Abstract
Two sand-dwelling cichlids from Lake Malawi (Aulonocara stuartgranti, Tramitichromis sp.) that feed on benthic invertebrates, but have different lateral line phenotypes, use lateral line and/or visual cues to detect prey under light versus dark conditions. The current study examined how ecologically relevant variation in light intensity [0-800 lux (lx)] influences detection of prey (mobile, immobile) in each species by analyzing six behavioral parameters. Both species fed at light intensities ≥1lxand trends in behavior among light intensities were informative. However,prey type and/or time of day (but not light intensity) predicted all four parameters analyzed with generalized linear mixed models in A. stuartgranti, whereas the interaction of light intensity and time of day predicted three of these parameters in Tramitichromis sp. Data suggest that the critical light intensity is 1-12lx for both species, thatthe integration of visual and lateral line input explains differences in detection of mobile and immobile prey and behavioral changes at the transition from 1 to 0lx in A. stuartgranti, and that Tramitichromis sp. likely uses binocular vision to locate prey. Differences in thesensory biology of species that exploit similar prey will have important implications for the trophic ecology of African cichlid fishes.
Highlights
Light in aquatic habitats varies in quality and quantity over time and space (Kirk 2011) and influences the ability of visual predators to detect and capture mobile prey (Vinyard and O’Brien1976; Confer et al 1978; Lythgoe 1979; Ryer and Olla 1999; Vogel and Beauchamp 1999; Rickel and Genin 2005)
Of the 360 total prey presented to fish during all 60 trials, A. stuartgranti struck at 299 prey (=83%) and Tramitichromis struck at 231 prey (=64%; see Figs. 3, 4)
A. stuartgranti fed on prey at a range of ecologically relevant light intensities, including 555 darkness, and Tramitichromis was able to feed at low light intensities, but not in darkness
Summary
Light in aquatic habitats varies in quality and quantity over time and space (Kirk 2011) and influences the ability of visual predators to detect and capture mobile prey (Vinyard and O’Brien1976; Confer et al 1978; Lythgoe 1979; Ryer and Olla 1999; Vogel and Beauchamp 1999; Rickel and Genin 2005). Fishes occupying similar habitats may demonstrate variation in visually-mediated prey detection abilities, such as visual thresholds and absorption spectra of visual pigments, which may provide a competitive advantage under particular light conditions (Vogel and Beauchamp 1999; Hofmann et al 2009). Morphological and/or physiological specializations of non-visual sensory systems, including the olfactory system (Parzefall 1993; Montgomery et al 1999), gustatory system (Atema 1971) and the lateral line system (Janssen 1997; Schwalbe et al 2012, reviewed in Webb 2014), have been used to predict how these senses provide alternatives to vision for prey detection in light-limited environments. Futhermore, the integration of different combinations of sensory inputs may explain variation in behavior under different environmental conditions
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