404
sexual maturation at 75 g and conclude it at 200 g. The histological evaluation of
testis gametic function and the endocrine evaluation by means of progesterone and
testosterone quantification allow us to identify three categories of mature males:
early, advanced and senescent (Olivares et al. 2003; Fig. 21.3).
Larger animals are mature and senescent, but their higher number of spermatophores enhances their fertilizing potential compared to males in the other two
categories. It remains unclear if they do not have the ability to copulate due to
structural and/or functional changes of the erectile tissue of the ligula in nature
(Thompson and Voight 2003) associated with age, or there might be a reduced acceptability by females as a result of the decreased production of testosterone or if
they have reached a size too large to be accepted by females. Advanced mature
males of O� mimus have the best morphological and physiological parameters and
they are the most suitable for mating. This assumption is useful in terms of management in captivity, especially in the event of establishing an integrated culture of the
species (Olivares et al. 2003).
21.3.3 Reproduction in Captivity
O� mimus is easily acclimated to captivity conditions. Covering the tanks using a
polyethylene mesh is useful in preventing the escape of octopus. In high density,
the animals show strong aggression which can be reduced by keeping low densities
close to 5 individuals m
−3
(4.0–6.0 kg m
−3
). It is also helpful to have similar initial
sizes during rearing to reduce aggressive behaviour. Fibreglass and cement tanks of
different sizes as well as high-density polyethylene (HDPE) tanks have been used
for O� mimus’s captivity with success. In addition, providing different types of refuges on the bottom of the tank such as polyvinylchloride (PVC) tubes with different
diameters and length (depending on individual sizes) results in excellent survival
rates. Rearing conditions used open flow and filtered water (5 % volume exchange
h
−1
) and constant aeration. Also, the daily removal of food debris using syphon suction prevents contamination caused by excessive ammonia.
Octopuses preferably consume live prey such as clams ( Protothaca thaca, Gari
solida), mussels ( Choromytilus chorus, Aulacomya ater) and crabs such as Cancer
setosus, Cancer porteri. Also, fresh or frozen fish can be provided. Live prey must
be supplied ad libitum and frozen food should be 5 % of the body weight. Sex ratio
in tanks can vary from 1:1 to 4:1 (female to male). All wild females with more than
500 g body weight are inseminated thus eliminating the need to keep males and females together in order to obtain fertilized eggs. In the absence of males, females in
captivity spawn and are able to complete the embryonic development (by maternal
care) with a 95 % hatching success of paralarvae. It is sound to use mature females
with more than 800 g of body weight just before laying eggs. To expedite the maturity of the females, it is recommended to maintain the animals in semi-darkness
conditions (Zúñiga et al. 1995).
Ó. Zúñiga et al.
sexual maturation at 75 g and conclude it at 200 g. The histological evaluation of
testis gametic function and the endocrine evaluation by means of progesterone and
testosterone quantification allow us to identify three categories of mature males:
early, advanced and senescent (Olivares et al. 2003; Fig. 21.3).
Larger animals are mature and senescent, but their higher number of spermatophores enhances their fertilizing potential compared to males in the other two
categories. It remains unclear if they do not have the ability to copulate due to
structural and/or functional changes of the erectile tissue of the ligula in nature
(Thompson and Voight 2003) associated with age, or there might be a reduced acceptability by females as a result of the decreased production of testosterone or if
they have reached a size too large to be accepted by females. Advanced mature
males of O� mimus have the best morphological and physiological parameters and
they are the most suitable for mating. This assumption is useful in terms of management in captivity, especially in the event of establishing an integrated culture of the
species (Olivares et al. 2003).
21.3.3 Reproduction in Captivity
O� mimus is easily acclimated to captivity conditions. Covering the tanks using a
polyethylene mesh is useful in preventing the escape of octopus. In high density,
the animals show strong aggression which can be reduced by keeping low densities
close to 5 individuals m
−3
(4.0–6.0 kg m
−3
). It is also helpful to have similar initial
sizes during rearing to reduce aggressive behaviour. Fibreglass and cement tanks of
different sizes as well as high-density polyethylene (HDPE) tanks have been used
for O� mimus’s captivity with success. In addition, providing different types of refuges on the bottom of the tank such as polyvinylchloride (PVC) tubes with different
diameters and length (depending on individual sizes) results in excellent survival
rates. Rearing conditions used open flow and filtered water (5 % volume exchange
h
−1
) and constant aeration. Also, the daily removal of food debris using syphon suction prevents contamination caused by excessive ammonia.
Octopuses preferably consume live prey such as clams ( Protothaca thaca, Gari
solida), mussels ( Choromytilus chorus, Aulacomya ater) and crabs such as Cancer
setosus, Cancer porteri. Also, fresh or frozen fish can be provided. Live prey must
be supplied ad libitum and frozen food should be 5 % of the body weight. Sex ratio
in tanks can vary from 1:1 to 4:1 (female to male). All wild females with more than
500 g body weight are inseminated thus eliminating the need to keep males and females together in order to obtain fertilized eggs. In the absence of males, females in
captivity spawn and are able to complete the embryonic development (by maternal
care) with a 95 % hatching success of paralarvae. It is sound to use mature females
with more than 800 g of body weight just before laying eggs. To expedite the maturity of the females, it is recommended to maintain the animals in semi-darkness
conditions (Zúñiga et al. 1995).
Ó. Zúñiga et al.