Substratum cavities affect growth-plasticity, allometry, movement and feeding rates in the sea urchinStrongylocentrotus purpuratus

Abstract

SUMMARYWe assessed the influence of rock cavities, or pits, on the growth dynamics and behavior of the purple sea urchin, Strongylocentrotus purpuratus. In a paired-designed, laboratory experiment, sea urchins were assigned to sandstone blocks that were either 'Flat' or had a 'Pit' drilled into the center. At the start, both groups were approximately the same shape and size. In just 2 months, the shapes of the tests were significantly different between the two treatments, with the Pit urchins having an increased height:diameter profile. This result demonstrates the plastic nature of the sea urchin test and that, despite its apparent rigidity, it is capable of deforming during growth. In addition, the presence of pits modified behavior and food consumption as well as allometric growth of the test and Aristotle's lantern. Sea urchins on Pit sandstone blocks tended to stay in the cavities and not move about the flat areas, whereas individuals on Flat blocks changed position. Sea urchins in the Pit treatment consumed less food and had relatively larger demipyramids (the 'jaw' ossicle in Aristotle's lantern). These morphological and allometric changes occurred over a short time-period (8-20 weeks). We conclude that microhabitat is an important factor in controlling the behavior and growth dynamics of the bioeroding sea urchin S. purpuratus.

Role of environmental change in rock-boring echinoid trace fossils

“…In turn, the adult animals are responsible for the large, groove-like borings produced when it bores slowly forward while grazing on algae. This is confirmed with experiments made by Hernández and Russel (2010), who observed that many sea urchins with identical food availability, such as Echinometra mathaei, Strongylocentrotus droebachiensis, S. purpuratus or Paracentrotus lividus, change their morphology during growth owing to the microhabitat conditions occupied (presence or absence of a cavity).…”

“…Circolites reproduces a dwelling structure where sea urchins are protected from predators and wave surge and where occasionally they act as macro-suspension feeders trapping organic material brought into the boring by the rising tide (Asgaard and Bromley, 2006). Hernández and Russel (2010) also attribute to these pits a more hospitable microhabitat by retaining water and moderating temperatures and desiccation during emersion at low tide. Ericichnus igen.…”

Long-term and trans-life-cycle effects of exposure to ocean acidification in the green sea urchin Strongylocentrotus droebachiensis

“…Sea urchins lack fast escape and are able to acclimate to a new environment by modulating their morphology and physiology. For example, it was shown that Strongylocentrotus purpuratus is able to reshape its skeleton and change its behavior in a matter of 8-20 weeks when exposed to a different habitat structure (Hernández and Russell 2010). As a consequence, short-term exposure may both over-(no acclimation) and underestimate (not enough time to induce lethal effects) the real impacts of a chronic exposure to high pCO 2 .…”

Annual reversible plasticity of feeding structures: cyclical changes of jaw allometry in a sea urchin

“…Changes in jaw and diameter allometry also have been induced under laboratory conditions of food manipulations in S. purpuratus [18,33,34], S. droebachiensis [24,35], M. franciscanus [36,37], D. antillarum [27], Paracentrotus lividus [38] and Lytechinus variegatus [39].…”