Feeding ecology of mysids in freshwater and coastal marine habitats; A review

Abstract This paper reviews the feeding ecology of mysids in freshwater and marine coastal environments, focusing particularly feeding mechanisms, stomach contents, feeding rate, food selectivity, and its impact on ecosystems. Mysids exhibit two distinct feeding modes; a suspension feeding mode in which small particles such as detritus, phytoplankton and small zooplankton are acquired; a raptorial feeding mode in which large preys are actively seized with the thoracic appendages. In addition, some species seem to be able to obtain benthic diets. Generally, most mysids exhibit omnivorous feeding habits consuming a wide range of prey items, including detritus, algae, diatoms, rotifers, copepods, cladocerans, amphipods, carrion, fragments of terrestrial plants' leaves and of macroalgae, seeds, etc. Diel and seasonal variations in stomach contents are noticed in many species. Most mysid species feed actively at night in association with vertical or horizontal migration. Seasonal change in diet is most probably related to food availability and ontogenetical change in diets. Small sized food items such as phytoplankton, rotifers, detritus are more frequently eaten by smaller individuals, whereas larger individuals exhibit a higher degree of carnivory. The tendency for carnivory increases with growth (1ife-history omnivory) reflect their increased success in prey capture. Laboratory and field measurements of predation rate indicate that mysids have a high potential to consume mesozooplankton. Predation rates range from 0.4 to 42.6 microgC ind**(-1) h**(-1) for copepods (3-30% of body carbon per day), and from 1.3 to 102 microgC ind**(-1) h**(-1) for cladocerans (24-301% of body carbon per day). Diatoms seem to be preferable food items compared to other planktonic algae such as green algae and blue-green algae. The significance of detritus as a diet is variable and depends on its origin and availability of other food items. Mysids can feed selectively on different species and size groups of zooplankton, depending on prey availability, predator-prey encounter frequency, prey escape response and mysid's ability to capture and handling. In some circumstances, mysids can optimize their feeding behavior by switching their feeding mode in relation to food abundance. Flexible omnivory in mysids is advantageous, providing effective feeding throughout the year. This feeding behavior also enables shallow water-dwelling mysids to utilize the organic matter from various sources, i.e. water column, benthic and terrestrial ecosystems.