191 Light-induced changes in pigmenta ion through ontogeny in cane toad tadpoles ( Rhinella marina ) Lynne E. Beaty 1 , Kwesi Nyarko 2 & Ximena E. Bernal 3,4 1 Department of Zoology, Oklahoma State University, Sillwater, Oklahoma, USA 2 Department of Biological Sciences, Texas Tech University, Lubbock, Texas, USA 3 Department of Biological Sciences, Purdue University, West Lafayete, Indiana, USA 4 Smithsonian Tropical Research Insitute, Gamboa, Republic of Panama Herpetological Journal SHORT NOTE Correspondence: Lynne E. Beaty (lynne.beaty@okstate.edu) Volume 25 (July 2015), 191–195 Published by the Briish Herpetological Society Light-induced pigmentaion changes are widespread among tadpole species. In this study we characterised light-induced changes in melanin dispersion through development in cane toad tadpoles (Rhinella marina). We describe a patern of light-induced pigmentaion change in which tadpoles are darker in the presence of light and lighter in darkness unil the onset of metamorphosis. This patern contrasts with that of other non-bufonid tadpole species, but mimics the patern of pigment change exhibited by embryonic anurans. We discuss our results in light of the ontogeneic changes in toxicity to evaluate the photoresponse of cane toad tadpole pigments as a potenial aposemaic signal, neotenic trait, and thermal adaptaion. Key words: aposemaic, Bufo marinus, camoulage, melanophore, ontogeny, pigment changes, toxicity C olour and pigmentation are used by animals in a variety of contexts. While many organisms develop colouraion paterns that are ixed throughout their life, individuals of some species have the ability to change their colouration in response to, for example, higher predaion risk (reviewed in Caro, 2005) and changing environmental condiions (Garcia et al., 2003, 2004; Kats & van Dragt, 1986). Among vertebrates, colour change can be achieved physiologically by acively moving the pigment within chromatophores (known as metachrosis) or morphologically by altering the amount of pigment in chromatophores or the number of chromatophores present in the integument (Oshima, 2001). Within physiological colour change, the movement of pigments may be driven by photo receptors such as eyes (secondary colour response; Oshima, 2001), or by photosensiive pigments found within chromatophores (primary colour response; Laurens, 1915; Bagnara, 1965). Melanin, a brown-black pigment, is a common light-sensitive pigment involved in colour changes of ectothermic vertebrates. The aggregaion of melanin into the centre of melanophores results in skin lightening, while its dispersal makes the skin appear darker (Visconti & Castrucci, 1993). Light-induced change in tadpole pigmentation, a primary colour response, corresponds with diel light cycles and is widespread throughout anuran taxa (Bagnara & Hadley, 1973; Altig & McDiarmid, 1999a; Viertel & Richter, 1999). Such light-induced pigmentaion changes, however, are not constant throughout development. In many anuran species, embryos exposed to light appear dark given the induced changes in melanin dispersion (e.g., Xenopus laevis, Obika & Bagnara, 1963), while later- stage tadpoles from the same species appear dark in the absence of light (Bagnara, 1974; Binkley et al., 1988). This pigmentaion change is thought to prevent the relecion of moonlight of the tadpoles’ lower layer of iridophores at night, increasing crypicity (van der Lek, 1967). In this study, we investigate how light-induced pigmentaion changes of cane toad (Rhinella marina) tadpoles vary through ontogeny. The black colouraion of cane toad tadpoles has been proposed to be an aposemaic signal linked to their unpalatability to most predators (Wassersug, 1971; Peterson & Blaustein, 1991). Conspicuous black colouraion in the presence of light, however, is unexpected given that other non- bufonid tadpole species appear lighter in the presence of light. We experimentally invesigate the photoresponse of cane toad tadpole colouraion. We report an unusual pattern of light-induced colouration changes, and discuss potenial causes underlying this patern within aposemaic, neotenic and thermal frameworks. Cane toads are a large (up to 1.25 kg, 230 mm) neotropical bufonid whose naive range extends from central Brazil to southern Texas (Zug & Zug, 1979), and have been introduced to many locaions in the Paciic and Caribbean (Lever, 2001). Tadpoles for this study were originally bought from Carolina Biological Supply, bred from adults collected from introduced populaions in Florida. Female cane toads are highly fecund, with each female producing up to 84,000 eggs (Lampo & Medialdea, 1996). The eggs hatch within 24–72 hours, and tadpoles