, 2009). These features include escape behaviour, cryptic coloration and structure, noxiousness or toxicity and encounter behaviour (Duellman & Trueb, 1994). Among urodeles, the family Salamandridae has the greatest diversity Erlotinib of antipredator mechanisms (Brodie Jr, Nussbaum & DiGiovanni,

1984). In the salamandrid genus Pleurodeles and in the closely related genus Echinotriton, unique strategies to decrease palatability and increase survival rates have been described (Nowak & Brodie Jr, 1978; Brodie Jr, 1983; Brodie Jr et al., 1984). When attacked by a potential predator (or provoked with an adequate artificial stimulus), sharp spines appear on the lateral trunk sides. This phenomenon was first mentioned in Pleurodeles waltl by Leydig (1879). This author examined preserved and living material and rebutted earlier (orally referred) notions that the lateral spines of

this animal were horny structures. Leydig suggested that the lateral spines of P. waltl are ribs that lie in a lymphatic sheath immediately beneath the skin. A study performed 99 years later by Nowak & Brodie Jr (1978) yielded similar conclusions. The present study shows new information on the morphological and functional integration of the body wall and the ribs. It also provides new data on how P. waltl protrudes its ribs and on the mechanism in the framework of the antipredator behaviour. We apply photo- and X-ray imaging along with computed tomography (CT) to examine the (micro-) anatomical features of the ribs and histological techniques RAD001 mw to study the emersion point of the ribs. We also discuss possible mechanisms preventing self-intoxication or microbial infection that could result from damaging the integrity of the skin. In this context, it is important to clarify whether the tips of the ribs learn more really penetrate the skin or remain covered by integument.

If the rib tips are uncoated, it should be determined whether the skin of P. waltl shows distinct and permanent pores or whether the body wall is penetrated de novo by every single antipredator posturing. Five male and four female adult (3–5 years old) P. waltl were used in the present study. The animals were obtained commercially and kept in a 300 L tank with a 12-h dark/12 h light cycle and fed with larval chironomids, earthworms and fish pieces. For behavioural experiments, the reactions to ‘predator-like stimulations’ were documented using a Canon EOS 350D digital camera (Canon Inc., Tokyo, Japan). To simulate a predator attack, the animals were touched repeatedly – but gently – with a cotton bud until they showed defensive behaviour. The animals recovered rapidly after the experiments and all showed natural behaviour such as feeding or mating immediately after the experiments. For radiographic analyses, dorsoventral radiographs were made with a Siemens Polydoros 80 S machine (Siemens AG, Munich, Germany).