400
even sex. The diet of O� mimus changes seasonally and this may be related to changes in prey availability. Mature males ingest a higher amount of prey in spring and
summer compared to the consumption in fall and winter (Cortez et al. 1995b). Thus,
feeding and predation patterns seem to be related to physiological changes occurring as the animal matures together with environmental variability. These constitute
important aspects that must be considered during O� mimus aquaculture. O� mimus
feeding seems to be affected by a combination of physiological and environmental
factors, being considered as an opportunistic species like other octopods. This feature may be a consequence of adaptive mechanisms related to the wide environmental and ecological variability that the habitat of this species is exposed to, e.g. the
frequent impacts of El Niño Southern Oscillation (ENSO) events.
21.3.2 Gonadal Development and Maturation on Males
and Females
O� mimus from northern Chile has high growth rates that depend on water temperature and develop rapidly during oceanographic warming events like ENSO. The
reproduction of this species occurs year-round with two maximum peaks occurring
in summer and another, but minor, during fall (Wolff and Pérez 1992; Olivares
et al. 1994; Cortez et al. 1995b; Olivares et al. 1996). Most of the octopus reproduction activity occurs at the rocky coastal platform, in shallow warm waters less
than 10 m in depth. During reproduction periods, the animals inhabit rocky burrows
surrounded by sandy bottoms. Females spawn and take care of the eggs during the
embryonic development (Olivares et al. 1996). This period can last between 45 and
90 days depending on the season and sea temperature. Variations on temperature,
light and food availability are the main factors that modulate the reproductive cycle
in cephalopods (Mangold 1987).
Successful reproduction of O� mimus seems to occur in semi-darkness conditions
while full illumination inhibits sexual maturation. It has been observed that low intensity of light (30 Lx cm
−1
approximately) stimulates spawning, while higher levels
inhibit it (Zúñiga et al. 1995). The role of this environmental factor in sexual maturity
of cephalopods is regulated by the optical gland through the secretion of the octopus
gonadotrophin-releasing hormone (Oct-GnRH) that promotes the synthesis and the
release of sexual steroids that leads to ovarian maturation and yolk synthesis carried by follicular cells (Wodinsky 1977; Minakata et al. 2009). In O� vulgaris reared
in dark conditions, the principal cells of the optical gland concentrate ARN associated with the synthesis and secretion of a protein with apparent gonadotropic effects
(Wells and Wells 1977). The gland has the highest levels of synthesis when the exposure to light decreases, demonstrating that the aqueous extracts stimulate glandular
tritiated thymidine incorporation and subsequent proliferation of germ cells and follicular cells under in vitro conditions (Koueta et al. 1995).
In the coast of northern Chile, the sex ratio of O� mimus fluctuates from 1:2 to 1:7
males per female from spring to fall, depending on the variation of the number of
Ó. Zúñiga et al.
even sex. The diet of O� mimus changes seasonally and this may be related to changes in prey availability. Mature males ingest a higher amount of prey in spring and
summer compared to the consumption in fall and winter (Cortez et al. 1995b). Thus,
feeding and predation patterns seem to be related to physiological changes occurring as the animal matures together with environmental variability. These constitute
important aspects that must be considered during O� mimus aquaculture. O� mimus
feeding seems to be affected by a combination of physiological and environmental
factors, being considered as an opportunistic species like other octopods. This feature may be a consequence of adaptive mechanisms related to the wide environmental and ecological variability that the habitat of this species is exposed to, e.g. the
frequent impacts of El Niño Southern Oscillation (ENSO) events.
21.3.2 Gonadal Development and Maturation on Males
and Females
O� mimus from northern Chile has high growth rates that depend on water temperature and develop rapidly during oceanographic warming events like ENSO. The
reproduction of this species occurs year-round with two maximum peaks occurring
in summer and another, but minor, during fall (Wolff and Pérez 1992; Olivares
et al. 1994; Cortez et al. 1995b; Olivares et al. 1996). Most of the octopus reproduction activity occurs at the rocky coastal platform, in shallow warm waters less
than 10 m in depth. During reproduction periods, the animals inhabit rocky burrows
surrounded by sandy bottoms. Females spawn and take care of the eggs during the
embryonic development (Olivares et al. 1996). This period can last between 45 and
90 days depending on the season and sea temperature. Variations on temperature,
light and food availability are the main factors that modulate the reproductive cycle
in cephalopods (Mangold 1987).
Successful reproduction of O� mimus seems to occur in semi-darkness conditions
while full illumination inhibits sexual maturation. It has been observed that low intensity of light (30 Lx cm
−1
approximately) stimulates spawning, while higher levels
inhibit it (Zúñiga et al. 1995). The role of this environmental factor in sexual maturity
of cephalopods is regulated by the optical gland through the secretion of the octopus
gonadotrophin-releasing hormone (Oct-GnRH) that promotes the synthesis and the
release of sexual steroids that leads to ovarian maturation and yolk synthesis carried by follicular cells (Wodinsky 1977; Minakata et al. 2009). In O� vulgaris reared
in dark conditions, the principal cells of the optical gland concentrate ARN associated with the synthesis and secretion of a protein with apparent gonadotropic effects
(Wells and Wells 1977). The gland has the highest levels of synthesis when the exposure to light decreases, demonstrating that the aqueous extracts stimulate glandular
tritiated thymidine incorporation and subsequent proliferation of germ cells and follicular cells under in vitro conditions (Koueta et al. 1995).
In the coast of northern Chile, the sex ratio of O� mimus fluctuates from 1:2 to 1:7
males per female from spring to fall, depending on the variation of the number of
Ó. Zúñiga et al.