males display an annual cycle. Spawning occurs once a year during March and
April, following a short recovery period in May. Gametogenesis begins again in
June, and maturity is reached in February (Salvat 1985). The pyloric caecum index
displays a clear annual cycle, with maximum index values occurring before the
maximum gonad weight, suggesting nutrient translocation. Except in males, in
which a one month lag was observed, no inverse relationship was found between
pyloric caeca and gonads (Gil and Zaixso 2007). In Punta Maqueda (46°01
0 S,
67°01
0 W), the brooding season of A. minuta shows the same pattern (Escudero
1999). The number of juveniles follows a linear regression with female size
(Escudero and Zaixso 2003). This sea star is a common predator and prominent
member of intertidal and shallow sublittoral communities (Gil 2002; Zaixso 2004;
Bertness et al. 2006; Gil and Zaixso 2007). The relationship between predatory and
brooding activities in RD was studied by Gil (2002) and by Gil and Zaixso (2007).
They found a seasonal feeding cycle with the maximum feeding frequency during
the austral summer that was related to the female brooding habits. During brooding
season, females with juveniles did not feed. The feeding frequency was also
positively correlated with seawater temperature and sea star size, but no differences were found along a shore-level gradient. Anasterias minuta consumes a wide
range of prey, including mollusks and crustaceans. The diet composition differed
among the study sites (GSJO and RD), and it varied with depth and body size. The
diversity of prey consumed by this sea star was highest on a semi-exposed coast
during the warmest season on the infralittoral fringe. Abundance of prey beneath
rocks within tide pools at the infralittoral fringe does not seem to determine diet
composition. Generally, the sea star consumes the purple mussel Perumytilus
purpuratus and the gastropod Pareuthria plumbea more than other prey, even
when they are not the most abundant prey present. However, at the midlittoral
zone of semi-exposed coast, it feeds on prey species according to their abundance.
A significant positive correlation was found between the size of the sea star and the
size of the most frequent prey. The authors suggested that A. minuta could have a
variable impact on the community structure since there appears to be an opportunistic feeding strategy, taking unattached, wave-washed mussels when available
rather that attached mussels (Gil and Zaixso 2008). An ascothoracid parasite
(Dendrogaster argentinensis) of A. minuta was found at RD (Grygier and Salvat
1984). It is the first ascothoracid described from the South American coast.
The sea star Asterina stellifera (= Patiria stellifer) is distributed from Cabo Frio
(Brazil) to Mar del Plata (MDP) (Argentina; 38°10
0 S, 57°10
0 W) in the West
Atlantic Ocean (Clark and Downey 1992) and is a very common sea star on MDP
shores (Salvat 1975a). The embryonic and larval development was studied by
Salvat (1975a). The dipleurula larvae appear 32 h after fertilization and the larva is
completely formed after one week. The size of the sea star varied with depth; the
largest individuals were found in deeper waters (Salvat 1975b). This sea star has
been defined as an omnivore and scavenging feeder (Meretta et al. 2009a). It feeds
on macroalgae, bryozoans, tunicates, polyps and biofilm. Between 2006 and 2009,
the size structure distribution changed from bimodal to unimodal, thus suggesting
that the younger cohort had grown to reach the maximum size and that there was
372
M. I. Brogger et al.
April, following a short recovery period in May. Gametogenesis begins again in
June, and maturity is reached in February (Salvat 1985). The pyloric caecum index
displays a clear annual cycle, with maximum index values occurring before the
maximum gonad weight, suggesting nutrient translocation. Except in males, in
which a one month lag was observed, no inverse relationship was found between
pyloric caeca and gonads (Gil and Zaixso 2007). In Punta Maqueda (46°01
0 S,
67°01
0 W), the brooding season of A. minuta shows the same pattern (Escudero
1999). The number of juveniles follows a linear regression with female size
(Escudero and Zaixso 2003). This sea star is a common predator and prominent
member of intertidal and shallow sublittoral communities (Gil 2002; Zaixso 2004;
Bertness et al. 2006; Gil and Zaixso 2007). The relationship between predatory and
brooding activities in RD was studied by Gil (2002) and by Gil and Zaixso (2007).
They found a seasonal feeding cycle with the maximum feeding frequency during
the austral summer that was related to the female brooding habits. During brooding
season, females with juveniles did not feed. The feeding frequency was also
positively correlated with seawater temperature and sea star size, but no differences were found along a shore-level gradient. Anasterias minuta consumes a wide
range of prey, including mollusks and crustaceans. The diet composition differed
among the study sites (GSJO and RD), and it varied with depth and body size. The
diversity of prey consumed by this sea star was highest on a semi-exposed coast
during the warmest season on the infralittoral fringe. Abundance of prey beneath
rocks within tide pools at the infralittoral fringe does not seem to determine diet
composition. Generally, the sea star consumes the purple mussel Perumytilus
purpuratus and the gastropod Pareuthria plumbea more than other prey, even
when they are not the most abundant prey present. However, at the midlittoral
zone of semi-exposed coast, it feeds on prey species according to their abundance.
A significant positive correlation was found between the size of the sea star and the
size of the most frequent prey. The authors suggested that A. minuta could have a
variable impact on the community structure since there appears to be an opportunistic feeding strategy, taking unattached, wave-washed mussels when available
rather that attached mussels (Gil and Zaixso 2008). An ascothoracid parasite
(Dendrogaster argentinensis) of A. minuta was found at RD (Grygier and Salvat
1984). It is the first ascothoracid described from the South American coast.
The sea star Asterina stellifera (= Patiria stellifer) is distributed from Cabo Frio
(Brazil) to Mar del Plata (MDP) (Argentina; 38°10
0 S, 57°10
0 W) in the West
Atlantic Ocean (Clark and Downey 1992) and is a very common sea star on MDP
shores (Salvat 1975a). The embryonic and larval development was studied by
Salvat (1975a). The dipleurula larvae appear 32 h after fertilization and the larva is
completely formed after one week. The size of the sea star varied with depth; the
largest individuals were found in deeper waters (Salvat 1975b). This sea star has
been defined as an omnivore and scavenging feeder (Meretta et al. 2009a). It feeds
on macroalgae, bryozoans, tunicates, polyps and biofilm. Between 2006 and 2009,
the size structure distribution changed from bimodal to unimodal, thus suggesting
that the younger cohort had grown to reach the maximum size and that there was
372
M. I. Brogger et al.