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Though tarantulas can sport relatively massive fangs that allow them to subdue their prey, these fangs aren't used for chewing up their food. In fact, tarantulas don't chew their food at all, so their digestive systems rely on powerful enzymes that start breaking down food before it even enters the body.
A Tarantula's Teeth
A tarantula is equipped with two fangs, the size of which depends on the species. In a goliath bird-eating tarantula, for example, these fangs are 1 inch long, delivering a severely painful bite. When the tarantula bites his prey with these fangs, he injects and subdues them with venom. This venom is typically non-lethal for humans, but for smaller game, it's a fatal blow that leaves prey ready for consumption.
Injecting an Enzyme
Unlike other types of spiders that have teeth for tearing apart and chewing food, the tarantula has to rely on other methods for breaking down his meals. The digestive process begins while his food sits in front of him, when he injects it with an enzyme that starts to break it down. In a creature like a human, food is chewed up into small pieces, then broken down by enzymes in the stomach. A tarantula, on the other hand, waits for his enzymes to break the food down into a liquid, which he then slurps up without having to chew it. In some cases, he may need to use his fangs to puncture the exoskeleton around his prey, giving him an entry point for injecting his enzymes.
The Sucking Stomach and Beyond
The tarantula's stomach is wrapped in strong muscles, which allow it to expand and contract, working like a pump -- this gives it the name "sucking stomach." It sucks up liquified food like a vacuum, and as the spider consumes more and more, it expands to accommodate the liquid. This is why a tarantula may look visibly full or bloated after a meal. Food is then stored as needed in the caeca, an elaborate system of sacs and pouches throughout the body that can hold food before it's digested and turned into energy. This means that when a tarantula eats a particularly significant meal, he can break it down, slurp it up and store whatever he can't digest right away, allowing him to go for several days without having to kill again.
The Power of Digestion
Thanks to his digestive enzymes, sucking stomach and caeca, the tarantula is able to consume prey significantly larger than himself. This includes mice and other rodents, lizards, bats, snakes, frogs and even birds. Despite his ability to break down and digest large game like these creatures, the tarantula also subsists on a diet of more modestly-sized prey: insects.
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