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Rhithropanopeus harrisii

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Datasheet

Rhithropanopeus harrisii

Summary

  • Last modified
  • 25 September 2018
  • Datasheet Type(s)
  • Invasive Species
  • Host Animal
  • Preferred Scientific Name
  • Rhithropanopeus harrisii
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Metazoa
  •     Phylum: Arthropoda
  •       Subphylum: Crustacea
  •         Class: Malacostraca
  • Summary of Invasiveness
  • R. harrisii is a small brackish water crab which belongs to the superfamily Xanthidae. It is native to the Atlantic coast of North America but has been introduced accidentally in over 20 different countries spann...

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Pictures

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PictureTitleCaptionCopyright
Rhithropanopeus harrisii collected in the Miraflores Third Lock Lake adjacent to the Panama Canal: male specimen, 17.1 mm carapace width, dorsal view.
TitleMale
CaptionRhithropanopeus harrisii collected in the Miraflores Third Lock Lake adjacent to the Panama Canal: male specimen, 17.1 mm carapace width, dorsal view.
CopyrightA. Anker/Aquatic Invasions
Rhithropanopeus harrisii collected in the Miraflores Third Lock Lake adjacent to the Panama Canal: male specimen, 17.1 mm carapace width, dorsal view.
MaleRhithropanopeus harrisii collected in the Miraflores Third Lock Lake adjacent to the Panama Canal: male specimen, 17.1 mm carapace width, dorsal view.A. Anker/Aquatic Invasions

Identity

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Preferred Scientific Name

  • Rhithropanopeus harrisii (Gould, 1841)

Other Scientific Names

  • Heteropanope tridentata (De Man, 1892)
  • Heteropanope tridentata (Tesch, 1922)
  • Pilumnus harrisii (Gould, 1841)
  • Pilumnus tridentatus (Maitland, 1874)
  • Rhithropanopeus harrisii (Rathbun, 1930)
  • Rhithropanopeus harrisii ssp. tridentatus (Buitendijk and Holtuis, 1949)

International Common Names

  • English: dwarf crab; estuarine mud crab; Harris mud crab; white-fingered mud crab; white-tipped mud crab; Zuiderzee crab
  • Russian: golandsky crab

Local Common Names

  • Denmark: ostamerikansk brakvandskrabbe
  • Germany: Zuiderzeekrabbe
  • Netherlands: zuiderzeekrabbetje
  • Poland: krabik amerykanski

Summary of Invasiveness

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R. harrisii is a small brackish water crab which belongs to the superfamily Xanthidae. It is native to the Atlantic coast of North America but has been introduced accidentally in over 20 different countries spanning both North and South America, Europe, northern Africa, and Asia (Roche and Torchin, 2007; Roche et al., 2009). Although R. harrisii has not yet been reported in Oceania, it figures among the top 30 species of concern from a list of 851 marine pests likely to invade Australia (Hayes and Sliwa, 2003). Possible vectors of introduction include accidental transport in vessel fouling, ballast water, and oyster shipments (Cohen and Carlton, 1995) as well as with fish stocking (Keith, 2008). Currently, no studies have quantified the impacts of R. harrisii on communities where it is introduced, but anecdotal evidence suggests that it may alter species interactions and cause some economic damage, notably through competition with native species, alteration of food webs, and fouling of water intake pipes (Roche and Torchin, 2007). R. harrisii’s tolerance to a broad range of environmental conditions, mainly salinity and temperature, is thought to have facilitated its success as a global invader (Williams, 1984; Petersen, 2006).

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Arthropoda
  •             Subphylum: Crustacea
  •                 Class: Malacostraca
  •                     Subclass: Eumalacostraca
  •                         Order: Decapoda
  •                             Suborder: Reptantia
  •                                 Unknown: Xanthoidea
  •                                     Family: Panopeidae
  •                                         Genus: Rhithropanopeus
  •                                             Species: Rhithropanopeus harrisii

Notes on Taxonomy and Nomenclature

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Rhithropanopeus harrisii (Gould, 1841), or the Harris mud crab, is a small euryhaline crab which reaches approximately 2 cm in carapace width as an adult and is greenish-brown in colouration. Its chelipeds are white at the tip and unequal in size. The front of its carapace is almost straight, slightly notched, with its margin transversely grooved, appearing double when viewed from the front. Four teeth (spines) line the side of its carapace below the eyestalks and its eight walking legs are long, thin and somewhat hairy (Ryan, 1956; Williams, 1984; Zaitsev and Öztürk, 2001). Illustrations of the crab are available in Williams (1984), in Christiansen (1969), and in Galil et al. (2002).

In its native range, R. harrisii occurs along the Atlantic coast of North America and inhabits the brackish waters of estuaries. In North America, R. harrisii was first described by Gould (1841) as Pilumnus harrisii. In Europe, the crab was mistakenly described as a native species from the Zuiderzee Bay in Holland by Maitland (1874), and given the name Pilumnus tridentatus. In 1892, De Man included the species in the genus Heteropanope. According to Wolff (2005) and Christiansen (1969), this classification was also used by Tesch (1922). Until the 1940s, the crab was therefore known by the name Heteropanope tridentata in Europe. In 1949, however, Buitendijk and Holthuis (1949) determined that it was similar to the American crab R. harrisii. Yet, because of morphological differences, mainly regarding the depth of the indentation at the front edge of its carapace, the authors considered the crab to be a European subspecies, R. harrisii (Gould) ssp. tridentatus (Maitland). In the Americas, Rathbun (1930) reclassified P. harrisii as R. harrisii.
 
A detailed synonymy of R. harrisii in Europe in available in Buitendijk and Holthuis (1949).

Description

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R. harrisii is a small euryhaline crab < 26 mm carapace width) which belongs to the family Panopeidae (mud crabs). Descriptions of the crab in its native range are provided in Rathbun (1930), Ryan (1956), Christiansen (1969), Williams (1984), and Galil et al. (2002) and are summarized below. The carapace is subquadrate and greatest in width at the fourth pair of lateral teeth, which line its sides below the eyestalks. The carapace is transversally and latitudinally convex. The front is slightly notched with its margin transversally grooved, appearing double when viewed from the front. The lateral teeth are not prominent and the first and second teeth are fused. The third, fourth and fifth teeth are blunt, pointing obliquely upward. The male’s abdomen has five segments: the third segment does not reach the coxae of the last pair of walking legs and the terminal segment has a rounded tip. The chelae are unequal in size and dissimilar. The major chela has a short fixed carpus and a strongly curved dactyl. The dactyl has a moderately developed basal tooth. The carpus has a subdistal groove and a tooth at an inner angle. The upper surface of the carpus is granular in juveniles, but smooth in adults. The walking legs are long, slender, compressed and somewhat hairy. The antennules have black chromatophores. The crab is generally brownish-green in colour with maroon blotches, but is often stained with bottom mud. The chelae are light at the tips with spots on the upper surface.

