Acquisition of new genes often results in the emergence of novel
functions and is a key step in lineage-specific adaptation. As the only
group of sessile crustaceans, barnacles establish permanent attachment
through initial cement secretion at the larval phase followed by
continuous cement secretion in juveniles and adults. However, the
origins and evolution of barnacle larval and adult cement proteins
remain poorly understood. By performing microdissection of larval cement
glands, transcriptome and shotgun proteomics and immunohistochemistry
validation, we identified 30 larval and 27 adult cement proteins of the
epibiotic turtle barnacle Chelonibia testudinaria, of which the majority
are stage- and barnacle-specific. While only two proteins, SIPC and
CP100K, were expressed in both larvae and adults, detection of protease
inhibitors and the cross-linking enzyme lysyl oxidase paralogs in larvae
and adult cement suggested functional convergence. Other barnacle
specific cement proteins such as CP100k and CP52k likely share a common
origin dating back at least to the divergent of Rhizocephala and
Thoracica. Different CP52k paralogs could be detected in larval and
adult cement, suggesting stage-specific cement proteins may arise from
duplication followed by changes in expression timing of the duplicates.
Interestingly, the biochemical properties of larval- and adult-specific
CP52k paralogs exhibited remarkable differences, reflecting the
composition of cement in different life stages of turtle barnacle might
be chemically different. We conclude that de novo gene formation and
duplicate neofunctionalization are pivotal to the evolution of
lineage-specific cement toolkits in barnacles, which may explain how
barnacles can inhabit diverse marine substrata.