laboratory, and under differing feeding regimens (Villares 2008; Villares et al.
2009). Split individuals showed the lowest feeding rates, lipids, energy in the
pyloric caeca, and gonad production. Regenerating individuals had the highest
feeding rate, lipids were allocated to the pyloric caeca and gametogenesis was
carried out. Individuals with arms in an advance regeneration state showed an
intermediate feeding rate and no allocation of lipids to the pyloric caeca. These
individuals spawned, demonstrating that the gonads were mature. Availability of
food and healthy nutritional state before fission seem to play key roles in survival.
The sea star appears to be extremely well adapted to carry out sexual and asexual
reproduction by increasing feeding rates. Regenerating individuals increase their
feeding rates to store energy for regeneration, gamete production and nutrient
storage. When gonads are mature, individuals have arms in an advanced state of
regeneration, and feeding rates decrease since spawning may inhibit feeding. After
fission, when capacity to attack prey is reduced, the stored energy is used for
survival. Only those individuals that were able to store energy through high
feeding rates can survive. During this period, individuals do not spend energy in
gamete production, but invest all energy resources in regenerating new arms,
which are necessary to increase feeding capacity for the following sexual reproduction period.
The great regenerative capacity of this sea star led Rubilar (2009) to study the
cellular mechanism involved in arm regeneration. The sea star regenerates through
a morphallatic mechanism (i.e. cellular migration, dedifferentiation and transdifferentiation), followed by a morphogenetic process producing a miniature arm.
Then new structures arise between the arm tip and the stump. The morphology of
the radial nerve cord and circumoral ring of the sea star was examined by Rubilar
et al. (2008b), using antisera raised against the gastropod neuropeptide Tritonia
Pedal Ganglia (TPep) (Lloyd et al. 1996). This peptide has been found in motorneurons as well as in neurons located in the pedal ganglia of the gastropod
Tritonia diomedea and appears to be involved in motor functions. In the sea star,
TPep-like immunoreactivity was detected in the hyponeural, ectoneural systems
and innervations of the tube feet. In the hyponeural system, the label was observed
in numerous neurons and groups of cell bodies in the radial nerve cord as well as in
the circumoral ring. In the ectoneural systems, the TPep-like immunoreactivity
was observed in isolated neurons as well as in the neuroepithelium.
The oral-brooding sea star Anasterias minuta (Fig. 11.3b) is the most abundant
intertidal sea star in Patagonia (Salvat 1985; Gil and Zaixso 2007). This species is
widely distributed along the Patagonian coast, including the Malvinas Islands, and
occurs from the middle intertidal zone to 80 m depth (Bernasconi 1964c).
Brooding females bend their arms in order to create a chamber to protect the
young. In Ría Deseado (RD; 47°45
0 S, 65°55
0 W), brooding occurs during the
coldest months of the year, from March to October (Salvat 1985; Gil and Zaixso
2007). Salvat (1985) suggested a biennial oogenic cycle. Gonads are in a recovery
phase from April to June after eggs are laid. Gametogenesis begins in July and
vitellogenesis continues during the second austral winter; maturity is reached in
January. Female gonads might take around 20 months to mature. On the contrary,
11 Echinoderms from Argentina
371
2009). Split individuals showed the lowest feeding rates, lipids, energy in the
pyloric caeca, and gonad production. Regenerating individuals had the highest
feeding rate, lipids were allocated to the pyloric caeca and gametogenesis was
carried out. Individuals with arms in an advance regeneration state showed an
intermediate feeding rate and no allocation of lipids to the pyloric caeca. These
individuals spawned, demonstrating that the gonads were mature. Availability of
food and healthy nutritional state before fission seem to play key roles in survival.
The sea star appears to be extremely well adapted to carry out sexual and asexual
reproduction by increasing feeding rates. Regenerating individuals increase their
feeding rates to store energy for regeneration, gamete production and nutrient
storage. When gonads are mature, individuals have arms in an advanced state of
regeneration, and feeding rates decrease since spawning may inhibit feeding. After
fission, when capacity to attack prey is reduced, the stored energy is used for
survival. Only those individuals that were able to store energy through high
feeding rates can survive. During this period, individuals do not spend energy in
gamete production, but invest all energy resources in regenerating new arms,
which are necessary to increase feeding capacity for the following sexual reproduction period.
The great regenerative capacity of this sea star led Rubilar (2009) to study the
cellular mechanism involved in arm regeneration. The sea star regenerates through
a morphallatic mechanism (i.e. cellular migration, dedifferentiation and transdifferentiation), followed by a morphogenetic process producing a miniature arm.
Then new structures arise between the arm tip and the stump. The morphology of
the radial nerve cord and circumoral ring of the sea star was examined by Rubilar
et al. (2008b), using antisera raised against the gastropod neuropeptide Tritonia
Pedal Ganglia (TPep) (Lloyd et al. 1996). This peptide has been found in motorneurons as well as in neurons located in the pedal ganglia of the gastropod
Tritonia diomedea and appears to be involved in motor functions. In the sea star,
TPep-like immunoreactivity was detected in the hyponeural, ectoneural systems
and innervations of the tube feet. In the hyponeural system, the label was observed
in numerous neurons and groups of cell bodies in the radial nerve cord as well as in
the circumoral ring. In the ectoneural systems, the TPep-like immunoreactivity
was observed in isolated neurons as well as in the neuroepithelium.
The oral-brooding sea star Anasterias minuta (Fig. 11.3b) is the most abundant
intertidal sea star in Patagonia (Salvat 1985; Gil and Zaixso 2007). This species is
widely distributed along the Patagonian coast, including the Malvinas Islands, and
occurs from the middle intertidal zone to 80 m depth (Bernasconi 1964c).
Brooding females bend their arms in order to create a chamber to protect the
young. In Ría Deseado (RD; 47°45
0 S, 65°55
0 W), brooding occurs during the
coldest months of the year, from March to October (Salvat 1985; Gil and Zaixso
2007). Salvat (1985) suggested a biennial oogenic cycle. Gonads are in a recovery
phase from April to June after eggs are laid. Gametogenesis begins in July and
vitellogenesis continues during the second austral winter; maturity is reached in
January. Female gonads might take around 20 months to mature. On the contrary,
11 Echinoderms from Argentina
371