Araujo, RafaelCampos, MiguelFeo, CarlesVarela Dopico, CatuxaSoler, JoaquínOndina Navarret, María Paz2024-01-192024-01-192018Araujo R., Campos M., Feo C., Varela C., Soler J., Ondina P. (2017). Who wins in the weaning process? Juvenile feeding morphology of two freshwater mussel species. Journal of morphology, 279 (1): 4-16.http://hdl.handle.net/10347/31901This is the pre-peer reviewed version of the following article: Araujo, R; Campos, M., Feo, C., Varela, C., Soler, J., Ondina, P. (2020). Who wins in the weaning process? Juvenile feeding morphology of two freshwater mussel species. Journal of Morphology, which has been published in final form at https://doi.org/10.1002/jmor.20748. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.The global decline of freshwater mussels can be partially attributed to their complex life cycle. Their survival from glochidium to adulthood is like a long obstacle race, with juvenile mortality as a key critical point. Mass mortality shortly after entering into a juvenile state has been reported in both wild and captive populations, thus weakening the effective bivalve population. A similar phenomenon occurs during metamorphosis in natural and hatchery populations of juvenile marine bivalves. Based on a morphological analysis using scanning electron microscopy of newly formed juveniles of the freshwater species Margaritifera margaritifera (L.)(Margaritiferidae) and Unio mancus Lamarck (Unionidae), we show that a second metamorphosis, consisting of drastic morphological changes, occurs that leads to suspension feeding in place of deposit feeding by the ciliated foot. We hypothesize that suspension feeding in these two species improves due to a gradual development of several morphological features including the contact between cilia of the inner gill posterior filaments, the inner gill reflection, the appearance of the ctenidial ventral groove and the formation of the pedal palps. Regardless of the presence of available food, a suspension feeding mode replaces deposit feeding, and juveniles unable to successfully transition morphologically or adapt to the feeding changes likely perish.engAttribution-NonCommercial-NoDerivatives 4.0 Internacionalhttp://creativecommons.org/licenses/by-nc-nd/4.0/Biodiversity conservationDevelopmentJuvenile mortalityMetamorphosisjournal article10.1002/jmor.20748open access