In Chesapeake Bay, Ryan (1956) reports a range of carapace width (cw) between 4.1 and 14.6 mm for adult males (n=527) and 4.4 to 12.6 mm for adult females (n=391). Williams (1984) reports a maximum carapace width of 21.3 mm for males and 16.0 mm for females. In comparison, European populations of R. harrisii appear to attain larger body sizes: Turoboyski (1973) reported a range of cw between 4.4 and 26.1 mm for males (n=637) and 4.4 to 19.0 mm for females (n=555) in the Dead Vistula, Poland. Body measurements of populations studied in other parts of Europe are generally in agreement with this data (Turoboyski, 1973).
 
Descriptions and illustrations of the larval stages of R. harrisii are provided in Conolly (1925), Hood (1962), and Rice and Tsukimura (2007).

Distribution

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In its native range, R. harrisii inhabits brackish waters along the east coast of North America from the Miramichi Estuary in New Brunswick, Canada, to Veracruz in the Gulf of Mexico (Williams, 1984). Although recent publications cite a record of this species from Brazil, (e.g., Morgan et al., 1988; Abele and Kim, 1989; Gonçalves et al., 1995b; Zaitsev and Öztürk, 2001), the specimens originally reported by Williams (1965) were later re-examined and reclassified as another species by the same author (Williams, 1984). Currently, R. harrisii has been reported as a non-indigenous species in over 20 different countries (Roche and Torchin, 2007; Roche et al., 2009).

R. harrisii is considered to be the first decapod crustacean introduced to Europe (Noël, 2001). Found for the first time in the Zuiderzee Bay in Holland, it has since been reported from brackish waters in the North Atlantic, Mediterranean, Baltic, Caspian, Azov, Aral, and Black Seas as well as in several estuaries in the English Channel (Reznitchenko, 1967; Christiansen, 1969; Zaitsev and Öztürk, 2001; Galil et al., 2002). Currently, its European distribution is expanding southward – the crab was recently found in the Iberian Peninsula (Mariscal et al., 1991; Gonçalves et al., 1995b), in the Pô Delta in the Mediterranean (Mizzan and Zanella, 1996), and in the Lake of Tunis (Ben Souissi et al., 2004). The most recent reports of introduced populations are from Panama (Roche and Torchin, 2007) and Japan (Iseda et al., 2007).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Sea Areas

Atlantic, NortheastLocalisedIntroducedWolff, 1954
Atlantic, NorthwestWidespreadNative Not invasive Williams, 1984Native range - up to New Brunswick (Canada)
Atlantic, Western CentralPresentWilliams, 1984; Roche and Torchin, 2007
Mediterranean and Black SeaPresentMarchand and Saudray, 1971; Ben et al., 2004
Pacific, Eastern CentralLocalised2001IntroducedPetersen, 2006Oregon, California

Asia

AzerbaijanWidespreadIntroducedZaitsev and Öztürk, 2001First recorded in the South Caspian Sea in 1961
IranWidespreadIntroducedZaitsev and Öztürk, 2001In 1970s, 760 ind/m2 in southeastern portion of Caspian Sea (Kasymov et al. 1974 cited in Zaitsev and Ozturk, 2001)
JapanPresentPresent based on regional distribution.
-HonshuLocalisedIntroducedIseda et al., 2007It was discovered in 2006 in Nagoya Canal in Nagoya City, Aichi prefecture (Honshu). 47 males, 39 females (8 ovigerous) were collected. The authors reanalyzed old samples from Kimura & Horii (2000) and found the R. harrisii had invaded the port of Nagora prior to the year 2000. They also suggest that their colleagues found R. harrisii in the ports of Nagoya, Osaka Bay and Tokyo Bay
KazakhstanWidespreadIntroducedZaitsev and Öztürk, 2001Northeastern part of Caspian Sea
TurkmenistanWidespreadIntroducedZaitsev and Öztürk, 2001Area of first discovery in Caspian Sea - 1961
UzbekistanLocalisedIntroducedAndreyev and Andreyeva, 1988Southern part of Aral Sea - first recorded in 1971

Africa

TunisiaPresent, few occurrencesIntroducedBen et al., 2004First recorded in 2003 in the South Tunis Lagoon (2 females, 7 and 12 mm cw)

North America

CanadaPresentPresent based on regional distribution.
-New BrunswickLocalisedNative Not invasive Williams, 1984Northernmost part of native range - restricted to estuaries
MexicoLocalisedNative Not invasive Williams, 1984Southernmost part of native range - restricted to estuaries
USAPresentPresent based on regional distribution.
-CaliforniaLocalisedIntroducedJones, 1940; Petersen, 2006; Petersen, 2006
-DelawareLocalisedNative Not invasive McDermott and Flower, 1952Upper Delaware Bay
-FloridaLocalisedNative Not invasive Odum and Heald, 1972Estuaries streams in southern Florida
-MarylandWidespreadNative Not invasive Ryan, 1956Chesapeake Bay
-North CarolinaLocalisedNativePetersen, 2006Neuse River
-OregonLocalisedIntroducedPetersen, 2006; Petersen, 2006
-TexasLocalisedWilliams, 1984; Keith, 2008
-VirginiaWidespreadNative Not invasive Ryan, 1956Chesapeake Bay

Central America and Caribbean

PanamaPresentIntroducedAbele and Kim, 1989; Roche and Torchin, 2007; Roche et al., 2009

South America

BrazilAbsent, invalid recordIntroducedWilliams, 1965Specimens originally reported by Williams (1965) were later re-examined and reclassified as another species by the same author (Williams, 1984)
VenezuelaAbsent, unreliable record1956IntroducedRodríguez, 1963Reported from the estuary of Lake Macaraibo at salinities between 2 and 22 ppt

