Effects of caudal fin size on tail-flip jump performance

Fishes are generally considered to be fully aquatic, but some voluntarily strand themselves on land to escape poor water conditions, predators, or to exploit terrestrial niches. The tail-flip jump is a method of terrestrial locomotion performed by small fishes without apparent morphological specialization, but few studies have investigated the role the caudal fin has on the tail-flip jump. We hypothesized that fish with larger caudal fins would perform shorter individual tail-flip jumps and not be able to sustain jumping in extended terrestrial excursions. Zebrafish (Danio rerio) are an excellent model to investigate this because these fish perform the tail-flip jump and some strains have been selectively bred in the pet trade industry for larger fins. In this study, wildtype and longfin zebrafish were compared because of the larger caudal fins of the longfin zebrafish. Individuals of each strain performed three consecutive jump trials with 48 h between each trial: kinematic, voluntary, and exhaustion. The kinematic trial used a high-speed camera to measure kinematic variables of individual jumps. The voluntary trial recorded each fish's voluntary response to stranding for three minutes. The exhaustion trial recorded the fish's response to be constantly elicited to jump until exhaustion was reached. Despite differences in caudal fin area, there were no differences in the kinematic characteristics of individual jump performances, including jump distance. However, wildtype zebrafish performed more jumps, jumped more than they flopped, and moved a greater total distance in both voluntary and exhaustion trials despite moving for similar durations and reaching exhaustion at similar times. These findings imply that larger fins do not affect a fish's ability to perform individual tail-flip jumps but does cause fish to employ different behavioral strategies when stranded for longer durations on land.