Studies of biodiversity of echinoderms from South America increased in the last years, leading to the recent publication of the book “Studies in Echinoderms from Latin America” (Alvarado & Solís-Marín, 2013). Particularly, for the Argentine Sea, several researchers have been studying reproduction in asteroids, echinoids, holothuroids and ophiuroids (Rubilar, Pastor de Ward & Díaz de Vivar, 2005; Marzinelli, Bigatti, Giménez & Penchaszadeh, 2006; Gil & Zaixso 2007; Brogger, Martinez & Penchaszadeh, 2010, 2013; Pérez, Boy, Morriconi & Calvo , 2010; Martinez, Giménez & Penchaszadeh, 2011), taxonomy of holothuroids and asteroids (Hernández, 1981, 1982; Hernández & Tablado, 1985; Martinez & Brogger, 2012; Martinez, Thandar & Penchaszadeh, 2013; Martinez, Solís-Marín & Penchaszadeh, 2014), ecology of asteroids (Brogger & Penchaszadeh, 2008; Gil & Zaixso, 2008), local biogeography of echinoderms (Zaixso & Lizarralde, 2000; Souto, Escolar, Genzano & Bremec, 2014), and physiology of echinoids and asteroids (Rubilar, Pastor de Ward & Díaz de Vivar, 2006; Pérez, Boy, Morriconi & Calvo, 2008).

Since 2009, studies on benthic communities were enhanced by the assistance of the oceanographic vessel B/O Puerto Deseado from CONICET (National Scientific and Tecnological Council). New descriptions of species as Thandarum hernandezi Martinez & Brogger, 2012, Havelockia pegi Martinez, Thandar & Penchaszadeh, 2013, Armadillogorgia arbertoi Cerino & Lauretta, 2013, Benthodytes violeta Martinez, Solís-Marín. & Penchaszadeh, 2014 among others, have resulted from campaigns performed by the oceanographic vessel along the Argentine coasts at different depths (Martinez & Brogger, 2012; Martinez et al., 2013; Cerino & Lauretta, 2013; Chiesa & Alonso, 2014; Martinez et al., 2014; Pastorino & Signorelli in press).

In this work we summarize the Echinodermata fauna collected during three expeditions, one from Antarctica and two from the Argentine Sea. The main goal of this report is to contribute on the knowledge of diversity of echinoderms, studying the proportion among classes and among the three campaigns in the Southwestern Atlantic Sea in order to update recent revisions and to enhance future contributions on the subject.

MATERIALS AND METHODS

The study was conducted in the Southwestern Atlantic Ocean, along the coast of Argentina. Three campaigns were performed: Mejillón II (hereafter M-II; Fig. 1 A), Summer Antarctic Campaign 2011 (CAV-III; Fig. 1 B) and the final stretch of the Summer Antarctic Campaign 2011 (CAV-IV; Fig. 1 C). M-II was conducted from 35º S to 39º S, between 10 and 140 m depth (31 stations) from September 9th to September 20th 2009. CAV-III took place around the Antarctic Peninsula, South Shetland and South Orkney Islands, covering 67-754 m depth (21 stations) from March 15th to March 27th 2011. CAV-IV corresponds to the final part of the Summer Antarctic Campaign conducted between 39º S and 55º S, at 30-140 m depth (22 stations) from March 15th to March 27th 2011. Samples were taken using fishing net and a dredge trawl. All samples were sorted, identified to the lowest taxonomic level possible and stored in 96 % ethanol. For each station the presence of each echinoderm class was analyzed, and the proportions were represented.

RESULTS

A total of 74 stations were analyzed in this work, of which in 68 was found at least one echinoderm individual (92 %). The total number of stations where each class appeared was: Asteroidea 50 (68 %), Echinoidea 47 (64 %), Ophiuroidea 41 (55 %), Holothuroidea 38 (51 %) and Crinoidea 15 (20 %) (Fig. 2 A).

In M-II campaign, 94% of the stations had a positive record of echinoderms, being Echinoidea the most common class (74 %; Fig. 2 B). For all CAV-III stations echinoderms were collected and Ophiuroidea was the best represented group. From the total of the stations at CAV-III, Ophiuroidea showed 100 % of occurrence and Asteroidea was the second with 90.5 %. On the other hand Crinoidea showed the lowest with 66.7 % (Fig. 2 C). Echinoderms were possible to obtain at 82 % of the stations during CAV-IV, being the lowest value comparing with the other two campaigns. Asteroidea had 73 % of representation during CAV-IV, in contrast, Crinoids were not found in this sampling (Fig. 2 D).

