11.3.2 Argentine Continental Shelf Waters
The study of benthic communities in ACS started four decades ago (Bastida et al.
2007). In some of these studies, echinoderm species showed high abundance and
diversity and were used to define different ecological areas along the ACS (Roux
et al. 1988, 1993; Bastida et al. 1992).
The ecological information on echinoderms from shelf waters comes from
monitoring studies aimed at determining the invertebrate by-catch associated with
commercial fisheries. The first faunistic inventory of the Patagonian shrimp
(Pleoticus muelleri) fishing grounds of SJOG was developed by Roux et al. (1995).
The benthic community between 27 and 98 m showed a total of 22 species of
echinoderms with a higher abundance in soft than in hard bottoms. Pseudechinus
magellanicus, together with four species of mollusks and one crustacean were
dominant in the benthic assemblage. Other species commonly collected in the gulf
were Henricia obesa, Cosmasterias lurida, Ophiomyxa vivipara and Ophiactis
asperula.
In external shelf areas the assemblage of macroinvertebrates dominated by the
Patagonian scallop Zygochlamys patagonica has been broadly studied. This
community is located along the shelf-break front, following the 100 m isobath,
between 37° and 44°S. Echinoderms comprise one of the most important taxa, in
terms of biomass and numbers. The northern sector (37–39°S) is characterized by
high density of Ctenodiscus australis, Diplasterias brandti, Labidiaster radiosus
(Asteroidea), Gorgonocephalus chilensis, O. asperula (Ophiuroidea) and the
echinoid Austrocidaris canaliculata. Sterechinus agassizii (Echinoidea), Ophiacantha vivipara and O. asperula (Ophiuroidea) and the sea star D. brandti stand
out in the southern sector (Bremec and Lasta 2002; Bremec et al. 2006; Schejter
et al. 2008).
Echinoderms, mainly sea stars, have a potentially important ecological role in
this community. The sea star Calyptraster sp. (possibly Diplopteraster clarki,
according to Escolar and Bremec 2009) appears as the top predator, preying on the
sea star C. australis, and the gastropods Odontocymbiola magellanica, Adelomelon
ancilla and Fusitriton magellanicus. These gastropod species are the main predators of the Patagonian scallop. Other echinoderm species such as L. radiosus,
C. australis and S. agassizii are intermediate predators, preying on scallops and
brittle stars, scallops being the principal item in the diet of L. radiosus (Botto et al.
2006).
Another conspicuous sea star in ACS is Astropecten brasiliensis. This is an
abundant species in the Buenos Aires Province coastal and shelf areas (Roux
2004). It inhabits soft bottoms (sand-mud) between 7 and 60 m. This species feeds
on banks of the mussel M. edulis platensis, commercially exploited until 1988
(Penchaszadeh 1980; Ciocco et al. 1998). This sea star is one of the most important
predators of mollusks, mostly young gastropods and bivalves (Penchaszadeh
1973). Astropecten brasiliensis shows a selective diet that varies with depth and
bottom type, limited only by the size of prey. This sea star ingests prey whole; the
11 Echinoderms from Argentina
381
The study of benthic communities in ACS started four decades ago (Bastida et al.
2007). In some of these studies, echinoderm species showed high abundance and
diversity and were used to define different ecological areas along the ACS (Roux
et al. 1988, 1993; Bastida et al. 1992).
The ecological information on echinoderms from shelf waters comes from
monitoring studies aimed at determining the invertebrate by-catch associated with
commercial fisheries. The first faunistic inventory of the Patagonian shrimp
(Pleoticus muelleri) fishing grounds of SJOG was developed by Roux et al. (1995).
The benthic community between 27 and 98 m showed a total of 22 species of
echinoderms with a higher abundance in soft than in hard bottoms. Pseudechinus
magellanicus, together with four species of mollusks and one crustacean were
dominant in the benthic assemblage. Other species commonly collected in the gulf
were Henricia obesa, Cosmasterias lurida, Ophiomyxa vivipara and Ophiactis
asperula.
In external shelf areas the assemblage of macroinvertebrates dominated by the
Patagonian scallop Zygochlamys patagonica has been broadly studied. This
community is located along the shelf-break front, following the 100 m isobath,
between 37° and 44°S. Echinoderms comprise one of the most important taxa, in
terms of biomass and numbers. The northern sector (37–39°S) is characterized by
high density of Ctenodiscus australis, Diplasterias brandti, Labidiaster radiosus
(Asteroidea), Gorgonocephalus chilensis, O. asperula (Ophiuroidea) and the
echinoid Austrocidaris canaliculata. Sterechinus agassizii (Echinoidea), Ophiacantha vivipara and O. asperula (Ophiuroidea) and the sea star D. brandti stand
out in the southern sector (Bremec and Lasta 2002; Bremec et al. 2006; Schejter
et al. 2008).
Echinoderms, mainly sea stars, have a potentially important ecological role in
this community. The sea star Calyptraster sp. (possibly Diplopteraster clarki,
according to Escolar and Bremec 2009) appears as the top predator, preying on the
sea star C. australis, and the gastropods Odontocymbiola magellanica, Adelomelon
ancilla and Fusitriton magellanicus. These gastropod species are the main predators of the Patagonian scallop. Other echinoderm species such as L. radiosus,
C. australis and S. agassizii are intermediate predators, preying on scallops and
brittle stars, scallops being the principal item in the diet of L. radiosus (Botto et al.
2006).
Another conspicuous sea star in ACS is Astropecten brasiliensis. This is an
abundant species in the Buenos Aires Province coastal and shelf areas (Roux
2004). It inhabits soft bottoms (sand-mud) between 7 and 60 m. This species feeds
on banks of the mussel M. edulis platensis, commercially exploited until 1988
(Penchaszadeh 1980; Ciocco et al. 1998). This sea star is one of the most important
predators of mollusks, mostly young gastropods and bivalves (Penchaszadeh
1973). Astropecten brasiliensis shows a selective diet that varies with depth and
bottom type, limited only by the size of prey. This sea star ingests prey whole; the
11 Echinoderms from Argentina
381