Forget the bite, beware of slime

A word of advice: Steer clear of prowling hagfish and nervous fulmar chicks. The former secrete massive quantities of gross-out slime; the latter, a type of seabird, upchuck on avian predators, inflicting grievous bodily harm.

Both can be seen in action -- along with vampire squid, puffer fish and other ingenious creatures of land and sea -- in “Weird Nature -- Devious Defenses,” a John Downer production for BBC and the Discovery Channel, screening Saturday in Caltech’s Beckman Auditorium.

This high-definition film reveals a remarkable array of animals equipped with fascinating and bizarre defense mechanisms. Other examples: Octopuses squish themselves into hidey-holes a tiny fraction of their size. A dresser crab adorns itself in fancy camouflage by sticking scattered pearls to its shell. A vampire squid, resembling something from a 1950s sci-fi movie, confounds would-be predators by inverting webbed arms to reveal toothy spikes.

Merrielle Spain of Caltech’s computation and neural systems department will introduce the film and lead a post-screening discussion. A scuba diver since she was a teenager, Spain hopes she’ll get a question or two about the film’s puffer fish. It’s one of her favorites.

“They puff up when they feel threatened, and they get quite big because they don’t have ribs attached to their skin, so they’re like a balloon,” Spain says. They make lethal eating too. “The poison stops your nerves from firing.” Yum.

-- Lynne Heffley

“Weird Nature -- Devious Defenses,” Beckman Auditorium, Caltech, 332 S. Michigan Ave., Pasadena. 2 p.m. Saturday. $5. (626) 395-4652, (888) 222-5832, www.events.caltech.edu