Research Article |
Corresponding author: Gustavo Darrigran ( invasion@fcnym.unlp.edu.ar ) Academic editor: Stephan Bullard
© 2017 Yamila Reshaid, Luciana Cao, Francisco Brea, María Ortiz Blanche, Santiago Torres, Gustavo Darrigran.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Reshaid Y, Cao L, Brea F, Blanche MO, Torres S, Darrigran G (2017) Variation in the distribution of Corbicula species (Mollusca: Bivalvia: Corbiculidae) after 25 years of its introduction in the Río de la Plata, Argentina. Zoologia 34: 1-6. https://doi.org/10.3897/zoologia.34.22181
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In 1981, Corbicula fluminea (Müller, 1774) and C. largillierti (Philippi, 1844) were recorded at the Río de la Plata River. During the 1980’s, C. largillierti was found on a continuous fringe in the shore of that river, while C. fluminea was only found North of Buenos Aires’ harbor. Ten years later, C. fluminea spread to Punta Indio, while C. largillierti remained restricted to tributary streams. The density and size frequency distribution of both species were compared with previous data from samples performed in the same area in 1985–1989. The aim of this research was to determine whether the densities of both species decreased; whether C. fluminea is still more abundant than C. largillierti; and whether the size frequency distributions indicate different population structures from those observed in the end of the 1980’s. Nine localities from the river shore were sampled, and each individual was identified and measured. The size of C. fluminea varied between 2 and 39 mm, showing the highest frequency of individuals between 20 and 25 mm; furthermore the density decreased 90% in 2015/2016. No specimens of C. largillierti were found. In conclusion, the populations of Corbicula inhabiting the Río de la Plata River are retracting.
Bivalves, freshwater, invasion, invertebrates, mussel
The Asiatic clam, Corbicula fluminea (Müller, 1774) naturally inhabits freshwater bodies from Southeast Asia, Africa, India, Pacific Islands and Australia (
In South America, two species of Corbicula Megerle, 1811, C. fluminea and C. largillierti (Philippi, 1844), arrived in the Río de la Plata River in the 1970’s, according to
In 1979,
Corbicula fluminea reached high densities when compared to the native bivalves, approximately 1,200 ind./m2 in the Río de la Plata River (
The aim of the present work was to ascertain the distribution of Corbicula in the Argentinian shore of the Río de la Plata River. The following hypotheses were tested: 1) the densities of both species have decreased; 2) C. fluminea is found in higher frequencies than C. largillierti; 3) the size frequency distributions indicate different population structures than those found in the end of the 1980’s.
Samples were taken from nine localities along the Argentinian shore of Río de la Plata River, between June 2015 and June 2016, during low tides (Table
Sampling localities. Geographical coordinates, sample date, number of samples (n), Presence (+), Absence (–) of C. fluminea and substrate type.
Locality | Geographical coordinate | Date | n | Presence/ Absence |
Substrate Type |
---|---|---|---|---|---|
Anchorena | 34°29’S, 58°13’W | 10 Dec 2015 | 3 | – | “Tosca” (tight sandy silt) and stone |
Quilmes | 34°42’S, 58°13’W | 20 Jun 2016 | 3 | + | Sand, stone |
Punta Lara | 34°45’S, 57°59’W | 6 Jun 2016 | 2 | + | Sand |
Bagliardi | 34°52’S, 57°48’W | 26 Oct 2015 | 3 | + | Sand-lime, stone |
La Balandra | 34°55’S, 57°43’W | 17 Jun 2015 | 4 | + | Sand, stone |
Punta Blanca | 31°56’S, 57°40’W | 28 Sep 2015 | 3 | + | Sand, rush |
Atalaya | 35°08’S, 57°31’W | 22 Jul 2015 | 4 | + | Sand |
Magdalena | 35°10’S, 57°30’W | 22 Jul 2015 | 3 | + | Sand |
Punta Indio | 35°16’S, 57°13’W | 7 Nov 2015 | 2 | – | Sand, stone, rush |
Corbicula fluminea was present in seven sampling sites (Table
Through a non-parametric statistical analysis Mann-Whitney U test (U = 1097, p = 0.000039), significant differences were found when comparing the densities obtained during this study with those previously registered for the same localities (
Figure
The comparison between the density values of the species of Corbicula obtained during this study and those recorded 25 years ago in the same samples sites, leads to the conclusion that these species are retracting from the shores of Río de la Plata River’. While in the 80’s C. fluminea and C largillierti showed frequency values of 75% and 37% respectively, the frequency value obtained for C. fluminea in this study was 52%, and no individuals of C. largillierti were found alive. Significant differences between densities recorded in 2015-2016 with those registered in 1990 for the same localities allow us to state that the density of the species has decreased by about 90%.
The decreasing density (e.g. C. fluminea) or the displacement of a species from an environment (e.g. C. largillierti), are frequent phenomena and their causes are very difficult to ascertain. Similar examples are the mass mortality of the native species Amarilladesma mactroides (Reeve, 1854) in South America (
In the Argentinian shore of the Río de la Plata River, the size of C. fluminea varied between 2 and 39 mm. The highest frequency of individuals between 20 and 25 mm was found in Magdalena’s beach, which is also the locality with the highest density of individuals in the present work (Fig.
It is possible that a decrease in population density could be caused by environmental changes such as extreme variations in the water level (
The first change could be the expected outcome of a three-phase process of invasion (
The influence of C. fluminea on benthic species was investigated by
This work was partially financed by the Facultad de Ciencias Naturales y Museo-UNLP-(11/N795), Beca Entrenamiento de la CIC, Beca Interna Doctoral CONICET, Beca de Experiencia Laboral FCNyM (UNLP) and CONICET. LC, ST and GD are researchers of CONICET. We thank C. Damborenea for helping in the assorted tasks.