Carbon Assimilation and Digestive Toxicity in Naïve Grass Shrimp (Palaemonetes pugio) Exposed to Dietary Cadmium

Abstract

Naïve grass shrimp Palaemonetes pugio were pulse-fed cadmium-contaminated meals containing carbon-14, fluorescent or near-infrared markers and analyzed for carbon assimilation efficiency, gut residence time, feces elimination rate, extracellular digestive protease activity or gut pH. Carbon assimilation efficiency (~83%), minimum gut residence time (~435 min) and proventriculus pH (~5.29 to ~6.01) were not impacted significantly by cadmium ingestion. A dose-dependent decrease in feces elimination rate (from ~14.4 to ~6.4 mm h(-1)) was observed for shrimp for 2 h following minimum gut residence time. Protease activities increased ~2.4-fold over the range of dietary cadmium exposures, however, this variation was not dose-dependent. Differential impacts of cadmium exposure on carbon and cadmium assimilation reported previously are consistent with work involving shrimp subjected to chronic field exposure. The influence of ingested cadmium on feces elimination rate may be related to pre-assimilatory impacts on packaging, intestinal transport or release of feces. Protease activities may have been influenced by pre-assimilatory interactions between available cadmium ions in gut fluid and enzyme-secreting cells of the hepatopancreatic epithelium or direct impacts on active enzymes.

Characterization and function analysis of Hsp60 and Hsp10 under different acute stresses in black tiger shrimp, Penaeus monodon

“…Cadmium toxicology has been studied in various aquaculture organisms (Wu et al 2006;Seebaugh et al 2012;Ma et al 2013). and previous studies have demonstrated that Hsps are involved in the defense against cadmium toxicity (Jing et al 2013;Jung and Lee 2013;Mazzei et al 2015).…”

Assimilation of Elements and Digestion in Grass Shrimp Pre-Exposed to Dietary Mercury

“…This phenomenon was also observed in shrimp subjected to chronic field exposure, where digestive plasticity may have played a role in maintaining nutrient assimilation (Seebaugh and Wallace 2009;Seebaugh et al 2011). In other studies, AE-14 C% was unresponsive to a pulse of Cd in meals or pre-exposure to dietary Cd for 15 days (Seebaugh 2010;Seebaugh et al 2012). Carbon assimilation by this species does not appear to be correlated with temperature, salinity, or gut transit time (Morgan 1980;Seebaugh et al 2011).…”

“…Previous studies have demonstrated that mode of internal exposure (i.e., pre-assimilatory vs. post-assimilatory exposure) after metal ingestion can exert differential impacts on end points related to consumer digestion (Seebaugh 2010;Seebaugh et al 2012). In the present work, we have shown that dietary Hg can elicit post-assimilatory impacts on grass shrimp digestion, which may, in turn, influence Hg assimilation during subsequent digestive cycles.…”

“…In addition, midgut epithelial secretions (peritrophic membranes or mucopolysaccharides) or intestinal musculature involved in fecal-strand packaging and transport of shrimp were not influenced by assimilated Hg in a manner that affected FER (Forster 1953;Lovett and Felder 1990). A dose-dependent increase in FER was observed in naïve shrimp after ingestion of a pulse of Cd with food, which may have been due to pre-assimilatory effects on the midgut resulting from direct exposure to metal circulating in gut fluid (Seebaugh et al 2012).…”

“…In other studies, gut pH in grass shrimp was not influenced by a pulse of ingested Cd, but was affected by pre-exposure to dietary Cd for 15 days, suggesting that post-assimilatory effects of dietary metal exposure may be important in determining free proton concentrations in gut fluid (Seebaugh 2010;Seebaugh et al 2012). Intracellular exposure to Hg induced lysosomal membrane destabilization in mussel hemolymph cells, which could result in leakage of acid hydrolases into the cytoplasm and intracellular damage (Viarengo et al 2000).…”