Tightly shut: flexible valve margins and microstructural asymmetry in pterioid bivalves
Metadatos
Mostrar el registro completo del ítemEditorial
Spinger Heidelber
Fecha
2020-05-06Referencia bibliográfica
Harper, E. M., & Checa, A. G. (2020). Tightly shut: flexible valve margins and microstructural asymmetry in pterioid bivalves. [https://doi.org/10.1007/s00227-020-03693-y]
Patrocinador
Instituto de Salud Carlos III Spanish Government CGL2013-48247-P CGL 2017-85118-P; Junta de Andalucía RNM363; Unidad Científica de Excelencia of the University of Granada UCE-PP2016-05Resumen
An organic-rich columnar prismatic outer shell layer, which extends far beyond the underlying nacre, has allowed pterioid
bivalves (the pearl oysters and their allies) to develop flexible valve margins, allowing a tight hermetic seal when shut. In some
taxa, the microstructural arrangement is known to be asymmetrically developed between the two valves. The asymmetry was
surveyed across 29 taxa of pterioids (including representatives of known genera) confirming that it is typically the right valve
which has a greater expanse of prism-only shell (and less nacre) and showing that this portion of the right valve has more
organic content (more than twice the value in some instances) than the equivalent in the left. A more detailed investigation
of prismatic material in Pteria penguin comparing the right and left valves revealed that the right valve flange has a higher
density of smaller prisms, each with its organic envelope, and not a greater thickness of the organic envelopes themselves.
The flange is also thinner on the right valve and shown here to be very flexible when wet. This allows it to bend against the
rigid left valve when the shell is closed. Comparison of this structural asymmetry in the pterioids with five outgroup taxa
in the Ostreidae and Pinnidae suggests that clades with the asymmetry have been freed from the constraints of a flattened
valve morphology and to develop inequivalved forms.