Vol.:(0123456789) 1 3 Zoomorphology https://doi.org/10.1007/s00435-018-0427-6 ORIGINAL PAPER Comparative investigation into the morphology of oral papillae and denticles of four species of lamnid and sphyrnid sharks Bianca de Sousa Rangel 1  · Thierry Salmon 2  · Aline Nayara Poscai 3  · José Roberto Kfoury Jr 2  · Rose Eli Grassi Rici 4 Received: 27 August 2018 / Revised: 16 November 2018 / Accepted: 22 November 2018 © Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract The microstructures of the oral cavity in sharks have received relatively little study, despite their potential functional impor‑ tance for gustation, feeding, and ventilation. Accordingly, here we conducted a preliminary comparative investigation into the structure and organization of oral papillae and denticles found on the ventral surface of the oral cavity in four species of shark (bigeye thresher, shortfn mako, scalloped hammerhead, and smooth hammerhead). Despite a limited sample size, diferences in complexity and ornamentation of oral papillae and denticles were found across the four species. The scal‑ loped hammerhead shark exhibited the largest oral papillae compared to the bigeye thresher and the shortfn mako. The most complex oral denticles, in terms of number of ridges and microstructures, were found in the scalloped hammerhead, followed by the bigeye thresher, smooth hammerhead and shortfn mako. For smooth hammerheads, in which samples were available from both juveniles and adults, diferences in denticle microstructures were found suggesting possible ontogenetic variations. These results suggest that shape, size and arrangement of oral papillae and denticles may be related to ecology and phylogeny of the species studied. Based on these emerging patterns we discuss several plausible hypotheses relating to the function of these structures for consideration in future studies. Keywords Ecomorphology · Gustation · RAM ventilation · Apex predators · Feeding ecology Introduction It is widely known that sharks present highly developed sen‑ sory specializations for olfaction, vision, electroreception, lateral line, vestibular control, gustation, and somatosensa‑ tions (temperature and touch) (Collin 2012; Gardiner et al. 2012). Such sensory systems are especially important for behavioral activities such as feeding, avoiding predators, spatial orientation, social interactions, navigation, among others which play a signifcant role in their survival and lon‑ gevity (Collin 2012). Although the sensory biology of sharks is well studied, the gustatory system has received relatively less attention, despite its likely importance in prey selection and capture (Atkinson and Collin 2010; Collin 2012; Rangel et al. 2017). Taste modality in sharks is mediated by oral papillae (composed of gustatory receptor cells) distributed along the ventral and dorsal epithelium of the oropharyngeal cav‑ ity, gill arches, gill rakers, but are more abundant on the jaw (maxillary and mandibular valve). Through direct con‑ tact, oral papillae allow sharks to evaluate the suitability of potential prey, leading to ingestion or rejection of the item (Atkinson and Collin 2010; Collin 2012; Kirino et al. 2013; Atkinson et al. 2016). The oral papillae appear to develop early in shark embryos, for example, Prionace glauca and Chiloscyllium punctatum, and are functional before birth or on emergence from the egg case (Atkinson et al. 2016; Ran‑ gel et al. 2017). These papillae increase in size and decrease * Bianca de Sousa Rangel biarangel.sharks@gmail.com 1 Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, Travessa 14, no 321, São Paulo, SP 05508‑090, Brazil 2 Departamento de Cirurgia da Faculdade de Medicina Veterinária e Zootecnia da Universidade de São Paulo, Rua Professor Orlando Marques Paiva, s/n, São Paulo, SP 05508‑270, Brazil 3 Laboratório de Pesquisa em Elasmobrânquios da Universidade Estadual Paulista Julio de Mesquita Filho, Praça Infante Dom Henrique, s/n, São Vicente, SP, Brazil 4 Central de Facilidades à Pesquisa da Faculdade de Medicina Veterinária e Zootecnia da Universidade de São Paulo, Rua Professor Orlando Marques Paiva, s/n, São Paulo, SP 05508‑270, Brazil