MEPS 161:93-101 (1997)  -  doi:10.3354/meps161093

Although recent studies have found that some invertebrate larvae can meet part of their metabolic needs through bacterivory, it is unclear to what extent bacterivory can compensate for reduced phytoplankton abundance. The present study determined whether larvae of a polychaete (Hydroides elegans)and a barnacle (Balanus amphitrite)can survive, grow, and develop to competence solely on a diet of bacteria. In laboratory experiments, H.elegans larvae provided with bacteria as their sole particulate food source completed larval development, attached, and metamorphosed into healthy early juveniles. In addition, several of these juveniles, when provided with phytoplankton after metamorphosis, developed to maturity and spawned viable offspring. Bacterial abundances measured in Port Shelter, a bay in Hong Kong waters where organisms for the present study were collected, would not sustain maximum development rates of H.elegans larvae. However, bacterial abundances were sufficiently high and consistent over time to constitute a reliable food source. Consequently, starvation may not be a direct cause of larval mortality in this species. On the other hand, B.amphitrite larvae provided with bacteria did not grow, and death occurred at the same age as in starved larvae, suggesting they cannot use bacteria as a supplementary food source. Available data suggests that most barnacle recruitment in Hong Kong waters occurs when phytoplankton abundance reaches peak levels. Recruitment of H.elegans, however, occurs throughout the year, suggesting that spawning and successful larval development may be independent of phytoplankton availability, and that larvae largely rely on alternate food sources such as bacteria.

Bacteria · Growth · Survival · Size at competence · Larval development · Feeding · Starvation