Archive for April, 2011

Daphnia lumholtzi is an invasive cladoceran native to Asia and Africa that has been found in the South-Eastern United states only in last twenty years. A study lead by J.E. Havel of Southwest Missouri State University conducted population counts of this invader in 119 reservoirs in Southwest Missouri during the years 1992-1993. The counts were structured to take place each month over the two year period in order to determine any fluctuations in seasonal populations of D. lumholtzi.

Havel found that D. lumholtzi populations were not constant year round, and instead were highest during the summer and fall, with very small during the winter and spring. Havel also found that during the periods of highest population density of the native Daphnia, D. lumholtzi experienced a period of lower population density.

In addition to population details, Havel discovered that D. lumholtzi was more likely to invade larger reservoirs than smaller ones and warmer reservoirs rather than colder ones. The studies findings are consistent with the predicted behavior of D. lumholtzi.

Canadian Journal of Fisheries and Aquatic Sciences, Volume 52, Pages 151-160, Published JAN 1995, “Invasion of the exotic cladoceran daphnia-lumholtzi in North American reservoirs.”

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Since its appearance in Texas in the early 1990’s, the invasive aquatic species Daphnia lumholtzi has been successful in colonizing in many aquatic regions of North America. Studies have yet to be done linking the reproductive strategy of the Daphnia to its success in invading new territories.  Most rotifers, especially Cladocerans, have the ability of changing between asexual reproduction via clonal reproduction and budding, as well as sexual reproduction in which resting eggs are used to avoid an overcrowded environment.

Scientists have been trying to find a link between nutrient supply, light availability, and algae content with the reproductive capacity of the spiny water flea.

Through rigorous experimentation, scientists found a direct correlation between low Phosphorous levels and the Daphnia population’s growth rates. The effects of overcrowding in aquatic systems were also noted in the growth rates of the water flea. It was shown that low levels of phosphorus, coupled with high quantities of Daphnia, effectively reduced the growth rates for the water flea.

References:

Hydrobiologia (2009) 618:47–56 DOI 10.1007/s10750-008-9546-2

Overcrowding, food and phosphorus limitation effects on ephipphia production and population dynamics in the invasive species Daphnia lumholtzi

Allison S. Smith Æ Kumud Acharya Æ Jeffrey Jack

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Native to the regions of Asia, Africa, and Australia, Daphnia lumholtzi has become successful in establishing their presence throughout the southern region of the United States within the past decades. Previous experiments conducted on other Daphnia species and theoir change in morphology has prompted Peder M. Yurista of Murray State University to conduct his own experiment on Daphnia lumholtzi and their undergoing of cyclomorphosis (changing of helmet and spine length).

Several scientists have claim that Daphnia’s undergo a change in their helmet or spine length because of higher survival rates from predation. Yurista believed that higher temperatures affect body changes and cyclomorphosis features are found to be more of an advantage to the D.lumholtzi swimming abilities, consequently indirectly increasing their survival rates.

After conducting his experiment with D. lumholtzi from Kentucky Lake in a diverse range of temperatures, Yurista discovered the D. lumholtzi that had the longest spines and helmets were those who were contained in an aquarium at 31 C’. Those who possess the smallest helmet and spine length were those who were contained in temperatures of 21- 28 C’.

Yurita, Peder M. Cyclomorphosis in Daphnia lumholtzi induced by temperature. Freshwater Biology. 2000 Issue 43:207-213

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The gowth and reproduction of Daphnia lumholei, an an invasive species in the Southern United States, is highly influenced by temperature and abundance of food. In the absence of predators, Daphnia is faced with a trade off. They can either live in the epilimnion where development in the

warm water is fast, but food shortage causes low egg production, or in the hypolimnion, where food availability is high but development is slow because of low temperatures.

In this study, Kessler and Lampert test whether Daphnia is affected by light to choose the best depth of the water for reproductive or growth purposes. They also tested the depth preferences of varying Daphnia size classes and egg-bearing females . However, they found no direct correlation between light and Daphnia’s physical necessities. In fact, large and egg-bearing females, being forced into deeper layers by the residual light response during the day , experienced a lower average temperature during day than juveniles.

Kessler, K., and Lampert, W. 2004. Depth distribution of Daphnia in response to a deep-water algal maximum: The effect of body size and temperature gradient. Freshwater Biology 49(4): 392-401.

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Daphnia lumholtzi, an exotic zooplankton, has invaded freshwater systems throughout the southern and midwestern United States. A study done by Dzialowski et al 2000 conducted regional surveys of eastern Kansas reservoirs to document the range of expansion of D. lumholtzi. It was found in five out of 35 reservoirs sampled in 1994, and 11 out of the 35 reservoirs when re-sampled in 1997. In addition, 40 small ponds inaccessible to recreational boats were sampled, where no D. lumholtzi was found. This suggests that non-human dispersal mechanisms play an insignificant role in the spread of the species.

This study suggests that further experimentation is needed to determine if the absence of D. lumholtzi from these ponds is due to insufficient dispersal mechanisms or the species’ inability to colonize in this environment.

Dzialowski A.R., O’Brien W.J., and Swaffar S.M. 2000. Range expansion and potential dispersal mechanisms of the exotic cladoceran Daphnia lumholtzi. Journal of Plankton Research. Volume 22. Issue 12: 2205-2223.

