consistent with a biocenosis previously described by Zaixso et al. (1998). Growth
studies were conducted by Rodríguez et al. (2008, 2009) using calcein as a
chemical marker. Growth was observed through a distinct green fluorescent label
on the jaws. Coulin et al. (2009) described jaw growth and related it to individual
body growth. The authors proposed a power function relationship between the
growth of the teeth and dental plate and the body size.
Echinoidea
Sixteen species of sea urchins have been reported from the region. However, there
is information available on the general biology and ecology of only six species:
Arbacia dufresnii, Pseudechinus magellanicus, Loxechinus albus, Tripylaster
philippii, Abatus cavernosus and Encope emarginata.
The sea urchin Arbacia dufresnii (= A. dufresnei; Fig. 11.3d) is widely distributed around the southern tip of South America, from RP on the Atlantic coast
to the north of Puerto Montt (Chile; 41°30
0 S, 72°56
0 W) on the Pacific coast, at a
depth range of 0–315 m (Bernasconi 1953). This species was associated with
shallow waters and areas with coarse sediments (sand) and hard substrates in SJG
and NG (Carriquiriborde et al. 1983; Zaixso and Lizarralde 2000; Brogger 2005;
Epherra 2009). A new turbellarian species (Syndesmis patagonica) was found and
described in the gut of A. dufresnii from NG. This is the first record of a sea urchin
of the genus Arbacia as host of an umagillid (Brogger and Ivanov 2010). The diet
of A. dufresnii was studied by using a qualitative analysis of prey items in gut
contents at different sites and across different depths from Buenos Aires to GSJ.
Arbacia dufresnii is primarily carnivorous (Vásquez et al. 1984), and its diet is
determined by the local composition of potential prey (Penchaszadeh and Lawrence 1999). Some aspects of the embryonic development were studied by Bernasconi (1942) and Brogger et al. (2004). Reproduction of A. dufresnii was studied
at NG (Brogger 2005; Brogger et al. 2010). There are two spawning periods, a first
spawning event occurs during spring and a second in summer. Gametogenesis is
synchronous between males and females and spawning is synchronized. Epherra
et al. (2009a) and Epherra (2009) found that A. dufresnii has a biochemical cycle
directly related to the reproductive cycle at NG and shows differences between
sexes. A similar prolonged spawning period during spring and summer was also
observed. The overall biochemical composition, in different organs, was similar to
that of other sea urchin species, with a high proportion of protein, followed by
lipids and carbohydrates. The population of A. dufresnii at NG displays a good
nutritional state, as both the gut and the gonads act as storage organs. The
reproduction of this species in southern populations (SJOG) has some interpopulation differences in the duration of spawning events and gonadal indices
(Epherra et al. 2009b).
Pseudechinus magellanicus (Fig. 11.4b) is the most common sea urchin in
southern South America. This species is distributed from 35°S on the Atlantic
Ocean coast through the Magellan Strait and throughout TF, to Puerto Montt,
11 Echinoderms from Argentina
375
studies were conducted by Rodríguez et al. (2008, 2009) using calcein as a
chemical marker. Growth was observed through a distinct green fluorescent label
on the jaws. Coulin et al. (2009) described jaw growth and related it to individual
body growth. The authors proposed a power function relationship between the
growth of the teeth and dental plate and the body size.
Echinoidea
Sixteen species of sea urchins have been reported from the region. However, there
is information available on the general biology and ecology of only six species:
Arbacia dufresnii, Pseudechinus magellanicus, Loxechinus albus, Tripylaster
philippii, Abatus cavernosus and Encope emarginata.
The sea urchin Arbacia dufresnii (= A. dufresnei; Fig. 11.3d) is widely distributed around the southern tip of South America, from RP on the Atlantic coast
to the north of Puerto Montt (Chile; 41°30
0 S, 72°56
0 W) on the Pacific coast, at a
depth range of 0–315 m (Bernasconi 1953). This species was associated with
shallow waters and areas with coarse sediments (sand) and hard substrates in SJG
and NG (Carriquiriborde et al. 1983; Zaixso and Lizarralde 2000; Brogger 2005;
Epherra 2009). A new turbellarian species (Syndesmis patagonica) was found and
described in the gut of A. dufresnii from NG. This is the first record of a sea urchin
of the genus Arbacia as host of an umagillid (Brogger and Ivanov 2010). The diet
of A. dufresnii was studied by using a qualitative analysis of prey items in gut
contents at different sites and across different depths from Buenos Aires to GSJ.
Arbacia dufresnii is primarily carnivorous (Vásquez et al. 1984), and its diet is
determined by the local composition of potential prey (Penchaszadeh and Lawrence 1999). Some aspects of the embryonic development were studied by Bernasconi (1942) and Brogger et al. (2004). Reproduction of A. dufresnii was studied
at NG (Brogger 2005; Brogger et al. 2010). There are two spawning periods, a first
spawning event occurs during spring and a second in summer. Gametogenesis is
synchronous between males and females and spawning is synchronized. Epherra
et al. (2009a) and Epherra (2009) found that A. dufresnii has a biochemical cycle
directly related to the reproductive cycle at NG and shows differences between
sexes. A similar prolonged spawning period during spring and summer was also
observed. The overall biochemical composition, in different organs, was similar to
that of other sea urchin species, with a high proportion of protein, followed by
lipids and carbohydrates. The population of A. dufresnii at NG displays a good
nutritional state, as both the gut and the gonads act as storage organs. The
reproduction of this species in southern populations (SJOG) has some interpopulation differences in the duration of spawning events and gonadal indices
(Epherra et al. 2009b).
Pseudechinus magellanicus (Fig. 11.4b) is the most common sea urchin in
southern South America. This species is distributed from 35°S on the Atlantic
Ocean coast through the Magellan Strait and throughout TF, to Puerto Montt,
11 Echinoderms from Argentina
375