File:Sargassum Triggerfish (Xanthichthys ringens).jpg
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DescriptionSargassum Triggerfish (Xanthichthys ringens).jpg |
Triggerfishes are members of the family Balistidae, sometimes considered one of the more evolutionarily advanced families of marine fish. A dozen genera comprise the family, which totals less than 40 species. Certain characteristics are shared by all members of the family, notably two dorsal fins but no pelvic fins, eight teeth on the front jaw followed immediately by an additional six teeth and a large, well-developed pharyngeal plate which is well-suited for crushing various hard-shelled crustaceans. Four species are represented in Indo-Pacific waters, yet Xanthichthys ringens is known only from the Atlantic Ocean. Specimens have been collected from as far north as South Carolina and extending as far south as Brazil. St. Lucia, Florida and Cuba all have healthy populations. Perhaps the largest geographical distribution of the genus occurs in X. caeruleolineatus, which is present from the Tuamotu Archipelago to the St. Brandon's Shoals. Another distribution point worth mentioning is the anti-tropical distribution of X. mento and how both pre-juveniles of X. mento and X. ringens have been found up to 500 miles off the coast. Like its Indo-Pacific brethren, X. ringens prefers deeper waters near steep dropoffs and is "rarely encountered at depths of less than 100 feet" (Randall, 1968). At least one submarine observation has noted X. ringens patrolling about 400 feet deep off the Jamaican coast. No specimens of X. caeruleolineatus have been collected using traditional SCUBA equipment, probably because most individuals have been found at depths of 600 feet or more. A slightly upturned mouth, which remains very small throughout the fish's lifespan, does not allow Xanthichthys to consume the same foods as many other triggerfishes. Instead, species of the genus Xanthichthys concentrate their diet on free-floating zooplankton, which they eagerly pluck from the water column. In fact, stomach contents of X. auromarginatus revealed the fish fed exclusively on zooplankton (Hobson, 1974). Additional notes from this study indicated the vast majority of the zooplankton were calanoid copepods. Two species are known to display distinct sexual dichromatism between the adult males and females. This led to some confusion about species classification, but that was nevertheless worked out more easily than in most other dichromatic genera. Xanthichthys auromarginatus and X. mento each have beautiful male colorations while the females are certainly less attractive and flashy <a href="http://reefkeeping.com/issues/2005-05/hcs3/index.php">reefkeeping.com/issues/2005-05/hcs3/index.php</a> |
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Date | |||
Source | originally posted to Flickr as Sargassum Triggerfish (Xanthichthys ringens) | ||
Author | Cliff | ||
Permission (Reusing this file) |
This file is licensed under the Creative Commons Attribution 2.0 Generic license.
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current | 06:53, 22 March 2009 | 1,600 × 1,067 (317 KB) | Flickr upload bot (talk | contribs) | Uploaded from http://flickr.com/photo/28567825@N03/3366490231 using Flickr upload bot |
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This file contains additional information such as Exif metadata which may have been added by the digital camera, scanner, or software program used to create or digitize it. If the file has been modified from its original state, some details such as the timestamp may not fully reflect those of the original file. The timestamp is only as accurate as the clock in the camera, and it may be completely wrong.
Camera manufacturer | Canon |
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Camera model | Canon EOS 5D |
Exposure time | 1/60 sec (0.016666666666667) |
F-number | f/5.6 |
ISO speed rating | 400 |
Date and time of data generation | 12:00, 30 December 2008 |
Lens focal length | 135 mm |
Orientation | Normal |
Horizontal resolution | 72 dpi |
Vertical resolution | 72 dpi |
Software used | ACD Systems Digital Imaging |
File change date and time | 23:56, 18 March 2009 |
Y and C positioning | Centered |
Exposure Program | Not defined |
Exif version | 2.21 |
Date and time of digitizing | 12:00, 30 December 2008 |
Meaning of each component |
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APEX shutter speed | 6 |
APEX aperture | 5 |
APEX exposure bias | 0 |
Metering mode | Pattern |
Flash | Flash fired, compulsory flash firing |
DateTime subseconds | 812 |
Supported Flashpix version | 1 |
Color space | sRGB |
Focal plane X resolution | 3,086.925795053 |
Focal plane Y resolution | 3,091.2951167728 |
Focal plane resolution unit | inches |
Custom image processing | Normal process |
Exposure mode | Auto exposure |
White balance | Auto white balance |
Scene capture type | Standard |