Origin of Energy Metabolism Impairments - Ecological Biomarkers: Indicators of Ecotoxicological Effects - page 294

unexpectedly noticed the highest protease activity (trypsin) in crustacean larvae ( Penaeus
japonicus ) provided with food of plant origin. These responses are linked not only to the
type of food, but also to the quantity of food available. By exposing copepods ( Calanus
pacificus) ) to different concentrations of the same food (diatoms), Hassett and Landry (1983)
recorded higher activities of two carbohydrases (cellobiase and maltase) in individuals
acclimatized to lower concentrations of food. These results suggest that the secretion of a
large quantity of enzymes may maximize the use of the component present in low quan-
tity in the food. Therefore, the maintenance of elevated enzyme activities when there is
little food present may be energy efficient while retaining the potential to digest and make
optimum use of high concentrations of food when these are present. Different studies sup-
port this hypothesis for different species of crustaceans and for different life stages (larva,
juvenile, adult), particularly in the case of proteases (Jones et al. 1997; Kumlu and Jones 1997;
Le Vay et al. 2001; Gutow et al. 2006). The same type of response has also been observed
in mollusks. For example, in the common cockle, Cerastoderma edule , Ibarrola et al. (1998)
recorded higher digestive enzyme activities in individuals subjected to nutritional stress
(fasting for 3 days) than in nonstressed individuals. This type of response may be associ-
ated with the implementation of an energy optimization strategy, the decrease in dietary
intake “encouraging” organisms to maintain, or even stimulate, their digestive enzymatic
activities, to ensure efficient assimilation of the low quantity of food ingested (De Coen and
Janssen 1998). This type of response has been observed by Palais et al. (2012) in the zebra
mussel Dreissena polymorpha during a biomonitoring study in which induction of amylase
and endocellulase digestive activities was observed in the digestive gland and crystalline
style of organisms faced with reduced dietary intake. The induction observed was most
marked during the period of gametogenesis, and indicated interactions between diges-
tive enzyme activities, availability of food, and energy requirements (related to reproduc-
tive condition). In the same manner, the correlation between dietary intake and digestive
activities in bivalves is not always obvious. Various studies have shown a decrease in the
digestive enzymatic activities of bivalves in response to a reduction in their dietary intake
(Teo et al. 1990; Yan et al. 1996; Ibarrola et al. 2000; Albentosa and Moyano 2008). Whatever
the alimentary regime and the nutritional preferences of different species, they may be
able to adapt to the available food, which may involve regulation of the synthesis of diges-
tive enzymes (Labarta et al. 2002).
11.5.2 Modulation according to Ontogenesis, Life Cycle, or Sex of Organisms
11.5.2.1 Aquatic Vertebrates: Fish Examples
During larval development, changes in digestive enzyme activity profiles can be cor-
related with anatomical and physiological modifications, such as the opening of the
mouth, the acquisition of a functional stomach, and also with changes in the type of food
ingested (Buddington and Doroshov 1986; Kolkovski 2001; Cara et al. 2003; Chakrabarti
et al. 2006; Zouiten et al. 2008; Galaviz et al. 2011). In the European sea bass Dicentrarchus
labrax , amylase mRNA was higher in young larvae than in older ones (Péres et al. 1998).
On the other hand, Douglas et al. (2000) noticed higher gene expression of amylase in
the adult flounder Pleuronectes americanus . Bolasina et al. (2006) have monitored trypsin
and lipase activities throughout the ontogenesis of Japanese flounder Paralichthys oliva-
ceus [between 2 and 39 days after hatching (DAH)]. In addition to the increase in trypsin
activity during feeding with Artemia (brine shrimp) (15 DAH), a decrease in lipase and
trypsin activities at the end of metamorphosis (33 DAH) was noted. Similar results were