Limnoperna fortunei (Dunker, 1857) is an invasive freshwater mussel species (family Mytilidae) native to China and Southeast Asia, which has since spread to and across South America and is now a significant cause of biofouling. Its shell is a distinctive golden color with an inner mother-of-pearl layer. It is dioecious and its larvae are free-swimming. As an adult, it typically forms clumps with members of its own species, attaching itself to hard surfaces with its hairlike byssus. L. fortunei is comparable to the zebra mussel (Dreissena polymorpha) in invasive strategy and success; methods of slowing its onslaught on non-native rivers are currently under study.
Brandt (1974) listed it from Mekong River south of Nakon Panom, Maenam Mun River, Lam Chi River, Chao Phraya and the Pasak River. In many klongs and tributaries to the Chao Phraya River, in the Maeklong River, in the south it reaches the Tapi River and Tale Luang near Pattalung.
This species has been introduced in Argentina in 1991 by commercial shipping, and is now present elsewhere in south America (e.g., the Paraguay River system and the Pantanal wetland in Brazil, and expansion into north American river systems could be expected; Oliveira et al. 2010). The native range of the species is unclear; Magara et al. (2001) consider the species native to China, and introduced to all other countries.
L. fortunei is native to Chinese and Southeast Asian streams and rivers (Morton, 1977). It has since spread to other areas. In the 1960s it colonized Hong Kong, where it was non-native (Morton, 1977); this likely occurred accidentally due to a shipment of water from China's East river (Morton, 1973). In 1991 it was introduced into the La Plata Basin in South America, likely transported in ballast water from ships arriving from Asia (Darrigran and Pastorino, 1995), and subsequently spread across Argentina, Brazil, Uruguay, and Paraguay (Darrigran and de Drago, 2000).
Shell: The outer surface of the shell of L. fortunei is golden in color, while the inner displays a layer of purple nacre (mother-of-pearl). Depending on the age of the specimen, the shell can range from 7 to 36 millimeters in length and 3 to 12 millimeters in width, with the length-to-width ratio staying relatively consistent regardless of size (Morton, 1973). The species is equivalve (both halves of the shell are the same size), and its periostracum (outer shell layer) is glossy and smooth. The shell of this species does not have hinge teeth. (Morton, 1973).
Siphons: The exhalant siphon is formed by fusion of the inner folds of the mantle, and, like the inhalant siphon, does not have tentacles or papillae. Waste particles from the mantle cavity (pseudofeces) are ejected through the exhalant siphon (rather than through the inhalant siphon as is more common) in an above-body direction, which allows L. fortunei to feed and eject waste at the same time-- a useful adaptation in fast-flowing waters where food is harder to come by (Morton, 1973).
Muscles: The anterior adductor muscle (a muscle which closes the shell) is small and located on the floor of the shell, while the posterior adductor muscle is large. L. fortunei has a small posterior pedal retractor muscle; anterior to this muscle are the posterior byssal retractor muscles (Morton, 1973).
Alimentary system: The alimentary system of L. fortunei is typical of Mytilidae, except for the unusually large food-sorting caecum it possesses (Morton, 1973).
Its distinctive golden shell coloration and nacreous layer within the shell are two key features allowing identification. Also, its outer demibranchs (halves) of the ctenidia (gills) are unusually long, and the outer demibranch is much longer than the inner demibranch in the dorso-ventral dimension, but much shorter in the antero-posterior direction (Morton, 1973).
While L. fortunei is similar in appearance and behavior to Mytilopsis leucophaeata and Dreissena polymorpha (Deaton et al., 1989; Morton, 1973), it can be distinguished from these species by the presence of a layer of nacre ("mother-of-pearl"), which all members of the genera Mytilopsis and Dreissena lack (Morton, 1973).
Habitat and Ecology
Mean shell length 2-8 mm, uses byssal threads to attach to substrates. The species is considered adults when they become sexually mature at about 1 year of age. Females typically comprise two-thirds of population. Ecological tolerances and parameters vary widely by geographical location; populations are capable of adapting to suit various habitats. Attach byssally to available substrates, forming dense aggregations (often establishing colonies with densities of 80,000 m-2) (Crosier and Molloy undated).
It is an Euryhaline freshwater species (primarily a freshwater species, capable of tolerating brackish waters and maintaining substantial populations in estuarine habitats). Tolerant of polluted and contaminated water conditions. Capable of inhabiting waters with relatively low calcium and pH levels (Table 1), heated waters, and organically-enriched waters subject to periodic hypoxia (Crosier and Molloy undated).
