Summary
Physical Description
Ecology
Life History & Behaviour
Feeding
Reproduction
Anatomy & Physiology
Sensory Systems (Focus Project)
Evolution & Systematics
Biogeographic Distribution
Conservation & Threats
References & Links | Feeding
In contrast to other urochordates, salps push water into their pharyngeal mucus filter via rhythmic musculature action instead of using ciliary movement to produce such a current (Bone et al. 1991). Locomotion is also controlled with these circumferential muscle bands in addition to inhalant and exhalent valves, which can regulate the direction of water flow-through (Madin 1974). Using this system, salps can filter up to 1L of water per hour (Madin 1974).
Water is filtered through the pharyngeal cavity over a mesh net made of mucous that is secreted from the endostyle (Madin and Kremer 1995). Nets are consistently re-ingested (along with all the food that has been caught in them) from the back and a new mucous net is secreted from the front (Madin and Kremer 1995). For the entire net to be re-ingested and a new one secreted takes from 10 to 300 seconds (Madin 1974).
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Adult Pegea Confoederata contracting circular muscles to move water through its body for filter feeding
(video by Helen Twaddle, Heron Island)
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Like other salps, Pegea confoederata is a filter feeder with no obvious mechanism for selection of particular foods. Anything that gets caught in the mucous net seems to be digested – mostly phytoplankton and detritus (Madin and Kremer 1995). This is generally a very effective system: it means that a wide range of sizes and types of matter can be utilised by the salp as a food source and allows for efficient filtering of food (Alldredge and Madin 1982). Filter rates in salps are also much higher than many of their competitors in the ocean (three to several hundred times higher in some cases) so they have a distinct advantage in terms of how much food they can filter over a select period of time (Alldredge and Madin 1982). A single Pegea confoederata can filter as much water as 450 copepods (Harbison and Gilmer 1976). However, some other prominent filter feeding plankton such as some copepods are able to adjust their filtering rates depending on the food density in the water (Frost 1972). This is not something that has ever been observed in salps. |
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