Abstract
The scale-eating cichlid Perissodus microlepis with asymmetric mouth is an attractive model of behavioral laterality: each adult tears off scales from prey fishes’ left or right flanks according to the direction in which its mouth is skewed. To investigate the development of behavioral laterality and mouth asymmetry, we analyzed stomach contents and lower jaw-bone asymmetry of various-sized P. microlepis (22≤SL<115mm) sampled in Lake Tanganyika. The shapes of the pored scales found in each specimen’s stomach indicated its attack side preference. Early-juvenile specimens (SL<45mm) feeding mainly on zooplankton exhibited slight but significant mouth asymmetry. As the fish acquired scale-eating (45mm≤SL), attack side preference was gradually strengthened, as was mouth asymmetry. Among size-matched individuals, those with more skewed mouths ate more scales. These findings show that behavioral laterality in scale-eating P. microlepis is established in association with development of mouth asymmetry which precedes the behavioral acquisition, and that this synergistic interaction between physical and behavioral literalities may contribute to efficient scale-eating.
Highlights
Behavioral laterality has been reported in a wide variety of vertebrates, including chimpanzees, gorillas, rats, mice, whales, chicks, toads and fish as well as humans [1], and even in crustaceans and insects [2]
We investigated the development of feeding habits including attack side preference in the scale-eater P. microlepis by analyzing the stomach contents of specimens with standard length (SL) of body size ranging from 22 to 115mm
The stage-dependent differences in P. microlepis stomach contents indicates that these cichlids change their primary food source from plankton and omnivores to fish scales as they grow larger than 45mm in SL
Summary
Behavioral laterality has been reported in a wide variety of vertebrates, including chimpanzees, gorillas, rats, mice, whales, chicks, toads and fish as well as humans [1], and even in crustaceans and insects [2]. The existence of behavioral laterality in lower vertebrates and even in invertebrates implies that it appeared in early Metazoan evolution and that it confers advantages for survival [3]. Chimpanzees that specialize at using one hand for termite fishing catch termites more efficiently than individuals lacking handedness [4]. The lateralized pecking behavior of the crossbill is adapted to its skewed mandible (left- or right-directed), which. Global Centre of Excellence Program “Formation of a Strategic Base for Biodiversity and Evolutionary Research: from Genome to Ecosystem”, from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan
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