Density and body size of the larval stages of the invasive golden mussel (Limnoperna fortunei) in two neotropical rivers

Abstract

AIM: The present study involved an analysis of the monthly variations in the population densities and body sizes of the different stages of planktonic larvae of the invasive golden mussel (Limnoperna fortunei), in the rivers Paraguay and Miranda; METHODS: The study was carried out between February 2004 and January 2005. Monthly collection of the plankton samples was accompanied by physical, chemical and biological analyses of the water; RESULTS: The Miranda River presented higher values of calcium, pH, alkalinity, conductivity and total phosphorous. Larval density varied from 0-24 individuals.L-1 in the Paraguay River, with a peak in March of 2004, while in the Miranda River, densities varied between 0-9 individuals.L-1 with a peak in February of 2004. No larvae were encountered during the coldest months, May and June. No significant correlations were found between environmental variables and larval density in either river. Only the valved larval stages were recorded. The "D" and veliger forms were most abundant; umbonate larvae were rare in the Miranda River samples. Mean body sizes of "D", veliger and umbonate larval stages were, respectively, 111, 135 and 152 µm, in the Paraguay River, and 112, 134 and 154 µm in the Miranda River. Principal Components Analysis indicated positive relationships between "D" larval stage size and the ratio between inorganic and organic suspended solids, while negative relationships were found between larval size and calcium and chlorophyll-<img border=0 width=7 height=8 src="/img/revistas/alb/2012nahead/ALB_AOP_230307car01.jpg">; CONCLUSIONS: The larvae were recorded in the plankton during most of the year, with the exception of the two colder months. Neither densities nor larval stage body sizes were significantly different between the two rivers. Possible positive effects of food and calcium concentrations on body size were not recorded. This species may be adapted to grow in environments with elevated sediment concentrations.

Environmental variables driving the larval distribution of Limnoperna fortunei in the upper Paraná River floodplain, Brazil

“…Although the dimensionality of dissolved oxygen and larval stages of L. fortunei were located in opposite quadrants in the RDA, the mean values of oxygen were considerably high, with a minimum of 7 mg.l -1 in February. Despite Eilers et al (2011) observed a decrease in the larval density of L. fortunei during periods of lower dissolved oxygen concentration, our results did not present such pattern, since the month with the lowest values of dissolved oxygen (February) had higher peaks of larval density (16,000 ind.m -3 ). February was the most populous month of our whole sample period.…”

“…The dominance of smaller larval stages at plankton (D-Shaped larvae and Straight Hinged) compared to larger ones, suggest that the last stages (Umbonated, Plantigrade and Pediveliger) have already tried some settlements on the substrates or they were naturally lost. Eilers et al (2011) when studying larval densities of L. fortunei in the Miranda and Paraguay Rivers also found higher densities of the initial stage (D-Shaped larvae), with a great population decrease together with the larvae maturing, with a reduction of ~80% of D-shaped larvae and ~10% of Umbonated.…”

Toxic Microcystis (cyanobacteria) inhibit recruitment of the bloom‐enhancing invasive bivalve Limnoperna fortunei

“…Abundance cycles of L. fortunei larvae in the water column indicate that the mussel has an extended (7–10 months) reproductive period spanning from spring to autumn, and a single relaxation phase centred on the winter. This pattern is characteristic of all the sites surveyed in Argentina (Cataldo & Boltovskoy, ; Rojas Molina & José de Paggi, ; Boltovskoy et al ., ) and elsewhere, including Brazil (Eilers et al ., ) and Japan (Nakano et al ., ), with the sole exception of Salto Grande reservoir. Here, in addition to the winter drop, there was a very marked decline in January–April.…”

More than two decades after the introduction of Limnoperna fortunei (Dunker 1857) in La Plata Basin

“…Santos et al (2005), from observations performed in Rio Grande do Sul State, reported that the minimum size of larvae is around 80 µm. (Eilers et al, 2011), through a discriminant analysis considering the proportion of different larval stage in samples collected in the Paraguay River, found that the stage "D" prevailed in 80% of the plankton larvae.…”