Europe

BelgiumPresentIntroducedAdema, 1991; DAISIE European Invasive Alien Species Gateway, 2009
BulgariaPresentIntroducedMarchand and Saudray, 1971First recorded in 1948 from the Black Sea (Beloslav Lagoon)
DenmarkLocalisedIntroducedWolff, 1954First recorded in 1953 in Copenhagen Harbour
FrancePresentIntroducedSaudray, 1956; Marchand, 1972; Marchand, 1979; Noël, 2001
GermanyPresentIntroducedSchubert, 1936; Nehring, 2000
ItalyLocalisedIntroducedMizzan and Zanella, 1996; Galil et al., 2002
NetherlandsWidespreadIntroducedMaitland, 1874First report in 1984 from the Zuiderzee now Ijsselmeer (last specimen found in 1943 after closure of Zuiderzee) now very scarce in dutch waters (Christiansen, 1969)
PolandLocalisedIntroducedDemel, 1953; Turoboyski, 1973; Normant et al., 2004
PortugalLocalisedIntroducedGonçalves et al., 1995First reported in 1991 from the Estuary of the Mondego river (patchy distribution)
RomaniaPresentIntroducedBacescu, 1967First reported in 1951 in the Black Sea (Razelm lagoon)
Russian FederationPresentPresent based on regional distribution.
-Southern RussiaPresentIntroducedGadzhiev, 1963; Marchand and Saudray, 1971; Zaitsev and Öztürk, 2001
SpainPresent, few occurrencesIntroducedMariscal et al., 1991First report in May of 1990 in Guadalquivir swamp (25 males, 3 females - considered established population)
UKLocalisedIntroducedEno et al., 1997First reported in 1996. Found in Roath Docks, Cardiff, South Wales. Established throughout Cardiff Docks in water at 12 ppt
UkrainePresentIntroducedMakarov, 1939; Zaitsev and Öztürk, 2001

History of Introduction and Spread

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In the United States, R. harrisii invaded San Francisco Bay between the late 1800s and the early 1900s, likely via translocations of the Atlantic oyster, Crassostrea virginica, from Chesapeake Bay in an attempt to initiate commercial oyster aquaculture (Cohen and Carlton, 1995; Ruiz et al., 1997; Wasson et al., 2001). Since then, R. harrisii has expanded its range northwards along the coast of California and Oregon, reaching several bays and estuaries where populations persist (Petersen, 2006). Interestingly, on the Atlantic Coast, the crab appears to have expanded its native range inland, successfully invading freshwater impoundments in Texas, where it has established reproducing populations (Howells, 2001; Keith, 2008).

In Europe, R. harrisii is thought to have spread through much of the continent between the 1870s and 1950s (Christiansen, 1969). In the 1870s, R. harrisii was described as a new species from the former Zuiderzee Bay, in Holland, at a time when Dutch biologists were studying the fauna of this inlet in the North Sea (Reise et al., 1998). However, at that time, Dutch vessels had already been sailing between Amsterdam (a former Zuiderzee port) and American ports (notably the port of New York) for nearly three centuries (Reise et al., 1998). Therefore, Resise et al. (1998) suspect that R. harrisii’s introduction to Europe may have occurred long before the 1880s when the species was first discovered. Since its first record in Holland, several authors have attempted to explain the rapid and broad dispersal of R. harrisii throughout Europe (see Reznitchenko, 1967; Christiansen, 1969; Mizzan and Zanella, 1996; Zaitsev and Öztürk, 2001; Wolff, 2005). In 1936, Schubert (1936) reported the presence of R. harrisii near the Kiel Canal, which he attributed to the use of Dutch tugboats and dredges to dig the canal which now links the North Sea to the Baltic Sea (Mizzan and Zanella, 1996). In the same year, Makarov (1939) also reported the occurrence of R. harrisii in the estuaries of the Dnieper and South Bug Rivers in Ukraine. Interestingly, Makarov (1939) and Buitendijk and Holthuis (1949) note that the crab was observed in Germany and in Ukraine for the first time in 1936, the year when the population of R. harrisii was most abundant in Holland. Since then, many authors have suggested that the crab was transported to other European countries via shipping (Makarov, 1939; Wolff, 1954; Wolff, 2005). For instance, Zaitsev and Öztürk (2001) ascribed the accidental introduction of R. harrisii in the Caspian Sea to ships transiting from the Azov Sea via the Volga-Don Canal. In the River Pô Delta, however, where R. harrisii was discovered in 1994, Mizzan and Zanella (1996) suggested that the crab might have been unintentionally introduced by local oyster farmers having transported Crassostrea gigas from France. In the latter country, Marchand (1972) asserts that the crab had arrived in the English Canal after 1948 (first reported by Saudray in 1955 in the Canal de Tancarville and in 1956 in the Canal de Caen à la Mer). However, its presence in the Gironde and Loire estuaries (reported in 1957 and 1968, respectively) probably dates back to the First World War (Marchand, 1972). A complete list of invaded countries and dates of first reports in Europe is provided in the Distribution section.
 
In Central America, Abele and Kim (1989) reported five specimens (one male, three non-ovigerous females and one juvenile) of R. harrisii collected in 1969 in the Pedro Miguel Locks of the Panama Canal. However, according to recent studies, the crab was not considered to be established in Panama (Cohen, 2006). In 2007, Roche and Torchin (2007) reported an established and reproducing population of R. harrisii in the Miraflores Third Lock Lake, an abandoned excavation adjacent to the Panama Canal. It is conceivable that crabs discovered in 2007 may have established following a different introduction event than that reported by Abele and Kim (1989) since no other populations R. harrisii were encountered during a survey across the entire Panama Canal (Roche et al., 2009).
 
Lastly, R. harrisii was recently reported from the coasts of Japan (Iseda et al., 2007). Observations by Iseda and colleagues (2007) were restricted to the Nakagawa Canal in Nagoya. In 2006, the authors collected a total of 86 individuals, including 47 males and 39 females, 8 of which were carrying eggs. However, in their report, Iseda et al. (2007) alluded to work conducted by colleagues evidencing that R. harrisii had also been found in the ports of Nagoya, Osaka Bay, and Tokyo Bay. A revision of samples collected in 2000 by these same colleagues suggested that R. harrisii had probably invaded to the port of Nagoya prior to the year 2000 (Iseda et al., 2007).

Introductions

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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
California USA 1937 Yes Cohen and Carlton (1995); Jones (1940); Ruiz et al. (1997); Wasson et al. (2001) First observed in the Pacific (1937) in Lake Merritt, Oakland, a brackish water lake near a shipping harbour. It invaded San Francisco Bay (late 1800s-early 1900s) presumably via translocations of Atlantic oyster
Europe North America late 1800s Yes Christiansen (1969); Demel (1953); Maitland (1874); Makarov (1939); Marchand and Saudray (1971); Saudray (1956); Schubert (1936); Wolff (1954); Zaitsev and Öztürk (2001) Maitland (1874) initially described R. harrisii as a native species, Pilumnus tridentatus, in the Netherlands. It was reported from Germany (1936), Ukraine (1932-1936), Russia (1948), Poland (1951), Denmark (1953) and France (1955)
Japan <2000 Yes Iseda et al. (2007)
Oregon California early 1900s Yes Petersen (2006) Molecular evidence suggests that current Pacific populations descend from a single introduction event and that the presence of R. harrisii in Oregon resulted from a northward range expansion
Panama 1969 Yes Abele and Kim (1989); Roche et al. (2009) Five specimens of R. harrisii were collected in the Panama Canal in 1969 but the crab was not considered to be established. In 2007 two populations were discovered in the Miraflores Third Lock Lagoons, adjacent to the Panama Canal

