Key result
Impeding swimming limbs or inducing environmental hypoxia in developing brine shrimp prior to cardiac ontogeny significantly increased the frequency of gut movements (p<0.001).
In brine shrimp, gut movements provide essential pre-cardiac circulatory currents before heart development, challenging the assumption that general body movements alone are adequate.
Gut movements may compensate for impaired limb function in pre-cardiac brine shrimp; leaves open whether analogous mechanisms exist in vertebrate cardiogenesis.
Before the appearance of a functional heart in many invertebrate species, the assumption was that general body movements provide circulatory function. Consequently, I investigated the frequency of gut movements in the brine shrimp, Artemia franciscana, immediately post-hatch to the point when a functional heart appeared. Prior to cardiac ontogeny, movements of internal musculature and gut provided pre-cardiac circulatory currents with the rate of gut movements increasing when swimming limbs were impeded. There was also some evidence that gut movements were responsive to low oxygen, indicating a possible regulatory function for the gut in early circulation. Overall, this suggests that general body movements are not always adequate to provide internal circulation in small, heartless individuals.
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John I. Spicer (2006) studied Pre-cardiac ontogeny in brine shrimp. Impeding swimming limbs and/or environmental hypoxia vs. Unimpeded swimming limbs and normoxia was evaluated on Frequency of gut movements (fG) (p=<0.001). Impeding swimming limbs or inducing environmental hypoxia in developing brine shrimp prior to cardiac ontogeny significantly increased the frequency of gut movements (p<0.001).
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