81
5 Nutrition as a Key Factor for Cephalopod Aquaculture
in the PE, as opposed to the 1:2 proportion generally reported for marine fish. Likewise, EPA is higher in shrimp than fish diets tested as cuttlefish food (Domingues
et al. 2003) and its importance for normal growth was proposed by Almansa et al.
(2006). The latter authors also indicated that cuttlefish metabolism of both EPA
and DHA might be somehow different from fish, where in general the reduction of
EPA and DHA sources implies a reduction of the level of these FA in several tissues
(Sargent et al. 1995). In addition, Domingues et al. (2003) indicated a 2:1 EPA:DHA
proportion in the prey supplied to hatchlings and, in the Ferreira et al. (2010) work,
cuttlefish juveniles attaining the best growth and survival rates were fed shrimp with
a similar EPA:DHA ratio and PUFA content. On the other hand, Koueta et al. (2002)
and Perrin et al. (2004) have suggested the importance of these FAs and PUFA in
cuttlefish hatchling survival when facing a stressful situation (either lower water
quality or improper prey size, respectively). This suggests the importance of PUFA
in cephalopod nutrition and may suggest, for example, that in addition to DHA, EPA
may play an important role in the brain and visual system of cephalopods.
A closer look at the available results on the FA profile of O� vulgaris paralarvae
(Navarro and Villanueva 2000; Miliou et al. 2006) reveals that, apart from the high
levels of DHA, 16:0 and EPA, arachidonic acid (20:4n-6, ARA) is one of the most
abundant FA, with surprisingly high values of 18:2n-6 and other n-6 FA being found
in marine species. From these and other findings in other marine molluscs (Uki
et al. 1986; Dunstan et al. 1996; Durazo-Beltran et al. 2003), it has been suggested
that 20:4n-6 might not be essential, since the ability for enzymatic bioconversion
from adequate precursors to 20:4n-6 could be present in this species. On the other
hand, 18:3n-3 is not present in octopus paralarval tissues (Navarro and Villanueva
2000, 2003; Miliou et al. 2006) although this FA is massively included through the
Artemia spp. feeding. Moreover, 18:3n-3 may compete with 24:5n-3 for the Δ6
desaturase in the metabolic route leading to DHA production. Therefore, it might
be possible that a diet rich in 18:3n-3 could be affecting the proper production
of n-3 essential FA (EFA) of paralarvae. An opposite hypothesis is that the C18
desaturation–elongation pathways of 18:3n-3 and 18:2n-6 may be active in O� vulgaris so as to produce physiologically essential n-3 and n-6 FA. To explore these
and other aspects of lipid metabolism research on dynamic aspects of lipid nutrition and metabolism by characterizing enzymes involved in lipid biosynthesis in
these organisms, i.e. desaturases and elongases, is an invaluable tool. Monroig et al.
(2012a) have recently isolated a complementary DNA (cDNA) with high homology
to fatty acyl desaturases (Fad) in adult octopus. Functional characterization of this
enzyme showed that the octopus Fad exhibited Δ5-desaturation activity towards
saturated and polyunsaturated fatty acyl substrates. Thus, it efficiently converted
16:0 and 18:0 to 16:1n-11 and 18:1n-13, respectively, and desaturated PUFA substrates 20:4n-3 and 20:3n-6 to 20:5n-3 (EPA) and 20:4n-6 (ARA), respectively.
Although the Δ5 Fad enables common octopus to produce EPA and ARA, the low
availability of its adequate substrates 20:4n-3 and 20:3n-6, either in the diet or by
limited endogenous synthesis from C18 PUFA, might indicate that EPA and ARA
are indeed EFA for this species. Interestingly, the octopus Δ5 Fad can also participate in the biosynthesis of non-methylene-interrupted diene (NMID) FA, PUFA that
5 Nutrition as a Key Factor for Cephalopod Aquaculture
in the PE, as opposed to the 1:2 proportion generally reported for marine fish. Likewise, EPA is higher in shrimp than fish diets tested as cuttlefish food (Domingues
et al. 2003) and its importance for normal growth was proposed by Almansa et al.
(2006). The latter authors also indicated that cuttlefish metabolism of both EPA
and DHA might be somehow different from fish, where in general the reduction of
EPA and DHA sources implies a reduction of the level of these FA in several tissues
(Sargent et al. 1995). In addition, Domingues et al. (2003) indicated a 2:1 EPA:DHA
proportion in the prey supplied to hatchlings and, in the Ferreira et al. (2010) work,
cuttlefish juveniles attaining the best growth and survival rates were fed shrimp with
a similar EPA:DHA ratio and PUFA content. On the other hand, Koueta et al. (2002)
and Perrin et al. (2004) have suggested the importance of these FAs and PUFA in
cuttlefish hatchling survival when facing a stressful situation (either lower water
quality or improper prey size, respectively). This suggests the importance of PUFA
in cephalopod nutrition and may suggest, for example, that in addition to DHA, EPA
may play an important role in the brain and visual system of cephalopods.
A closer look at the available results on the FA profile of O� vulgaris paralarvae
(Navarro and Villanueva 2000; Miliou et al. 2006) reveals that, apart from the high
levels of DHA, 16:0 and EPA, arachidonic acid (20:4n-6, ARA) is one of the most
abundant FA, with surprisingly high values of 18:2n-6 and other n-6 FA being found
in marine species. From these and other findings in other marine molluscs (Uki
et al. 1986; Dunstan et al. 1996; Durazo-Beltran et al. 2003), it has been suggested
that 20:4n-6 might not be essential, since the ability for enzymatic bioconversion
from adequate precursors to 20:4n-6 could be present in this species. On the other
hand, 18:3n-3 is not present in octopus paralarval tissues (Navarro and Villanueva
2000, 2003; Miliou et al. 2006) although this FA is massively included through the
Artemia spp. feeding. Moreover, 18:3n-3 may compete with 24:5n-3 for the Δ6
desaturase in the metabolic route leading to DHA production. Therefore, it might
be possible that a diet rich in 18:3n-3 could be affecting the proper production
of n-3 essential FA (EFA) of paralarvae. An opposite hypothesis is that the C18
desaturation–elongation pathways of 18:3n-3 and 18:2n-6 may be active in O� vulgaris so as to produce physiologically essential n-3 and n-6 FA. To explore these
and other aspects of lipid metabolism research on dynamic aspects of lipid nutrition and metabolism by characterizing enzymes involved in lipid biosynthesis in
these organisms, i.e. desaturases and elongases, is an invaluable tool. Monroig et al.
(2012a) have recently isolated a complementary DNA (cDNA) with high homology
to fatty acyl desaturases (Fad) in adult octopus. Functional characterization of this
enzyme showed that the octopus Fad exhibited Δ5-desaturation activity towards
saturated and polyunsaturated fatty acyl substrates. Thus, it efficiently converted
16:0 and 18:0 to 16:1n-11 and 18:1n-13, respectively, and desaturated PUFA substrates 20:4n-3 and 20:3n-6 to 20:5n-3 (EPA) and 20:4n-6 (ARA), respectively.
Although the Δ5 Fad enables common octopus to produce EPA and ARA, the low
availability of its adequate substrates 20:4n-3 and 20:3n-6, either in the diet or by
limited endogenous synthesis from C18 PUFA, might indicate that EPA and ARA
are indeed EFA for this species. Interestingly, the octopus Δ5 Fad can also participate in the biosynthesis of non-methylene-interrupted diene (NMID) FA, PUFA that