472
The study of enzyme activity in the digestive system of the paralarvae shows that
until 10 DAH at 12 °C, the paralarvae show less enzyme activity of trypsin and chymotrypsin, independent of the diet. After this age, when they are fed with Artemia or
maintained in a fasting state (without food) the paralarvae present little trypsin and
chymotrypsin activity, while the enzymes are significantly activated in paralarvae
when they feed on zoea of king crab, Lithodes santolla (Pereda et al. 2009).
Even though the zoea of king crab is a diet that allows a normal development
throughout the paralarval life until benthic settlement, the paralarvae show a high
level of mortality during the first 15 DAH with an absence of growth. The exponential growth of paralarvae starts only after 22 DAH. Consequently, this early period
is characterized by a high level of mortality and zero growth could be related with
two phenomena: (1) the arms do not reach enough length to manipulate the zoeae of
king crab according to Uriarte et al. (2010) and (2) the digestive system is immature
according to Pereda et al. (2009). Therefore, only paralarvae with enough energy
reserve to manage surviving the first 2 or 3 weeks post hatching could capture the
zoeae and survive.
The complete development of R� fontaniana is documented for paralarvae fed
with L� santolla (Uriarte et al. 2010), but the paralarvae fed only with Artemia at
12 °C survived but did not grow during 70 days of culture (Uriarte et al. 2011a).
Amphipod prey was not consumed by the paralarvae, and the consumption of
zoea of Pagurus sp� and Petrolisthes laevigatus did not allow the growth and survival of R� fontaniana. This was due to the zoeae behaviour and the lower organic content in these species in comparison to the king crab zoeae (Uriarte et al. 2011a, b).
Furthermore, R� fontaniana paralarvae presented a high mortality due to cannibalism. According to Miranda et al. (2011), this behaviour increases significantly
along with paralarvae cultivation density. This prevents cultivation of this species
at densities higher than 4 paralarvae L
−1
. Below this density no cannibalism is observed, even though the paralarvae remain in fasting. According to the authors, cannibalism causes between 12.5 and 65.6 % mortality when cultivation has a density
between 8 and 56 paralarvae L
−1
, respectively.
The tendency of a linear growth of AL and eye diameter with regard to the total
length is maintained after finishing the paralarval period and throughout the early
juvenile period.
The juvenile growth rate reached only 3.19 % day
−1
in R� fontaniana during 90 days
after settlement; this value was lower than the specific growth rate observed during
the previous paralarval stage that reached a value of 4.43 % day
−1
(Uriarte et al. 2010).
Settlement and transition to juvenile stage mark the beginning of the consumption of
benthic preys such as small crabs from the Petrolisthes genus (Uriarte et al. 2010).
At the HIM-UACh, females with egg laying in the subtidal zone are caught and
transported to the laboratory. They are kept in a recirculating system at 11 ± 1 °C
until paralarvae hatching. Once they hatch, paralarvae are cultured in 3 L cylindrical
tanks with mild and constant aeration, and total replacement of seawater filtered to
1 µm and UV sterilized every 24 h. The cultures are performed at 11 ± 1°C. Culture
density is 5 paralarvae L
−1
, ruling out daily mortality. The supplied food is zoeae
of king crab ( L� santolla) and Artemia nauplii, at a density of 1–2 prey paralarva
−1
Í. Uriarte and A. Farías
The study of enzyme activity in the digestive system of the paralarvae shows that
until 10 DAH at 12 °C, the paralarvae show less enzyme activity of trypsin and chymotrypsin, independent of the diet. After this age, when they are fed with Artemia or
maintained in a fasting state (without food) the paralarvae present little trypsin and
chymotrypsin activity, while the enzymes are significantly activated in paralarvae
when they feed on zoea of king crab, Lithodes santolla (Pereda et al. 2009).
Even though the zoea of king crab is a diet that allows a normal development
throughout the paralarval life until benthic settlement, the paralarvae show a high
level of mortality during the first 15 DAH with an absence of growth. The exponential growth of paralarvae starts only after 22 DAH. Consequently, this early period
is characterized by a high level of mortality and zero growth could be related with
two phenomena: (1) the arms do not reach enough length to manipulate the zoeae of
king crab according to Uriarte et al. (2010) and (2) the digestive system is immature
according to Pereda et al. (2009). Therefore, only paralarvae with enough energy
reserve to manage surviving the first 2 or 3 weeks post hatching could capture the
zoeae and survive.
The complete development of R� fontaniana is documented for paralarvae fed
with L� santolla (Uriarte et al. 2010), but the paralarvae fed only with Artemia at
12 °C survived but did not grow during 70 days of culture (Uriarte et al. 2011a).
Amphipod prey was not consumed by the paralarvae, and the consumption of
zoea of Pagurus sp� and Petrolisthes laevigatus did not allow the growth and survival of R� fontaniana. This was due to the zoeae behaviour and the lower organic content in these species in comparison to the king crab zoeae (Uriarte et al. 2011a, b).
Furthermore, R� fontaniana paralarvae presented a high mortality due to cannibalism. According to Miranda et al. (2011), this behaviour increases significantly
along with paralarvae cultivation density. This prevents cultivation of this species
at densities higher than 4 paralarvae L
−1
. Below this density no cannibalism is observed, even though the paralarvae remain in fasting. According to the authors, cannibalism causes between 12.5 and 65.6 % mortality when cultivation has a density
between 8 and 56 paralarvae L
−1
, respectively.
The tendency of a linear growth of AL and eye diameter with regard to the total
length is maintained after finishing the paralarval period and throughout the early
juvenile period.
The juvenile growth rate reached only 3.19 % day
−1
in R� fontaniana during 90 days
after settlement; this value was lower than the specific growth rate observed during
the previous paralarval stage that reached a value of 4.43 % day
−1
(Uriarte et al. 2010).
Settlement and transition to juvenile stage mark the beginning of the consumption of
benthic preys such as small crabs from the Petrolisthes genus (Uriarte et al. 2010).
At the HIM-UACh, females with egg laying in the subtidal zone are caught and
transported to the laboratory. They are kept in a recirculating system at 11 ± 1 °C
until paralarvae hatching. Once they hatch, paralarvae are cultured in 3 L cylindrical
tanks with mild and constant aeration, and total replacement of seawater filtered to
1 µm and UV sterilized every 24 h. The cultures are performed at 11 ± 1°C. Culture
density is 5 paralarvae L
−1
, ruling out daily mortality. The supplied food is zoeae
of king crab ( L� santolla) and Artemia nauplii, at a density of 1–2 prey paralarva
−1
Í. Uriarte and A. Farías