352
J. Nabhitabhata
The interval between mating and spawning is approximately 32 days (range of
20–40 days). After spawning, the male is excluded and removed from the tank. The
female broods her eggs by regular cleaning and cradling them in her arm web behind the mantle. The spawning female stops feeding until the hatching of her eggs
and onward to her subsequent senescent death. The number of eggs laid by a single
octopus female is on average 6,900 (5,500–8,500).
18.4 Nursing of Eggs and Brooding Females
Since the eggs are brooded by the female, there is no direct management for the
incubation of the egg masses. The open system and facilities used for broodstocks
can be also used in this phase. The management focuses on not disturbing the
females and reducing stress from any external stimuli, i.e. sudden change of physical, particularly light, and chemical (water quality) parameters. Eggs during the
early stages of a disturbed female are rejected, and those in the later development
stages hatch prematurely. Near to hatching, around day 13 (at 28 °C), the brooding
female with her shelter is carefully transferred to 50-L-capacity cylindrical PVC
tanks containing 30 L of fresh sea water with aeration. Tanks are cleaned by siphoning and the water is changed daily to about 40 % of their volume. Any temperature
change is minimized by means of an outside running water bath around the tank
base (Nabhitabhata et al. 2005; Promboon et al. 2011).
The eggs are small (as categorized by Boletzky 1977), approximately 4.4 % of
the adult ML, and each egg produces a planktonic hatchling. Each egg has a size
of about 3.2 × 1.25 mm (Ignatius and Srinivasan 2006; Nabhitabhata et al. 2010;
Promboon et al. 2011). The egg is telolecithal, with a rice-grain shape and a fine
peduncle attached to the festoon (Fig. 18.2). The newly laid egg is opaque white
and gradually turns more transparent after 5 days at 30 °C. Organogenesis and the
subsequent first inversion occur simultaneously at this time. Genesis of the chromatophores, the black retina and the ink sac happens from day 9 onwards. The
second reversion is from day 13 after the laying of the egg. After this embryonic
stage, the female is transferred to another tank. The first hatching occurs on day 16
(Fig. 18.3) with an average embryonic period of 18.3 days (16–22) at 28 °C. Eggs
hatching from the same cluster of a single female continue to do so for a period of
3–8 days. The hatching rate is higher than 90 %.
18.5 Nursing of the Young
18.5.1 Feed and Tank Management
After hatching, the female is removed from the tank, and all hatchlings are retained
for nursing. The tank previously used for maintenance of the brooding female is
J. Nabhitabhata
The interval between mating and spawning is approximately 32 days (range of
20–40 days). After spawning, the male is excluded and removed from the tank. The
female broods her eggs by regular cleaning and cradling them in her arm web behind the mantle. The spawning female stops feeding until the hatching of her eggs
and onward to her subsequent senescent death. The number of eggs laid by a single
octopus female is on average 6,900 (5,500–8,500).
18.4 Nursing of Eggs and Brooding Females
Since the eggs are brooded by the female, there is no direct management for the
incubation of the egg masses. The open system and facilities used for broodstocks
can be also used in this phase. The management focuses on not disturbing the
females and reducing stress from any external stimuli, i.e. sudden change of physical, particularly light, and chemical (water quality) parameters. Eggs during the
early stages of a disturbed female are rejected, and those in the later development
stages hatch prematurely. Near to hatching, around day 13 (at 28 °C), the brooding
female with her shelter is carefully transferred to 50-L-capacity cylindrical PVC
tanks containing 30 L of fresh sea water with aeration. Tanks are cleaned by siphoning and the water is changed daily to about 40 % of their volume. Any temperature
change is minimized by means of an outside running water bath around the tank
base (Nabhitabhata et al. 2005; Promboon et al. 2011).
The eggs are small (as categorized by Boletzky 1977), approximately 4.4 % of
the adult ML, and each egg produces a planktonic hatchling. Each egg has a size
of about 3.2 × 1.25 mm (Ignatius and Srinivasan 2006; Nabhitabhata et al. 2010;
Promboon et al. 2011). The egg is telolecithal, with a rice-grain shape and a fine
peduncle attached to the festoon (Fig. 18.2). The newly laid egg is opaque white
and gradually turns more transparent after 5 days at 30 °C. Organogenesis and the
subsequent first inversion occur simultaneously at this time. Genesis of the chromatophores, the black retina and the ink sac happens from day 9 onwards. The
second reversion is from day 13 after the laying of the egg. After this embryonic
stage, the female is transferred to another tank. The first hatching occurs on day 16
(Fig. 18.3) with an average embryonic period of 18.3 days (16–22) at 28 °C. Eggs
hatching from the same cluster of a single female continue to do so for a period of
3–8 days. The hatching rate is higher than 90 %.
18.5 Nursing of the Young
18.5.1 Feed and Tank Management
After hatching, the female is removed from the tank, and all hatchlings are retained
for nursing. The tank previously used for maintenance of the brooding female is