373
19 Enteroctopus megalocyathus
At HIM-UACh, male and female octopuses are placed in the conditioning tanks
where 101.6-mm polyvinyl chloride (PVC) elbows with perforated lids on one end
are offered as dens. For the females, this lair serves as nest for egg laying. During
the maturation period, the females are fed crabs only at a rate of 5–15 % of their
wet body weight (Table 19.3). The crabs are offered alive without chelae, to prevent
damage when defending from the octopus. The ration of crab every other day is
maintained until spawning, after they are fed at demand since females require low
amounts of food at this stage.
19.4 Egg Incubation
The length of octopus eggs is linked to lifestyle after hatching so that a species
laying small eggs (under 10 % of the adult ML) generates a planktonic paralarvae;
therefore, it is a merobenthic species. However, species that lay larger eggs (more
than 10 % of the adult ML) originate benthic juveniles that hatch directly from the
egg; therefore, it is a hobenthic species (Boletzky 2003; Ignatius and Srinivasan
2006). These strategies are also linked to fecundity, so that species laying smaller
eggs are more fertile and originate many planktonic paralarvae that ensure their
survival when they are dispersed and colonize new habitats. In the case of E� megalocyathus, a merobenthic species whose eggs measure between 5.8 and 6.4 % of the
ML (Table 19.3), an intermediate strategy with medium-sized eggs and hatchlings
that are planktonic during more than 60 days is observed (Uriarte et al. 2011b).
Currently, the length of the embryonic period of E� megalocyathus is reported
for temperatures between 10 and 12 °C with normal embryo development (Uriarte
et al. 2011a, 2013).
The embryos of Patagonian red octopus observed at HIM-UACh grow exponentially in total length, arm length and ML, and also in eye diameter. This occurs in
other embryonic octopods such as Robsonella fontaniana but only for total length
and arm length (Uriarte et al. 2009). The exponential growth rate observed in Patagonian red octopus embryos at HIM-UACh is 2 % day
−1
, a value below the exponential growth rate observed in R� fontaniana which is 3 % day
−1
, and paralarvae
take 70 days to hatch at 12 °C (Uriarte et al. 2009). In contrast, O� maya embryos
reach 182 % day
−1
and take 30 days at 25 °C hatching directly to a benthic juvenile
(Rosas et al. 2006). These different strategies could be due to the interaction between egg size, temperature at which embryos are developed and quantity of yolk
available after hatching.
Eggs incubated under controlled conditions show a complete embryonic development when the fertilization of the females is assured (Uriarte et al. 2011a,
2013). For E� megalocyathus, embryonic development under laboratory conditions
at 12 °C takes between 150 and 180 days (Table 19.3), being similar to E� dofleini
as described by Villanueva and Norman (2008). During this long period, the eggs
are exposed to bacterial contamination and detachment from the walls of the tanks,
usually caused by the same female reproducers (Uriarte et al. 2011a). Therefore,
19 Enteroctopus megalocyathus
At HIM-UACh, male and female octopuses are placed in the conditioning tanks
where 101.6-mm polyvinyl chloride (PVC) elbows with perforated lids on one end
are offered as dens. For the females, this lair serves as nest for egg laying. During
the maturation period, the females are fed crabs only at a rate of 5–15 % of their
wet body weight (Table 19.3). The crabs are offered alive without chelae, to prevent
damage when defending from the octopus. The ration of crab every other day is
maintained until spawning, after they are fed at demand since females require low
amounts of food at this stage.
19.4 Egg Incubation
The length of octopus eggs is linked to lifestyle after hatching so that a species
laying small eggs (under 10 % of the adult ML) generates a planktonic paralarvae;
therefore, it is a merobenthic species. However, species that lay larger eggs (more
than 10 % of the adult ML) originate benthic juveniles that hatch directly from the
egg; therefore, it is a hobenthic species (Boletzky 2003; Ignatius and Srinivasan
2006). These strategies are also linked to fecundity, so that species laying smaller
eggs are more fertile and originate many planktonic paralarvae that ensure their
survival when they are dispersed and colonize new habitats. In the case of E� megalocyathus, a merobenthic species whose eggs measure between 5.8 and 6.4 % of the
ML (Table 19.3), an intermediate strategy with medium-sized eggs and hatchlings
that are planktonic during more than 60 days is observed (Uriarte et al. 2011b).
Currently, the length of the embryonic period of E� megalocyathus is reported
for temperatures between 10 and 12 °C with normal embryo development (Uriarte
et al. 2011a, 2013).
The embryos of Patagonian red octopus observed at HIM-UACh grow exponentially in total length, arm length and ML, and also in eye diameter. This occurs in
other embryonic octopods such as Robsonella fontaniana but only for total length
and arm length (Uriarte et al. 2009). The exponential growth rate observed in Patagonian red octopus embryos at HIM-UACh is 2 % day
−1
, a value below the exponential growth rate observed in R� fontaniana which is 3 % day
−1
, and paralarvae
take 70 days to hatch at 12 °C (Uriarte et al. 2009). In contrast, O� maya embryos
reach 182 % day
−1
and take 30 days at 25 °C hatching directly to a benthic juvenile
(Rosas et al. 2006). These different strategies could be due to the interaction between egg size, temperature at which embryos are developed and quantity of yolk
available after hatching.
Eggs incubated under controlled conditions show a complete embryonic development when the fertilization of the females is assured (Uriarte et al. 2011a,
2013). For E� megalocyathus, embryonic development under laboratory conditions
at 12 °C takes between 150 and 180 days (Table 19.3), being similar to E� dofleini
as described by Villanueva and Norman (2008). During this long period, the eggs
are exposed to bacterial contamination and detachment from the walls of the tanks,
usually caused by the same female reproducers (Uriarte et al. 2011a). Therefore,