Sensory Systems in Sawfishes. 1. The Ampullae of Lorenzini

Abstract

The distribution and density of the ampullary electroreceptors in the skin of elasmobranchs are influenced by the phylogeny and ecology of a species. Sensory maps were created for 4 species of pristid sawfish. Their ampullary pores were separated into pore fields based on their innervation and cluster formation. Ventrally, ampullary pores are located in 6 areas (5 in Pristis microdon), covering the rostrum and head to the gills. Dorsally, pores are located in 4 areas (3 in P. microdon), which cover the rostrum, head and may extend slightly onto the pectoral fins. In all species, the highest number of pores is found on the dorsal and ventral sides of the rostrum. The high densities of pores along the rostrum combined with the low densities around the mouth could indicate that sawfish use their rostrum to stun their prey before ingesting it, but this hypothesis remains to be tested. The directions of ampullary canals on the ventral side of the rostrum are species specific. P. microdon possesses the highest number of ampullary pores, which indicates that amongst the study species this species is an electroreception specialist. As such, juvenile P. microdon inhabit low-visibility freshwater habitats.

Habitat use and site fidelity of neonate and juvenile green sawfish Pristis zijsron in a nursery area in Western Australia

“…Preliminary data suggest that P. zijsron possess the least intricate lateral line system (used for mechanoreception of prey, orientation, and predator avoidance) of all 4 Australian sawfishes (Wueringer et al 2011a). P. zijsron has a much lower number of ampullae of Lorenzini (a close-range sensory system) on both the ventral and dorsal surface of the head compared to P. pristis, which is an electroreception specialist in turbid estuaries and freshwaters (Wueringer et al 2011b). Thus, the absence of acoustic detections from the Ashburton River estuary and Hooley Creek during flooding periods may have been due to an avoidance of the highly turbid waters, which may have reduced feeding efficiency, and increased predation risk.…”

What Is the Fate of Amputee Sawfish?

“…The medial canal, which is the largest and present in all species, represents an elongation of the brain cavity (Hoffmann 1912). The rostrum is covered in a dense array of electroreceptors (ampullae of Lorenzini), and between 80% and 84% of all receptors are restricted to the rostrum in the three species assessed by Wueringer et al (2011).…”

The Neuroecology of Cartilaginous Fishes: Sensory Strategies for Survival

“…) and new data from a further 35 spp.) has revealed that rays exhibit a high proportion of ventrally located electrosensory pores, with dense clusters around the oral region, which may assist in guiding the mouth during the final phase of the feeding strike [Raschi, 1986;Jordan, 2008;Wueringer et al, 2011a;Kempster et al, 2012]. Pore distribution is significantly different between orders, as is pore abundance, with the Myliobatiformes exhibiting the highest proportion of ventral pores and the Pristiformes the highest total abundance of pores [Jordan, 2008;Marzullo et al, 2011;Wueringer et al, 2011;Kempster et al, 2012;Wueringer, this issue] ( fig.…”