Feeding preference of Littorina snails (Gastropoda) for bleached and photosynthetic tissues of the seaweed Mazzaella parksii (Rhodophyta) by Christine Heaven
Background • Littorina sp.shows a preference for Mazzaella parksii (Kim & DeWreede 1996) • High irradiance and desiccation levels lead to bleaching of tips; constitutes disruptive stress (Scrosati & DeWreede 1998) • Bleached tissue is less rigid; increased susceptibility to herbivory (Cronin & Hay 1996)
Importance? • If red tissue is preferred: • Whole blade is removed • Potential for Littorina sp. to control community structure • If bleached tissue is preferred: • Herbivore pressure is diverted away from healthy tissues • Blade can regenerate • Reproduction is enhanced
Research Question • Does Littorina sp. have a preference for certain tissue types?
Hypothesis • Littorina sp. will show a preference for either bleached, yellow-green, or red tissues
Experimental Design • Goal: To measure the percent change in biomass due to herbivory • Study Site: Prasiola Point, Vancouver Island, B.C. • Experimental Unit: Mazzaella parksii tissue fragments
What does this mean? • Herbivore pressure is diverted to dead tissues • Littorina sp. may not have strong control over this community • Biomass remains in the system • Divergence of herbivore pressure through bleaching may be a result of algal evolution in response to grazing
Future Work • Determine chemical content of three tissues for nutritional value • Examine other locations for this preference • Field experiment to test whether dead tissues are removed by herbivores