Risk of Introduction

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To date, R. harrisii has successfully colonized several different habitats ranging from freshwater lakes in Texas, bays and estuaries on the eastern and western Pacific, ports and estuaries in the Mediterranean, in inland Europe and Asia, and also a tropical lagoon system in Panama (reviewed in Roche and Torchin, 2007). At present time, its introduced range spans more than 45° of latitude (Roche et al., 2009) and its tolerance to a wide range of environmental conditions is likely to promote further spread (Turoboyski, 1973; Williams, 1984; Petersen, 2006). Recently, R. harrisii has been identified as one of the top 30 species of concern from a list of 851 marine pests likely to invade Australia (Hayes and Sliwa, 2003). There is also a risk that it may reach New Zealand given its recent occurrence in Japan, the source country of two other decapods introduced to New Zealand (see Brockerhoff and McLay, 2008).

Habitat

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R. harrisii is tolerant to a wide range of salinities and is typically associated with sheltered estuarine habitats (Roche and Torchin, 2007). The crab usually inhabits oyster reefs, woody debris and shoreline vegetation and has previously been recorded at a depth of approximately 37 m (Turoboyski, 1973; Williams, 1984; Petersen, 2006). Although it is a mud crab, R. harrisii will avoid mudflats and areas of the bottom which are muddy but devoid of shelter (Turoboyski, 1973). Turoboyski (1973) points out that, in Poland, the distribution of R. harrisii in the Dead Vistula was markedly limited by the composition of the substrate and the availability of shelters. In its native range, in Chesapeake Bay, Ryan (1956) found the crab between 0 and 10 m depth and between 2.8 and 18.6 ppt salinity. He also noted that R. harrisii was the only species of Xanthidae studied in Chesapeake Bay known to occur in freshwater. Similarly, in the Newport River Estuary, North Carolina, Cronin (1982) found crabs in salinities varying between 0.5 and 25 ppt. Adult crabs have previously been observed to migrate into freshwater (Williams, 1984), but low salinity is believed to be the most important factor limiting the distribution of R. harrisii larvae which typically have reduced survival rates below 5 ppt (Costlow et al., 1966; Christiansen and Costlow, 1975; Cronin, 1982; Gonçalves et al., 1995a). Nonetheless, reproducing populations have recently been found in water bodies with salinities as low as 0.4 ppt (Keith, 2008; Roche et al., 2009).

Habitat List

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CategorySub-CategoryHabitatPresenceStatus
Brackish
Inland saline areas Present, no further details
Estuaries Principal habitat Natural
Estuaries Principal habitat Productive/non-natural
Lagoons Secondary/tolerated habitat
Littoral
Coastal areas Principal habitat Natural
Coastal areas Principal habitat Productive/non-natural
Intertidal zone Secondary/tolerated habitat Natural
Freshwater
Lakes Secondary/tolerated habitat Harmful (pest or invasive)
Lakes Secondary/tolerated habitat Productive/non-natural
Reservoirs Secondary/tolerated habitat Harmful (pest or invasive)
Reservoirs Secondary/tolerated habitat Productive/non-natural
Rivers / streams Present, no further details Productive/non-natural
Marine
Inshore marine Principal habitat Natural
Inshore marine Principal habitat Productive/non-natural

Biology and Ecology

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Genetics

Few studies have investigated the genetics of R. harrisii. In the crab’s native range, Grosholz and Ruiz (1995) looked for evidence supporting a genetic basis for resistance to the parasite L. panopaei in two different North American populations by estimating the heritability of susceptibility to infection. Heritability of the trait (susceptibility to infection) was low and comparisons of infection levels between populations showed no significant differences suggesting that there may be considerable gene flow among populations occurring along the Atlantic coast of North America (Grosholz and Ruiz, 1995). In the crab’s introduced range in the Pacific, Petersen (2006) used a sequence of mtDNA cytochrome oxidase I to identify the source and direction of range expansion of the population discovered in San Francisco Bay (Jones, 1940). Three Pacific populations in Oregon and central California were sampled and compared to crabs collected in the Neuse River, North California. Although the source population could not be identified, it could be deduced that the current Pacific populations resulted from a single introduction event which lead to a northward expansion from San Francisco Bay towards Oregon (Petersen, 2006).
 
Reproductive Biology
 
The reproductive biology of R. harrisii has been extensively studied, both in its native range (e.g. Costlow et al., 1966; Christiansen and Costlow, 1975; Cronin, 1982; Morgan et al., 1983; 1988) and its European introduced range (e.g. Marchand, 1972; Turoboyski, 1973; Marchand, 1979; Gonçalves et al., 1995b).
 
R. harrisii reproduces sexually and is oviparous. As in other crab species, the sperm is transferred by a spermatophore which is placed in the female’s spermatheca during copulation (Turoboyski, 1973). Although there is variation in the period of reproduction depending on the population (Gonçalves et al., 1995b), copulation generally occurs during late spring and summer with the peak periods of juvenile recruitment occurring from May until July (Grosholz and Ruiz, 1995). In most crab species, copulation is restricted to the period immediately following the moulting of the females, when the carapace is soft (Turoboyski, 1973). However, R. harrisii is one of the few crab species whose females copulate during the intermoult, after the carapace has hardened (Turoboyski, 1973; Morgan et al., 1983). According to Turoboyski (1973), the copulatory activity of the male is probably stimulated by a substance which the females release in the water. Approximately three to four days after copulation, females bury themselves in the bottom sediment up to the eye stalks to lay their eggs, a behaviour thought to facilitate the attachment of the eggs to the pleopods of the female abdomen. Ovigerous females then remain sheltered for approximately ten days in debris, shells, or sediment, and produce abdominal movements to increase the water flow over the eggs and enhance oxygen supply (Turoboyski, 1973). Females can lay from 1,200 to 4,800 eggs at a time depending on their size. In the Kiel Canal, Germany, large females were observed to lay as many as 16,000 eggs (Kinne and Rotthauwe, 1952 cited in Turoboyski, 1973). Interestingly, Morgan et al. (1983) observed that females were able to oviposit as many as four times without mating repeatedly. These authors hypothesized that multiple spawnings and the production of fewer, larger eggs may result from adaptations to harsh environments in estuaries which are characterized by drastic fluctuations in salinity and strong currents.
 
