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      Bythotrephes longimanus (Photo: Henk Ketelaars) - Click for full size   Pop-up stage of Bythotrephes longimanus (Photo: Henk Ketelaars) - Click for full size   Fourth stage of Bythotrephes longimanus (Photo: Henk Ketelaars) - Click for full size   Bythotrephes longimanus (Photo: Henk Ketelaars) - Click for full size   B. longimanus with resting eggs (Photo: Henk Ketelaars) - Click for full size   Bythotrephes longimanus (Photo: Henk Ketelaars) - Click for full size
    Taxonomic name: Bythotrephes longimanus Leydig 1860
    Synonyms: Bythotrephes cederstroemii Schodler, 1877
    Common names: Cederstroem-Blattflusskrebs (German), Eurasian spiny water flea, spiny water flea, spiny waterflea (English)
    Organism type: crustacean
    Bythotrephes longimanus, the spiny water flea, is a predatory cladoceran native to northern Europe and Asia. It was introduced to the North American Great Lakes through ballast water and has since spread to a number of inland lakes. B. longimanus competes directly for prey with juvenile and small fish along with predatory zooplankton. It can foul fishing lines and downrigger cables, and can have substantial impacts on zooplankton community structure.
    The spiny water flea is a freshwater crustacean characterised by a well developed abdominal region (metasoma), a cauda continued into a long, thin caudal appendage, a head clearly delimited from the trunk and the ocular part of the head globular and filled with a large eye separated by a depression from the head shield. Adult Bythotrephes from the Great Lakes measure between about 1.5 and 5mm in length (excluding caudal spine). They are characterised by a long caudal tail spine that is barbed and can be up to 7mm in length (Rivier, 1998)
    Similar Species
    Cercopagis pengoi

    Occurs in:
    estuarine habitats, lakes, marine habitats, water courses, wetlands
    Habitat description
    B. longimanus is a Palaearctic species, native to northern Europe and Asia (Rivier, 1998). Within both its native and introduced range, MacIsaac et al. (2000) have documented a preference for large, deep, clear lakes with relatively low summer bottom temperatures. Enz et al. (2001) hypothesised that its absence from shallow eutrophic lakes was due to a need for deep, oxygenated water to escape from fish predation.
    General impacts
    The invasion of B. longimanus into the Laurentian Great Lakes has resulted in substantial and sustained decreases in the populations of a number of (mostly cladoceran) native zooplankton species (Barbiero and Tuchman, 2004). Similar zooplankton community shifts have also been seen in Harp Lake, Ontario (Yan and Pawson, 1997). Given what is known of B. longimanus's feeding habits (e.g., Schultz and Yurista, 1999), these impacts have presumably resulted from direct predation. The impacts of B. longimanus on fish community dynamics is unclear at present. While directly competing with small fish for food, B. longimanus is also utilised as food by some fish species (Coulas et al. 1998).

    "Surveys of Ontario anglers indicate that B. longimanus is widely regarded as a nuisance. With its long caudal process, it can foul fishing lines and downrigger cables, potentially resulting in the loss of hooked fish" (Boudreau and Yan, 2004).

    Straile and Haelbich (2000) report that, "Because of its large body size and conspicuousness, B. longimanus is a preferred prey of freshwater fish." In the Great Lakes it has been shown to be a preferred prey of alewife (Alosa pseudoharengus) (Pothoven and Vanderploeg, 2004; Mills et al. 1992) and lake herring (Coregonus artedii) (Coulas et al. 1998). However, it is probably not utilised by smaller fish (Barnhisel and Harvey, 1995).
    B. longimanus exhibits a high degree of morphological variability both throughout its range and seasonally within a locality. Until recently several different species were recognised, although these are now seen to be simply manifestations of the extreme polymorphism of B. longimanus. Currently, only the species longimanus is recognised in the genus Bythotrephes (Rivier, 1998). Initial reports of Bythotrephes longimanus in North America referred to the organism as Bythotrephes cederstroemi.
    Geographical range
    Native range: Asia and Europe (Rivier, 1998).
    Known introduced range: Laurentian Great Lakes, inland lakes in Ontario (Therriault et al. 2002) and the US (Yan and Pawson, 1998).
    Introduction pathways to new locations
    Ship ballast water: “Normally, oceangoing ships take on salt water as ballast (and salt water animals), so a freshwater organism such as B. longimanus would not be in the ballast water. However, in the spring, St. Petersburg becomes a freshwater port due to runoff from snowmelt, and freshwater animals may be taken into the ballast tanks. Thus, spring may provide conditions that enable B. longimanus and other freshwater organisms to be transported to the Great Lakes” (Berg, 1992)

