Herrnkind, W.. (1978). “Mass Migration of Spiny Lobster, Panulirus Argus (Crustacea: Palinuridae): Behavior and Environmental Correlates.” Bulletin of Marine Science, Volume 28, Number 4.
Herrnkind, W., Kanciruk, P., Halusky, J., McLean, R.. (1973). “Descriptive characterization of mass autumnal migrations of spiny lobster Panulirus argus.” Proceedings of the Gulf and Caribbean Fisheries Institute, 25, 79-98.