During its life cycle, R. harrisii passes through four larval stages (zoea I, zoea II, zoea III, zoea IV) and one post-larval stage, the megalopa (Connolly, 1925; Hood, 1962). After R. harrisii megalopae settle out in a suitable habitat, they quickly grow to reproductive size (Morgan et al., 1983). According to Morgan et al. (1983), R. harrisii is capable of growing to reproductive maturity in only three months at 25°C: 10 days to incubate and hatch eggs after oviposition, 20 days to metamorphose to the crab stage, and two months to attain a carapace width of 8 mm, the size of most ovigerous females observed in the field. This duration may be further reduced as developmental time in R. harrisii has been observed to decrease with increasing temperature (Williams, 1984; Gonçalves et al., 1995a). Indeed, Gonçalves et al. (1995b) observed that the time from the first zoea to the megalopa may vary between 7 and 35 days and that the first crab can be reached between 11 to 43 days, depending on the temperature of the water.
 
Nutrition
 
R. harrisii is considered a generalist scavenger (Grosholz and Ruiz, 1995) and known to feed on a variety of plant detritus, bivalve molluscs, and dead fish (Odum and Heald, 1972). Small crabs feed on planktonic crustaceans such as amphipods and copepods (Williams, 1984). However, the diet of R. harrisii is said to vary in different habitats (Turoboyski, 1973). Detailed accounts are provided in Turoboyski (1973) with accompanying citations: in the Kiel canal (Germany), the crab feeds readily on snails, amphipods of the genus Gammarus, and on plants such as Enteromorpha sp. and Ulva sp. (Kinne and Rotthauwe, 1952); in the Azov Sea, it does not attack living prey but consumes various organic matter of animal and vegetable origin (Mordukhai-Boltovskoy, 1952), namely plants of the genus Idothea (Rieznichenko, 1958); in the Vistula (Poland), Murina and Rieznichenko (1960) found that the crab feeds mainly on the shrimp Neomysis integer and the worm Hediste diversicolor, as well as larvae of Chironomidae, whereas Kujawa (1957) mentions the mussel Dreissena polymorpha as the main food item; in the Dead Vistula, the main food sources of R. harrisii include Hediste diversicolor, Mytilus edulis (mussel), Dreissena polymorpha, Cordylophora caspia (hydroid), dead organic matter of animal origin, and the plants Cladophora sp. and Enteromorpha sp. (Turoboyski, 1973). Additionally, R. harrisii zoea are important consumers of larvae of the barnacle Balanus improvisus [Amphibalanus improvisus] found in plankton (Turoboyski, 1973).
 
Associations
 
R. harrisii is always associated with some form of shelter: rocks, wood debris, oyster shells, or shoreline vegetation (Williams, 1984; Everett and Ruiz, 1993; Roche and Torchin, 2007). In the Dead Vistula, where Turoboyski (1973) extensively studied its ecology, the crab was often found in the vicinity of the barnacle Balanus improvisus [Amphibalanus improvisus] and the hydroid Cordylophora caspia, which the author described as commensals. In Cardiff Docks (England), Eno et al. (1997) reported that R. harrisii may associate, possibly on trophic levels, with other introduced species, including the tube worm Ficopomatus enigmaticus.
 
Environmental Requirements
 
Turoboyski (1973) lists, in order of importance, several environmental conditions which R. harrisii requires: (1) salinity - crab larvae thrive best in brackish waters, with lower salinities being more important than higher salinities in limiting their spatial distribution; (2) a rich food supply - the abundance of planktonic organisms is particularly important to feed larval stages; (3) the nature of the substrate - the crab requires shelter in the form of rocks, shells, vegetation, or woody debris; (4) temperature - water temperatures must be relatively high (above 14°C) during the breeding season, which typically occurs during the summer months.
 
Since the larvae have the lowest potential for osmoregulation, salinity is the most important factor in determining the distribution of R. harrisii in nature (Kujawa, 1965). Several studies have investigated the optimum salinity and temperature conditions which facilitate larval development (Costlow et al., 1966; Costlow and Bookout, 1971; Christiansen and Costlow, 1975; Laughlin and French, 1989; Gonçalves et al., 1995a). The results of these studies are in agreement in showing that R. harrisii larvae survive best at intermediate salinities and that the time for larval development decreases notably with increasing temperature (Gonçalves et al., 1995a).
 
Experiments in R. harrisii’s native range by Costlow et al. (1966) indicated maximal survival up to the megalopa stage at salinities of 15 and 25 ppt and temperatures of 20, 25 and 30°C. At extreme salinities of 1 and 40 ppt, survival decreased markedly, with no larva surviving at 1 ppt. Interestingly, at high temperatures, survival was highest at salinities below 15 ppt, whereas at lower temperatures, survival was higher at greater salinities (Costlow et al., 1966).
 
Christiansen and Costlow (1975) performed similar experiments on a native population from North Carolina and found that R. harrisii larvae survived to the megalopa and first crab stage in all combinations of salinities and temperatures other than 5 ppt at 30-35°C. Optimum survival to the megalopa and first crab stages occurred in 20 ppt at 20-25°C; in all other combinations of salinities and temperatures there was a reduction in survival to the first crab stage.
 
Laughlin and French (1989) studied one native and one introduced population; their findings showed higher survival of the larvae at 25°C and salinities of 20 ppt in an introduced population from California, and higher survival at 30°C and 15 ppt in a native population from Florida.
 
In an introduced population in Portugal, Gonçalves et al. (1995a) showed that extreme salinities resulted in increased development time for the first larval stage, and that this delay was further pronounced for subsequent stages. They found that larval development was optimum at 25°C and 15 ppt and that larval survival was maximal at 10, 15 and 20 ppt at temperatures of 20, 25 and 30°C. They also found that the percentage of abnormal megalopae increased with increasing salinity to a maximum of 100% at 30 ppt, but that, overall, the incidence of abnormality was not affected by temperature (Gonçalves et al., 1995a).
 
More recent studies on populations found in quasi-freshwater habitats in Texas and Panama have shown that R. harrisii larvae are able to survive in salinities as low as 0.4-0.5 ppt (Keith, 2008) and 0.4-0.6 ppt (Roche et al., 2009). Although the results of laboratory experiments on larvae from these populations have yet to be published, some larvae from Texas populations have successfully been hatched in water at a salinity of 0.5 ppt (Keith, 2008). Additionally, Roche et al. (2009) showed that, although crabs do not survive in water at 0 ppt, adult crabs could survive a period of 30 days in water prepared in the lab at 0.1 ppt. In water collected from Gatun Lake in the Panama Canal (0.1 ppt), 44% of juveniles and 100% of adults survived throughout the duration of the experiment (Roche et al., 2009). The fact that populations of R. harrisii have established in quasi-freshwater habitats in Texas and Panama is concordant with Costlow et al.’s (1966) observations that R. harrisii is better able to survive in low salinity water at higher temperatures.

