Many species of saltwater fish have the amazing ability to change color. This can serve purposes like camouflage, communication, thermoregulation and more. The color change is made possible by specialized cells called chromatophores that contain pigments. By dispersing or concentrating the pigments, fish can alter their coloration. Let’s take a look at some of the most dramatic examples of saltwater fish that are able to shift their hues.
Chromatophores and Pigments
Chromatophores are cells that contain pigments and reflect light. There are several types of chromatophores, each containing a different pigment:
– Xanthophores – These contain yellow pigments like carotenoids and pteridines.
– Erythrophores – These contain red pigments like carotenoids and pteridines.
– Melanophores – These contain black or brown pigments like melanin.
– Leucophores – These contain white or silvery pigments like guanine.
– Iridophores – These contain reflective pigments like guanine.
By dispersing the pigment throughout the cell, the fish appears more colorful. By concentrating the pigment in the center, the cell appears clear. The dispersion and concentration of pigment is controlled by hormones and signals from the nervous system.
Flounders
One of the most dramatic examples of fish that change color are flounders. Flounders are a type of flatfish that blend in with the seafloor by having the ability to alter their upper side to match the substrate.
When flounder larvae hatch, they have a normal, vertically symmetrical shape. At metamorphosis, one of the eyes migrates to the other side of the head and the body flattens horizontally. The side facing up develops into the top side or dorsal surface. This side changes color and patterns to camouflage with the surrounding environment.
| Fish Species | Color Change Mechanism |
|---|---|
| Peacock Flounder | Rapid color change using melanophores. Both sides are white and can be altered to sandy or dark mottled patterns. |
| Winter Flounder | Long-term seasonal color change using xanthophores, melanophores and iridophores. Dorsal side changes from brown/green in summer to white in winter. |
Peacock flounders can change color extremely quickly, within seconds, using melanophores. Both sides of their body are white to start with, allowing rapid alterations between dark mottled colors for sandy areas and plain white for light colored substrate.
Winter flounders exhibit long-term seasonal changes that take weeks or months. In the summer, their dorsal side is speckled brown or greenish to match eelgrass and algae. In the winter when the vegetation dies back, they slowly change to solid white to blend with the snow and ice.
Cephalopods
Cephalopods like octopuses, squid and cuttlefish are marine masters of disguise and color change. They possess complex skin containing multiple types of chromatophores as well as structural reflectors called iridophores. By controlling pigment dispersal and contraction, they can generate patterns, textures, flashing displays and camouflage that matches their surroundings.
Some remarkable examples include:
– Mimic octopus – Shapeshifts between patterns that impersonate poisonous animals like sea snakes, lionfish and eels.
– Caribbean reef squid – Displays red and white flashing patterns for communication.
– Cuttlefish – Adjusts skin textures and patterns to precisely mimic colors, textures and shapes in the environment such as coral, seaweed and rock.
Anemonefish
Anemonefish like clownfish and damselfish live symbiotically with certain sea anemone species. They have evolved resistance to the anemone’s stinging tentacles. In return, the anemone provides protection for the fish.
Many anemonefish exhibit strong color shifts based on their life stage and environment:
– Juveniles tend to be transparent or solid black to blend into the anemone.
– Females and subordinate males are typically orange, red or yellow.
– Dominant males turn much darker overall, even black in some species.
– Some species darken at night and lighten during the day.
– Color intensity reflects the individual’s mood and aggression level.
– Anemonefish living among colorful anemones like bubble-tip anemones can develop similar coloration.
The color shifts in anemonefish are caused by rapid dispersion and aggregation of melanin in the melanophores. Higher aggression and stress hormones stimulate melanin dispersion, leading to rapid darkening.
Parrotfish
Parrotfish get their name from their fused beak-like teeth used for biting coral and algae off the reef. But they’re also capable of major color shifts, especially between their juvenile and adult phases.
– As juveniles, parrotfish often resemble surgeonfish and tangs with subdued coloration of grey, brown or green.
– When they mature, parrotfish exhibit vivid hues of blue, green, red, orange and yellow. Some develop dramatic designs on the head and fins.
– Supermale parrotfish transition to a phase with bolder red and orange coloring on the head, belly and fins.
Parrotfish change color gradually over several months. The shifts are controlled by hormones that regulate pigment production and concentration in chromatophores. Color patterns signal maturity, sex and dominance status.
| Species | Juvenile Color | Initial Phase | Terminal Phase |
|---|---|---|---|
| Stoplight Parrotfish | Pale brown | Green with yellow tail | Brilliant red head, green body |
| Queen Parrotfish | Dusky grey | Purplish with yellow fins | Blue and green stripes |
Wrasses
Wrasses are another large fish family that commonly displays major changes in coloration. Species like clown wrasses, rainbow wrasses and fairy wrasses showcase shifts between juvenile and adult color patterns:
– Many juveniles are transparent or have dull brown camouflage.
– Initial phase males and females develop blue, yellow, orange or green hues.
– Terminal phase males transition to bolder red coloration on the head, fins and anal area.
– Fairy wrasses exhibit the most striking shifts from brown or grey as females to brilliant purple, orange, electric blue and more as males.
As with parrotfish, the gradual color changes in wrasses are controlled by hormones acting on chromatophores and reflect pigment production. The different color patterns help signal sex, maturity and dominance.
Conclusion
The ability to shift color is extremely beneficial for many marine organisms. Fish like flounders use it for concealment from predators and prey. Cephalopods employ color changes for stunning displays and adaptive camouflage. Variations in anemonefish and other species help communicate mood, sex, dominance and life phase.
Specialized cells called chromatophores make this adaptability possible by housing pigments that can be rapidly dispersed or concentrated to alter coloration. Through evolution, many fish have developed impressive capabilities to match their environments and communicate through living color.
