BRIEF COMMUNICATION New insights into patterns and rates of tooth replacement in serrasalmid and characid fishes, with implications for the subsistence fishery of Peru's remote ribereños villages Courtney E. Stuart 1,2 | Stephanie J. Green 2 | Oksana Vernygora 2 | Aaron R. H. LeBlanc 2 | Mary H. Bertschi 1 | Maria Brown 1 1 School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York 2 Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada Correspondence Courtney E. Stuart, University of Alberta, Z 616 Biological Sciences Bldg., Edmonton, AB T6G 2E9, Canada. Email: cestuart@ualberta.ca Funding information Funding for this project was provided by the Stony Brook Foundation and Marine Sciences Research Center Endowment Fund through a grant to C.E.S. and M.H.B. (Grant/Award Number: 236124). Abstract We explored patterns, rates and unexpected socio-ecological consequences of tooth replacement in serrasalmids and characids of the Peruvian Amazon using micro- computed tomography. Of 24 specimens collected in February 2019, representing a mix of red-bellied piranha Pygocentrus nattereri, redeye piranha Serrasalmus rhombeus, silver dollar fish Ctenobrycon hauxwellianus and mojara Astyanax abramis, six individ- uals possessed edentulous jaw quadrants. On average, 22.9% of fish collected per day from these species featured incomplete dentition, a value three to five times higher than anticipated based on replacement rates estimated from captive fish, differences that may be driven by ontogeny, seasonality or environmental quality. KEYWORDS Amazon basin, Characidae, fisheries ecology, microcomputed tomography, Serrasalmidae, tooth replacement Freshwater serrasalmid and characid fishes exhibit unique dental mor- phologies and patterns of tooth replacement. Rather than spacing teeth along the jaw and displaying alternating “waves” of replace- ment, as is common in osteichthyans, the teeth of serrasalmids and characids form interlocking rows that are developed and shed simulta- neously in each quadrant of the jaw (Berkovitz & Shellis, 1978, 2016; Roberts, 1967; Shellis & Berkovitz, 1976; Trapani, 2001). This unilat- eral method of tooth replacement is exemplified by the carnivorous redeye piranha Serrasalmus rhombeus (Linnaeus 1766) and was origi- nally thought to be an adaptation for maintaining the sharp, blade-like teeth required for slicing prey (Berkovitz, 1975; Berkovitz & Shellis, 1978; Shellis & Berkovitz, 1976). However, Kolmann et al. (2019) recently identified unilateral tooth replacement in herbiv- orous serrasalmid species, suggesting that the interlocking tooth mechanism and simultaneous replacement of all teeth in a jaw quad- rant evolved first in an herbivorous ancestor to support grazing on stiff plant materials and was later exapted for shearing in carnivorous piranhas. Moreover, a similar tooth replacement pattern has been observed across several characiform families (e.g., Alestidae, Bryconidae, Roberts, 1967, 1975), yet descriptions of the underlying process remain scant. The unilateral tooth replacement cycle begins with the develop- ment of resorptive medullary cavities below the functional tooth row, deep within the bone of the jaw. Developing full sets of replacement teeth within the medullary cavity (i.e., intraosseous development) reduces the edentulous (i.e., toothless) period between the time that older functional teeth are shed and new replacement teeth are anky- losed (i.e., attached by mineralized tissue) to the jaw (Kolmann et al., 2019; Roberts, 1967). Examining laboratory-raised S. rhombeus, Berkovitz and Shellis (1978) suggested that individuals lack functional teeth along a jaw quadrant for only one day and that replacement teeth are firmly ankylosed to the jaw within 3–4 days. The rapid nature of unilateral tooth replacement relative to the operational lifespan of the teeth (estimated to be 65–130 days; Berkovitz & Shellis, 1978) likely explains why few individuals have been observed in the edentulous period between functional tooth loss and Received: 2 September 2020 Accepted: 26 November 2020 DOI: 10.1111/jfb.14634 FISH 1196 © 2020 Fisheries Society of the British Isles J Fish Biol. 2021;98:1196–1201. wileyonlinelibrary.com/journal/jfb