 

Water Tolerances

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ParameterMinimum ValueMaximum ValueTypical ValueStatusLife StageNotes
Depth (m b.s.l.) 0 10 Optimum Found to depth of 36.6 m in its native range (Williams, 1984)
Salinity (part per thousand) 10 20 Optimum 0.2-40 tolerated. Lower and upper limits of tolerance differ among studies/populations
Water temperature (ºC temperature) 20 25 Optimum 0-35+ tolerated (Christiansen and Costlow, 1975). Lowest temperature tolerance has not been assessed in the lab., but the crab thrives in New Brunswick, where water temperatures are near freezing

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Ameiurus catus Predator Adult not specific Williams, 1984
Anguilla anguilla Predator Adult not specific Turoboyski, 1973
Loxothylacus panopaei Parasite Adult/Larval to species Grosholz and Ruiz, 1995
Minchinia Parasite not specific Marchand, 1974
Myoxocephalus scorpius Predator Adult not specific
Platichthys flesus Predator Adult not specific
Zoarces viviparus Predator Adult not specific

Notes on Natural Enemies

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Several predators have been reported to feed on R. harrisii: the white catfish, Ictalurus catus, in the crab’s native range (Heard, 1975 cited in Williams, 1984); the European eel, Anguilla anguilla, in Poland (Turoboyski, 1973); the flounder Pleuronectes flesus, the sculpin Myoxocephalusscorpius, and the blenny Zoarces viviparus in the Bay of Gdansk in the Baltic Sea (Kujawa, 1965); and sturgeon species in the Caspian Sea (Zaitsev and Öztürk, 2001). R. harrisii’s most important natural enemy, however, is probably the introduced rhizocephalan barnacle, Loxothylacus panopaei.L. panopaei is native to the Gulf of Mexico, but was introduced to Chesapeake Bay around 1969, where it parasitizes R. harrisii (Grosholz and Ruiz, 1995). Female larvae of L. panopaei typically infect recently moulted crabs and develop as an endoparasite; this initial infection is followed by the emergence of an externa (the reproductive body of the parasite) through the abdomen of the crab, which then has to be fertilized by a male L. panopaei larva for the parasite to mature and reproduce (Walker et al., 1992; Alvarez et al., 1995; Glenner et al., 2000). Parasitism by a rhizocephalan results in complete castration and cessation of growth in the host crab (Alvarez et al., 1995). In Chesapeake Bay, R. harrisii is most abundant in areas of the bay where the water is below 10 ppt salinity, conditions which do not allow the survival of L. panopaei (Walker et al., 1992; Grosholz and Ruiz, 1995; Petersen, 2006). Currently, no specimens of R. harrisii have been reported to harbour L. panopei outside of the crab’s native range. However, a protozoan parasite of the genus Minchinia (Haplosporidiidae), which is also present in Chesapeake Bay, has been reported to parasitize an introduced population in the Canal de Caen, France (Marchand, 1974). According to Marchand (1974), infections by the protozoan significantly reduced the abundance of R. harrisii by lowering the competitive ability of parasitized individuals. Lastly, Payen and Bonami (1979) identified particles of a white spot baculovirus in the testicular germinative zone of R. harrisii from North Carolina, but did not examine the effects of the virus on its host or reported introduced populations harbouring the disease.

Means of Movement and Dispersal

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Natural Dispersal (Non-Biotic)

R. harrisii is not a species capable of long distance dispersal by natural means. Adults are known to move over short distances (e.g. up lower portions of rivers; Williams, 1984), and larvae are pelagic but use vertical migration to remain in the estuary where they are born (Cronin, 1982; Forward, 1985; Cronin and Forward, 1986). For instance, in the crab’s introduced range in Portugal, Goncalves et al. (1995b) reported that only a small proportion of larvae were observed exiting the Mondego River Estuary towards the sea. Cronin (1982) showed that the larvae of R. harrisii actively move in the water column to avoid being swept out to sea by the tides. Indeed, the larvae risk being transported to hostile environments if they are exported from their home estuary. However, dispersal must be occurring in nature since there appears to be gene flow among populations of R. harrisii in the western Atlantic (Grosholz and Ruiz, 1995) and R. harrisii is believed to have spread along the west coast of the USA from its initial site of introduction in San Francisco Bay (Petersen, 2006). Petersen (2006) suggests that a small fraction of larvae may spread from their home estuary every year or that large amounts of larvae are swept out sporadically during flood events that increase the flow of water seaward.
 
Accidental Introduction
 
Accidental transport of larvae and adults in the ballast water or on the hull fouling of ships is considered the main vector of introduction of R. harrisii (Wolff, 1954; Christiansen, 1969; Turoboyski, 1973; Cohen and Carlton, 1995; Eno et al., 1997; Zaitsev and Öztürk, 2001; Wolff, 2005; Cohen, 2006; Iseda et al., 2007; Roche and Torchin, 2007). Other vectors have also been reported. On the west coast of the United States, R. harrisii was most likely introduced to the San Francisco Bay between 1907 and the 1920s via translocations of the Atlantic oyster, Crassostrea virginica, by train from Chesapeake Bay (Cohen and Carlton, 1995; Ruiz et al., 1997; Wasson et al., 2001; Petersen, 2006). However, this entry route was never confirmed since the first observation of R. harrisii in California occurred in 1937, several decades after other invertebrates introduced with the oysters were detected (Petersen, 2006). Unintentional transport of R. harrisii with oyster shipments is also cited as a plausible mechanism responsible for the introduction of the crab in Italy (Mizzan and Zanella, 1996). In Texas, Keith (2008) suspected that that fish stocking programmes may be responsible for the introduction of R. harrisii into freshwater impoundments, but this route has yet to be confirmed.
 
Intentional Introduction
 
There are no recorded cases of intentional introduction of R. harrisii.

Pathway Causes

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CauseNotesLong DistanceLocalReferences
AquacultureFrom Chesapeake Bay (Atlantic USA) to San Francisco Bay (Pacific USA) Yes Cohen and Carlton, 1995; Ruiz et al., 1997; Wasson et al., 2001
HitchhikerOn ships from North America to Europe; Panama and Japan Yes Christiansen, 1969; Iseda et al., 2007; Roche et al., 2009

Pathway Vectors

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Impact Summary

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CategoryImpact
Economic/livelihood Negative
Environment (generally) Negative

Economic Impact

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In Texan impoundments and in the Caspian Sea, where R. harrisii reaches high densities, the crab is reported to cause fouling problems in water intake pipes of shoreline properties and also of nuclear power plants (Glen Rose, Texas) (Zaitsev and Öztürk, 2001; Keith, 2008). In the Caspian Sea, R. harrisii is reported to cause economic losses to fishermen by spoiling fishes in gill nets (Zaitsev and Öztürk, 2001).

