“How reversible is development? Contrast between developmentally plastic gain and loss of segments in barnacle feeding legs”.
Tomonari Kaji and A. Richard Palmer. 2017. Evolution, 71: 756–765. doi:10.1111/evo.13152
Barnacles (Balanus glandula) are well known for developmental plasticity of feeding leg appendages in response to wave-exposed versus wave-protected environments (Marchinko 2003; Neufeld 2012). This plastic change in leg length is achieved by changes in both shape and number of leg segments, and functions to improve feeding ability under different water flow regimes.
Barnacles were reciprocally transplanted between low- and high-wave exposed areas, and sequential exuvium from known individuals were examined over successive moults, using confocal laser scanning microscopy. Segment additions occurred relatively rapidly near the limb base, whereas segment loss (fusion of segments) took longer, and occurred throughout the leg.
Asymmetrical gain and loss of barnacle feeding appendages, in terms of ease or time lag of development, identifies a new cost associated with developmentally plastic change.
Figure 1B segment addition; Figure 1D segment fusion. Kaji & Palmer 2017