Spooky interaction at a distance in cave and surface dwelling electric fishes

Abstract

Glass knifefish (Eigenmannia) are a group of nocturnal weakly electric fishes found throughout the Amazon basin. We made recordings of the electric fields of two populations of freely behaving Eigenmannia in their natural habitats: a troglobitic population of blind cavefish (Eigenmannia vicentespelaea) and a nearby epigean population (Eigenmannia trilineata). These recordings were made using a grid of electrodes to determine the movements of individual fish in relation to their electrosensory behaviors. Cavefish showed continuous evidence of territoriality whereas epigean fish modulated their social behavior in response to diurnal cues. Surprisingly, we routinely found nearby surface fish but not cavefish with sustained differences in electric field frequencies that were below 10 Hz. Such low-frequency differences in electric field frequencies should both cause detrimental sensory interference and trigger the jamming avoidance response. Both surface fish and cavefish showed significant interactions between their electric field frequencies and relative movements at unexpectedly large distances, of at least two meters, and at high differences in frequencies, often greater than 50 Hz. Results General observationsEigenmannia at both the epigean and cave sites were found in clear water streams with rock and sand substrate 6,7,9,12 . At the epigean site, there was a marked diurnal modulation of behavior. During the day, fish were found alone or in groups along the 10/10

Electrocommunication signals indicate motivation to compete during dyadic interactions of an electric fish

“…In contrast, A. leptorhynchus has been shown to use similar signals (non-selective responses, Dye, 1987) to battle with their EOD frequencies, both in the lab between females (Triefenbach and Zakon, 2008) and in the field (Benda, 2020). A recent field study also observed similar active jamming behaviors in Eigenmannia in the field (Fortune et al, 2020). If at all we observed only a few of such signals, but they appeared more like merged rises.…”

“…At time scales longer than many seconds electric fish produce another category of signals where EODf stays at an elevated or reduced EODf (jamming avoidance responses: Bullock et al, 1972;Fortune et al, 2020, nonselective responses: Dye, 1987Triefenbach and Zakon, 2008;Benda, 2020). If at all we observed only a few of such signals, but they appeared more like merged rises.…”

New species of glass knifefish genus Eigenmannia (Gymnotiformes: Sternopygidae) with comments on the morphology and function of the enlarged cephalic lateral‐line canals of Sternopygidae

“…Gasteropelecids, on the contrary, live just under the surface of the water and keep the top of head on the surface line – in this case is the widened supraorbital canal that is possibly being used to capture vibration caused by insects or other potential food particles that disturb the water surface. Available information on Eigenmannia behaviour show that this taxon is a bottom feeder that is most active during night‐time (Fortune et al ., 2019; Peretti & Andrian, 1999). It is a benthophagous invertivore taxon, with a diet composed of insect larvae, crustaceans and occasional autochthonous insects (Bichuette & Trajano, 2017; Giora et al ., 2005; Peretti & Andrian, 1999).…”

Dark world rises: The emergence of cavefish as a model for the study of evolution, development, behavior, and disease

“…Several significant impediments to research on these issues were discussed, including geopolitical barriers to accessing the caves and the need to adapt behavioral assays commonly used in laboratories to the natural environment. Such obstacles in the cave environment could be overcome by technological innovations, including the application of long‐term tracking (Fortune et al, 2019), the use of water monitors to track seasonal changes in conductivity, pH, and temperature (Tabin et al, 2018), and the application of environmental DNA sequencing to identify differences in biodiversity among different cave habitats (Stat et al, 2017). Helena Bilandžija (Ruđer Bošković Institute, Zagreb) presented a laboratory study showing that troglomorphic phenotypes are strongly impacted by developmental environment (Bilandžija et al, 2019), emphasizing the importance of characterizing differences between cave environments (Bilandžija et al, 2019).…”