The influence of three algal filtrates on the grazing rate of larval oysters ( Crassostrea gigas), determined by fluorescent microspheres

• Published in: Aquaculture Vol. 119; no. 2; pp. 237 - 247
• Main Authors: Thompson, Peter A., Montagnes, David J.S., Shaw, Barbara A., Harrison, Paul J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.01.1994; Elsevier Science; Elsevier Sequoia S.A
• Subjects: ALGAE; Animal aquaculture; Animal productions; Aquaculture; Biological and medical sciences; CONCHYLICULTURE; CRASSOSTREA GIGAS; CRIA DE MOLUSCOS; Fundamental and applied biological sciences. Psychology; Gonyaulax grindleyi; Invertebrate aquaculture; LARVAE; LARVAS; LARVE; Marine; MOLLUSC CULTURE; Mollusca; Oysters; Thalassiosira pseudonana; Thalassiosira pseudonana; Animal feeding; Algae; Filtrate; Phaeodactylum tricornutum; Chrysophycophyta; Feeding; Marine environment; Larva; Bivalvia; Food intake; Animal plant relation; Phytoplankton; Inhibition; Invertebrata; Mollusca; Crassostrea gigas; Thallophyta; Aquaculture
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/0044-8486(94)90178-3

Fluorescently labelled microspheres (FLMs) were used to measure the grazing rates of 6- to 12-day-old larval oysters. FLMs were mixed in a 1:1 ratio with algal cells and fed to the oysters at different concentrations. Ingested FLMs were enumerated using epifluorescent microscopy. FLMs were good tracers of algal grazing rates and experiments with FLMs were easy and rapid to conduct and required very little apparatus. Tests were conducted to determine if filtrates from three microalgae species inhibited feeding. Filtrates from dense cultures were tested against controls (containing no filtrates) for their impact on the grazing rates of larvae. The grazing rates of Crassostrea gigas larvae were significantly reduced when the animals were exposed to filtrates from Phaeodactylum tricornutum and Gonyaulax grindleyi. Filtrate from dense cultures of Thalassiosira pseudonana did not reduce grazing rates. Grazing rate ( G) versus particle concentration ( c, microspheres and T. pseudonana in a 1:1 mixture) was fitted to the equation G = (G max ·c) (K c+c) . The concentration required to reach half the saturating rate of particle grazing ( K c ) was 24 particles μl −1 and the maximum grazing rate ( G max) was 0.415 particles min −1.