Larval pigmentation patterns of closely related newt species (Triturus cristatus and T. dobrogicus) in laboratory conditions

Abstract

Triturus cristatus (Laurenti, 1768) and T. dobrogicus (Kiritzescu, 1903) belong to a monophyletic closely related group of crested newts (Wielstra & Arntzen 2011). Triturus cristatus is widely distributed across Europe, while T. dobrogicus distribution is restricted to the valleys within the Danube River system. Triturus dobrogicus and, to a lesser extent, T. cristatus, inhabit permanent large water bodies T. dobrogicus can be even found in slow running waters (e.g. Arntzen 2003). These two species come in contact and hybridize (Mikuliček et al. 2012) along the contact zone of their ranges, from Ukraine on the east to the Czech Republic on the west (Arntzen et al. 2014). Identifying adults of Triturus species based on external morphology rely on their divergence in body size and shape (e.g., Arntzen & Wallis 1999, Jehle et al. 2011, Vukov et al. 2011), as well as on external qualitative traits (black dots on the ventral side of the head and body), which have been proven to be useful in discrimination of crested newt species (e.g., Arntzen & Wallis 1999). However, little is known about morphological differentiation of crested newt species at the larval stage (Schmidt & Van Buskirk 2005). The Triturus larvae can be easily recognized and distinguished from those of other European newts by having three pairs of external and protruding gills, which extend from either side of the neck like feathery plumes, and by having long toes and tapering tail fin with irregular black spots (Griffiths 1996, Arnold & Ovenden 2002). So far, larvae of crested newt species are considered as being morphologically very similar (Arntzen 2003). Study of variation in body shape among crested newt larvae (Ivanović et al. 2011) found that larvae, like adults and freshly metamorphosed juveniles (Vinšálková & Gvoždík 2007), differentiate in body shape (lateral head shape, interlimb distance). Here, we focused on larval pigmentation patterns of two crested newt species, Triturus cristatus and T. dobrogicus. Such qualitative traits would be helpful in species identification at larval stage.