Environmental Impact

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Impact on Habitats

At the present time, no studies have quantified the impacts of R. harrisii on the communities where it has been introduced. However, anecdotal evidence suggests that the crab may alter species interactions and cause some economic damage (reviewed in Roche and Torchin, 2007).

Impact on Biodiversity

In Europe and on the West Coast of North America, R. harrisii is said tocompete with native crabs (Marchand and Saudray, 1971; Jazdzewski and Konopacka, 1993; Cohen and Carlton, 1995) as well as with species of fish feeding on benthos (Zaitsev and Öztürk 2001) and can alter food webs by acting as a predator and serving as prey of native species (Turoboyski, 1973; Cohen and Carlton, 1995; Zaitsev and Öztürk, 2001). In Texas, R. harrisii’s presence in inland impoundments may have displaced a native species of freshwater crayfish (Keith, 2008). According to Payen and Bonami (1979), R. harrisii can also be a potential host of white spot baculoviruses, which can be transmitted to co-occurring native crustaceans.

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Has a broad native range
  • Abundant in its native range
  • Highly adaptable to different environments
  • Is a habitat generalist
  • Pioneering in disturbed areas
  • Capable of securing and ingesting a wide range of food
  • Fast growing
  • Has high reproductive potential
  • Has high genetic variability
Impact outcomes
  • Altered trophic level
  • Infrastructure damage
  • Negatively impacts livelihoods
Impact mechanisms
  • Competition - monopolizing resources
  • Competition
  • Pest and disease transmission
  • Fouling
Likelihood of entry/control
  • Highly likely to be transported internationally accidentally
  • Difficult to identify/detect as a commodity contaminant
  • Difficult to identify/detect in the field
  • Difficult/costly to control

Uses

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In its native range, R. harrisii has been used repeatedly as an experimental animal in developmental and physiological studies as well as in experimental studies testing the effects of pesticides on aquatic invertebrate fauna. Williams (1984) lists a number of these studies with accompanying references: Jones (1941) and Capen (1972), osmoregulation; Christiansen et al. (1977a,b), effects of hormone mimics on development; (Costlow, 1966), effect of eyestalk removal on development; Costlow and Sastry (1966), free amino acids in development stages; Forward (1976), shadow-sinking response of larvae; Gooch (1977) and Morgan et al. (1978), allozyme genetics; Kalber and Costlow (1966; 1968), ontogeny of osmoregulation and its neurosecretory control; Rosenberg and Costlow (1976), effects of cadmium on development. Other studies not listed by Williams (1984) include: Payen and Costlow (1977) effects of a juvenile hormone mimic on gametogenesis; Christiansen (1978) and Christiansen and Costlow (1980; 1982), effects of the insect growth regulator Dimilin on adults and larvae; Clare et al. (1992), developmental toxicity of four pesticides; Celestial et al. (1994), effects of an insect growth regulator (S-methoprene) on larval development; Nates and McKenney (2000), effects of the insect juvenile hormone analogue fenoxycarb on larval growth; Cripe et al. (2003) effects of fenoxycarb exposure on larval development; McKenney (2005), effects of juvenile hormone agonists (pyriproxyfen, methoprene and fenoxycarb) on metamorphosis and reproduction.

R. harrisii has yet to become a popular test subject in any of its introduced ranges.

Diagnosis

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R. harrisii can easily be mistaken for other species of xanthid crabs and even crabs from other closely related families. For instance, in the eastern USA, Petersen (2006) states that similarities in the general morphology of R. harrisii and the co-occurring indigenous shore crab Hemigrapsus oregonensis would make it difficult for non-specialists to distinguish both species (see Figure 1 in Petersen, 2006).

Similarities to Other Species/Conditions

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R. harrisii is a small and cryptic crab which can easily be mistaken for many other brackish and marine xanthids (e.g. Panopeus cf miraflorensis in Panama, Abele and Kim, 1989; Pilumnopeus makianus in Japan, Iseda et al., 2007). Features which can be used to distinguish R. harrisii from other xanthid crabs are the following: chelae white at the tip, slight notch on the frontal margin, margin transversally grooved, moderately developed basal tooth on dactyl of the major chela, red spot absent on inner surface of third maxilliped.

Prevention and Control

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As dispersal via hull fouling of ships is believed to have decreased with the advent of metallic hulls and antifouling paints (Rodríguez and Suárez, 2001), the major current vector of introduction for R. harrisii is likely to be transport in ballast water tanks (Brockerhoff and McLay, 2008). Therefore, reducing the discharge of overseas ballast water from ships is potentially an effective method of decreasing the risk of invasion by R. harrisii. In the Great Lakes, the USA and Canada have implemented regulations for mid-ocean ballast exchanges to reduce propagule pressure at ports of arrival (Costello et al., 2007). Although some authors question the effectiveness of ballast water exchanges due to continued discoveries of introduced species in the Great Lakes, Costello et al. (2007) argue that several more years of data collection will be required to draw conclusions about the effectiveness of this prevention method as recent detections are likely to result from a lag between introduction and detection. Other countries such as Australia and New Zealand have also implemented mandatory ballast water exchanges following the guidelines of the International Convention on the Control and Management of Ship’s Ballast Water and Sediments - BWM (Hewitt and Campbell, 2007). This convention was adopted by the International Maritime Organization in 2004 but the date of entry into force has yet to be determined (BWM, 2005).

Public Awareness
 
Citizen science initiatives, whereby volunteers are trained to identify introduced species and report their presence, are increasingly advocated by researchers because they reduce the costs associated with environmental assessments and detection of invasive species (Fore et al., 2001; Delaney et al., 2008). Despite the highly cryptic nature of xanthid mud crabs, non-specialists have previously identified R. harrisii outside of its native range in the past (Makarov, 1939; Marchand, 1972) and public awareness programmes may prove useful to identify future introductions of this species in areas which are prone to invasion, such as Australia (see Hayes and Sliwa, 2003).
 
Eradication
 
Eradication of R. harrisii has never been attempted in the past, but initiatives are currently being undertaken by the Panama Canal Authority to extirpate populations discovered at a site designated for the expansion of the Panama Canal (see Roche et al., 2009).
 
