244
X.-D. Zheng et al.
14.3.2 Spawning
The sperm live for a certain period in the sperm receptacle near the buccal membrane of the female. When a suitable breeding site is found, the eggs mature in
batches and are transferred to the sperm receptacle, fertilized and then laid one by
one (Zheng et al. 2010). The fertilized eggs are wound onto seaweed, branches or
ropes. Most of the parents die after spawning. The main spawning period is from
mid-April to late June under the conditions of 5–50 m depth with abundant seaweed
and hard bottom; however, there are two spawning periods along the coastal waters of Fujian Province: April–May in spring and September–October in autumn.
As for the rearing indoors, the settled substrata such as ropes and pieces of mesh
should be treated to have rough surfaces, and put into the cultivating pools. After
3–5 days, beneficial bacterium will develop on the substrata surface, which will
help the eggs to attach (Zheng et al. 2010). During the spawning period, the male
always swims around to protect the female from other males and mates with the
female (Fig. 14.1b). In cases where there are other males, the male usually fights
fiercely with them. The mated female can lay eggs without a male. The spawning
period usually lasts from several days to 10 days. S� japonica prefers substrata with
egg clusters, and usually there is more than one female laying eggs together. Putting
the substrata with eggs together can induce the females to lay eggs continuously and
attract more females to come and lay eggs. Parents do not take care of the eggs after
spawning; instead, they die very soon.
14.3.3 Nursing of Eggs
In general, one female can lay 1,000–2,000 eggs. The fertilized eggs should be
hatched under stable room temperature, and should be checked regularly. The seawater in the cement pools keeps flowing all day, and the salinity should be above
20 psu.
The number of days required for hatching depends on the water temperature—
the higher the temperature, the shorter the hatching period (Table 14.1). The newly
laid eggs are soft, black in colour and look like grapes (Fig. 14.2a), with an average
diameter of 11.0 mm × 7.6 mm and wet weight of 0.31 g. After 10 days, the egg
becomes larger, and the embryo can be seen inside (Fig. 14.2b). Figure 14.2c shows
a 20-day embryo under the temperature of 22 °C. There are yellowish pigment granules on the arms and at the ventral edge of the mantle, and an initially developed ink
sac. On the 24th day, a well-developed embryo hatches, still with a little external
yolk and 4 mm long in mantle. The hatching rate can reach 80 % or over. The hatchlings can swim, and their morphology is similar to the adults. The yolk is consumed
in 1–2 days, and the hatchling starts to look for food (Fig. 14.2d). It is capable of
moving actively by water ejecting.
X.-D. Zheng et al.
14.3.2 Spawning
The sperm live for a certain period in the sperm receptacle near the buccal membrane of the female. When a suitable breeding site is found, the eggs mature in
batches and are transferred to the sperm receptacle, fertilized and then laid one by
one (Zheng et al. 2010). The fertilized eggs are wound onto seaweed, branches or
ropes. Most of the parents die after spawning. The main spawning period is from
mid-April to late June under the conditions of 5–50 m depth with abundant seaweed
and hard bottom; however, there are two spawning periods along the coastal waters of Fujian Province: April–May in spring and September–October in autumn.
As for the rearing indoors, the settled substrata such as ropes and pieces of mesh
should be treated to have rough surfaces, and put into the cultivating pools. After
3–5 days, beneficial bacterium will develop on the substrata surface, which will
help the eggs to attach (Zheng et al. 2010). During the spawning period, the male
always swims around to protect the female from other males and mates with the
female (Fig. 14.1b). In cases where there are other males, the male usually fights
fiercely with them. The mated female can lay eggs without a male. The spawning
period usually lasts from several days to 10 days. S� japonica prefers substrata with
egg clusters, and usually there is more than one female laying eggs together. Putting
the substrata with eggs together can induce the females to lay eggs continuously and
attract more females to come and lay eggs. Parents do not take care of the eggs after
spawning; instead, they die very soon.
14.3.3 Nursing of Eggs
In general, one female can lay 1,000–2,000 eggs. The fertilized eggs should be
hatched under stable room temperature, and should be checked regularly. The seawater in the cement pools keeps flowing all day, and the salinity should be above
20 psu.
The number of days required for hatching depends on the water temperature—
the higher the temperature, the shorter the hatching period (Table 14.1). The newly
laid eggs are soft, black in colour and look like grapes (Fig. 14.2a), with an average
diameter of 11.0 mm × 7.6 mm and wet weight of 0.31 g. After 10 days, the egg
becomes larger, and the embryo can be seen inside (Fig. 14.2b). Figure 14.2c shows
a 20-day embryo under the temperature of 22 °C. There are yellowish pigment granules on the arms and at the ventral edge of the mantle, and an initially developed ink
sac. On the 24th day, a well-developed embryo hatches, still with a little external
yolk and 4 mm long in mantle. The hatching rate can reach 80 % or over. The hatchlings can swim, and their morphology is similar to the adults. The yolk is consumed
in 1–2 days, and the hatchling starts to look for food (Fig. 14.2d). It is capable of
moving actively by water ejecting.