Hurt yourself to hurt your enemy: new insights on the function of the bizarre antipredator mechanism in the salamandridPleurodeles waltl

Abstract

The Spanish ribbed newt Pleurodeles waltl shows a bizzare defensive mechanism against predators. X-ray analysis before and after a simulated threat shows that this newt rotates its ribs anteriorly. The maximum measured angle to which the ribs moved was 651. This forward movement causes the sharply pointed rib tips to lacerate the body wall and project freely from the sides of the trunk as spines. Light microscopy shows the microanatomy, and computed tomography shows the 3D morphology of these unusual weapons. They are 'spear-shaped' and hollow proximally, massive distally and are connected to the corresponding vertebra by a well-developed, two-headed joint. The skin in the penetration areas lacks permanent pores through which the ribs could be projected and is pierced de novo by every antipredator posturing. This investigation provides new insight into the functionality of a highly complex, integrated and unusual defensive strategy.

Venomous Frogs Use Heads as Weapons

“…There are other amphibians that probably should be considered as venomous, including salamanders with ribs that pierce through the skin (Echinotriton and Pleurodeles) [10][11][12] and frogs with spines in the head region (Diaglena spatulata [13], Anotheca spinosa [14], and Polypedates ranwellai [15]), but information on the toxicity of their skin secretions is lacking. Polypedates ranwellai belongs to a genus known to have tetrodotoxin in skin secretions [16], but tetrodotoxin has not been assessed in that species.…”

Mechanical properties and adaptations of some less familiar bony tissues

“…Perhaps most bizarre are the ribs of the newt Pleurodeles waltl. Ribs normally lie inside the body but this newt, if threatened, will push its pointed ribs through the body wall, the ribs becoming coated with poison as they go, resulting in a rather formidable object to contend with (Heiss et al, 2010). The part of the each rib that remains inside the body is hollow and fat filled.…”

Morphological and genetic differentiation of Bufo toads: two cryptic species in Western Europe (Anura, Bufonidae)

“…Toads in the B. bufo species group have no aposematic coloration, no particular odours and they do not bite. They have no elongated ribs with protruding epipleural processes as in the salamander Pleurodeles waltl Michahelles, 1830 that function as a concealed weapon, capable of actively piercing through the skin to hurt a predator, even if at the same time hurting itself (Leydig, 1879;Nowak and Brodie, 1978;Heiss et al, 2009). Bufo toads are poor jumpers and do not rely on escape behaviour to defer predators and also they do not use the 'Unken reflex' (Duellman and Trueb, 1986).…”