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Bizarre newt sticks ribs out of body for protection

24/08/2009 22:34:43

P. waltl releases a viscous milky and poisonous secretion onto the skin (a). Arrows show areas of high secretory activity, P. waltl holds a posture stretching the skin (b) to the point of penetration by the sharply pointed rib tips (indicated by arrows).

Newt forces rib points out of body to act like spines

Courtesy of Egon Heiss of the University of Vienna

August 2009. The Spanish ribbed newt Pleurodeles waltl displays a bizarre defensive mechanism against predators. X-ray analysis before and after a simulated threat shows that this newt can rotate its ribs until they project from the animal's body. 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.

Skeleton of a Spanish newt showing the rib points that are forced through the skin.

Microscopy shows the micro-anatomy, and computed tomography shows the 3D morphology of these unusual weapons. They are ‘spear-shaped' 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 by every anti-predator posturing. This investigation provides new insight into the functionality of a highly complex, integrated and unusual defensive strategy.

Radiographs showing anterior rotation of ribs from before (a) to after (b) a mildly threatening stimulus of the same animal. Journal of Zoology ]] (2009) 1–7 c 2009 The Authors. Journal compilation c 2009 The Zoological Society of London.

Poisonous secretions
Remarkably, the same newts have another defence mechanism. They have several special glands that are especially concentrated in body parts that are presented to an attacking predator and produce repellent poisonous substances to thwart potential aggressors.

Click here to see the full paper on the ribs.

Click here to see the full paper on the poison glands.

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