Daphnia

http://www.google.com/imgres?imgurl=http://webs.lander.edu/rsfox/rsfoximages3/clad99L_x550_x_643x.gif&imgrefurl=http://webs.lander.edu/rsfox/invertebrates/daphnia.html&usg=__09ofo2pt9Bd-r-A-6fXP9-gi4I4=&h=643&w=550&sz=35&hl=en&start=0&zoom=1&tbnid=58Zgl26JdhCeyM:&tbnh=144&tbnw=121&ei=r7wMTtJ5o4mwAunhmIQK&prev=/search%3Fq%3DDAphnia%26um%3D1%26hl%3Den%26sa%3DN%26rlz%3D1C1DVCL_enUS413US413%26biw%3D1366%26bih%3D667%26tbm%3Disch&um=1&itbs=1&iact=hc&vpx=584&vpy=289&dur=5185&hovh=243&hovw=208&tx=125&ty=127&page=1&ndsp=19&ved=1t:429,r:9,s:0&biw=1366&bih=667Daphnia are crustaceous plankton that filter feeds on many things including: yeast, bacteria, and unicellular algae. They have a large habitat found in most of the temperate areas of the Americas and other moderate climates.

When conditions are good they reproduce using parthenogenesis, an asexual means of reproduction producing perfect "copies" of the mother daphnia. When conditions are not favorable, they begin to reproduce using sexual means. The female then creates an ephippia. This is two eggs that lie within a protective layer. The ephippium in described is greater detail in the daphnia ephippia page. 

Common uses for daphnia are being used to test toxicity of aquatic environments. This is because the daphnia are extremely sensitive to many environmental factors. They are also used to feed planktivorous fish and small frogs.

Our research centers its focus on the ephippia production of the Daphnia. More can be found on the Daphnia ephippia page on this website.

Daphnia Ephippia

Daphnia ephippia are created through sexual means and contain two eggs within one shell. These are created when unfavorable conditions begin to occur such as approaching winter (versus parthenogenesis in favorable conditions). These ephippia diapause which means they are dormant for a period of time, and they hatch when the receive certain cues such as photo-period and temperature.

 

Dark EphippiaLight ephippia

It was noticed that some of the ephippia where "dark" while other were "light". The pigmentation is from melanin production. Melanin is an extremely costly pigment to produce as to date there is no evidence why daphnia produce these pigmented ephippia.

In a paper published by Dr. Gretchen Gerrish, there was found to be a correlation between population size and pigmentation. We are now testing whether or not fungal infection is related to the pigmentation of the ephippia.