|Title||Re-examination of the effects of food abundance on jaw plasticity in purple sea urchins|
|Publication Type||Journal Article|
|Year of Publication||2019|
|Authors||deVries M.S, Webb S.J, Taylor J.RA|
|Type of Article||Article|
|Keywords||Availability; diadema-antillarum; dynamics; growth; heliocidaris-erythrogramma; Marine & Freshwater Biology; phenotypic plasticity; populations; size; spine damage; strongylocentrotus-purpuratus|
Morphological plasticity is a critical mechanism that animals use to cope with variations in resource availability. During periods of food scarcity, sea urchins demonstrate an increase in jaw length relative to test diameter. This trait is thought to be reversible and adaptive by yielding an increase in feeding efficiency. We directly tested the hypotheses that (1) there are reversible shifts in jaw length to test diameter ratios with food abundance in individual urchins, and (2) these shifts alter feeding efficiency. Purple sea urchins, Strongylocentrotus purpuratus, were collected and placed in either high or low food treatments for 3 months, after which treatments were switched for two additional months in La Jolla, CA (32.8674 degrees N, 117.2530 degrees W). Measurements of jaw length to test diameter ratios were significantly higher in low compared to high food urchins, but this was due to test growth in the high food treatments. Ratios of low food urchins did not change following a switch to high food conditions, indicating that this trait is not reversible within the time frame of this study. Relatively longer jaws were also not correlated with increased feeding efficiency. We argue that jaw length plasticity is not adaptive and is simply a consequence of exposure to high food availability, as both jaw and test growth halt when food is scarce.