375
19 Enteroctopus megalocyathus
new strategies and incubation systems are required to ensure the paralarval hatching. The first would be to separate the eggs from females as soon as they have been
released, because eggs could be incubated without parental control at HIM-UACh.
At HIM-UACh, after the eggs are laid they are separated from females and their
clusters are suspended in incubation tanks with recirculating system, UV sterilization, temperature control, tank water exchange of 70 % day
−1
and concentration of
O 2 over 85 % saturation.
The eggs are incubated until hatching, a period of 4–5 months for this species.
The percentage of egg fertilization reaches 75 % success, and is detected by the appearance of the eye pigmentation which occurs at stage IX described by Naef (1928).
19.5 Paralarval Growth
At the moment, the production of a merobenthic octopus species is a challenge.
So far, juveniles from five octopus species are reported to have been obtained
under controlled conditions: E� dofleini (Okubo 1980), O� vulgaris (Villanueva
et al. 1994, 1996; Villanueva 1995; Iglesias et al. 2004; Carrasco et al. 2006),
O� joubini (Forsythe 1984), R� fontaniana (Uriarte et al. 2010) and Amphioctopus
aegina (Promboon et al. 2011).
The growth of paralarvae would allow juvenile cultivation under controlled conditions in adequate and stable quantities to sustain industrial ongrowing. This could
mitigate the overfishing impact on this valuable resource. However, until now the
technology to cultivate paralarvae either is incomplete or results in low survival
rates (Villanueva and Norman 2008; Iglesias et al. 2007; Berger 2010; Uriarte et al.
2011a), limiting commercial culture development.
Ortiz et al. (2006) observed paralarvae of E� megalocyathus of up to 5 days of
post-hatch age with suprabenthic behaviour, so these paralarvae share both paralarvae and benthic juvenile characteristics. Uriarte et al. (2011a) described that the
length of the paralarval period was too extended, reporting it to be more than 60
days, ending with a den-searching behaviour. Currently, at HIM-UACh at 12 °C the
paralarval period lasts between 90 and 114 days, similar to E� dofleini paralarvae as
described by Villanueva and Norman (2008). At 114 days post hatching, paralarvae
settle definitely and exhibit a juvenile morphological character and behaviour using
dens permanently (Fig. 19.4).
In general, the feeding habit of octopus paralarvae is one of the most complex
and limiting aspects for its cultivation. The scarce nutritional knowledge and the
lack of an appropriate prey to satisfy their food requirements (Iglesias et al. 2007;
Berger 2010; Uriarte et al. 2011a) are the most critical aspects for rearing paralarvae
during more than 90 days, as in the case of Patagonian red octopus.
Another critical issue with paralarval cultivation is cannibalism in E� megalocyathus. Uriarte et al. (2013) observed that the cannibalism in well-fed paralarvae accounts for 4 % of total mortality, while poorly fed paralarvae cannibalism accounts
for up to 13 % mortality. This means that another of the greatest challenges in the
cultivation of these paralarvae is the reduction of cannibalistic behaviour.
19 Enteroctopus megalocyathus
new strategies and incubation systems are required to ensure the paralarval hatching. The first would be to separate the eggs from females as soon as they have been
released, because eggs could be incubated without parental control at HIM-UACh.
At HIM-UACh, after the eggs are laid they are separated from females and their
clusters are suspended in incubation tanks with recirculating system, UV sterilization, temperature control, tank water exchange of 70 % day
−1
and concentration of
O 2 over 85 % saturation.
The eggs are incubated until hatching, a period of 4–5 months for this species.
The percentage of egg fertilization reaches 75 % success, and is detected by the appearance of the eye pigmentation which occurs at stage IX described by Naef (1928).
19.5 Paralarval Growth
At the moment, the production of a merobenthic octopus species is a challenge.
So far, juveniles from five octopus species are reported to have been obtained
under controlled conditions: E� dofleini (Okubo 1980), O� vulgaris (Villanueva
et al. 1994, 1996; Villanueva 1995; Iglesias et al. 2004; Carrasco et al. 2006),
O� joubini (Forsythe 1984), R� fontaniana (Uriarte et al. 2010) and Amphioctopus
aegina (Promboon et al. 2011).
The growth of paralarvae would allow juvenile cultivation under controlled conditions in adequate and stable quantities to sustain industrial ongrowing. This could
mitigate the overfishing impact on this valuable resource. However, until now the
technology to cultivate paralarvae either is incomplete or results in low survival
rates (Villanueva and Norman 2008; Iglesias et al. 2007; Berger 2010; Uriarte et al.
2011a), limiting commercial culture development.
Ortiz et al. (2006) observed paralarvae of E� megalocyathus of up to 5 days of
post-hatch age with suprabenthic behaviour, so these paralarvae share both paralarvae and benthic juvenile characteristics. Uriarte et al. (2011a) described that the
length of the paralarval period was too extended, reporting it to be more than 60
days, ending with a den-searching behaviour. Currently, at HIM-UACh at 12 °C the
paralarval period lasts between 90 and 114 days, similar to E� dofleini paralarvae as
described by Villanueva and Norman (2008). At 114 days post hatching, paralarvae
settle definitely and exhibit a juvenile morphological character and behaviour using
dens permanently (Fig. 19.4).
In general, the feeding habit of octopus paralarvae is one of the most complex
and limiting aspects for its cultivation. The scarce nutritional knowledge and the
lack of an appropriate prey to satisfy their food requirements (Iglesias et al. 2007;
Berger 2010; Uriarte et al. 2011a) are the most critical aspects for rearing paralarvae
during more than 90 days, as in the case of Patagonian red octopus.
Another critical issue with paralarval cultivation is cannibalism in E� megalocyathus. Uriarte et al. (2013) observed that the cannibalism in well-fed paralarvae accounts for 4 % of total mortality, while poorly fed paralarvae cannibalism accounts
for up to 13 % mortality. This means that another of the greatest challenges in the
cultivation of these paralarvae is the reduction of cannibalistic behaviour.