Gustavo Darrigran

Potential Impact of Filter-feeding Invaders on Temperate Inland Freshwater Environments

Since the 1990s, biological invasions have captured the attention of the scientific community as an important element of global change and a major threat to biodiversity. The inland waters of South America provide two examples of biological invasions. This review examines bivalve invasions in South America, summarizes the research results for two species, the Asian clam (Corbicula fluminea) and the golden mussel (Limnoperna fortunei), and suggests further studies. The rapid expansion of invasive bivalves into these environments involves significant changes. Until now, C. fluminea, the Asian clam, did not produce generalized macrofouling in the Neotropical region, as is common in the Holarctic region. However, the first specific cases of macrofouling by C. fluminea were recently detected in heat interchangers of power stations in Brazil. On the other hand, L. fortunei is provoking new economic impacts in South American freshwaters through macrofouling. Before the invasion by the golden mussel, macrofouling was recorded only in the marine and estuarine environments of the Neotropical region. The impact caused by invasive bivalves in this region is not only economic, however. Rapid changes in the benthic community, favoring the presence of Oligochaeta and Hirudinea, as well as the displacement of native species of mollusks, are among the problems related to the presence of the golden mussel. Another issue is the settlement of golden mussels on native bivalves. This bivalve is now a new element in the diet of some native fish species, being the main food item in some cases.

Ecosystem engineering impact of Limnoperna fortunei in South America

Limnoperna fortunei, or golden mussel, has invaded aquatic ecosystems in the Americas following it introduction from Southeast Asia. It is not only an aggressive invasive species, it is also a very effective ecosystem engineer, altering both ecosystem structure and function, and causes great ecological and economic impacts. This paper describes its impact as an ecosystem engineer (on benthic communities and the water column). A review of the existing scientific literature is presented, and the impact and the mechanisms by which the golden mussel modifies, maintains, and creates new environmental conditions in the invaded South American inland freshwater environments are analyzed. Understanding the ecosystem engineering roles of L. fortunei is important for its management and/or control in the invaded areas, and in cases of future invasions.

An Evaluation Pattern for Antimacrofouling Procedures: Limnoperna fortunei Larvae Study in a Hydroelectric Power Plant in South America

Abstract The effects of global change and globalization of trade on the biosphere spur an increase in bioinvasions and their subsequent impact on ecosystems. Continental invading bivalves are important because of their impact on artificially-constructed structures. Limnoperna fortunei was first found in the Neotropical region in 1991. Since then it has dispersed upstream in the Plata and Guaíba basins at a rate of 240 km y−1. This species causes macrofouling in a manner similar to that caused by Dreissena polymorpha. This paper describes the biology of L. fortunei larvae from a hydroelectric power plant in South America. We suggest the importance of knowing the biology of the invading species and the need to consider the settlement patterns and densities of larvae in each of the sectors of the facility in order to achieve a sustainable prevention/control of macrofouling. This study acquires a global significance under the assumption that L. fortunei will eventually invade North America and Europe.

Bivalve distribution in hydrographic regions in South America: historical overview and conservation

Based on literature review and malacological collections, 168 native freshwater bivalve and five invasive species have been recorded for 52 hydrographic regions in South America. The higher species richness has been detected in the South Atlantic, Uruguay, Paraguay, and Amazon Brazilian hydrographic regions. Presence or absence data were analysed by Principal Coordinate for Phylogeny-Weighted. The lineage Veneroida was more representative in hydrographic regions that are poorer in species and located West of South America. The Mycetopodidae and Hyriidae lineages were predominant in regions that are richest in species toward the East of the continent. The distribution of invasive species Limnoperna fortunei is not related to species richness in different hydrographic regions there. The species richness and its distribution patterns are closely associated with the geological history of the continent. The hydrographic regions present distinct phylogenetic and species composition regardless of the level of richness. Therefore, not only should the richness be considered to be a criterion for prioritizing areas for conservation, but also the phylogenetic diversity of communities engaged in services and functional aspects relevant to ecosystem maintenance. A plan to the management of this fauna according to particular ecological characteristics and human uses of hydrographic regions is needed.

Invasion process of Limnoperna fortunei (Bivalvia: Mytilidae): the case of Uruguay River and emissaries of the Esteros del Iberá Wetland, Argentina

Limnoperna fortunei (Dunker, 1857), during its invasion process in South America, has caused severe impacts both on natural environments altering native biodiversity, ecosystem structure and function-, and on man-made structures causing economic looses. Twenty-one samples were taken from the right bank of the Uruguay River, from tributaries of the Uruguay and Parana Rivers, the drainage of the Esteros del Ibera Wetland. Based on this fieldwork, the presence of larvae and adults of L. fortunei was determined. Also, through the comparison of environmental characteristic with the known tolerance limits for the species, the possibility of its establishment in environments not yet invaded was determined. Most of the sampling stations have features that allow the development of stable populations L. fortunei, including the rivers that drain the Esteros del Ibera, allowing access of this invasive species to this important wetland.

