11.3 Research
11.3.1 Biological Studies
Crinoidea
Crinoids are the least species-rich class of the Argentine echinoderms and therefore the least studied among them. Only two species are known from the region.
Andersson (1904) and Mortensen (1917, 1920b) studied the brooding habits of
Isometra vivipara on the Argentine shelf using samples collected by the Sweden
South Polar Expedition. Austin H. Clark (1915 et seq.) covered the Argentine
species in his monograph. Speel and Dearborn (1983) provided important tools for
the identification of crinoids from the Southern Ocean.
Tommasi described crinoids from Argentina and Brazil, collected by the
expeditions of the Brazilian vessel N/Oc. Almirante Saldanha between 26–38°S
(Tommasi 1969b; Tommasi et al. 1988a, 1988b). Only one publication (Bernasconi 1934) deals exclusively with Argentine taxa.
Asteroidea
Research has been focused mainly on eight species of sea stars: Allostichaster
capensis, Anasterias minuta, Asterina stellifera, Cosmasterias lurida, Astropecten
brasiliensis, Luidia ludwigi scotti, Ctenodiscus australis and Diplopteraster clarki.
Allostichaster capensis (= A. inaequalis; Fig. 11.3D) is a fissiparous sea star
inhabiting South Atlantic Ocean coasts (Clark and Downey 1992). This sea star
has been extensively studied. Pucheta and Urban (1989) focused on trophic
behavior. The authors carried out laboratory and in situ observations by SCUBA
diving in NG. Allostichaster capensis is a relatively specialized predator, feeding
on the gastropod Tegula patagonica and on the mussels Lithophaga patagonica
and Aulacomya atra atra, selecting this last species over the other prey regardless
of their abundance. Rubilar et al. (2005) found that A. capensis has a very low
percentage of females and displays an annual sexual and asexual reproductive
cycle. Fission is most frequent in summer (November-January) and arm regeneration occurs during the rest of the year. In March, gametogenesis begins when
gonads appear in the regenerating arms. In August, sexual maturity is achieved.
Shedding of gametes does not take place until the arms are almost fully regenerated and individuals are ready to undergo fission. Spawning occurs during
September and October followed by a long recovery phase from November to
March while arms are in the first stages of regeneration. The pyloric caecum index
displays a clear annual cycle and a reciprocal relationship with gonad index,
demonstrating the storage function of pyloric caeca and suggesting nutrient
transfer. Biochemical analysis revealed that only lipids are translocated from
pyloric caeca to gonads at the beginning of gametogenesis (Rubilar et al. 2008a).
11 Echinoderms from Argentina
369
11.3.1 Biological Studies
Crinoidea
Crinoids are the least species-rich class of the Argentine echinoderms and therefore the least studied among them. Only two species are known from the region.
Andersson (1904) and Mortensen (1917, 1920b) studied the brooding habits of
Isometra vivipara on the Argentine shelf using samples collected by the Sweden
South Polar Expedition. Austin H. Clark (1915 et seq.) covered the Argentine
species in his monograph. Speel and Dearborn (1983) provided important tools for
the identification of crinoids from the Southern Ocean.
Tommasi described crinoids from Argentina and Brazil, collected by the
expeditions of the Brazilian vessel N/Oc. Almirante Saldanha between 26–38°S
(Tommasi 1969b; Tommasi et al. 1988a, 1988b). Only one publication (Bernasconi 1934) deals exclusively with Argentine taxa.
Asteroidea
Research has been focused mainly on eight species of sea stars: Allostichaster
capensis, Anasterias minuta, Asterina stellifera, Cosmasterias lurida, Astropecten
brasiliensis, Luidia ludwigi scotti, Ctenodiscus australis and Diplopteraster clarki.
Allostichaster capensis (= A. inaequalis; Fig. 11.3D) is a fissiparous sea star
inhabiting South Atlantic Ocean coasts (Clark and Downey 1992). This sea star
has been extensively studied. Pucheta and Urban (1989) focused on trophic
behavior. The authors carried out laboratory and in situ observations by SCUBA
diving in NG. Allostichaster capensis is a relatively specialized predator, feeding
on the gastropod Tegula patagonica and on the mussels Lithophaga patagonica
and Aulacomya atra atra, selecting this last species over the other prey regardless
of their abundance. Rubilar et al. (2005) found that A. capensis has a very low
percentage of females and displays an annual sexual and asexual reproductive
cycle. Fission is most frequent in summer (November-January) and arm regeneration occurs during the rest of the year. In March, gametogenesis begins when
gonads appear in the regenerating arms. In August, sexual maturity is achieved.
Shedding of gametes does not take place until the arms are almost fully regenerated and individuals are ready to undergo fission. Spawning occurs during
September and October followed by a long recovery phase from November to
March while arms are in the first stages of regeneration. The pyloric caecum index
displays a clear annual cycle and a reciprocal relationship with gonad index,
demonstrating the storage function of pyloric caeca and suggesting nutrient
transfer. Biochemical analysis revealed that only lipids are translocated from
pyloric caeca to gonads at the beginning of gametogenesis (Rubilar et al. 2008a).
11 Echinoderms from Argentina
369