File:Astyanax fasciatus (Mexican blind cavefish) 2 (15099483704).jpg
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[edit]DescriptionAstyanax fasciatus (Mexican blind cavefish) 2 (15099483704).jpg |
Astyanax fasciatus (Cuvier, 1819) (or Astyanax mexicanus (De Filippi, 1853), depending on one's taxonomic preferences) - Mexican blind cavefish from southern Mexico (captive, Newport Aquarium, Newport, Kentucky, USA). Many caves are known to have blind fish in subterranean bodies of water. Members of several unrelated families have become blind cavefish. This is the Mexican blind cavefish, Astyanax fasciatus (sensu lato), which has been recorded from throughout Central America. It completely lacks eyes (eyes are useless in a permanently dark environment) and also has no pigmentation (hence the pinkish color from blood). However, this species does still possess the genes for eyes. Why? It’s ancestors did have eyes - they’ve been lost through evolution. This is the ultimate fate for all vestigial organs. However, the genes for lost structures are often retained for long geologic intervals of time (for example, chickens still have genes that code for teeth, despite the lack of teeth in chicken beaks). New info. - recent published research has determined that young cavefish of this species do have functioning eyes and have a light-sensitive area in their brains. The eyes degenerate with ontogeny, as does the light-sensitive area in the brain. The adults have zero light sensing ability. Classification: Animalia, Chordata, Vertebrata, Actinopterygii, Cypriniformes, Characoidei, Characidae |
Date | |
Source | Astyanax fasciatus (Mexican blind cavefish) 2 |
Author | James St. John |
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This image was originally posted to Flickr by jsj1771 at https://www.flickr.com/photos/47445767@N05/15099483704. It was reviewed on 4 May 2015 by FlickreviewR and was confirmed to be licensed under the terms of the cc-by-2.0. |
4 May 2015
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Camera manufacturer | NIKON CORPORATION |
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Camera model | NIKON D70s |
Exposure time | 1/60 sec (0.016666666666667) |
F-number | f/5.6 |
Date and time of data generation | 11:54, 19 March 2007 |
Lens focal length | 170 mm |
Orientation | Normal |
Horizontal resolution | 300 dpi |
Vertical resolution | 300 dpi |
Software used | Adobe Photoshop CS2 Macintosh |
File change date and time | 15:21, 5 November 2014 |
Y and C positioning | Co-sited |
Exposure Program | Not defined |
Exif version | 2.21 |
Date and time of digitizing | 11:54, 19 March 2007 |
Meaning of each component |
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Image compression mode | 4 |
APEX exposure bias | 0 |
Maximum land aperture | 5 APEX (f/5.66) |
Metering mode | Pattern |
Light source | Unknown |
Flash | Flash fired, strobe return light detected, auto mode |
DateTime subseconds | 00 |
DateTimeOriginal subseconds | 00 |
DateTimeDigitized subseconds | 00 |
Supported Flashpix version | 1 |
Color space | sRGB |
Sensing method | One-chip color area sensor |
File source | Digital still camera |
Scene type | A directly photographed image |
Custom image processing | Normal process |
Exposure mode | Auto exposure |
White balance | Auto white balance |
Digital zoom ratio | 1 |
Focal length in 35 mm film | 255 mm |
Scene capture type | Standard |
Scene control | None |
Contrast | Normal |
Saturation | Normal |
Sharpness | Normal |
Subject distance range | Unknown |
Supported Flashpix version | 1 |
Image width | 1,474 px |
Image height | 1,339 px |
Date metadata was last modified | 10:21, 5 November 2014 |