File:Astyanax fasciatus (Mexican blind cavefish) 3.jpg
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[edit]DescriptionAstyanax fasciatus (Mexican blind cavefish) 3.jpg |
English: Astyanax fasciatus (Cuvier, 1819) (or Astyanax mexicanus (De Filippi, 1853), depending on one's taxonomic preferences) - Mexican blind cavefish (captive, American Cave Museum, Horse Cave, 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). Published research has shown 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. Adults have zero light sensing ability. Classification: Animalia, Chordata, Vertebrata, Actinopterygii, Cypriniformes, Characoidei, Characidae |
Date | |
Source | https://www.flickr.com/photos/47445767@N05/52554859633/ |
Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/52554859633. It was reviewed on 12 December 2022 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
12 December 2022
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current | 01:57, 12 December 2022 | 3,079 × 1,630 (2.92 MB) | Ser Amantio di Nicolao (talk | contribs) | Uploaded a work by James St. John from https://www.flickr.com/photos/47445767@N05/52554859633/ with UploadWizard |
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Camera manufacturer | Canon |
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Camera model | Canon PowerShot D10 |
Exposure time | 1/60 sec (0.016666666666667) |
F-number | f/4.5 |
ISO speed rating | 250 |
Date and time of data generation | 11:53, 4 December 2022 |
Lens focal length | 14.303 mm |
Width | 4,000 px |
Height | 3,000 px |
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Pixel composition | RGB |
Orientation | Normal |
Number of components | 3 |
Horizontal resolution | 180 dpi |
Vertical resolution | 180 dpi |
Software used | Adobe Photoshop Elements 18.0 (Macintosh) |
File change date and time | 08:32, 10 December 2022 |
Y and C positioning | Co-sited |
Exif version | 2.21 |
Date and time of digitizing | 11:53, 4 December 2022 |
Meaning of each component |
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Image compression mode | 3 |
APEX shutter speed | 5.90625 |
APEX aperture | 4.34375 |
APEX exposure bias | −0.66666666666667 |
Maximum land aperture | 4.34375 APEX (f/4.51) |
Metering mode | Pattern |
Flash | Flash fired, compulsory flash firing, red-eye reduction mode |
Supported Flashpix version | 1 |
Color space | sRGB |
Focal plane X resolution | 16,460.905349794 |
Focal plane Y resolution | 16,483.516483516 |
Focal plane resolution unit | inches |
Sensing method | One-chip color area sensor |
File source | Digital still camera |
Custom image processing | Normal process |
Exposure mode | Manual exposure |
White balance | Auto white balance |
Digital zoom ratio | 1 |
Scene capture type | Standard |
Lens used | 6.2-18.6 mm |
Date metadata was last modified | 03:32, 10 December 2022 |
Unique ID of original document | 5AEFCCA78BD939BA210BD698715D7184 |