Limnoperna fortunei
(golden mussel)

Preferred Common Name

• golden mussel

Other Scientific Names

• Dreissena siamensis (Morelet, 1866)
• Limnoperna depressa (Brandt & Temcharoen, 1971)
• Limnoperna lacustris (von Martens, 1875)
• Limnoperna supoti Brandt, 1974
• Modiola fortunei (Reeve 1858)
• Modiola lacustris (von Martens, 1875)
• Volsella fortunei Dunker, 1857

International Common Names

• Spanish: mejillón dorado
• Portuguese: mexilhão-dourado

• Domain: Eukaryota
•     Kingdom: Metazoa
•         Phylum: Mollusca
•             Class: Bivalvia
•                 Subclass: Pteriomorphia
•                     Order: Mytiloida
•                         Unknown: Mytiloidea
•                             Family: Mytilidae
•                                 Genus: Limnoperna
•                                     Species: Limnoperna fortunei

The generic name Limnoperna Rochebrune 1888 was erected to distinguish this monotypic genus from the other mytilids. Limnoperna fortunei has been cited under a variety of names (Morton, 1973; Ricciardi, 1998). One species and its subspecies of the genus Limnoperna was recognized from Japan: Limnoperna fortunei fortunei (Dunker, 1857) and Limnoperna fortunei kikuchii Habe, 1981 (Habe, 1981). Kimura et al. (1999) confirmed that L. fortunei kikuchii isa synonym of Xenostrobus securis Lamarck, 1819.

L. fortunei is a bivalve mollusc that belongs to the Mytilidae. Adult L. fortunei are sessile and are generally found in clumps on hard substrates.

The shells of adult L. fortunei are equivalve and heteromyarian. It is dark-brown above the umbonal keel and paler yellow-brown below.This is caused by the nacre of the interior of the shell being purple above and white below the keel. The presence of a nacreous layer in L. fortunei removes this genus from all contact with Dreissenacea.

The outer periostracal layer of the shell is smooth and shiny, and thick where it curls inwards at the shell margin. The umbones are very nearly terminal and the dorsal ligamental margin is straight or, at most, only slightly curved. The ventral margin of the shell is the most variable feature and in different specimens varied between the two extremes of being either straight or distinctly arcuate. There are no hinge teeth or byssal notches.

The shells are yellow-brown. In clear water, for example in northern Argentina, they look golden; so it is called the ‘golden mussel’.

Its longevity is variable. In the natural environment of Bagliardi Beach, Argentina, longevity was recorded as 3.2 years (Maroñas et al., 2003). Boltovskoy and Cataldo (1999) estimated it as 3 years in Cuenca del Plata, Argentina. Iwasaki and Uryu (1998) suggested a longevity of 2 years in the Uji River, Japan, from 4 to 5 years in Korea and over 10 years in central China.

It is dioecious and reaches sexual maturity in the first year of its life span. Spawning occurs at temperatures of 16-28°C. After spawning and fertilization, the trocophore is the first planktonic stage. Several stages of free-swimming planktonic veliger (D-larvae about 7 days, between 80 and 146 mm; veliconcha between 90 and 237 mm and pediveliger or umbonate, more than 256 mm). Then the larvae settle as plantigrade mussels and attach to the substrate as juveniles. These larvae are free-swimming and planktonic and live in the water column. These stages of the mussel’s life cycle are the most vulnerable to environmental fluctuations.

The larvae settle to the bottom and securely attach to a hard substrate by byssal threads, which are secreted from a gland at the base of the mussel’s muscular foot.

L. fortunei are epifaunal, unlike most other South American native freshwater bivalves, and not overly selective, therefore they colonize almost any solid, submerged surface such as buoys, water intake pipes, rocks, rooted aquatic plants, boat hulls, and the shells of other molluscs. Its eurioic status allows a quick and effective distribution in water bodies. The juveniles differentiate into males and females; with lengths of 5 mm in the spring and 9 mm in the summer, and can reach sexual maturity after 6 mm total length (Darrigran et al., 2003).

Morton (1975) first recorded it in Hong Kong where it had been introduced from China via supplied potable water. The species has been recorded in Taiwan, fouling potable water supply systems (Tan et al.,1987). In Japan, L. fortunei was first recorded in the ancient Lake Biwa in 1991 (Kimura, 1994) and has subsequently invaded associated potable water treatment systems (Nakai, 1995). It was first recorded in South America in the 1990s (Pastorino et al., 1993).

Natural Dispersal (Non-Biotic)

The natural dispersal of L. fortunei is passive, and occurs as veliger larvae that are passively transported from colonized areas through connected streams. The natural dispersal is downstream and dependent on water currents.

