Articulation and growth of skeletal elements in balanid barnacles (Balanidae, Balanomorpha, Cirripedia) Checa González, Antonio G. Salas, Carmen Rodríguez-Navarro, Alejandro Grenier Romero, Cristian Lagos, Nelson Biomineralization Barnacle Plate Growth Structure Morphology The morphology and ultrastructure of the shells of two balanid species have been examined, paying special attention to the three types of boundaries between plates: (i) radii-parietes, (ii) alae-sheaths, and (iii) parietes-basal plate. At the carinal surfaces of the radii and at the rostral surfaces of the alae, there are series of crenulations with dendritic edges. The crenulations of the radius margins interlock with less prominent features of the opposing paries margins, whereas the surfaces of the longitudinal abutments opposing the ala margins are particularly smooth. The primary septa of the parietes also develop dendritic edges, which abut the internal surfaces of the primary tubes of the base plates. In all cases, there are chitino-proteinaceous organic membranes between the abutting structures. Our observations indicate that the very edges of the crenulations and the primary septa are permanently in contact with the organic membranes. We conclude that, when a new growth increment is going to be produced, the edges of both the crenulations and the primary septa pull the viscoelastic organic membranes locally, with the consequent formation of viscous fingers. For the abutting edges to grow, calcium carbonate must diffuse across the organic membranes, but it is not clear how growth of the organic membranes themselves is accomplished, in the absence of any cellular tissue. 2019-11-15T09:12:55Z 2019-11-15T09:12:55Z 2019 journal article Checa AG, Salas C, Rodríguez- Navarro AB, Grenier C, Lagos NA. 2019 Articulation and growth of skeletal elements in balanid barnacles (Balanidae, Balanomorpha, Cirripedia). R. Soc. open sci. 6: 190458. http://hdl.handle.net/10481/57911 10.1098/rsos.190458 eng http://creativecommons.org/licenses/by/3.0/es/ open access Atribución 3.0 España The Royal Society Puplishing