Coloration
The Role of Color on the Reef
Introduction
Fish vision
Rods and cones
Different from humans[1]
Broad color spectrum picked up
UV visual sensitivity
It is a common, but certainly not dominant, feature for coral reef fish to possess short wavelength vision. This allows them to see a broader spectrum of light than other species. There are three categories used to describe this vision: ultraviolet (UV)-sensitive, UV-specialized, and violet-specialized.[2]
UV-Sensitive: This type of fish vision is characterized by a lack of specialized UV receptors. In this case, the UV blockers simply fail to function below 400nm. These fish probably do not have true UV color vision and cannot discriminate between hues. [2]
UV-Specialized: These eyes allow transmission of UV light to the retina. They fail to block some of the light in the UV spectrum. This category of fish vision is characterized by the possession of receptor cells that are responsive to visual pigments absorbed at 360nm. These fish possess UV-sensitive cone cells with peak absorption between 300nm and 400nm. They may have true color vision and recognize UV as a color. [2]
UV-Sensitive Cone Cells: These cells allow for true color vision and hue discrimination. It is likely that they provide the fish with separate perceptual functions, such as prey detection.[2]
Violet-Specialized: Fish with this type of vision are capable of blocking some radiation below 435nm. Their receptor cells are most sensitive to radiation that is between 400nm and 435nm. This allows for increased sensitivity to violet light in deeper water where UV radiation is less than violet radiation and there is a lower risk of ocular damage from harmful UV radiation. These fish display improved color constancy and focusing ability and are able to retain some of the advantages of UV-specialized vision (i.e. prey detection).[2]
Fish Coloration
Specific colors and patterns
blue, red, orange, yellow, green, gray, white, black, brown, silver[3]
brightness
bands, stripes, bars, speckles, spots, lines, blotches, eye markings, ocellated spots
The Role of the Environment in Coloration
Depth, temperature, etc
Roles of Colors
Protection Against Predation: warning colors, camouflage
Mate Selection
Life cycle phases
purpose of color as a juvenile vs. adult[4][5]
specific examples: Queen Angelfish, Schoolmaster, Dusky Damselfish
Polymorphism
Permanent color variations in species (geographical)[6]
Color and marking phases
temporary changes to enhance camouflage, to indicate mood, or for intraspecies communication (courtship)
instantaneous or over a long period of time
Coral Coloration
Location
Depth, sedimentation, etc
Zooxanthallae
algae give coral its color
Fluorescent proteins
give color to algae[7]
cyan, green, yellow, red, purple-blue, chromo-red
Lighting
Lighting is one of the most defining factors in determining the color of corals. Intensity, concentration, and wavelength (color), all play a role in how coral expresses its color. The wavelength of light determines how effectively the zoxanthellae can use the light to photosynthesize and produce nutrients for the coral. It's important to have a baseline understand of ultraviolet light, which is not detectable by the human eye, to fully understand the different types of light the zooxanthellae can utilize. UV-A: 315-400 nm The upper region of wavelength spectrum can pass through normal silicate glass and exhibits few, if any harmful effects on living tissue. UV-B: 280-315 nm This range of wavelength is responsible for most sunburns. It can not pass through silicate glass and is usually stopped in a few feet of water. However, in the crystal clear waters of reef areas, these rays can penetrate up to 30m deep. UV-C: 100-280nm The
Nutrition
Coral Bleaching
mainly focus on effects of lack of color
Coral Bleaching is the lack of color on various types of coral. This colorlessness is due to the death of the coral's symbiotic partner, the zooxanthellae algae. As the algae provides the coral with most of its color, the death of these creatures can prove quite detrimental to the life of corals. While some corals can live for short periods of time without their zooxanthellae partner, the majority of events that result in loss of zooxanthellae also result in death for the corals. Apart from these direct consequences that bleaching events have on the coral themselves, the stark white environment the bleaching creates can also render the area unsustainable for the otherwise vibrant fish. The white backgrounds create an environment that don't allow the fish to camouflage themselves to hide from predators as well as stalk prey.
References
- ↑ Losey, G. S., W. N. McFarland, E. R. Loew, J. P. Zamzow, P. A. Nelson, and N. J. Marshall. "Visual biology of Hawaiian coral reef fishes. I. Ocular transmission and visual pigments." Journal Information 2003, no. 3 (2003).
- ↑ 2.0 2.1 2.2 2.3 2.4 Marshall, N. J., K. Jennings, W. N. McFarland, E. R. Loew, and G. S. Losey. "Visual biology of Hawaiian coral reef fishes. III. Environmental light and an integrated approach to the ecology of reef fish vision." Journal Information 2003, no. 3 (2003).
- ↑ Marshall, N. J., K. Jennings, W. N. McFarland, E. R. Loew, and G. S. Losey. "Visual biology of Hawaiian coral reef fishes. II. Colors of Hawaiian coral reef fish." Journal Information 2003, no. 3 (2003).
- ↑ Longley, W. H. "Studies upon the biological significance of animal coloration. I. The colors and color changes of West Indian reef‐fishes." Journal of Experimental Zoology 23, no. 3 (1917): 533-601.
- ↑ Cardwell, J. R., and N. R. Liley. "Hormonal control of sex and color change in the stoplight parrotfish,< i> Sparisoma viride." General and comparative endocrinology 81, no. 1 (1991): 7-20.
- ↑ Messmer, Vanessa, Lynne van Herwerden, Philip L. Munday, and Geoffrey P. Jones. "Phylogeography of colour polymorphism in the coral reef fish Pseudochromis fuscus, from Papua New Guinea and the Great Barrier Reef." Coral Reefs 24, no. 3 (2005): 392-402.
- ↑ Alieva, Naila O., Karen A. Konzen, Steven F. Field, Ella A. Meleshkevitch, Marguerite E. Hunt, Victor Beltran-Ramirez, David J. Miller, Jörg Wiedenmann, Anya Salih, and Mikhail V. Matz. "Diversity and evolution of coral fluorescent proteins." PLoS one 3, no. 7 (2008): e2680.