Spiders belong to the class Arachnida, a group of arthropods that evolved a feeding system fundamentally different from creatures with jaws and grinding teeth. The common perception that spiders possess teeth, like a mammal, is a misunderstanding rooted in their predatory nature. Their specialized mouthparts and unique digestive process allow them to consume prey without ever needing to chew solid food. This adaptation is a defining feature of their biology.
The Direct Answer: Zero Teeth
The definitive answer to how many teeth a spider has is zero. Spiders, like all arachnids, lack the mandibles and jaw structures necessary to support the mineralized, grinding teeth found in mammals or reptiles. Their evolutionary history led to a two-part body structure where the head and thorax are fused into a cephalothorax, which contains their specialized feeding appendages.
Instead of traditional teeth, spiders use structures called chelicerae and fangs to capture and process their meals. These appendages are not used for cutting or chewing, as spiders are physically incapable of ingesting solid matter. This anatomical limitation dictates the unique way they must prepare their prey. The chelicerae and fangs serve as effective tools for subduing prey and initiating the feeding process.
Chelicerae and Fangs: The Spider’s Tools for Capture
The spider’s primary feeding apparatus consists of a pair of appendages called chelicerae, positioned directly in front of the mouth opening. Each chelicera is composed of a stout basal segment connected to the cephalothorax and a second, moveable segment known as the fang. These structures function like grasping or puncturing tools rather than the crushing tools of a jaw.
The fang is a sharp, hollow structure attached to the basal segment, often used like a hypodermic needle. This fang is connected to venom glands, which are housed within the chelicerae or extend back into the cephalothorax. The primary role of the fang is to inject venom into the captured prey to immobilize it or begin internal breakdown.
The orientation of the chelicerae varies across major spider groups, affecting how they capture prey. Mygalomorph spiders, which include tarantulas, have an orthognathous arrangement where the two fangs point straight down and move parallel to the body axis. In contrast, the vast majority of spiders, known as araneomorphs, possess labidognathous chelicerae that point diagonally inward and cross over each other in a pincer-like motion.
The Unique Process of Spider Digestion
Since spiders cannot ingest solid food, they employ external digestion, where the meal is liquefied outside the body. Once the prey is immobilized, the spider injects a cocktail of powerful digestive enzymes into the prey’s body through the fang punctures. In some cases, the spider may also regurgitate digestive fluids onto the prey’s surface.
These enzymes rapidly break down the prey’s internal tissues and organs, turning the solid contents into a nutrient-rich fluid. The spider then uses its specialized pharynx, a muscular foregut often referred to as a sucking stomach, to draw the liquid meal into its digestive tract. This muscular pump generates significant suction to pull the liquefied tissues through the narrow mouth opening.
The process continues as the spider pumps and sucks the digestive fluids back and forth, ensuring complete liquefaction and nutrient extraction. Filters within the mouth cavity and pharynx ensure that only liquid particles are ingested, leaving behind the indigestible hard parts, such as the prey’s exoskeleton. This leaves only a desiccated, hollow husk when the spider is finished feeding.