Pearlfish

Pearlfish are marine fish in the ray-finned fish family Carapidae. Pearlfishes inhabit the tropical waters of the Atlantic, Indian, and Pacific Oceans at depths to 2,000 m (6,600 ft), along oceanic shelves and slopes. They are slender, elongated fish with no scales, translucent bodies, and dorsal fin rays which are shorter than their anal fin rays. Adults of most species live symbiotically inside various invertebrate hosts, and some live parasitically inside sea cucumbers. The larvae are free living.

"Pearlfish" is also used for some Rivulidae, unrelated American freshwater killifish.

Pearlfish
Echiodon rendahli
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Ophidiiformes
Suborder: Ophidioidei
Family: Carapidae
Poey, 1867[1]
Sub-families & Genera

Characteristics

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.[2]

Ecology
Pearlfish preserved emerging from anus of sea cucumber, Zoology Museum, Cambridge

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. Pearlfish usually live alone, or in pairs.[3]

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.[2]

Genera

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

References
  1. Richard van der Laan; William N. Eschmeyer & Ronald Fricke (2014). "Family-group names of Recent fishes". Zootaxa. 3882 (2): 001–230. doi:10.11646/zootaxa.3882.1.1. PMID 25543675.
  2. Nielsen, Jørgen G. (1998). Paxton, J.R.; Eschmeyer, W.N. (eds.). Encyclopedia of Fishes. San Diego: Academic Press. p. 133. ISBN 0-12-547665-5.
  3. The fish that lives in a sea cucumber anus, Australian Geographic, 8 August 2014
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