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Those strange cases

Huevos de tiburones

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The beach woke up littered with small cases, they look like flexible plastic cases. Bewildered walkers observe them and notice that inside them small snails roam: “Snail eggs,” they declare. But snail eggs are notably different. These cases have the appearance and consistency of a burned piece of X-ray film.

These eggs, resembling cases, have an H shape, and a thin ribbon hangs from each of their ends, coiling upon itself. Their color is usually dark green or black, and their size rarely exceeds ten centimeters. Perhaps some small snails sought refuge inside them or are feeding on yolk remains, but they are not snail eggs; they are “mermaid’s purses,” a small wonder of nature—they are shark eggs.

Sharks have multiple forms of reproduction, varying among the more than 310 species according to evolution. They can be viviparous, ovoviviparous, or oviparous. “Mermaid’s purses” belong to the latter category. Female sharks abandon their eggs near the coast, and ocean currents and luck will determine whether the ribbon-like parts at the ends of the egg become entangled and attach to the algae on the seabed. The dark color hides them from predators’ view, while the hard consistency of the case eliminates the possibility of being smelled, thus discouraging smaller predators.

The egg will take seven months to hatch. Meanwhile, the large yolk sac inside it will gradually decrease in size as the embryo consumes its content until it almost disappears completely. At the moment of hatching, the small shark will slide out of the case. Newborn sharks are active, swimming vigorously and ready to search for food immediately. Their small size will prevent them from accessing significant prey yet, but since the egg was abandoned by the mother among the algae and in shallow waters, the young shark will find itself in a habitat where it has easy access to small crabs, polychaetes, other invertebrates, and slow-moving fish.

As it grows, the young shark will venture further away from the coast in search of larger prey, gradually entering the realm of the adults. Meanwhile, the abandoned “mermaid’s purse” now occupied by small snails will float, carried by the currents, towards the shore, to the perplexity of humans. After all, don’t sharks always manage to perplex us?

“You cannot protect what you do not love, and you cannot love what you do not know.”