Evaluation of sampling and analysis techniques for early detection of Limnoperna fortunei (Mytilidae) in limit areas of its distribution

on numerous South American rivers includes, among others, alteration of benthonic communities, alteration of fish diet, as well as severe macrofouling problems at industrial water intakes (Darrigran, 2002). Thus, it is fundamental to know the dynamic distribution of this invading species to explain its invading process and to have access to basic informa-tion to predict its distribution/ dispersion pattern.In the framework of a larger Project, in which we try to establish the extreme distribution limits of this species in South America, this work has as its goal to evaluate the efficiency of the sampling techniques of larvae and adults for the early detection of the invading species. For this purpose, sampling was carried out in different water bodies in limit areas of the species distribution in the en-dorreic system in the Province of Cordoba, Argentina.Between December 15 and 18, 2006, quantitative and qualitative samples of benthos and plankton were taken in eight localities looking for adults and larvae of the golden mussel (Table 1). Differing from sam-pling techniques in environments already invaded by the golden mussel where the aim is to know the population distribution of the settlement (e.g. Mansur et al., 2003), the goal of the sampling done in this work was early de-tection of the invading bivalve. The presence of adults of

Reproductive pattern of the aggressive invader Limnoperna fortunei (Bivalvia, Mytilidae) in South America

Abstract Limnoperna fortunei is an aggressive freshwater invader species recorded for the first time in 1991 at Balneario Bagliardi, Río de la Plata Estuary, Argentina. Since then it has spread rapidly within South America. We tested the hypothesis that invasive species need a time span for the development of a reproductive pattern once settled in a new environment. We analyzed the reproductive cycle of a population of L. fortunei from Guaiba Lake (29°55′S; Rio Grande do Sul, Brazil) and compared it with previous studies at Balneario Bagliardi (34°52′S). We studied 834 specimens from Guaiba, following routine histological techniques. At any sampled period, the highest proportion of specimens were mature and gonads showed no resting periods. Female gonad maturation periods and oocyte growth were recorded throughout the year. Five periods of spawning of different intensity were differentiated. The reproductive pattern of the Guaiba population showed more spawning events and a remarkable recovery capacity of the female gonad compared to the Balneario Bagliardi population. The reproductive patterns of L. fortunei from Guaiba two years after invasion shows similarities with the reproductive pattern described previously from Balneario Bagliardi after two and three years of invasion.

Gonadal cycle of Corbicula fluminea (Bivalvia: Corbiculidae) in Pampean streams (Southern Neotropical Region)

Corbicula fluminea is an aggressive invasive species of bivalve that arrived into the Río de la Plata River between the late 60’s and early 70’s, and dispersed widely throughout the Neotropical region, evidencing a great adaptive flexibility to different environmental conditions. This species is a functional hermaphrodite with larval incubation inside the inner demibranch. Despite its widespread distribution, there are no previous studies of complete gonadal histology and reproductive cycle for this species in the Neotropical region. In this study, the reproductive dynamics of C. fluminea in a temperate region, the Santa Catalina Pampean stream, Argentina, is described. Samples of 20–30 individuals were collected monthly from April 2003-April 2005 and processed using traditional histological techniques. During the two years of this study, seven spawning events were recognized. Three major spawns occurred in spring and summer, and other four minor ones during summer and autumn. Events of oocyte recovery were observed after spawning. A high number of incubating individuals was detected. The results stressed the difficulty of identifying a particular pattern of gamete release and of spawning behaviour in this invasive species, especially when inhabiting an unstable environment.

Ecosystem Engineering Impact ofLimnoperna fortuneiin South America

Limnoperna fortunei, or golden mussel, has invaded aquatic ecosystems in the Americas following it introduction from Southeast Asia. It is not only an aggressive invasive species, it is also a very effective ecosystem engineer, altering both ecosystem structure and function, and causes great ecological and economic impacts. This paper describes its impact as an ecosystem engineer (on benthic communities and the water column). A review of the existing scientific literature is presented, and the impact and the mechanisms by which the golden mussel modifies, maintains, and creates new environmental conditions in the invaded South American inland freshwater environments are analyzed. Understanding the ecosystem engineering roles of L. fortunei is important for its management and/or control in the invaded areas, and in cases of future invasions.