Understanding the spatial learning ability of gobies

Date Published: October 5, 2014

Source: Behavioral Ecology

Summary: A study was conducted to determine the effect of the complexity of a habitat on a species’ spatial learning. The results demonstrated that habitat complexity and environment determine how the fish navigates.

Many species, including fish, use highly developed spatial systems to navigate their aquatic environments. These systems, which rely on a combination of landmarks and body orientation, not only allow the fish to navigate through the water but to also remember their surroundings.

The type of environment affects a fish’s spatial perception. Species that are normally found in turbulent, transient environments (such as rivers or sandy beaches) are accustomed to the constant changes to their surroundings—therefore, they rely less on landmarks and more on cues such as the number of turns required to move to a particular location. On the other hand, species found in calmer waters (such as intertidal pools or ponds) rely on fixed landmarks for navigation.

A recent study attempted to find whether the complexity of the fish’s surroundings would impact its spatial learning. To conduct this study, the researchers collected two species of rock-pool-dwelling gobies (the Cocos frillgoby and Krefft’s goby) and two species of sand-dwelling gobies (the Eastern long finned goby and Hoese’s sandgoby).

They then constructed a four-armed cross-shaped maze and placed certain objects in each arm (see figure). The arrow in the figure shows the path the fish would have to take to either reach the food reward or hide in the shelter, which was included to make the organisms feel more comfortable.

Prior to the experiment, the fish were placed into pre-training to allow them to acclimatize to the maze. Subsequent training sessions trained half the fish to turn left and the remainder to turn right from the starting arm. The actual experiment involved 3 probe trials, each of which tested preference for spatial cues. For example, fish trained to turn right and find the food reward were then placed in a setup where landmarks were positioned on the left side. The researchers observed which arm the fish entered to determine which cue (landmarks or body orientation) was used to navigate. The fish needed to successfully find the food reward in 4 out of 5 trials to meet the minimum criterion.

The results were in stride with the researchers’ predictions—the rock pool gobies learnt the location of the reward much faster and made fewer errors during training than their sand-dwelling counterparts. In terms of spatial cues, the rock pool fish were more reliant on landmarks (such as the turn direction and the plant landmark) while the sand-dwelling fish primarily utilized turn direction. The researchers concluded that the species’ environment (either rock pools or sandy beaches) may have selected for specific spatial learning abilities and cues. Specifically, the rock-dwellers commonly utilized landmarks since their rock pool environment is relatively stable; this also means that they have a sharper memory of their surroundings, which could explain the faster learning time. The sand-dwellers, on the other hand, live in a transient environment and thus cannot rely on permanent landmarks; therefore, they require less memory power, a factor which may explain their increased error frequency during training.

Overall, this study is relevant since it focuses on how fish use spatial learning to navigate their environment. Future studies can build upon the current research and focus on how the environment affects spatial learning by pushing organisms to rely on certain cues and abilities to navigate. 

Citation: White, G. E., and Brown, Culum. 2014. Cue choice and spatial learning ability are affected by habitat complexity in intertidal gobies. Behavioral Ecology. 26(1): 178-184.