Who wins in the weaning process? Juvenile feeding morphology of two freshwater mussel species

Comunicación dada en: euromal - 8th European Congress of Malacological Studies (10-14 September 2017, Kraków, Poland).
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 effec - tive bivalve population. A similar phenomenon oc - curs during metamorphosis in natural and hatchery populations of juvenile marine bivalves. Based on a morphological analysis of newly formed juveniles of the freshwater species Margaritifera margaritifera (Margaritiferidae) and Unio mancus (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 hypothesise that suspension feed - ing in these two species develops and improves grad - ually due to 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 transi - tion morphologically or adapt to the feeding changes perish.