Behavior

Gobies get by with a little help from their friends

Citation: Encel, Stella A., and Ashley JW Ward. “Social context affects camouflage in a cryptic fish species.” Royal Society open science 8.10 (2021): 211125. DOI: 10.1098/rsos.211125

 

Life for a lone goby fish is dangerous. Ranging from a few millimeters to 10cm in length, gobies hide between crevices and even change their colors to blend in with their surroundings. But in groups, gobies appear more at ease. Or at least that is what scientists at the University of Sydney suggest in their new paper published in the Royal Society Open Science journal in October of 2021. According to their research, gobies barely camouflage when paired with other members of their own species. This behavior might align with a similar pattern seen in other animals – like in humans where stress levels drop with a little bit of company.

Gobies are small to medium size fish found in marine and freshwater environments. Credit: Hiroko Yoshii, Creative Commons
Over 2,211 species make up the Gobiiformes order. Credit: Wikimedia Commons

 

Color Changing Abilities

Chromatophores are at the center of the goby’s change in color. These cells contain different pigments, which squeeze or stretch and move closer or further away from the animal’s skin to create a specific color. Cephalopods like octopus, squids, and cuttlefish are masters of camouflage thanks to these color-shifting cells. Fish, amphibians, reptiles, and crustaceans use chromatophore cells for camouflage, but not to the astonishing levels of cephalopods.

While scientists know a lot about how chromatophores work, little is known about the many factors that determine a fish’s decision to change color. In fact, only one previous study from 1952 studied how the social context of fish affects the animal’s changing color decisions. With new tools to study color, there is lots of room for discovery.

Chromatophores cells on a squid. Credit: Wikimedia Commons
Camouflage might be particularly important when gobies are alone. Credit: Wikimedia Commons

Gobies to the Test

Blackeye goby blending with its environment. Credit: Wikimedia Commons

Therefore, scientists at the University of Sydney designed a clever experiment to test how the social context of fish affects their camouflage abilities. In a laboratory setting, scientists acclimated gobies (Pseudogobius sp.) to either black or white backgrounds. Then, they introduced the fish, in pairs and alone, to a new environment with a different background color. Gobies acclimated to a white background were introduced to a black environment and gobies acclimated to a black background were introduced to a white background. After 15 minutes, scientists compared their color to the background color.

The results from this study show that gobies change color faster and blend with their environment better when they are alone. On the other hand, gobies who were paired in this experiment took longer to change color and did not match their environment as effectively as gobies who performed the experiment on their own.

Safety in Numbers & Lower Stress Levels

This behavior might be the result of an evolutionary trade-off. Lone gobies are at a greater risk of predation, therefore, they camouflage quickly and efficiently. In contrast, gobies living in groups lower their risk of predation due to safety in numbers. Each fish is on the lookout for predators and hide quickly when a predator is detected. Since changing colors uses energy, gobies save energy by reducing their camouflaging abilities when they are in a low-risk environment. 

In addition, stress levels might limit the fish’s color-changing abilities. Studies have shown that humans, fish, and many other animals experience a calming effect when we are surrounded by other individuals. Overall, when we have company, stress levels drop and we feel more at ease. In fish, stress hormones like cortisol and adrenaline play an important role in the color change of fish. Therefore, it is possible that in a low-stress environment, cortisol and adrenaline levels might be too low to trigger the fish’s rapid change in color. Since stress hormones regulate the change in color in many species of fish, it is possible that the pattern seen in this study might also be at play in other species of fish. More research will be needed to make sense of the broader implications of this study.

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