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).
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).
References: (click for full 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.
Ebert, D. 2005. Chapter 9, Population Dynamics and Community Ecology in Ecology, Epidemiology, and Evolution of Parasitism in Daphnia. National Center for Biotechnology Information. Bethesda, MD.
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.
GLMRIS. 2012. Appendix C: Inventory of Available Controls for Aquatic Nuisance Species of Concern, Chicago Area Waterway System. U.S. Army Corps of Engineers.
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 22(5): 839-845.
Hulsmann, S., and T. Mehner. 1997. Predation by underyearling perch (Perca fluviatilis) on a Daphnia galeata population in a short-term enclosure experiment. Freshwater Biology 38(1):209-219.
Leibold, M., and A.J. Tessier. 1991. Contrasting patterns of body size of Daphnia species that segregate by habitat. Oecologia 86: 324-348.
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.
Mills, E.L., and J.L. Forney. 1983. Impact on Daphnia pulex of predation by young yellow perch in Oneida Lake, New York. Transactions of the American Fisheries Society 112:151-161.
Post, J.R., and D.J. McQueen. 1987. The impact of planktivorous fish on the structure of a plankton community. Freshwater Biology 17(1):79-89.
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.
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