Cell size-based, passive selection of the blue diatom Haslea ostrearia by the oyster Crassostrea gigas

Fiddy Prasetiya (1) , Priscilla Decottignies (1) , Laurent Barillé (1) , Romain Gastineau (1) , Boris Jacquette (2) , Amandine Figiel (1) , Michèle Morançais (1) , Réjean Tremblay (2) , Jean-Luc Mouget (1) , Bruno Cognie (1)

1 MMS - Mer, molécules et santé EA 2160
2 UQAR - Université du Québec à Rimouski

Pre-ingestive selection has been identified as a feeding mechanism of oysters that may influence their uptake of particles and microalgal cells. Oysters can feed specifically on the pennate diatom Haslea ostrearia, which produces the blue pigment marennine that is responsible for the greening of oysters. Because the size of particles or cells plays a significant role in the selection process, and given that diatoms experience a decrease in size as a consequence of vegetative reproduction, H. ostrearia consumption and marennine uptake might be influenced by pre-ingestive selection. We examined the role of H. ostrearia cell size in the selective feeding of Crassostrea gigas. Individual flow-through chambers were used to deliver mixtures of H. ostrearia of varying cell length to oysters. Inflow, outflow and pseudofaecal samples were collected from chambers during oyster feeding. Video-endoscopy was used to sample material in the dorsal and ventral particle tracts. Diatom cells counts showed that pseudofaeces contained on average larger cells than the ambient medium. However, proportions of the different populations of H. ostrearia in pseudofaeces were identical to those in the ventral tracts, indicating that no selection was performed by the labial palps. Video-endoscopy, plus imaging by scanning electron microscopy, of gills and labial palps revealed that only those larger H. ostrearia that were orientated dorsoventrally could enter the principal filaments (pfs) and then access the dorsal acceptance tract. These results show that for particles like Haslea cells with only one axis exceeding the width of the pfs, the selection on the oyster gills is passive and based on cell size.

Domaines: Sciences du Vivant [q-bio]

Fiddy Prasetiya, Priscilla Decottignies, Laurent Barillé, Romain Gastineau, Boris Jacquette, et al.. Cell size-based, passive selection of the blue diatom Haslea ostrearia by the oyster Crassostrea gigas. Journal of Molluscan Studies, 2017, 83 (2), pp.145-152. ⟨10.1093/mollus/eyx012⟩. ⟨hal-03941995⟩