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Daphnia lumholtzi most notable characteristics are its pointed helmet and large spines.  2 features that make the D. lumholtzi difficult to feed on allowing it to prosper as an aquatic invasive species. It was first introduced in 1990 in Texas and can now be found throughout southeastern USA.

Philip W. Lienesch and Moshe Gophen of the University of Oklahoma’s department of Zoology and Biological Station, are interested if inland silverside (Menidia beryllina) are size-selective predators of D. lumholtzi. By placing 3 various sizes of  inland silversides in tanks with various sizes of D. lumholtzi, Lienesch and Gophen were able to determine inland silverside’s feeding habits. Smaller inland silversides preferred smaller D. lumholtzi, while the larger fish ate the large D. lumholtzi. Next Lienesch and Moshe tested their results in Lake Texcoma, comparing D. lumholtzi to native Daphnia, results were similar to labratory experiment, suggesting that when zooplankton is scarce, D. lumholtzi could become a food source for juvenile silversides.

Lienesch, P.W., and M. Gopen. 2005. Size-selective predation by inland silversides on an exotic cladoceran, Daphnia lumholtzi. The Southwestern Naturalist 50, 158-165.

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The water flea (Daphnia lumholtzi) is a cladoceran native to Eastern Africa, Australia and the Asian subcontinent of India and was first reported in 1991 in an Eastern Texas.

Dagram Frisch and Lawrence Weider of the University of Oklahoma are examining the ecological genetics of D. lumholtzi in Lake Texoma, Texas, USA. As no spatial and or temporal survey of the genetic variation of the specie was ever conducted in this lake, they took a combined approach of field surveys and controlled lab experiments to examine the seasonal variation of in the Lake Texcoma population.

The population genetic structure of the D. lumholtzi was observed on 22 dates for a three year period along with temperature and salinity gradient. A two-allele polymorphism at the PGI locius was discovered. Frisch and Weider concluded that the rapid expansion and micro evolutionary dynamics of D. lumholtzi throughout North America might be a result of the genetic and environmental interactions. [156]
Sources: Freshwater Biology 2010, 55:1327-1336 DOI: 10.1111/j.1365-2427.2009.02356.x

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Daphnia lumholtzi, commonly known as the spiny waterflea, is an invader to many aquatic ecosystems. After they establish themselves in a foreign environment, they often become a prominent member of the local zooplankton community. Currently, not all of the reasons they are such successful invaders are known, but scientists are working to better undertand them.

J.T. Lennon, V.H. Smith and K. Williams of Dartmouth College department of Biological Sciences and the department of Ecology and Evolutionary Biology of the University of Kansas have been working to determine the temperature tolerance of D. lumholtzi. They measured this through observing fluctuations in D. lumholtzi’s reproductive rate, survivorship and molting rates. All these traits demonstrated that D. lumholtzi has a large temperature tolerance ranging from about 20 to 30oC, and that they do not proliferate well when water temperatures fall below 10oC. This suggests that D. lumholtzi may be limited to spreading through only the southern United States.

Lennon JT, Smith VH and Williams K. Influence of temperature on exotic Daphnia lumholtzi and implications for invasion success. Journal of Plankton Research. 425-434. 2001.

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Daphnia lumholtzi is a spiny water flea that has been invading freshwater lakes and reservoirs in the southern United States since the early 1990s. Though it has become established in many ecosystems, its full environmental effects, positive or negative, have not yet been determined.

To explore the predation of inland silversides (Menidia beryllina) on D. lumholtzi, Lienesch and Gophen from the University of Oklahoma measured the size of D. lumholtzi consumed by several different size classes of silversides. Placing hungry silversides of a particular size in a tank with a mix of D. lumholtzi sizes, they correlated the each silverside size to its preferred D. lumholtzi size. They found smaller silversides most commonly preyed on smaller daphnia, though they did not lack the capacity to consume larger water fleas. Similarly, large silversides preferred to consume large D. lumholtzi. These results suggest that D. lumholtzi could become an important food source for juvenile silversides when native zooplankton is scarce.

Lienesch, P.W., and M. Gopen. 2005. Size-selective predation by inland silversides on an exotic cladoceran, Daphnia lumholtzi. The Southwestern Naturalist 50, 158-165.

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Scientists currently have contrasting views on the correlation between a biome’s diversity and its vulnerability to invasive species.  Some believe that an environment with many species has higher competition for resources and will discourage invaders, while others believe that if many species can already share a niche in the environment an invasive one will logically be able to as well.  Dzialowski (2010) tested these theories with the invasive plankton, Daphnia lumholtzi.

D. lumholtzi is invasive to North American lakes and rivers, so three native Daphnia species were raised both separately and in combination, then D. Lumholtzi was introduced to each test.  While the number of species in the test did not directly correlate to the population of D. lumholtzi, one of the native species, D. magna, lowered the D. lumholtzi populations significantly in all tests where it was present.  Dzialowski concludes that certain native species are more capable of outcompeting exotics, and that species-rich environments are more likely to contain such a species.

Dzialowski, A.R., 2010.  Experimental effect of consumer identity on the invasion success of a non-native cladoceran.  Hydrobiologia 652: 139-148.

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