Origin of Energy Metabolism Impairments - Ecological Biomarkers: Indicators of Ecotoxicological Effects - page 296

activities would be higher in ovigerous females, in relation to a particular nutritional need
at the time of oogenesis, notably for phosphorus. This would be obtained from the algal
diet. Higher amylase activity in females may thus reflect a predominantly plant-based
alimentary regime in comparison to that of the males.
11.5.3 Modulation according to Physicochemical Properties
of Water: Light, Salinity, Temperature
During exposure in the laboratory, variations of enzymatic activity in juvenile European
sea bass ( Dicentrachux labrax ) could be observed in relation to the light intensity (Cuvier-
Péres et al. 2001). Trypsin and chymotrypsin activities were slightly affected at the time of
weaning, whereas pepsin activities were considerably reduced at extreme values of light
exposure (5 and 4000 lx). Variations in digestive enzyme activities in crustaceans have
also been observed in relation to the time of day and following an internal circadian cycle
(Harms et al. 1991; Ceccaldi 1998; Hernandez et al. 1999), principally with two peaks per
day (Ceccaldi 1998). However, these diurnal variations are not always clearly established
given the seasonal variation in the digestive enzyme activities (Baars and Oosterhuis 1984;
Biesiot and Capuzzo 1990).
In a coastal bivalve ( Scrobicularia plana ), Fossi Tankoua et al. (2011) highlighted the effect
of salinity on digestive enzyme activities notably concerning the amylase and cellulase
activities of the crystalline style.
The rate of digestion and the quantity of enzymes produced is generally heavily depen-
dent on the temperature (Vonk and Western 1984; Galgani 1985; Brock et al. 1986). General
increases in activity are observed with a rise in temperature (Vonk and Western 1984;
Brock et al. 1986; Ceccaldi 1998; Papoutsoglou and Lyndon 2005). However, differential
effects of temperature on digestive enzyme activities have been observed, according to
whether the fish concerned were hot or cold water species (Vonk and Western 1984; Hazel
1993; Savoie et al. 2008). Digestive enzyme activity response to temperature variation is
thus specific to the species under consideration. In addition, it has been shown that tem-
perature affects digestive enzyme activities in different ways according to the section of
the digestive tract being examined. This suggests that fishes, which are poikilotherms,
possess enzymatic digestion mechanisms capable of being active at different tempera-
tures (Papoutsoglou and Lyndon 2005) as regards the expression of different isoenzymes
with different temperature optima (literature cited by Papoutsoglou and Lyndon 2005).
Temperature also plays an important role in the digestive enzyme activities of further
invertebrates (Ceccaldi 1998). Han et al. (2002) observed in the crustacean copepod species
Calanus sinicus a negative correlation between the level of protease or amylase activity and
temperature. In fact, this species goes into diapause at higher temperatures (25°C) and is
then characterized by low enzyme activities.
In direct or indirect relation to annual temperature variations, seasonal variations in
the digestive enzyme activities (amylase, cellulase) of various bivalve and crustacean
species have been observed (Stuart et al. 1985; Guarna and Borwsky 1995; Ibarrola et al .
1998; Wong and Cheung 2001; Le Pennec and Le Pennec 2002; Palais et al. 2012). However,
these seasonal variations are not expressed in the whole digestive system, but, for exam-
ple, in the crystalline style in bivalves (Wong and Cheung 2001; Palais et al. 2012). Unlike
the digestive gland, the crystalline style forms a noncellular structure, not subjected
to seasonal weight variation, probably explaining the lower variations in digestive
enzyme activities observed in this structure. Thus variations in digestive organ weight
(e.g., bivalve digestive gland linked to seasonal variations in food availability and/or the