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Thalia democratica


Brook Anderson (2013)     


Fact Sheet



Physical Description

Sexual Form

Asexual Form


Biogeographical Location

Feeding Ecology

Life History & Behaviour

Asexual Reproduction

Sexual Reproduction

Anatomy & Physiology

Sensory System

Muscular System

Feeding Structures and Function

Evolution & Systematics

Conservation & Threats

References & Links

T. democratica is an efficient filter feeder inhabiting coastal marine ecosystems (Henschke et al., 2013, Vargas and Madin, 2004). The retention efficiency of the species has been measured at greater than 80% and 40 - 50% for large and small (<2 µm) particles respectively (Henschke et al., 2013). The species' rates of grazing far outweigh that of other planktonic consumers, and thus T. democratica is among the most versatile colonising species of marine ecosystems, where in some instances the species has been documented removing the entirety of daily primary production from a region (Henschke et al., 2013). High densities of T. democratica in coastal  waters has been correlated with negligible densities of other herbivorous zooplankton (Alldredge and Madin, 1982). T. democratica is regularly observed in high densities after the onset of a spring plankton bloom. Species on which T. democratica have been documented feeding include bacteria, flagellates, diatoms, radiolarians, detritus, copeopods and pteropods (Vargas and Madin, 2004). The size of consumable particles for T. democratica varies between < 1 µm and 1 mm. 

Phytoplankton and zooplankton vary within coastal marine ecosystems both spatially and temporally. T. democratica have evolved as an adapted species to persist with these fluctuations in food availability. Strategies such as high volume filter feeding, the ingestion of a range of food particle sizes, and the species life history allowing for exponential population growth in response to favourable ocean conditions have ensured the species persistence within these ecosystems worldwide (Vargas and Madin, 2004).