Data from: Life in the unthinking depths: energetic constraints on encephalization in marine fishes

Several hypotheses have been proposed to explain the limitation of brain size in vertebrates. Here we test three hypotheses of brain size evolution using marine teleost fishes: the direct metabolic constraints hypothesis, the expensive tissue hypothesis, and the temperature-dependent hypothesis. Our analyses indicate that there is a robust positive correlation between encephalization and basal metabolic rate that spans the full range of depths occupied by teleosts from the epipelagic ( 4000m). Our results disentangle the effects of temperature and metabolic rate on teleost brain size evolution, supporting the direct metabolic constraints hypothesis. Our results agree with previous findings that teleost brain size decreases with depth, however, we also recover a negative correlation between trophic level and encephalization within the mesopelagic zone, a result that runs counter to the expectations of the expensive tissue hypothesis. We hypothesize that mesopelagic fishes at lower trophic levels may be investing more in neural tissue related to the detection of small prey items in a low-light environment. We recommend that comparative encephalization studies control for basal metabolic rate in addition to controlling for body size and phylogeny.

Usage Notes

Marine_Teleost_Encephalization_dataCSV file containing data for the 489 species used in our analyses. Data includes: genus and species names, maximum depth (meters), maximum absolute latitude, trophic level, body mass (grams), brain mass (grams), and encephalization quotient (EQ). EQ was calculated as the species average residual deviation from log-log regression of brain mass on body mass for 1,137. species. Data sources listed as FishBase include data from Froese & Pauly, 2014, Albert et al., 1999, Bauchot et al., 1979, Bauchot et al., 1989, Chin, 1996, Bauchot & Bauchot, 1986 (cited in paper) and new collections conducted by authors of this paper are indicated as "Field collection Guam" and "Field collection Curacao".Teleost_Encephalization_data.csv