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| NAS - Nonindigenous Aquatic Species |
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Common Name: waterflea
Taxonomy: available through 
Identification:
This waterflea has a short and prominent antennae mound. Its helmet is narrow, pointed at the top, and somewhat undulating along the margins. The rostrum is blunt and obtuse. The ventral side of the head is convex above the optic vesicle and concave behind it. These features are important to note in order to avoid confusing D. g. galeata with the native North American subspecies, D. g. mendotae (Brooks 1957; Glagolev 1986; Taylor and Hebert 1993).
The North American and European subspecies have hybridized in the Great Lakes basin. Morphologies and genetics of hybrid D. g. galeata x D. g. mendotae tend more toward the European D. g. galeata form in Lake Erie and more towards the North American D. g. mendotae form in the Lake Ontario drainage (Taylor and Hebert 1993).
Mature parthenogenetic females of European D. galeata can reach up to a maximum of 2.8 mm in length, although most females range from 1.3–2 mm. Males grow up to 1.4 mm but most are around 1.2 mm. The hybrid D. g. galeata x D. g. mendotae is slightly larger than native D. g. mendotae, which can grow up to a maximum of around 1.75–2.5 mm, depending on conditions, but is usually around 0.6–1.6 mm long (Heisey and Porter 1977; Flobner and Kraus 1986; Glagolev 1986; Lynch et al. 1986; Dodson 1988; Leibold and Tessier 1991; Taylor and Hebert 1993; Boersma 1995).
Size: 1-3mm
Native Range: D. g. galeata is native to the Palearctic region, in northern Africa, Europe, and Asia north of the Himalayas (Taylor et al. 1996).
Nonindigenous Occurrences: Genetic and morphological evidence indicates that D. g. galeata was likely introduced to Lake Erie in the 1970s or early 1980s and subsequently spread from there. Hybrid D. g. mendotae x D. g. galeata was first noticed in the early 1990s in Lake Erie and outlying areas of the Lake Ontario watershed, in Onondaga Lake, Oneida Lake, and Grenadier Pond, Toronto (Taylor and Hebert 1993).
Ecology: D. g. galeata is a planktonic species that prefers large lakes. However, some populations are found in ponds, relatively lentic rivers, and hyporheic zones, or regions of groundwater recharge. Many populations occur in eutrophic habitats. This species has been recorded in European water bodies where bottom water can reach salinities of 3.6‰ but where surface salinities are lower than 1‰. This species is typically found in freshwater (Lysebo 1995; Dumont and Negrea 1996; Taylor et al. 1996; Schwenk et al. 2000).
Cladocerans are capable of reproducing asexually through parthenogenesis. They can also produce resting eggs that are able to survive periods of desiccation in the sediment (Taylor and Hebert 1993).
Within the water column Daphnia spp. are generalist filter feeders on small particles and more selective feeders on larger particles. Particle size selection varies with body size (Repka 1997).
Means of Introduction: D. g. galeata was very likely introduced to the Great Lakes basin in ballast water (Taylor and Hebert 1993).
Status: Hybrid clones are established where recorded.
Impact of Introduction:
A) Realized: After D. g. galeata was introduced to Lake Erie it rapidly hybridized with native D. g. mendotae. Hybrid clones are now very common, especially during the summer months in Lake Erie (Taylor and Hebert 1993).
B) Potential: It is possible that hybrid clones of D. g. mendotae x D. g. galeata are more vigorous and fit than parent clones, especially in times of environmental stress. This could have led to rapid expansion of the hybrid population, especially in parts of Lake Erie (Taylor and Hebert 1993).
Remarks: Some authors, such as Glagolev (1986) indicate that morphological variation of D. galeata is so great within one region that it is not possible to differentiate subspecies from different regions. However, genetic studies indicate that there are true distinct forms of D. galeata from different regions (Taylor and Hebert 1993).
References
Boersma, M. 1995. The allocation of resources to reproduction in Daphnia galeata: against the odds? Ecology 76(4):1251-1261.
Brooks, J. L. 1957. The systematics of North American Daphnia. Memoirs of the Connecticut Academy of Arts and Sciences 13:1-180.
Dodson, S. I. 1988. Cyclomorphosis in Daphnia galeata mendotae Birge and D. retrocurva Forbes as a predator-induced response. Freshwater Biology 19:109-114.
Dumont, H. J. and S. Negrea. 1996. A conspectus of the Cladocera of the subterranean waters of the world. Hydrobiologia 325:1-30.
Flobner, D. and K. Kraus. 1986. On the taxonomy of the Daphnia hyalina-galeata complex (Crustacea: Cladocera). Hydrobiologia 137:97-115.
Glagolev, S. M. 1986. Species composition of Daphnia in Lake Glubokoe with notes on the taxonomy and geographical distribution of some species. Hydrobiologia 141:55-82.
Heisey, D. and K. G. Porter. 1977. The effect of ambient oxygen concentration on filtering and respiration rates of Daphnia galeata mendotae and Daphnia magna. Limnology and Oceanography
Lynch, M., L. J. Weider, and W. Lampert. 1986. Measurement of the carbon balance in Daphnia. Limnology and Oceanography 31(1):17-33.
Lysebo, E. M. 1995. Behavioural and morphological changes in polymorphic Daphnia related to different predation regimes. Hydrobiologia 307:185-191.
Repka, S. 1997. Effects of food type on the life history of Daphnia clones from lakes differing in trophic state. I. Daphnia galeata feeding on Scenedesmus and Oscillatoria. Freshwater Biology 37:675-683.
Schwenk, K., D. Posada, and P. D. N. Hebert. 2000. Molecular systematics of European Hyalodaphnia: the role of contemporary hybridization in ancient species. Proceedings: Biological Sciences 267(1455):1833-1842.
Taylor, D. J. and P. D. N. Hebert. 1993. Cryptic intercontinental hybridization in Daphnia (Crustacea): the ghost of introductions past. Proceedings of the Royal Society of London Series B 254:163-168.
Taylor, D. J., P. D. N. Hebert, and J. K. Colbourne. 1996. Phylogenetics and evolution of the Daphnia longispina group (Crustacea) based on 12S rDNA sequence and allozyme variation. Molecular Phylogenetics and Evolution 5(3):495-510.
Other Resources: Great Lakes Water Life
Author: Rebekah M. Kipp
Contributing Agencies: 
NOAA - GLERL
Revision Date: 2/13/2007 Citation for this information:
Rebekah M. Kipp. 2009. Daphnia galeata galeata. USGS Nonindigenous Aquatic Species Database, Gainesville, FL.
<http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=2732> Revision Date: 2/13/2007
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