319
S� lessoniana reproduce in tanks, but the acclimatization period depends on the
condition of the animals. A healthy pair will mate within a few hours after release
into a tank. Consequent spawning takes place soon after (Nabhitabhata et al. 2005).
The female swims around touching substrates with her arms in order to examine
the surface and shape of materials before attaching her egg capsules. Each female
spawns one to three egg masses. Each egg mass contains 100–400 egg capsules
that are attached to each other at the capsule stalks. Spawned egg capsules are
sometimes removed from their substrates by other males, although the male mate
will attempt to defend them. The spawning period may last for as long as 10 days
(Nabhitabhata 1983, 1996). After the last spawning of the female mate, the healthy
male turns to another female. If another female is already accompanied by her male
mate, agonistic contests between two males will occur. The larger male (regardless
of the prior mating status of the male) generally prevails, provided he is healthy
(normal performance of routine and ritual behaviour is observed).
In vitro fertilization between mature oocytes from the female oviducts and sperm
from the spermatophores in the male Needham’s sac has been studied. About 50 %
of the oocytes were successfully fertilized (Nabhitabhata et al. 2001a). The oviducal
and nidamental gland jellies are not applied to the eggs. The eggs develop for about
4–10 h to the blastula stage before ceasing.
17.3.1.3 Nursing of Egg Capsules
Egg-Capsule Characteristics
Egg capsules are white, opaque, slender, and cylindrical in the first stage of development. Between 2 and 11 eggs in separate chambers aggregate into a onestring capsule. About five to six eggs per capsule are regularly observed in tropical
waters with an average temperature of 28 °C. Larger females tend to lay longer
capsules with larger numbers of eggs than smaller females (Nabhitabhata 1983).
Egg capsules are attached in clusters of 100–400 capsules. Egg capsules gradually
absorb water and increase in size along with the size of the embryos. The shape
of each egg capsule changes to a tamarind- or finger-like shape, and the capsule
wall becomes more transparent as development proceeds. Eggs can better tolerate transportation and handling during early embryonic developmental stages than
during later stages.
Egg capsules collected from the wild vary in size (Fig. 17.1) and embryonic stages. Therefore, the egg capsules must be graded. Newly spawned capsules are at least
50 % smaller than those almost ready to hatch. Egg capsules are graded into four
stages according to their size and shape. Newly spawned egg capsules are in the
first stage and have a cylindrical shape. Egg capsules in the second stage are similar
in shape to those in the first stage, but have comparatively larger egg chambers. In
the third stage, the capsules have a finger-like shape, and each chamber of the egg
capsule is globular in shape and has become more transparent. Each chamber of the
egg capsule becomes cube shaped in the fourth stage.
17 Sepioteuthis lessoniana
S� lessoniana reproduce in tanks, but the acclimatization period depends on the
condition of the animals. A healthy pair will mate within a few hours after release
into a tank. Consequent spawning takes place soon after (Nabhitabhata et al. 2005).
The female swims around touching substrates with her arms in order to examine
the surface and shape of materials before attaching her egg capsules. Each female
spawns one to three egg masses. Each egg mass contains 100–400 egg capsules
that are attached to each other at the capsule stalks. Spawned egg capsules are
sometimes removed from their substrates by other males, although the male mate
will attempt to defend them. The spawning period may last for as long as 10 days
(Nabhitabhata 1983, 1996). After the last spawning of the female mate, the healthy
male turns to another female. If another female is already accompanied by her male
mate, agonistic contests between two males will occur. The larger male (regardless
of the prior mating status of the male) generally prevails, provided he is healthy
(normal performance of routine and ritual behaviour is observed).
In vitro fertilization between mature oocytes from the female oviducts and sperm
from the spermatophores in the male Needham’s sac has been studied. About 50 %
of the oocytes were successfully fertilized (Nabhitabhata et al. 2001a). The oviducal
and nidamental gland jellies are not applied to the eggs. The eggs develop for about
4–10 h to the blastula stage before ceasing.
17.3.1.3 Nursing of Egg Capsules
Egg-Capsule Characteristics
Egg capsules are white, opaque, slender, and cylindrical in the first stage of development. Between 2 and 11 eggs in separate chambers aggregate into a onestring capsule. About five to six eggs per capsule are regularly observed in tropical
waters with an average temperature of 28 °C. Larger females tend to lay longer
capsules with larger numbers of eggs than smaller females (Nabhitabhata 1983).
Egg capsules are attached in clusters of 100–400 capsules. Egg capsules gradually
absorb water and increase in size along with the size of the embryos. The shape
of each egg capsule changes to a tamarind- or finger-like shape, and the capsule
wall becomes more transparent as development proceeds. Eggs can better tolerate transportation and handling during early embryonic developmental stages than
during later stages.
Egg capsules collected from the wild vary in size (Fig. 17.1) and embryonic stages. Therefore, the egg capsules must be graded. Newly spawned capsules are at least
50 % smaller than those almost ready to hatch. Egg capsules are graded into four
stages according to their size and shape. Newly spawned egg capsules are in the
first stage and have a cylindrical shape. Egg capsules in the second stage are similar
in shape to those in the first stage, but have comparatively larger egg chambers. In
the third stage, the capsules have a finger-like shape, and each chamber of the egg
capsule is globular in shape and has become more transparent. Each chamber of the
egg capsule becomes cube shaped in the fourth stage.
17 Sepioteuthis lessoniana