Anuran Vocal Communication: Effects of Genome Size, Cell Number and Cell Size

Significant variation in genome size occurs among anuran amphibians and can affect cell size and number. In the gray treefrog complex in North America, increases in cell size in autotriploids of the diploid (Hyla chrysoscelis) altered the temporal structure of mate-attracting vocalizations and auditory selectivity for these properties. Here, we show that the tetraploid species (Hyla versicolor) also has significantly fewer brain neurons than H. chrysoscelis. With regard to cell size in tissues involved in vocal communication, spinal motor neurons were larger in tetraploids than in diploids and comparable to differences in erythrocyte size; smaller increases were found in one of the three auditory centers in the torus semicircularis. Future studies should address questions about how environmental conditions during development affect cell numbers and size and the causal relationships between these cellular changes and the vocal communication system.