''Bathylychnops exilis'', the Javelin spookfish, is a species of
barreleye found in the northern
Pacific and in the eastern
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...
near the
Azores
)
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, anthem= ( en, "Anthem of the Azores")
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, map_alt=Location of the Azores within the European Union
, map_caption=Location of the Azores wi ...
where it is found at depths of around . This species grows to a length of
SL.
The species is notable for unusual protuberances that grow from its eyes, which each have "a well developed lens"
[Pearcy WG, Meyer SL, Munk O (1965). A 'Four-Eyed' Fish from the Deep-Sea: ''Bathylychnops exilis'' Cohen, 1958. ''Nature'' 207, 1260-1262.] and a retina, and which have led to the species being called a "four-eyed" fish.
It has been suggested that the purpose of these extra eyes is detection of threats from below, since these eyes point downwards. The Javelin spookfish have a distinct and advantageous secondary globe to their eyes. They use mirrors to collect and focus light, instead of a lens to divert the path of light. This feature provides great benefits in their chances for survival.
References
Opisthoproctidae
Fish described in 1958
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