Many people mistakenly believe sharks are born toothless, like many mammals. The surprising truth is that most shark pups enter the world fully armed with a complete set of functional teeth. This immediate dentition is part of an evolutionary design that prepares them for immediate survival in the ocean, providing them with the tools they need from day one.
The Simple Answer: Shark Pups Emerge Ready
Shark pups emerge with small, fully formed teeth that are instantly functional. This necessity stems from the fact that most shark species offer no parental care after birth. The neonate must hunt and feed immediately to survive and grow, securing its first meals of small fish or invertebrates.
In some live-bearing species, the teeth may be softer or covered by a protective membrane while inside the mother’s reproductive tract. This temporary feature prevents the pup from causing internal injury during gestation. However, the teeth quickly harden or become exposed upon birth, ensuring the young shark is ready to secure its own food source.
The Unique Replacement System
The ability to be born with functional teeth is rooted in the shark’s unique dental structure, known as polyphyodonty, or continuous tooth replacement. Unlike humans, sharks possess multiple rows of replacement teeth growing constantly behind the functional front row. This system acts like a biological conveyor belt, ensuring a steady supply of sharp dentition.
New teeth develop from specialized tissue at the inner margin of the jaw. As the functional outer tooth becomes damaged or lost, the tooth directly behind it moves forward to take its place. This process can happen rapidly; some sharks replace a tooth in as little as eight to ten days. A single shark can cycle through tens of thousands of teeth over its lifetime. The teeth are not set into the jawbone but are embedded in the gum tissue, which facilitates their forward migration and eventual shedding.
Different Birth Methods, Different First Teeth
The state and timing of the first functional teeth are influenced by the shark’s reproductive strategy, which falls into three main categories.
Oviparous Species
Oviparous species lay eggs encased in a protective shell. Pups must hatch with fully hardened teeth, sharp enough to tear through the tough egg case (sometimes called a “mermaid’s purse”) and immediately begin hunting upon entering the ocean.
Viviparous Species
Viviparous species give live birth, often with a placental connection to the mother. The teeth are present but may be delayed in full hardening until just before birth.
Ovoviviparous Species
The most dramatic variation is found in ovoviviparous sharks, where eggs hatch internally and the developing embryos are sustained within the mother. For species like the sand tiger shark, the first teeth are functional while still in the womb. In this mode, the earliest pups use their teeth for oophagy, or feeding on unfertilized eggs produced by the mother. Some species exhibit adelphophagy, or “sibling-eating,” where the largest embryo consumes its smaller siblings. In these cases, the teeth are a tool for survival and growth long before the pup is born.