The effects of seawater acidity induced by intraspecific competitor on food ingestion behavior of the white Pacific shrimp Litopenaeus vannamei were investigated. By using shrimp biomass as a proxy of their body odor concentration, food ingestion responses of the shrimp, as influenced by conspecific excreta-borne chemical cues, were monitored. The treatments produced pH variations, which in turn, affected ingestion responses. The effect of conspecific chemical cues on foraging behavior was monitored while presenting pelleted food amounting to 5% of the shrimp biomass. In aged seawater (ASW) containing chemical cues from conspecifics, L. vannamei food ingestion rose with increasing body odor concentration. The hypothesis that food ingestion is mediated by chemical cues excreted or secreted by shrimps was supported. Water acidification, however, as a result of shrimp soluble excreta, seemed to counteract the effect of those chemical cues. During the 24 h of shrimp fasting, acidification of odorless ASW increased with increasing shrimp biomass, from pH 8.08 to 7.90. After 2-h feeding, the same experimental set gained body odors generated during the feeding period and pH decreased to 7.2. Results show that, to an increase in ASW acidity corresponds an increase in food ingestion rate to those values observed for odorless ASW.
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Vol. 35 • No. 1