230
J. Nabhitabhata
most young cephalopods, particularly sepiid cuttlefish, largely corresponds to the
benthic mode of the adult, as in S� pharaonis (Fig. 13.4). They usually hatch out
with an external yolk sac, which is smaller than their own head. The yolk sac is
abandoned on the first day after hatching. Hatchlings swim hovering at an angle of
about 60–80° to the tank bottom. Chromatophores function and their normal colour
pattern is dark brown, white or transparent, with a dark red spot of the anal gland
at the posterior tip of the dorsum. The size of the anal gland is comparatively large
with a diameter of more than about 20 % of their own mantle length (Nabhitabhata
1997). Fins are separated and projected to the posterior and their length is about
80 % of the mantle length.
At 3 days old, hatchlings dive to the floor, entering their benthic juvenile stage.
However, the period of the planktonic stages varies among hatchlings from different
batches. Such periods range from less than 12 h to 5 days, probably due to slight
differences of their embryonic stages at hatching. At this early benthic stage, the
young cuttlefish hold on to the floor with the tips of their arms. They touch the floor
while their head and mantle are still hovering at an angle of about 20–30° to the
floor (Nabhitabhata et al. 1984). Their colour is dark brown with the dark red spot at
the anal gland. After 5 days, the cuttlefish completely adopt the benthic phase, lying
on the floor. At this age, the cuttlefish do not burrow into the substratum but prefer
lying under shelters. The tentacles begin to function for attacking prey. Their arms
are still short but strong enough to catch prey up to twice their mantle length in size.
Table 13.1 Comparison of culture conditions and production of Sepiella inermis from various
studies
Aspect
Boonprakob
et al. (1977a, b)
Nabhitabhata
et al. (1984);
Nabhitabhata
(1997)
Sivalingam
(1999)
Anil (2003)
Tank system
Open
Open
Open
Open
Egg incubation (days)
12.5 (11–20)
12.6 (8–19)
13
13–20
Temperature (°C)
28
28
–
27–32
Hatching period (d)
7
3–10
10
7
Hatchling size (mm, g)
3.3, 0.01
4.3, 0.04
2
4, 0.02
Initial density
–
100 ind m
−2
–
500 ind m
−3
First spawning (d)
98.7
87 (79–96)
75
86
Size at maturity (mm, g)
69.5, 61.8
61, 36.6
57.2, 37.9
64, 46.5
Daily growth (%: ML, W) 2.4, 6.8
2.4, 5.5
–
2.5, 6.0
Mean final size (mm, g)
69.5, 61.8
68.2, 48.2
–
69, 54.7
Max size (mm, g)
–
77, 52.6
–
–
Mean lifespan (days)
109.7–114.6
117–115.1,
116.2
(84–149)
–
–
Max lifespan (days)
138
149
–
110
J. Nabhitabhata
most young cephalopods, particularly sepiid cuttlefish, largely corresponds to the
benthic mode of the adult, as in S� pharaonis (Fig. 13.4). They usually hatch out
with an external yolk sac, which is smaller than their own head. The yolk sac is
abandoned on the first day after hatching. Hatchlings swim hovering at an angle of
about 60–80° to the tank bottom. Chromatophores function and their normal colour
pattern is dark brown, white or transparent, with a dark red spot of the anal gland
at the posterior tip of the dorsum. The size of the anal gland is comparatively large
with a diameter of more than about 20 % of their own mantle length (Nabhitabhata
1997). Fins are separated and projected to the posterior and their length is about
80 % of the mantle length.
At 3 days old, hatchlings dive to the floor, entering their benthic juvenile stage.
However, the period of the planktonic stages varies among hatchlings from different
batches. Such periods range from less than 12 h to 5 days, probably due to slight
differences of their embryonic stages at hatching. At this early benthic stage, the
young cuttlefish hold on to the floor with the tips of their arms. They touch the floor
while their head and mantle are still hovering at an angle of about 20–30° to the
floor (Nabhitabhata et al. 1984). Their colour is dark brown with the dark red spot at
the anal gland. After 5 days, the cuttlefish completely adopt the benthic phase, lying
on the floor. At this age, the cuttlefish do not burrow into the substratum but prefer
lying under shelters. The tentacles begin to function for attacking prey. Their arms
are still short but strong enough to catch prey up to twice their mantle length in size.
Table 13.1 Comparison of culture conditions and production of Sepiella inermis from various
studies
Aspect
Boonprakob
et al. (1977a, b)
Nabhitabhata
et al. (1984);
Nabhitabhata
(1997)
Sivalingam
(1999)
Anil (2003)
Tank system
Open
Open
Open
Open
Egg incubation (days)
12.5 (11–20)
12.6 (8–19)
13
13–20
Temperature (°C)
28
28
–
27–32
Hatching period (d)
7
3–10
10
7
Hatchling size (mm, g)
3.3, 0.01
4.3, 0.04
2
4, 0.02
Initial density
–
100 ind m
−2
–
500 ind m
−3
First spawning (d)
98.7
87 (79–96)
75
86
Size at maturity (mm, g)
69.5, 61.8
61, 36.6
57.2, 37.9
64, 46.5
Daily growth (%: ML, W) 2.4, 6.8
2.4, 5.5
–
2.5, 6.0
Mean final size (mm, g)
69.5, 61.8
68.2, 48.2
–
69, 54.7
Max size (mm, g)
–
77, 52.6
–
–
Mean lifespan (days)
109.7–114.6
117–115.1,
116.2
(84–149)
–
–
Max lifespan (days)
138
149
–
110