    Local dispersal methods
    Boat: "Bythotrephes longimanus has spread to almost 50 inland lakes in Ontario, Canada, most likely moved there from the Great Lakes by anglers and recreational boaters" (Boudreau and Yan, 2004).
    Consumption/excretion: Charalambidou et al. (2003) speculate that, "The recent expansion of B. longimanus may be a result of endozoochorous avian dispersal." The authors investigated the survival of B. longimanus eggs in diapause after their passage through the digestive tract of four species of ducks. The authors concluded that, "The probability of endozoochorous dispersal by individual ducks is low but becomes significant when considering the thousands of ducks moving among wetlands. Endozoochorous dispersal of B. longimanus would most likely involve the transport of newly produced diapause eggs from north to south, during the autumn migration of ducks. Based on flight speed estimates of ducks we estimate dispersal probability to drop sharply at distances over 60-80 km."
    Management information
    Preventative measures: Ontario has initiated its own volunteer monitoring program for B. longimanus. Boudreau and Yan (2004) conducted an investigation to determine if the monitoring program was successful. The authors determined that, "Volunteer monitoring programs not only benefit the parent or supporting organisation by helping carry out their mandates, they also serve a great purpose in educating the public. The best way to prevent the further spread of these organisms into Ontario's inland lakes is to educate the boaters that frequent the province's waterways."

    Johnson (2003) has been promoting education and word of mouth in Wisconsin to prevent the further spread of the species within that state. Fliers have been posted in strategic locations, and Boaters are informed firsthand of precautions they should take in order to prevent the spread of B. longimanus.

    Sikes (2002) states that, "Personal management practices for boaters and anglers include cleaning of boating equipment with high-pressure water or heated water upwards of 104ºF. Also bait buckets should not be emptied into waters, instead empty on land. Visual inspection of rigging, fishing, and anchor lines as well as the props and hulls of boats can help limit B. longimanus spread. Boats should be allowed to dry for at least 5 days before transport between lakes, but because of B. longimanus resting eggs longer periods are recommended. Boats and trailers can be towed through carwashes if exposed to infected waters for long time periods."

    Sikes (2002) reports that, "Current management practices for the spiny water flea seek to limit its spread to other lakes. Predictions can be made on the invasion potential for surrounding areas using the vectors of transfer, namely humans. One main factor is the lakes proximity to major roads and lakes within 3.4 km show particular vulnerability." The author also reports that, "The accidental introduction of ballast water invaders like B. longimanus, the zebra mussel, and others could possibly have been avoided by ships using open water ballast exchange practices."

    Crustaceans, and in particular cladocerans, appear to be preferred prey items B. longimanus (Schultz and Yurista, 1999), although copepods and rotifers are also apparently utilised (Schultz and Yurista, 1999; Vanderploeg et al. 1993). "B. longimanus seizes prey with long arm-like antennae and hold them in place with its legs. One spiny water flea may consume as many as 20 prey organisms in a day" (Berg, 1992).
    B. longimanus can reproduce both by parthenogenetic (cloning) and gamogenetic (sexual) reproduction. Parthenogenetic reproduction occurs throughout the whole life cycle, while gamogenesis occurs at the end of a growing season and results in the formation of resting eggs capable of surviving unfavourable conditions (Rivier, 1998).
    Lifecycle stages
    Sikes (2002) states that, "Through parthenogenesis the spiny water flea can exhibit explosive population growth, but its ability to produce sexual eggs allows it to increase genetic variability as well as survive and disperse under adverse environmental conditions. Development time till primaparity (1st time mom) is not significantly different for the two modes of reproduction, averaging about 14 days. Sexually reproduced eggs can go into a semi-static metabolic condition called diapause. Through these sexual reproduced "resting eggs", the next generation of B. longimanus can overwinter and hatch usually when temperatures exceed 4ºC. The spiny water flea can survive a wide range of temperatures, but has lowest mortality between 5ºC and 30ºC. Its development time is temperature dependent and maximised between 20-25ºC without suffering higher mortality. Besides protection from winter conditions, many diapaused eggs can also survive passage through fish digestive tract. A female with a full clutch is double her usual weight . This fact causes increased predation on pregnant females above their conspicuous body with a single large eye and long tail spine and thereby further aids in dispersal."
    Reviewed by: Richard P. Barbiero, Ph.D. Senior Environmental Scientist CSC Chicago USA
    Principal sources: Sikes, 2002 Spiny Water Flea Bythotrephes longimanus Leydig 1860
    Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
    Last Modified: Wednesday, 10 August 2005

ISSG Landcare Research NBII IUCN University of Auckland