Unlike its close relatives, L. fortunei is a freshwater animal, living in freshwater lakes, reservoirs, rivers, and creeks; however, it is capable of living in brackish estuaries as well (Morton, 1977). In general, larvae prefer to settle at depths of 20-30 feet (6-9 meters) (Morton, 1977). L. fortunei also shows an overwhelming preference for crevices (Morton, 1977). The species is epifaunal - it lives on hard substrates rather than in the sediment. These substrates can be natural, such as aquatic plants or compacted sand; or they can be manmade, such as docks, walls, and pipes (Darrigran, 2002).
The larvae of this species are free-swimming by means of cilia, allowing them to disperse widely until they settle (Cataldo et al., 2005). Adults are typically sessile, attaching themselves to hard surfaces by means of the hairlike adhesive byssus. However, they do exhibit crawling behavior using their muscular foot (typical of bivalves). Members of the species move away from light and towards the field of gravity (downwards). They tend to move towards one another, forming clumps; once a clump has been formed, the byssus is secreted (Uryu et al., 1996).
This species is a heterotrophic filter-feeder, and is a consumer (Morton, 1973).
L. fortunei's success as an invasive species is likely due to its early sexual maturity, high fertility, tolerance to wide variations in environmental conditions, and lack of competition within the niche of epifaunal attached organisms (Darrigran, 2002). It is very similar to the invasive zebra mussel (Dreissena polymorpha) in these characteristics (Karatayev et al., 2007).
Natural oxygen depletion events in freshwater systems such as the Pantanal in South America reduce the population size of L. fortunei by preventing spawning and killing juvenile and adult mussels, but the species consistently rebounds (Oliveira et al., 2010).
In Brazilian rivers, complex communities of sponges have been all but replaced by beds of Limnoperna fortunei, which severely impacts the ecosystem by (for instance) eliminating the habitat of sponge-dwelling aquatic insects (chironomids) (Fusari et al., 2008).
In areas where L. fortunei has been introduced, the new surface created by the beds of mussels allows the settlement of invertebrate populations that were not previously there, chiefly Gastropods, Oligochaetes, and Hirudineans (Darrigran et al., 1998b).
In South America, L. fortunei is preyed upon by the native fish Leporinus obtusidens Valenciennes, 1846 (Penchaszadeh et al., 2000).
Life History and Behavior
L. fortunei larvae prefer to settle in shaded crevices (Morton, 1977). Young and adult mussels exhibit crawling behavior; crawling distance typically decreases with increasing shell length. These animals display positive geotaxis (downward movement) as a rule, although they sometimes prefer to settle just below the water surface; they also show marked negative phototaxis (movement toward the dark). They show a strong preference for settlement in angled crevices, and those settling in crevices are much more likely to secrete byssal threads than those that do not. Members of this species tend to aggregate into clumps, which also stimulates a higher rate of byssal secretion (Uryu et al., 1996). When L. fortunei is living in fast-flowing waters, it will orient itself with siphons facing toward the current (Morton, 1973).
2-3 years (Morton, 1977).
This species is dioecious as a rule (any individual will produce just one type of gamete); however, very rare instances of hermaphroditism have been observed, in around .55% of the population (Darrigran et al., 1998a). They spawn once or twice per year (Darrigran et al., 1999).
Evolution and Systematics
The similarity in anatomical characters such as mid-gut loops on the right side of the stomach, as well as in the occupation of estuarine habitats, between L. fortunei and the Australian mussels Xenstrobus securis and Xenostrubus inconstans, suggests that L. fortunei may have evolved from a common ancestor similar to Xenostrubus (Morton, 1973).
Apart from L. fortunei, seven other Recent species are currently placed in the genus Limnoperna: L. atrata, L. balani, L. inconstans, L. mangle, L. pulex, L. sambasensis, and L. securis.
Molecular Biology and Genetics
Pie et. al. (2006) sequenced the cytochrome oxidase subunit 1 (CO1) gene of L. fortunei. They found that unique primers that bind only to this gene could be used to detect the presence of L. fortunei larvae, which could potentially aid in population control for this species.
