The use of pelvic fins for benthic locomotion during foraging behavior in Potamotrygon motoro (Chondrichthyes: Potamotrygonidae)

Akemi Shibuya,Marcelo R De Carvalho,Jansen Zuanon,Sho Tanaka

doi:10.1590/s1984-46702015000300001

Abstract

Synchronized bipedal movements of the pelvic fins provide propulsion (punting) during displacement on the substrate in batoids with benthic locomotion. In skates (Rajidae) this mechanism is mainly generated by the crural cartilages. Although lacking these anatomical structures, some stingray species show modifications of their pelvic fins to aid in benthic locomotion. This study describes the use of the pelvic fins for locomotory performance and body re-orientation in the freshwater stingray Potamotrygon motoro (Muller & Henle, 1841) during foraging. Pelvic fin movements of juvenile individuals of P. motoro were recorded in ventral view by a high-speed camera at 250-500 fields/s-1. Potamotrygon motoro presented synchronous, alternating and unilateral movements of the pelvic fins, similar to those reported in skates. Synchronous movements were employed during straightforward motion for pushing the body off the substrate as well as for strike feeding, whereas unilateral movements were used to maneuver the body to the right or left during both locomotion and prey capture. Alternating movements of the pelvic fins are similar to bipedal movements in terrestrial and semi-aquatic tetrapods. The pelvic fins showed coordinated movements during feeding even when stationary, indicating that they have an important function in maintaining body posture (station holding) during prey capture and manipulation. The use of pelvic fins during prey stalking may be advantageous because it results in less substrate disturbance when compared to movements generated by pectoral fin undulation. The range of pelvic fin movements indicates more complex control and coordination of the pelvic radial muscles.

Highlights

Contrasting with most sharks, which mainly use axial and caudal fin movements during locomotion, batoids tend to use undulation or oscillation of the pectoral fins as their primarily locomotory mode
This study describes the use of the pelvic fins for locomotory performance and body reorientation in the freshwater stingray Potamotrygon motoro (Müller & Henle, 1841) during foraging
They are known to play an important role in swimming and body maneuvering in batoids, especially during benthic locomotion (HOLST & BONE 1993, LUCIFORA & VASSALLO 2002, MACESIC & KAJIURA 2010, MACESIC et al 2013)

Summary

Introduction

Contrasting with most sharks, which mainly use axial and caudal fin movements during locomotion, batoids tend to use undulation or oscillation of the pectoral fins as their primarily locomotory mode. Even though the role of the pectoral fins during swimming is well documented in batoids, the specific role of the pelvic fins in the locomotion of many species is unknown They are known to play an important role in swimming and body maneuvering in batoids, especially during benthic locomotion (HOLST & BONE 1993, LUCIFORA & VASSALLO 2002, MACESIC & KAJIURA 2010, MACESIC et al 2013). GARRONE-NETO & SAZIMA (2009) observed that Potamotrygon motoro (Müller & Henle, 1841) and P. falkneri Castex & Maciel, 1963 in the field undulate their pectoral fins in the bottom to uncover buried prey They do not mention the movement of the pelvic fins, which may be employed during foraging to decrease disturbance of the benthos, allowing for prey detection by the lateral line canals (ROSENBERGER 2001, SHIBUYA et al 2010, 2012). Detailed observation of pelvic fin movements of stingrays in their natural habitats is frequently difficult due to the ventral location of these structures as well as the turbid waters

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