Meeting Abstract
It is well-established that many fishes will go onto land for a variety of reasons, from searching for better resources to avoiding predation. However, little is known about how fish determine where to go when on land, and which senses they use for terrestrial navigation. The goals of the present study were to determine which sensory cues the mangrove rivulus (Kryptolebias marmoratus), a quasi-amphibious, hermaphroditic fish, use to orient and navigate in an unfamiliar terrestrial environment. In a laboratory setting, K. marmoratus were placed on a terrestrial test arena and exposed to a variety of visual stimuli, as well as a slope, to determine the role of visual cues and the vestibular-otolith system in their terrestrial navigation. Circular statistics were used to determine the mean direction of travel in each treatment. Overall, K. marmoratus moved (1) toward reflective surfaces, supporting the findings of previous studies that found fish to use vision – and specifically the reflection of light as a cue – to navigate while on land; (2) toward water; (3) toward dark coloration, which may be associated with shade; and (4) toward orange coloration. Males showed a stronger preference for moving toward orange coloration than hermaphrodites, suggesting that the response may be associated with male-male competition, since only males display orange coloration. A slope also had a significant effect on orientation, with more movement downhill, suggesting the otolith-vestibular system is important for the terrestrial orientation of K. marmoratus. By understanding the orientation and navigation of extant amphibious fishes, we may be able to infer how sensory biology and behavior evolved in relation to the invasion of land by amphibious vertebrates millions of years ago.