Barcode data: Limnoperna fortunei
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Statistics of barcoding coverage: Limnoperna fortunei
Public Records: 19
Specimens with Barcodes: 19
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
Methods of controlling this invasive species' spread are currently under study. L. fortunei is very resistant to desiccation, with resistance increasing with larger mussel size. This means that structures that colonized by L. fortunei need to be kept out of contact with water for 9 days to kill all the mussels. This is not a feasible option for clearing pipes, but can work in some situations (Montalto and de Drago, 2003). Blooms of cyanobacteria also limit the reproduction of L. fortunei, a fact which has implications for the creation of natural molluscicides in the future (Boltovskoy et al., 2009).
Relevance to Humans and Ecosystems
L. fortunei has a chiefly negative impact on humans. In water treatment plants, refrigeration systems, and power stations, the species can obstruct pipes and slow down their flow velocity, corrode surfaces, and pollute waterways when mass mussel death occurs. This poses a significant economic problem for South America's Neotropical region, necessitating expensive system shutdowns, chemical cleaning, and replacement of pipes and filters (Darrigran 2002).
Limnoperna fortunei, the golden mussel, is a medium-sized fresh water bivalve mollusc in the family Mytilidae, the true mussels. The native range of the species is China, but it has accidentally introduced to South America where it has become an invasive species. It is considered to be an ecosystem engineer because it alters the nature of the sediment at the bottom of lakes and dramatically changes the associated invertebrate communities.
The golden mussel can grow to a length of about 45 millimetres (1.8 in) but a more usual size is 20 to 30 millimetres (0.79 to 1.2 in). The general colour of the shell is golden brown, the umbones are very close to the end of the valves and there are no hinge teeth. The mantle is fused on the dorsal side and the shell is attached to the substrate by byssal threads.
The golden mussel is native to China. Between 1965 and 1990, it spread into Hong Kong, Taiwan and Japan. In 1989 or 1990 it appeared in Argentina. It flourished there and by 2006 it had spread to Uruguay, Paraguay, Bolivia, and Brazil. It is considered an invasive species in South America and is expected to spread further.
The golden mussel is a filter feeder. When it occurs in great numbers it filters large quantities of water and has a significant effect on the amount of suspended material in the water column. Its faeces add to the sediment and supply abundant food for detritivores. It has a planktonic larval stage and populations can grow fast. The adults live close together in aggregations that alter the substrate of the lakebed. When this happens there is a considerable increase in associated invertebrates that can make use of the nooks and crannies among the mussels, and feed on their faeces. However there is a concomitant great decline in the presence of native freshwater mussels in the family Unionidae.
In a research study undertaken in the Rio Tercero Reservoir in Argentina, it was found that the preferred habitat of the golden mussel was stones and gravel. It tolerated sandy bottoms and generally avoided silt. However, one of the largest aggregations found was on a plastic bottle on a silty bottom. On sandy bottoms, aggregations were often attached to large sand grains that were glued together with byssus threads. Nestling among the mussels were a wider range of invertebrate species than were found in the surrounding areas. A particularly noticeable increase occurred in gastropods, leeches, caddisflies, mayfly larvae and midge larvae. The only invertebrates that decreased in number were the segmented worms (Oligochaeta) which burrow in the sediment and perhaps found it depleted of oxygen by the degradation of the mollusc faeces.
The study compared the golden mussel with the zebra mussel (Dreissena polymorpha) which is another aggressive invasive species. The golden mussel is more tolerant of increased salinity, low pH values and higher temperatures than the zebra mussel. The study considered the likely effect if the golden mussel were to reach North America. It seemed likely that it would be able to colonise water masses that did not suit the zebra mussel, and thus would devastate native unionids in their few remaining strongholds.
- Huber, Markus (2010). "Limnoperna fortunei (Dunker, 1857)". In P. Bouchet, S. Gofas & G. Rosenberg. World Marine Mollusca database. World Register of Marine Species. http://www.marinespecies.org/aphia.php?p=taxdetails&id=506081. Retrieved 2012-04-21.
- Karatayev, A. Y.; Burlakova, L. E.; Karatayev, V. A.; Boltovskoy, D. (2010). "Limnoperna fortunei versus Dreissena polymorpha: population densities and benthic community impacts of two invasive freshwater bivalves". Journal of Shellfish Research (via HighBeam Research (subscription required)) 29 (4): 975–984. doi:10.2983/035.029.0432. http://www.bioone.org/doi/abs/10.2983/035.029.0432.
- Golden mussel - Limnoperna fortunei Retrieved 2012-04-22.