A ‘Four-Eyed’ Fish from the Deep-Sea: Bathylychnops exilis Cohen, 1958

Pearcy, William G.; Meyer, Samuel L.; Munk, Ole Lajord

doi:10.1038/2071260a0

Cited by 9 publications

(13 citation statements)

References 2 publications

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“…and Opisthoproctus sp. [2,3,5] to the complex type described here for R. natalensis and elsewhere for D. longipes [22] or to the scleral lens containing diverticulum of B. exilis [21]. This family of teleosts thus presents a highly unusual taxon, exhibiting diverse and unique ocular morphologies that extend the characteristics and capabilities of more common tubular eyes.…”

Section: Discussionmentioning

confidence: 92%

“…The fish was removed from the storage medium and rehydrated by immersion for 2 h in a series of reducing concentrations of ethanol (steps in concentration: 50, 25 and 10%). After rehydration, the fish was placed overnight in 0.1 M phosphate buffer saline (pH 7.4, 300 mOsm kg 21 ) to which was added the magnetic resonance imaging (MRI) contrast agent, 1% ionic Gd-DTPA (Magnevist, Bayer, Germany), prior to MRI following a protocol developed for zebrafish [23]. The sample was placed in an imaging tube containing fomblin oil (perfluoropolyether, Ausimont, Morristown, NJ, USA) to reduce artefacts caused by air-tissue boundaries and to prevent dehydration.…”

Section: (A) Magnetic Resonance Imagingmentioning

confidence: 99%

“…Two species of opisthoproctids, however, have evolved extensive diverticula that almost certainly provide well-focused images. Bathylychnops exilis has dorsally directed spherical eyes and ventrally directed secondary eyes with scleral lenses [21]. Dolichopteryx longipes , on the other hand, has dorsally directed tubular eyes as well as extensive ventro-laterally directed diverticula which, uniquely among vertebrates, produce focused images using Fresnel-type mirrors [22].…”

Section: Introductionmentioning

confidence: 99%

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Reflecting optics in the diverticular eye of a deep-sea barreleye fish ( Rhynchohyalus natalensis )

et al. 2014

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We describe the bi-directed eyes of a mesopelagic teleost fish, Rhynchohyalus natalensis, that possesses an extensive lateral diverticulum to each tubular eye. Each diverticulum contains a mirror that focuses light from the ventro-lateral visual field. This species can thereby visualize both downwelling sunlight and bioluminescence over a wide field of view. Modelling shows that the mirror is very likely to be capable of producing a bright, well focused image. After Dolichopteryx longipes, this is only the second description of an eye in a vertebrate having both reflective and refractive optics. Although superficially similar, the optics of the diverticular eyes of these two species of fish differ in some important respects. Firstly, the reflective crystals in the D. longipes mirror are derived from a tapetum within the retinal pigment epithelium, whereas in R. natalensis they develop from the choroidal argentea. Secondly, in D. longipes the angle of the reflective crystals varies depending on their position within the mirror, forming a Fresnel-type reflector, but in R. natalensis the crystals are orientated almost parallel to the mirror's surface and image formation is dependent on the gross morphology of the diverticular mirror. Two remarkably different developmental solutions have thus evolved in these two closely related species of opisthoproctid teleosts to extend the restricted visual field of a tubular eye and provide a well-focused image with reflective optics.

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Section: Discussionmentioning

confidence: 92%

Section: (A) Magnetic Resonance Imagingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Reflecting optics in the diverticular eye of a deep-sea barreleye fish ( Rhynchohyalus natalensis )

et al. 2014

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“…Bathylychnops exilis is an uncommon bathypelagic species of opisthoproctid fish, distributed in Transition waters of the northeastern Pacific Ocean.? Its most striking morphological feature is the possession of the equivalent of four eyes, each with its own lens, cornea, and eyeball, although the retinas are not entirely separate (Pearcy et al, 1965;Munk, 1966). The larger (primary) pair of eyes looks dorsally; the smaller (auxiliary) globes are directed ventrally.…”

Section: Introductionmentioning

confidence: 99%

“…The larger (primary) pair of eyes looks dorsally; the smaller (auxiliary) globes are directed ventrally. Published descriptions are of juveniles (Cohen, 1958(Cohen, , 1960; there are no published records or descriptions of adults other than one specimen ( O W 0 535) partially described by Pearcy et al (1965). (Pearcy, 1980).…”

Section: Introductionmentioning

confidence: 99%

Observations on the morphology, ecology, and behaviour of Bathylychnops exilis Cohen

Stein¹,

Bond²

1985

Journal of Fish Biology

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Barhylychnops exilis is an unusual north-eastern Pacific mesopelagic fish of which adults have previously been undescribed and the biology is poorly known. Its sensory and digestive systems are highly modified. Sensory modifications include the equivalent of four functional eyes, welldeveloped nasal rosettes, and lateral line canals up to 4 mm in diameter. Digestive adaptations include a peculiar mouth, large tongue, crumenal organ, and a large caecal stomach. Bathylychnops exilis apparently lacks an anal light organ. Ontogenetic changes OCCUK in the morphology of the head, eyes, body, and coloration. Bathylychnops exilis eats crustaceans and maybe medusae and microscopic organisms. Reproduction probably occurs in late summer. Adults occur most commonly at about 500 m depth, possibly in groups, and may be diurnal vertical migrators.

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Adaptations to the Deep-Sea Environment

Locket¹

1977

Handbook of Sensory Physiology

149

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A ‘Four-Eyed’ Fish from the Deep-Sea: Bathylychnops exilis Cohen, 1958

Cited by 9 publications

References 2 publications

Reflecting optics in the diverticular eye of a deep-sea barreleye fish ( Rhynchohyalus natalensis )

Reflecting optics in the diverticular eye of a deep-sea barreleye fish ( Rhynchohyalus natalensis )

Observations on the morphology, ecology, and behaviour of Bathylychnops exilis Cohen

Adaptations to the Deep-Sea Environment

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