Meeting Abstract
Barnacles inhabit a wide range of habitats. While evolution and functional morphology of the sessile adults are well studied, little attention have been given to that of the planktonic larval stages, especially the nauplius. We performed the first meta-analysis on outlines of barnacle nauplii head shield. A total of 103 species were analyzed with normalized elliptic Fourier analysis. Principal component analysis showed that most species were distributed around the center of a shared morphospace but a few minor groups occupied the periphery and contributed the most to the overall shape variance. The peripheral groups include the lecithotrophic nauplii and the large Lepadidae nauplii with exaggerated morphology. We hypothesize that trophic mode is important in morphological evolution of barnacle nauplii and drives the nauplii to deviate from the ‘generalized’ shape. To tease apart the effect of allometry on naupliar morphology, we decomposed the overall shape variation into common allometric component (CAC) and residual shape components (RSC). Feeding Lepadidae nauplii separated from the others along CAC, suggesting difference in habitats and/or evolutionary history might have accounted for the difference in size. RSC significantly explained the differentiation between lecithotrophic and planktotrophic nauplii. Visualization of shape changes along first RSC showed a change in length of frontal horns. Such shape change highlights the potential importance of frontal horns in feeding. Future detailed analysis of the function of such feature is much needed for it is unique to barnacle nauplii and used to support monophyly of barnacles.
