86
J. C. Navarro et al.
energy to somatic growth and, later, to reproduction (Wells and Clarke 1996). Therefore, the animal has to feed on a diet correctly balanced to its metabolic needs at a
given temperature (André et al. 2009). The existing information is resumed to two
theories that clash in terms of what the cephalopods use as energy substrate. The first
one, by Lee (1994) and Boucher-Rodoni and Mangold (1994), considers that under
normal feeding conditions, both growth and energy use the protein fraction as fuel.
The second theory, by Storey and Storey (1983) and Hochachka (1994), considers
that the CH fraction is used as energy source and the protein fraction is exclusively
used for growth. Such contrasting theories may originate from the fact that the same
species is physiologically adapted to a given geographical location, with different
temperature regimes and food nutritional composition. For instance, S� officinalis
populations from the English Channel and southern Portugal have been reported to
be genetically different (Wolfram et al. 2006). In addition, this species displays a
physiological plasticity (Oellermann et al. 2012), which is temperature- and fooddependent (reliant on the lifestyle of cephalopods and their low energy reserves).
Cephalopods have appropriate catabolic pathways to breakdown protein to amino
acids to obtain energy (Ballantyne et al. 1981). However, most cephalopods’ living
strategy is to lay down protein reserves into rapid growth to convert them into gametes (O’Dor et al. 1984; Moltschaniwskyj and Carter 2013). Hypothetically, it would
be a waste to partially use amino acids for energy, these being reserves only used
in case of starving or at reproduction. This would point to the use of other reserves
before protein and amino acids at early stages of life. Fast-growing cephalopods,
when fed properly, are extremely efficient in converting food to protein, display
low protein degradation and exhibit increased efficiency of retaining synthesized
protein (Carter et al. 2009). On the other hand, cephalopods are said to have a limited capacity for lipid oxidation (Ballantyne et al. 1981), and its digestion becomes
slow and inefficient due to the lack of emulsifiers (biliary salts) in the digestive tract
(Vonk 1962). On the contrary, Moltschaniwskyj and Johnston (2006) have shown
that Euprymna tasmanica has the ability to digest lipids (very high levels of lipase
were found in the digestive gland) but these are not stored in the digestive gland,
which indicates the species capacity of using lipids as a source of fuel (Swift et al.
2005). This species is known to have a very sedentary lifestyle (it does not move a
lot, so there are not many mantle burst activities) in Southern Australia temperate
waters. A similar ability to use lipids had already been displayed by individuals of S�
officinalis from the English Channel populations, which metabolized lipids instead
of protein or CHs when facing prolonged starvation (Castro et al. 1992). On the
other hand, Lamarre et al. (2012) observed the mixed use of lipids and protein, and
after 8 days the exclusive use of protein in short starvation, in cuttlefish from the
Mediterranean Sea. This use of lipids by cuttlefish might be eventually identical, at
the cellular level, to what is described by Finn and Dice (2006) in vertebrates.
The higher growth rates observed in cephalopods that live or are cultured in subtropical regions (with high temperatures than those observed in temperate waters)
would mean that from a given temperature threshold, cephalopods would use CHs
as energy, while at lower temperatures, they would preferably use other sources such
as lipids and protein (depending on food availability). The enzyme content of the
J. C. Navarro et al.
energy to somatic growth and, later, to reproduction (Wells and Clarke 1996). Therefore, the animal has to feed on a diet correctly balanced to its metabolic needs at a
given temperature (André et al. 2009). The existing information is resumed to two
theories that clash in terms of what the cephalopods use as energy substrate. The first
one, by Lee (1994) and Boucher-Rodoni and Mangold (1994), considers that under
normal feeding conditions, both growth and energy use the protein fraction as fuel.
The second theory, by Storey and Storey (1983) and Hochachka (1994), considers
that the CH fraction is used as energy source and the protein fraction is exclusively
used for growth. Such contrasting theories may originate from the fact that the same
species is physiologically adapted to a given geographical location, with different
temperature regimes and food nutritional composition. For instance, S� officinalis
populations from the English Channel and southern Portugal have been reported to
be genetically different (Wolfram et al. 2006). In addition, this species displays a
physiological plasticity (Oellermann et al. 2012), which is temperature- and fooddependent (reliant on the lifestyle of cephalopods and their low energy reserves).
Cephalopods have appropriate catabolic pathways to breakdown protein to amino
acids to obtain energy (Ballantyne et al. 1981). However, most cephalopods’ living
strategy is to lay down protein reserves into rapid growth to convert them into gametes (O’Dor et al. 1984; Moltschaniwskyj and Carter 2013). Hypothetically, it would
be a waste to partially use amino acids for energy, these being reserves only used
in case of starving or at reproduction. This would point to the use of other reserves
before protein and amino acids at early stages of life. Fast-growing cephalopods,
when fed properly, are extremely efficient in converting food to protein, display
low protein degradation and exhibit increased efficiency of retaining synthesized
protein (Carter et al. 2009). On the other hand, cephalopods are said to have a limited capacity for lipid oxidation (Ballantyne et al. 1981), and its digestion becomes
slow and inefficient due to the lack of emulsifiers (biliary salts) in the digestive tract
(Vonk 1962). On the contrary, Moltschaniwskyj and Johnston (2006) have shown
that Euprymna tasmanica has the ability to digest lipids (very high levels of lipase
were found in the digestive gland) but these are not stored in the digestive gland,
which indicates the species capacity of using lipids as a source of fuel (Swift et al.
2005). This species is known to have a very sedentary lifestyle (it does not move a
lot, so there are not many mantle burst activities) in Southern Australia temperate
waters. A similar ability to use lipids had already been displayed by individuals of S�
officinalis from the English Channel populations, which metabolized lipids instead
of protein or CHs when facing prolonged starvation (Castro et al. 1992). On the
other hand, Lamarre et al. (2012) observed the mixed use of lipids and protein, and
after 8 days the exclusive use of protein in short starvation, in cuttlefish from the
Mediterranean Sea. This use of lipids by cuttlefish might be eventually identical, at
the cellular level, to what is described by Finn and Dice (2006) in vertebrates.
The higher growth rates observed in cephalopods that live or are cultured in subtropical regions (with high temperatures than those observed in temperate waters)
would mean that from a given temperature threshold, cephalopods would use CHs
as energy, while at lower temperatures, they would preferably use other sources such
as lipids and protein (depending on food availability). The enzyme content of the