Biology Reference
In-Depth Information
to lindane (0.5-6 mg L
-1
) or 2.4-D (100-600 mg L
-1
) (De Coen et al. 1998; De Coen and
Janssen 1998). Furthermore, the exposure of fish to pyrethroid and organophosphorous
pesticides has led to the inhibition of certain digestive enzymes (Golovanova et al. 1994;
Simon et al. 1999). For example, in rainbow trout (Li et al. 2010), exposure to propicon-
azole (500 μg L
-1
) for 30 days significantly inhibited the intestinal digestive enzymes
(proteolytic enzymes and amylase) compared with lower concentrations of exposure (0.2
and 50 μg L
-1
).
11.5 Responses of Digestive Enzyme Activities to
Factors Other than Contaminants
In addition to their sensitivity to chemical stressors, digestive enzyme activities are also
sensitive to various biotic or abiotic environmental factors likely to bring about the natural
(and often seasonal) variations in significant activities. The life stage of the organism, the
availability of food sources or the physicochemistry of the aquatic medium are just some
of the many potentially confounding natural factors for which knowledge, and above
all characterization, are needed for any perceptive interpretation of measured enzyme
responses.
11.5.1 Modulation according to Quality/Quantity of Alimentary Resources
11.5.1.1 Aquatic Vertebrates: Fish Examples
According to the proportion of different components (carbohydrates, lipids, and proteins)
in the food ingested, different enzymes will participate in digestion (Barnard 1973; Stevens
1988; Gilles et al. 2006). Thus, qualitative and quantitative differences in enzyme activities
are generally observed between various species according to their alimentary regime (her-
bivorous, omnivorous, carnivorous).
Amylase activity in trout (
Oncorhynchus mykiss
) and eel (
Anguilla anguilla
), both omnivo-
rous species, is much lower than in carp (
Cyprinus carpio
) or tench (
Tinca tinca
) (Hidalgo
et al. 1999). Thus, measured amylase activities in herbivorous and omnivorous fish are
higher than those found in carnivorous species, apparently to facilitate the digestion of the
carbohydrates present in algae and other plants (Vonk and Western 1984; Sabapathy and
Teo 1993; Hidalgo et al. 1999).
Similar differences have been found in lipase activities. Lipase activity (Chakrabarti et
al. 1995) in carnivorous species, which generally have a diet richer in fats, is found to
be higher than that in omnivorous or herbivorous fish (Opuszynski and Shireman 1995;
Tengjaroenkul et al. 2000).
As regards proteins, carnivorous fish frequently show higher proteolytic enzyme activi-
ties, which encourage the digestion of food rich in animal proteins (Sabapathy and Teo
1993). Kuz'mina et al. (2002) thus observed protease activities that were higher in the car-
nivorous zander (
Stizostedion lucioperca
), moderate in the case of the perch (
Perca fluviatilis),
),
and lower in the omnivorous bream (
Abramis brama
). However, some results concerning
proteolytic activities are contradictory. Indeed, Hidalgo et al. (1999), who studied protease
activities in different species of fish, were not able to carry out a classification of species
according to their feeding behavior. Rainbow trout (
O. mykiss
) and common carp (
C. carpio
)
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