31
Females brood the eggs continuously and become increasingly pale during this period. When the eggs begin to hatch, the female may aid the process by manipulating the eggs. After paralarvae hatch, or in some cases before, when the female is
completely spent, she will crawl out of her den and a short distance away to die.
When a female dies prior to paralarvae hatching, her eggs may be quickly predated
or overcome by algae and fungi.
2.5.6 Hatching and Paralarvae
Cuttlefish hatch as juveniles, without distinct paralarvae. Immediately after hatching, cuttlefish begin to learn to capture size-appropriate prey in a fashion similar
to adults (e.g. Hanlon and Messenger 1988; Guibé et al. 2012). Cuttlefish hatch
with fully differentiated tentacles and use these for prey capture from the start. In
contrast, Teuthid squid also have no true larval form but some species do have an
ecological and morphological paralarvae stage wherein they do not yet assume the
adult form and lifestyle (Boletzky 2003a). Social interactions, such as schooling
of adult Loliginid squid, do not occur in newly hatched cephalopods. Loliginid
squid begin schooling several weeks after hatching and this continues into adult life
(Boletzky 2003a). Like cuttlefish, Loliginid squid begin learning attack behaviours
by experience, foraging immediately post hatching (Boletzky 2003a; Darmaillacq
et al. 2008) but prey choice is partially cued prior to hatching. However, because
Loliginid squid do not hatch with fully formed tentacles, their prey capture methods
must change during ontogeny. For both of these cephalopod groups, hatchlings learn
to position themselves appropriately to attack prey from a direction most likely to
yield success, and to adopt different attack behaviours depending on the availability
and density of both prey and competitors (Boletzky 2003a).
Octopus hatchlings will still have a remnant of the yolk sac attached that may
sustain them for the first few days out of the egg. As for squid, hatchlings that do
not yet have the adult form and lifestyle are termed paralarvae (Young and Harman 1988). These are planktonic, positively phototaxic (causing them to swim
upwards in the water column), and neustonic (orienting towards the water–air
interface); at the ocean’s surface they hunt planktonic crustaceans and molluscs
appropriate for their size. Prey are located visually (Villanueva et al. 1996) and
must be provided at sufficient density and frequency to facilitate growth. Adequate
nutrition for paralarvae of meroplanktonic octopus species poses one of the greatest challenges to cultivation. Paralarvae grow rapidly and move about by jetting
(Villanueva et al. 1995). As they approach the size at which they settle, they may
cling to floating objects (Nixon and Mangold 1996). Recruitment of meroplanktonic species to the benthic population is heavily influenced by oceanographic
parameters including temperature influencing growth rate, and current patterns
influencing retention and recruitment to the source population (Katsanevakis and
Verriopoulos 2006a). Octopus hatchlings with adult form and lifestyle are termed
juveniles, and these occur in the large-egged forms (Voight and Grehan 2000;
Anderson and Wood 2012), many of which are found in deep sea. They adopt a
2 Behaviour
Females brood the eggs continuously and become increasingly pale during this period. When the eggs begin to hatch, the female may aid the process by manipulating the eggs. After paralarvae hatch, or in some cases before, when the female is
completely spent, she will crawl out of her den and a short distance away to die.
When a female dies prior to paralarvae hatching, her eggs may be quickly predated
or overcome by algae and fungi.
2.5.6 Hatching and Paralarvae
Cuttlefish hatch as juveniles, without distinct paralarvae. Immediately after hatching, cuttlefish begin to learn to capture size-appropriate prey in a fashion similar
to adults (e.g. Hanlon and Messenger 1988; Guibé et al. 2012). Cuttlefish hatch
with fully differentiated tentacles and use these for prey capture from the start. In
contrast, Teuthid squid also have no true larval form but some species do have an
ecological and morphological paralarvae stage wherein they do not yet assume the
adult form and lifestyle (Boletzky 2003a). Social interactions, such as schooling
of adult Loliginid squid, do not occur in newly hatched cephalopods. Loliginid
squid begin schooling several weeks after hatching and this continues into adult life
(Boletzky 2003a). Like cuttlefish, Loliginid squid begin learning attack behaviours
by experience, foraging immediately post hatching (Boletzky 2003a; Darmaillacq
et al. 2008) but prey choice is partially cued prior to hatching. However, because
Loliginid squid do not hatch with fully formed tentacles, their prey capture methods
must change during ontogeny. For both of these cephalopod groups, hatchlings learn
to position themselves appropriately to attack prey from a direction most likely to
yield success, and to adopt different attack behaviours depending on the availability
and density of both prey and competitors (Boletzky 2003a).
Octopus hatchlings will still have a remnant of the yolk sac attached that may
sustain them for the first few days out of the egg. As for squid, hatchlings that do
not yet have the adult form and lifestyle are termed paralarvae (Young and Harman 1988). These are planktonic, positively phototaxic (causing them to swim
upwards in the water column), and neustonic (orienting towards the water–air
interface); at the ocean’s surface they hunt planktonic crustaceans and molluscs
appropriate for their size. Prey are located visually (Villanueva et al. 1996) and
must be provided at sufficient density and frequency to facilitate growth. Adequate
nutrition for paralarvae of meroplanktonic octopus species poses one of the greatest challenges to cultivation. Paralarvae grow rapidly and move about by jetting
(Villanueva et al. 1995). As they approach the size at which they settle, they may
cling to floating objects (Nixon and Mangold 1996). Recruitment of meroplanktonic species to the benthic population is heavily influenced by oceanographic
parameters including temperature influencing growth rate, and current patterns
influencing retention and recruitment to the source population (Katsanevakis and
Verriopoulos 2006a). Octopus hatchlings with adult form and lifestyle are termed
juveniles, and these occur in the large-egged forms (Voight and Grehan 2000;
Anderson and Wood 2012), many of which are found in deep sea. They adopt a
2 Behaviour