Morphology and function of the forelimb in arboreal frogs: specializations for grasping ability?

Abstract

Frogs are characterized by a unique morphology associated with their saltatory lifestyle. Although variation in the form and function of the pelvic girdle and associated appendicular system related to specialized locomotor modes such as swimming or burrowing has been documented, the forelimbs have typically been viewed as relatively unspecialized. Yet, previous authors have noted versatility in forelimb function among arboreal frogs associated with feeding. Here we study the morphology and function of the forelimb and hand during locomotion in two species of arboreal frogs ( Litoria caerulea and Phyllomedusa bicolor ). Our data show a complex arrangement of the distal forelimb and hand musculature with some notable differences between species. Analyses of high-speed video and video fluoroscopy recordings show that forelimbs are used in alternating fashion in a diagonal sequence footfall pattern and that the position of the hand is adjusted when walking on substrates of different diameters. Electromyographic recordings show that the flexors of the hand are active during substrate contact, suggesting the use of gripping to generate a stabilizing torque. Measurements of grasping forces in vivo and during stimulation experiments show that both species, are capable of executing a so-called power grip but also indicates marked differences between species, in the magnitude of forces generated. Stimulation experiments showed an increased control of digit flexion in the more specialized of the two species, allowing it to execute a precision grip paralleled only by that seen in primates.

In vivo bite and grip forces, morphology and prey-killing behavior of North American accipiters (Accipitridae) and falcons (Falconidae)

“…Although there exists a voluminous literature on grip force in the fields of kinesiology and physical anthropology, studies in non-primate vertebrates lag considerably behind those of bite force. Studies of grip force in some frogs (Manzano et al, 2008) and lizards (Abdala et al, 2009) have revealed insights into the role of gripping for arboreal locomotion, along with myological and physiological specializations for enhancing grip forces. The few published studies of in vivo grip force in raptorial birds have contributed substantially, by revealing mechanisms of prey capture and killing, and their implications for foraging behavior and ecology (e.g.…”

The specialisation of the third metacarpal and hand in arboreal frogs: Adaptation for arboreal habitat?

“…There are many arboreal frogs around the world, including most of the hylids, centrolenids, rhacophorids and hyperolids (Manzano et al, 2008). There are many arboreal frogs around the world, including most of the hylids, centrolenids, rhacophorids and hyperolids (Manzano et al, 2008).…”

A rare variant innervation of adductor pollicis muscle from median nerve in an adult cadaver in middle east: a case report

“…Ability to perform these complex movements is interpreted as an significant factor for the specialization of the forelimbs for locomotion. [1] Grays et al in 1997 described that adduction of the thumb towards the digits such that the palmar surfaces of the thumb and digit touch each other is required for a precision grip. Precision grip is thought to be used during locomotion and in the manipulation of some food items.…”