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"Pearlfish" is also used for some Rivulidae, unrelated American freshwater killifish.
Echiodon rendahli (no common name).gif
Echiodon rendahli
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Ophidiiformes
Family: Carapidae
D. S. Jordan & Fowler, 1902
Sub-families & Genera

Pearlfish is a general name for a variety of marine fish species in the Carapidae family. Pearlfishes have been found in tropical waters of the Atlantic, Indian, and Pacific Oceans at depths to 2,000 m (6,600 ft) along oceanic shelves and slopes.

Pearlfishes are slender, distinguished by having dorsal fin rays that are shorter than their anal fin rays. They have translucent, scaleless bodies reminiscent of eels. The largest pearlfish are about 50 cm (20 in) in length. They reproduce by laying oval-shaped eggs, about 1 mm in length.[1]

Pearlfishes are unusual in that the adults of most species live inside various types of invertebrates. They typically live inside clams, starfish, or sea squirts, and are simply commensal, not harming their hosts. However, some species are known to be parasitic on sea cucumbers, eating their gonads and living in their anal pores. Though usually Pearlfish live alone, or in pairs, in 1977 the New Zealand biologist Victor Benno Meyer-Rochow recorded 15 pearlfish all living in a shared habitat - the anus of a single sea cucumber.[2]

Regardless of the habits of the adults, the larvae of pearlfish are free-living among the plankton. Pearlfish larvae can be distinguished by the presence of a long filament in front of their dorsal fins, sometimes with various appendages attached.[1]

The genera are divided into three major groupings based on their level of symbiosis:


  1. ^ a b Nielsen, Jørgen G. (1998). Paxton, J.R. & Eschmeyer, W.N., ed. Encyclopedia of Fishes. San Diego: Academic Press. p. 133. ISBN 0-12-547665-5. 
  2. ^ The fish that lives in a sea cucumber anus, Australian Geographic, 8 August 2014