8
or intermittently, over several weeks or months. Declining physiological conditions
in spawning females are often recognizable by the production of more or less disorganized egg masses (Boletzky 1987). Under normal conditions, egg masses are
structured at spawning in a specific way that sets the stage for a more or less complex process of modifications taking place during the development of the embryos,
from the initial condition having permitted the passage of spermatozoa to the final
condition allowing the young animals to hatch out (Boletzky 1998).
1.2.1 Fecundity
Depending on the species considered, average fecundities vary from a few hundred (e.g. sepiolid squids) to several thousands (e.g. sepiid cuttlefish) or hundreds
of thousands (e.g. merobenthic octopods like Octopus vulgaris or O� cyanea) or
around one million eggs as in the pelagic octopod Ocythoe tuberculata (Salman
and Akalin 2012). The maximum potential fecundity estimated for the jumbo squid
Dosidicus gigas is 32 million oocytes; so far, this is the largest number recorded
for any cephalopod (Nigmatullin and Markaida 2009). When spawning is drawn
out over weeks or months, there may be pauses of variable lengths, but there is no
state of sexual rest (regression of reproductive organs). The terminology used with
cephalopods therefore has the term multiple spawning. The sum total of eggs laid
over a long time by a single female may be several times the instantaneous holding capacity of the ovary sac (see Sect. 1.2.2). Apart from the high number of eggs
thus produced, the staggered hatching of young individuals, which results from the
staggered spawning events, may open up some interesting possibilities for cephalopod culture. In particular, it would be interesting to test broad mating combinations
among the offspring (e.g. involving descendants of different males).
1.2.2 Growth
No matter whether it is attained through fast or slow growth (Moltschaniwskyj
2004), reaching a large adult size is not necessary for carrying through a successful
cephalopod culture. If sexual maturity is attained at a comparatively small adult size,
in many bottom-living species a long spawning activity based on continued maturation of ova can still lead to a high lifetime fecundity of reared individuals (Boletzky
1988). The highest growth rates observed under wild conditions (as deduced from
postmortem analysis of periodic growth structures, e.g. statoliths) can be equalled
under ideal culture conditions, with varied, high-quality food, especially when the
maximum amount of food ingested per day represents a tissue mass nearly 10 % of
the body mass of the young cephalopod (Mangold and Boletzky 1973). Rations of
30 % of the body mass have been reported for juvenile benthic octopuses (Quintana
et al. 2011). However, the actual investment of ingested energy in body mass
production changes with age (Briceño et al. 2010). The observations of Pecl and
S. von Boletzky and R. Villanueva
or intermittently, over several weeks or months. Declining physiological conditions
in spawning females are often recognizable by the production of more or less disorganized egg masses (Boletzky 1987). Under normal conditions, egg masses are
structured at spawning in a specific way that sets the stage for a more or less complex process of modifications taking place during the development of the embryos,
from the initial condition having permitted the passage of spermatozoa to the final
condition allowing the young animals to hatch out (Boletzky 1998).
1.2.1 Fecundity
Depending on the species considered, average fecundities vary from a few hundred (e.g. sepiolid squids) to several thousands (e.g. sepiid cuttlefish) or hundreds
of thousands (e.g. merobenthic octopods like Octopus vulgaris or O� cyanea) or
around one million eggs as in the pelagic octopod Ocythoe tuberculata (Salman
and Akalin 2012). The maximum potential fecundity estimated for the jumbo squid
Dosidicus gigas is 32 million oocytes; so far, this is the largest number recorded
for any cephalopod (Nigmatullin and Markaida 2009). When spawning is drawn
out over weeks or months, there may be pauses of variable lengths, but there is no
state of sexual rest (regression of reproductive organs). The terminology used with
cephalopods therefore has the term multiple spawning. The sum total of eggs laid
over a long time by a single female may be several times the instantaneous holding capacity of the ovary sac (see Sect. 1.2.2). Apart from the high number of eggs
thus produced, the staggered hatching of young individuals, which results from the
staggered spawning events, may open up some interesting possibilities for cephalopod culture. In particular, it would be interesting to test broad mating combinations
among the offspring (e.g. involving descendants of different males).
1.2.2 Growth
No matter whether it is attained through fast or slow growth (Moltschaniwskyj
2004), reaching a large adult size is not necessary for carrying through a successful
cephalopod culture. If sexual maturity is attained at a comparatively small adult size,
in many bottom-living species a long spawning activity based on continued maturation of ova can still lead to a high lifetime fecundity of reared individuals (Boletzky
1988). The highest growth rates observed under wild conditions (as deduced from
postmortem analysis of periodic growth structures, e.g. statoliths) can be equalled
under ideal culture conditions, with varied, high-quality food, especially when the
maximum amount of food ingested per day represents a tissue mass nearly 10 % of
the body mass of the young cephalopod (Mangold and Boletzky 1973). Rations of
30 % of the body mass have been reported for juvenile benthic octopuses (Quintana
et al. 2011). However, the actual investment of ingested energy in body mass
production changes with age (Briceño et al. 2010). The observations of Pecl and
S. von Boletzky and R. Villanueva