Vector Transmission (Biotic)

There is little information about biotic vector transmission. The specimens could be eaten and carried in the gut of fishes (Belz, 2006) birds, etc.

Accidental Introduction

L. fortunei has been accidentally introduced in South America. Darrigran and Pastorino (1995) proposed the non-intentional introduction of L. fortunei into the Río de la Plata in 1991, through ballast water of ocean vessels. At that time an increase of trade between Argentina and two countries that L. fortunei inhabits occurred. In Guaíba Basin, it was also probably introduced via ballast water (Mansur et al., 1999) and in the Itaipu reservoir (Zanella and Marenda, 2002) probably via boats used for sport.

Freshwater macrofouling is a new economic/environmental problem for South America. Until the beginning of the 1990s, macrofouling in the neotropical region occurred only in marine and mixohaline waters. Since the introduction of L. fortunei, macrofouling also extended to freshwaters in Argentina, Brazil, Paraguay and Uruguay (Darrigran and Damborenea, 2005). This kind of problem (freshwater macrofouling) is caused by the appearance of larvae or juveniles of L. fortunei. It impacts the sources of water supply of many water-treatment plants, industrial refrigeration systems, and power stations. Among the usual problems involved, the following are the most significant: pipe obstruction; reduction in flow velocity in pipes due to friction loss (turbulent flows); accumulation of empty valves and pollution of water ways by massive mortality; filter occlusion; and increase in the corrosion of surfaces due to mussel infestation. This new economical and environmental problem for the neotropical regions produces unexpected expenses, for example, due to system shutdowns, the need for chemical or mechanical cleaning, and pipe and filter replacement.

Impact on Habitats

The large biomass associated with high densities of L. fortunei impacts on aquatic food chains. Several species of native fish consume L. fortunei (López Armengol and Casciotta, 1998; Montalto et al., 1999) and it has become the main food source for Leporinus obtusidens (Anostomidea) in the Río de la Plata (Penchaszadeh et al., 2000).

However, many other aspects of the biology of L. fortunei are poorly understood (Sylvester et al., 2005), including its filtering capacity. Because of its high density in the Plata basin, L. fortunei could increase water clarity in a manner similar to that caused by Dreissena polymorpha in North America (Darrigran and Damborenea, 2005).

Impact on Biodiversity

The impact caused by L. fortunei it is not restricted to the economic aspect. Darrigran et al. (1998) showed that since the introduction of L. fortunei at Bagliardi Beach, two gastropods commonly found have been displaced: one of them, Chilina fluminea, is no longer found; whereas the other, Gundlachia concentrica, is becoming rare. In contrast, several benthic species, uncommon or absent before the occurrence of L. fortunei in this microenvironment, are now present, including the Annelids: Oligochaeta (eight species), Aphanoneura (one species) and Hirudinea (eight species). In addition, several species of crustaceans and insects never cited at the invaded areas are now present (Darrigran et al., 1998).

The most direct and severe ecological impact has been the epizoic colonization of native naiads (Hyriidae and Mycetopodidae) by L. fortunei, similar to the impact of D. polymorpha on native bivalves in North America (Ricciardi et al., 1997).The displacement of the native naiads resulted from their inability to open and shut their valves because of the byssally-attached mussels on their shells. The quantitative impact of L. fortunei on native naiads in South America is unknown. L. fortunei alsosettles on other native fauna, such as Pomacea canaliculata (Gastropoda, Ampullariidae) and Aegla platensis (Anomura, Aeglidae), as well as on the introduced Corbicula fluminea (Bivalvia, Corbiculidae) (Darrigran et al., 2000; Darrigran, 2002).

• Proved invasive outside its native range
• Highly adaptable to different environments
• Is a habitat generalist
• Pioneering in disturbed areas
• Benefits from human association (i.e. it is a human commensal)
• Fast growing
• Has high reproductive potential
• Gregarious

• Altered trophic level
• Damaged ecosystem services
• Ecosystem change/ habitat alteration
• Infrastructure damage
• Modification of natural benthic communities
• Modification of nutrient regime
• Negatively impacts aquaculture/fisheries
• Reduced native biodiversity
• Threat to/ loss of native species

• Competition - smothering
• Competition (unspecified)
• Filtration
• Fouling
• Interaction with other invasive species
• Rapid growth

• Highly likely to be transported internationally accidentally
• Difficult to identify/detect as a commodity contaminant
• Difficult/costly to control

No productive benefit (economic, social or environmental) is known for L. fortunei invasion (Darrigran, 2002).