The eyes of larval T. spelaeus grow by negative allometry, but in allometric coefficients they are not greatly different from E. lucifuga. The major differences in eye size, both absolute and relative to body size, between T. spelaeus and E. lucifuga are established prior Io the larval growth period. The eyes of T. spelaeus cease to grow at metamorphosis and are reduced in size thereafter. In addition, there is increased individual variability and bilateral asymmetry of eye size in adult T. spelaeus compared to both adult E. lucifuga and larval T. spelaeus. This variability, expressed as relative dispersion about mean eye size, is significantly greater than in E. lucifuga, and appears to result from three factors: 1) postmetamorphic cessation of eye growth, 2) wide variation in body size and eye size at metamorphosis, and 3) postmetamorphic shape changes and reduction of eye size.
Besharse, Joseph C. and Ronald A. Brandon.
Size and growth of the eyes of the troglobitic salamander Typhiotriton spelaeus.
International Journal of Speleology,
Available at: https://digitalcommons.usf.edu/ijs/vol6/iss3/7