Why Do Starfish Burrow?

Starfish -- more correctly called sea stars -- are marine invertebrate echinoderms: they live in the seas and oceans of the world, have no bony internal skeleton and are protected by a spiny skin. Some crawl over tropical reefs and others live on the bottom. They are both predators and scavengers, eating whatever they can catch or find. Burrowing is part of the normal behavior of some species. Sea stars burrow into the bottom using the tube feet and spines on the underside of their arms.

  1. Protection

    • Sea stars bury themselves in and under sand and mud to hide from predators, such as puffers and trigger fish, even their own larger relatives. They usually conceal themselves during the daylight hours and emerge to feed at night. Burrowers tend to have more camouflage-like coloration, while reef-dwelling sea stars can be very brightly colored. There is a species from the eastern Atlantic and western Mediterranean specifically called the burrowing sea star (Astropecten irregularis) that spends most of its time at least partially buried, possibly to help camouflage its pink upper surface.

    Food

    • Some sea stars, such as the tropical sand sifting sea star (Astropecten polycanthus) from Indo-Pacific waters, get most of their food by foraging in a sand environment. They move large amounts of sand around as they burrow and take in virtually any organic matter they find, including live animals such as shrimp and hard-shelled mollusks, along with dead animals. This species is popular in marine and reef aquaria because they aerate the sand bottom and clean up food leftovers and fish waste.

    Aquarium Requirements

    • No starfish can survive in fresh water, so you must have a saltwater tank, whether marine fish-only or a tropical reef type. The tank needs at least five to six inches of sand bottom to give a sea star room to hide and hunt. The minimum size for hosting a sea star is 75 to 80 gallons.

    Care And Feeding

    • Be sure your sea star has plenty of food, or it will starve and die. If you have multiple stars in a small tank, supplemental feeding will probably be required. To be sure the stars get the food and not the fish, create a large flat area of sand as a feeding place and insert small pieces of chopped shrimp or squid deep into the sand with tongs or forceps so that the slow-moving sea stars can find them as they burrow.
      Sea stars do not like sudden changes in the temperature or oxygen level of the water, so never try to remove them from the tank into the air, even for a very brief time. Always handle them under water.