DISCUSSION

Echinoderms are well represented along the Argentine coast and Antarctica, since of the 74 stations only six have negative occurrence of echinoderms, reinforcing observations of other authors (e.g., O´Loughlin, Paulay, Davey & Michonneau, 2011). In this study all five classes of Echinodermata were present, which is in accordance with observed by different authors that studied the fauna of the Argentine Sea and Antarctica (O´Loughlin, 2002; Eléaume, Bohn, Roux & Améziane, 2012; Stöhr, O’Hara & Thuy 2012; Brogger et al., 2013).

At the Argentine Sea, Asteroidea is the most representative class. At CAV-IV, 72.7 % of the total stations showed sea stars (Fig. 2 D). This observation is consistent with Brogger et al. (2013) whom indicated that for this area Asteroidea is the most speciose class (58 %). As for M-II campaign, the fauna from the Buenos Aires coast presented all the classes. Bernasconi (1941) described six species of Asteroidea, four of Echinoidea, three of Ophiuroidea and only one of Holothuroidea from that region, with no records of Crinoidea. At that study she analyzed species that were collected up to 109 m. The Crinoidea from the M-II was collected at 145 m, which could explain why Crinoidea were not described in previous studies (Fig. 2 B).

The high number of echinoderms present per stations for the M-II could be related with the high productivity in this area by the confluence between Brazil and Malvinas currents (Rivas, Dogliotti & Gagliardini, 2006; Brogger et al., 2013). In Antarctica (CAV-III), echinoderms appear in all the studied stations (Fig. 2 C). On the contrary and apart from the close and affinities reported by de Moura Barboza, de Moura, Lanna, Oackes and Campos (2011), Argentine Sea presents in this study a different scenario with some stations with no echinoderms. This great appearance of the phylum in Antarctica leads to some authors to define Antarctica as a hot spot of echinoderms diversity (O´Loughlin et al., 2011).

This short report contributes to the knowledge about relationship within classes of this group at the Southwestern Atlantic, an area of high diversity and with benthic communities with a high presence of echinoderms. Future works will study and describe the species not yet analyzed. Besides, studies on the interactions between echinoderms and other invertebrates are going to be the next step for a better understanding of these phyla in the Argentine Sea and near waters. This work could lead to a global known of these benthic communities.

ACKNOWLEDGMENTS

We thank the crew of the B/O Puerto Deseado, and especially to all the participants of the first Latin American Echinoderm Congress (CLE) for providing productive discussions about biogeography and on species diversity and distribution. Authors are members of CONICET. Partial financial support was provided by Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET PIP-0253) and by Agencia Nacional de Promoción Científica y Tecnológica (PICT 2012-0561 and PICT 2013-2504).

RESUMEN

Diversidad de equinodermos del Atlántico suroccidental. En los últimos años se han incrementado los estudios sobre la biodiversidad de equinodermos de Latinoamérica. En el presente trabajo, se exponen los resultados sobre muestras obtenidas en tres expediciones a lo largo de la costa argentina (35 - 55º S) y cerca de la Península Antártica. La primera campaña analizada, Mejillón II (M-II; 2009), se llevó acabo entre 35º - 39º S cubriendo profundidades entre 10 y 140 m. La segunda, parte de la Campaña Antártica de Verano 2011 (CAV-III; 2011), tuvo lugar en el área de la Península Antártica, Shetland del Sur e islas Orcadas del Sur (profundidad entre 67 hasta 754 m). La última expedición analizada en este trabajo fue el último tramo de la Campaña Antártica de Verano (CAV-IV; 2011) desde 39º - 55º S y entre 30 - 140 m de profundidad. Como resultado, 74 estaciones fueron estudiadas, en las cuales en 68 se encontró al menos un espécimen del Phylum Echinodermata. Considerando todas las estaciones, el porcentaje de encuentro para cada clase fue Asteroidea (68 %), Echinoidea (64 %), Ophiuroidea (55 %), Holothuroidea (51 %) and Crinoidea (20 %). En la campaña M-II, los equinodermos estuvieron presentes en el 94 % de las estaciones muestreadas, siendo Echinoidea el más frecuente (74 %). En relación a la Campaña CAV-III, los equinodermos estuvieron presentes en todas las estaciones muestreadas; Ophiuroidea fue la clase más representativa en número de estaciones (100 %). El valor más bajo de aparición de equinodermos fue encontrado en la campaña CAV-IV (82 %), donde Asteroidea estuvo presente en el 73 % de las muestras, y los crinoideos estuvieron ausentes.

Palabras clave: Echinodermata, Biodiversidad, B/O Puerto Deseado, Mar Argentino, Antártida.

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