pearlfish

/perrl"fish'/, n., pl. pearlfishes, (esp. collectively) pearlfish.

any of several small fishes of the family Carapidae, living within pearl oysters, sea cucumbers, starfishes, etc.

[1585-95; PEARL¹ + FISH]

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▪ fish

also called  fierasfer , or  cucumber fish 

      any of about 32 species of slim, eel-shaped marine fishes of the family Carapidae noted for living in the bodies of sea cucumbers (sea cucumber), pearl oysters, starfishes, and other invertebrates. Pearlfishes are primarily tropical and are found around the world, mainly in shallow water. They are elongated, scaleless, and often transparent. The long dorsal and anal fins meet at the tip of the long pointed tail, and the anus is near the throat. Most pearlfishes are about 15 cm (6 inches) or less in length. They penetrate sea cucumbers by way of the anus of the host, in some instances apparently feeding on its reproductive and respiratory organs.

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