Control
 
Physical/mechanical control
 
Studies have shown that trapping can prove useful to mechanically control introduced crustaceans such as the rusty crayfish, Orconectes rusticus (Hein et al., 2006; 2007). However, this method is unlikely to be effective against R. harrisii since few individuals have been observed to enter traps, even when baited (Petersen, 2006; D Roche, McGill University, Montreal, Canada, personal communication, 2009). Roche et al. (2009) used collectors made of artificial habitat to survey populations of R. harrisii in vicinity of the Panama Canal, but these collectors have never been used as a means of controlling the crab and it is unclear whether removing crabs with this technique could substantially reduce their abundance in the field.
 
Biological control
 
Two means of biological control have been considered so far for managing introduced populationsof R. harrisii. In Glen Rose, Texas, where the crab is reported to cause fouling problems in the cooling system of a nuclear power plant, a consulting firm is currently evaluating the potential for native fish to prey on the crab and reduce its abundance in freshwater impoundments (G Hildebrand, Austin Ecology, Texas, USA, personal communication, 2009). Predation by fish has previously been shown to significantly reduce the population density of other introduced crustaceans in freshwater systems (e.g. Hein et al., 2007). Other suggested biological control agents are parasitic rhizocephalan barnacles. The rhizocephalan Loxothylacus panopaei infects R. harrisii in the crab’s native range and has been shown to stunt growth and castrate adult crabs, preventing further reproduction (Alvarez et al., 1995). L. panopaei is native to the Gulf of Mexico, where it infects seven species of xanthid crabs, but in upper Chesapeake Bay, where it is introduced, its life cycle involves no hosts other than R. harrisii (Grosholz and Ruiz, 1995). Biological control of R. harrisii could therefore be investigated either by using native rhizocephalans to infect the crabin its introduced range or by introducing L. panopaei as a control agent where it is not native. Extensive research will be required, however, before implementing either of these methods in order to determine both the host specificity of the chosen parasite and potential undesired effects to non-target species (see Goddard et al., 2005).
 
Chemical control
 
Diflubenzuron, the active compound in the pesticide Dimilin, is a chitin inhibitor which prevents cuticle formation in arthropods. Since it disrupts moulting, diflubenzuron is highly toxic to early life stages of crustaceans and has been suggested for chemical control of R. harrisii (McEnnulty et al. 2001). Christiansen et al. (1978) found that it was lethal to all larval stages of R. harrisii at a concentration of 10 mg/L and observed 100% mortality within 12 days of exposure (95% mortality was observed after three days). Christiansen and Costlow (1980) observed no reduction in mortality rates of the larvae until 21 days after the application of diflubenzuron in brackish water and found that eight weeks were required for the compound to degrade below a level at which R. harrisii larvae were no longer affected (1 mg/L; Christiansen et al., 1978). However, a range of degradation rates have been reported for diflubenzuron in the literature, which vary primarily on the basis of on temperature and pH differences (reviewed in Fischer and Hall, 1992). To date, Dimilin has not been employed to control populations of R. harrisii in the field and careful preliminary trails should be conducted to determine the effectiveness, persistence, and non-target effects of this pesticide under given environmental conditions (see Bax et al., 2001).
 
Monitoring and Surveillance
 
Monitoring is crucial for early detection of novel invaders and allowing the possibility of rapid response to improve the likelihood of successful eradication (FICMNEW, 2003; NISC, 2003). In aquatic systems, eradication is highly dependent upon monitoring and early detection since extirpation is generally impossible when invaders become abundant and populations are not localized (Bax et al., 2001; but see Edwards and Leung, 2009). However, detecting cryptic invaders such as R. harrisii before they become abundant and spread is a challenging task. As time and resources limit the extent of monitoring programs, the likelihood of early detection can be improved by targeting likely points of entry and areas of suitable habitat (NISC, 2003; Pederson et al., 2003; Meinesz, 2007). In the case of R. harrisii, monitoring can involve surveying brackish water habitats in areas of high shipping traffic such as ports and canals. This can be achieved with the use of crab collectors (Roche et al., 2009), which are similar to settlement plates for monitoring sessile marine invertebrates (see Hewitt and Martin, 2001). Another possible monitoring technique is the use of plankton tows in areas of high invasion risk (Hewitt and Martin, 2001) with assistance from taxonomists (Hewitt and Martin, 2001; FICMNEW, 2003) and the use of molecular tools (Darling and Blum, 2007) to identify the presence of R. harrisii larval stages in the water column.
 

Gaps in Knowledge/Research Needs

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Much research has been conducted on R. harrisii in its native and introduced ranges, which has contributed to our knowledge of its biology and ecology. However, little is currently known about the crab’s impacts in its introduced range, aside from anecdotal reports, and quantitative studies are urgently needed to evaluate the potential damages caused by this increasingly widespread invader. Furthermore, means of controlling or eradicating the crab have been suggested, but they remain to be tested in order to establish protocols for managing invasions of R. harrisii when they occur.

References

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Links to Websites

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WebsiteURLComment
Ecology of Rhithropanopeus harrisii - ISSG databasehttp://www.issg.org/database/species/ecology.asp?si=1217&fr=1&sts=sss&lang=EN
Harris mud crab (Rhithropanopeus harrisii)http://www.frammandearter.se/0/2english/Alert_list_091120.pdf/Rhithropanopeus_harrisii.pdf
Least wanted aquatic invaders : Harris mud crab (Elkhorn Slough Research)http://www.elkhornslough.org/research/aquaticinvaders.pdf
Mud crab (Rhithropanopeus harrisii) Chemical Toxicity Studieshttp://www.pesticideinfo.org/List_AquireAll.jsp?Species=103&Effect='Development'
Occurence of the estuarine mud crab, Rhithropanopeus harrisii, in Texas reservoirs (Keith D E, 2008)http://www.tarleton.edu/Faculty/dekeith/MudCrab.html
Rhithropanopeus harrisii (Gould, 1841) (Harris mud crab) in Encyclopedia of Lifehttp://www.eol.org/pages/345055
Rhithropanopeus harrisii (Perry, H. 2007.)http://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=197
White-tipped mud crab - Wikipedia, the free encyclopediahttp://en.wikipedia.org/wiki/White-tipped_mud_crab

Organizations

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Europe: DAISIE - Delivering Alien Invasive Species Inventories for Europe, Web-based service, http://www.europe-aliens.org

UK: Joint Nature Conservation Committee (JNCC), Monkstone House, City Road, Peterborough, PE1 1JY, http://www.jncc.gov.uk/

Canada: Sealifebase, Web based, www.sealifebase.org

New Zealand: World Register of Marine Speces (WoRMS), info@marinespecies.org, http://www.marinespecies.org/

Contributors

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25/05/09 Original text by:

Dominique Roche, McGill University - STRI, Department of Biology, Canada

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