Documentation

Introduction

The Complex Fish Maze is used to study the spatial learning and navigation abilities of fish. It consists of multiple T-junctions, which increases the complexity of the maze and challenges the subject’s decision-making abilities and memory. Unlike other apparatuses such as the T-Maze, Y-Maze, or the Zebrafish Three-Chamber Choice, which assess spatial learning and memory in a two-choice or three-choice paradigm, the Complex Fish Maze contains six consecutive T-junctions.

The Complex Fish Maze is placed in the corner of a large glass tank, with the remaining part of the tank comprising of a home sector used to hold conspecifics as a social reward. The maze contains a start chamber, narrow corridors with multiple T-junctions, and an exit. The Complex Fish Maze can easily be adapted for different experimental needs. Visual cues such as different colored panels can be placed on the walls or floor of the T-junctions, making each junction visually distinct from the other. However, the task can also be performed without the aid of visual cues so that the subjects’ cognitive abilities are challenged further. Essentially, the subjects can solve the task by using distant landmarks to create a spatial map or by learning the order of the T-junctions. 

Other apparatuses used to assess the learning abilities of fish includes the Latent Learning Apparatus, the Zebrafish Plus Maze, and the Zebrafish Associative Leaning Chamber. 

Apparatus and Equipment

The Complex Fish Maze measures 32 × 32 cm and is placed at one corner of a larger glass tank, 2 cm below the water surface. The glass tank measures 68 × 68 cm and includes the Complex Fish Maze and a home sector making up the tank’s remaining part. The glass tank is covered with black plastic to prevent the subjects from viewing the experimental room. The home sector includes plats and gravel to resemble the subjects’ maintenance tanks. A start chamber is present at the beginning of the maze, measuring 9 × 6 cm. The maze walls are 5 cm high and are perforated to allow water exchange with the home sector. The maze corridors are narrow, measuring 3 cm in width, to motivate the subjects to exit the maze. The end of the maze emerges into the home sector of the tank. Visual cues such as colored plastic panels can be fixed to the walls or the floor of the maze. 

Training Protocol

Change the tank’s water after each trial to avoid olfactory cues from previous trials interfering with task performance. Appropriately light the apparatus. A tracking and recording system such as the Noldus Ethovision XT can be used to assist with observations.

Habituation 

Place a male and female conspecific together with 25 immature guppies in the home sector to serve as social companions. Place the subject in the home sector of the tank. Allow the subject to habituate with the home sector for 48 hours before starting trials. Occlude the exit of the maze to prevent the subject from entering the maze to avoid latent learning during habituation. 

Complex Fish Maze Task

Place a male and female conspecific together with 25 immature guppies in the home sector to serve as social reward and motivation to exit the maze. Move the subject into the start chamber of the maze using a fishnet. Allow the subject to explore the maze and find the exit within 30 minutes. Deliver a small number of food flakes when the subject exits the maze. If the subject does not exit the maze within 30 minutes, consider the trial null and remove the subject from the maze. Trials can be performed with identical T-junctions or different colored visual cues attached to the walls or floor of the T-junctions. Conduct six trials a day over five consecutive days with an inter-trial interval of 1 hour. 

Literature Review

Investigation of complex maze learning in guppies (Poecilia reticulate)

Lucon-Xiccato and Bisazza (2016) investigated the navigation abilities of guppies in a maze consisting of consecutive T-junctions. The Complex Fish Maze was used in the experiment, and the subjects’ abilities to exit the maze within 30 minutes were analyzed. Two experiments were performed in which experiment 1 consisted of different colored panels attached to the walls or floors of the maze, while experiment 2 consisted of no visual cues present in the maze so that all the T-junctions were identical. In addition, experiment 2 utilized descendants of wild-caught guppies, and experiment 1 used domestic guppies. Results from experiment 1 indicated that the subjects improved maze performance as trials progressed. It was observed that the subjects made more errors when the correct arm was left than when it was right. The presence of color cues did not affect the amount of time taken to solve the task. Results from experiment 2 indicated that the wild-derived guppies also decreased their number of errors as trials progressed. It was observed that the wild-derived guppies were faster at solving the task compared to the domestic guppies.  

Data Analysis

The following parameters can be observed using the Complex Fish Maze:

• Number of times the subject entered the incorrect arm first 
• Number of times the subject entered the correct arm first
• Time taken for the subject to exit the maze 

Strengths and Limitations

Strengths 

The Complex Fish Maze can be used to assess the spatial learning, memory, and navigation abilities of fish. The maze contains six consecutive T-junctions to provide multiple decision-making points in the maze. The narrow corridors of the maze provide motivation to exit the maze. Since the maze exits into the home sector of the tank, motivation to reunite with conspecifics is also provided. The Complex Fish Maze can easily be adapted for different experimental needs. Different colored visual cues can be attached to the walls or floor of the T-junctions to make them visually distinct from each other. The walls of the tank can also be covered with opaque plastic to avoid the interference of external cues on task performance. 

Limitations 

The exploratory behavior of the subjects is highly important for task performance. Factors such as age, gender, and strain of the subject can affect task performance. 

Summary

• The Complex Fish Maze is used to study spatial learning and memory in fish.
• It consists of a complex maze with six consecutive T-junctions connected by narrow corridors. The maze also includes a start chamber and an exit.
• The Complex Fish Maze is placed in the corner of a large glass tank. The rest of the tank makes up the home sector used to hold conspecifics. 
• The Complex Fish Maze can easily be modified by placing different visual cues on the walls or floor of each T-junction to make them visually distinct from each other.  

References

1. Lucon-Xiccato, T., & Bisazza, A. (2017). Complex maze learning by fish. Animal Behaviour, 125, 69-75. https://doi.org/10.1016/j.anbehav.2016.12.022