Ecomorphology of oral papillae and denticles of Zapteryx brevirostris (Chondrichthyes, Rhinobatidae)

Abstract

Elasmobranchs have an impressive range of highly specialized sensory systems shaped over 400 million years of evolution. The morphological analysis of oral papillae and denticle in elasmobranchs elucidates the biological role that these structures play during feeding and ventilation, bringing important descriptive information about ecological implications in an evolutionary context. The present study provides descriptions of the distribution patterns, histological characteristics and three-dimensional aspects of oral papillae and denticles in the lesser guitarfish Zapteryx brevirostris, through light microscopy and scanning electron microscopy. The presence of oral denticles in the oropharyngeal cavity suggests that this structure may have the following functions: protect against abrasion and parasites, increase the ability to grasp and hold prey and assist in reduction in hydrodynamic drag. The denticles in Z. brevirostris are similar to those found in pelagic sharks with forced ventilation (RAM). The structural conformity of denticles observed in the gill slits may facilitate water flow during prey grasp and food processing. This study supports the hypothesis that these structures may be an adaptive reflection shaped by feeding habits, capture strategies and processing prey.

A preliminary investigation into the morphology of oral papillae and denticles of blue sharks (Prionace glauca) with inferences about its functional significance across life stages

“…In terms of design, hexagonal ornaments restricted to the ventral and dorsal anterior portion of the crown (simpler) were observed in the oral denticles. The disposition of these structures in the crown of denticles varies between species and may have different patterns (Ciena et al 2015;Rangel et al 2016). The absence or reduction of denticle ornaments is considered a plesiomorphic feature for the group (Mello et al 2011), being absent in basal species such as Rhinobatos horkelii (Rhinobatiformes) and Zapteryx brevirostris (Rangel et al 2016).…”

“…In addition to the papillae, oral denticles are also found in the oropharyngeal cavity of all sharks and guitarfishes studied so far (Nelson, 1970;Atkinson & Collin, 2012;Rangel et al 2016). In some species, they fill the entire surface, protecting against abrasion during food consumption, increasing adhesion during prey intake and assisting in the reduction of hydrodynamic drag (Atkinson & Collin, 2010, 2012.…”

Microstructural morphology of dermal and oral denticles of the sharpnose sevengill shark Heptranchias perlo (Elasmobranchii: Hexanchidae), a deep‐water species

“…This morphotype has been described in other shark species, such as Prionace glauca (Rangel et al, ), Isurus oxyrinchus , Alopias superciliosus , Sphyrna spp. (Rangel et al, ), Rhizoprionodon lalandii (Ciena et al, ), and some batoid species (e.g., Zapteryx brevirostris , Rangel et al, ; Aptychotrema rostrata , Atkinson & Collin, ). The reduction of hydrodynamic drag may be mainly beneficial for pelagic sharks, including sharpnose sevengill, which have RAM ventilation (i.e., the water flows through the mouth during swimming; Atkinson & Collin, ; Rangel et al, ).…”

“…The reduction of hydrodynamic drag may be mainly beneficial for pelagic sharks, including sharpnose sevengill, which have RAM ventilation (i.e., the water flows through the mouth during swimming; Atkinson & Collin, ; Rangel et al, ). Additionally, other functions of oral denticles have been suggested, including protection of the oral epithelium from parasites and injury caused by food items, and to facilitate food retention (Atkinson & Collin, ; Rangel et al, ).…”

“…(e, f, i) 100 μm [Color figure can be viewed at wileyonlinelibrary.com] have been suggested, including protection of the oral epithelium from parasites and injury caused by food items, and to facilitate food retention (Atkinson & Collin, 2012;Rangel et al, 2016).…”