RECOGNIZABILITY OF ALGAE INGESTED BY ABALONE

Studies of the diet of abalone and other herbivorous gastropods, based on gut contents, may be biased against some species of algae, especia lly those that are most preferred, The blacklip abalone Haliotis rubra was fed for short periods on monospecific diets of eight algae, inclu ding red, brown and green species that span the range of preference. I n addition, two preferred species were fed to abalone after one month' s, one week's, or no starvation. The number of recognizable fragments of each alga per unit volume of crop contents was examined. Although k ey characters of some species remained recognizable even at an advance d stage of digestion, other algae were intrinsically less recognizable . Preferred red algae disappeared rapidly after one week's or no starv ation but more slowly after one month's starvation. Less preferred alg ae were not eaten without a long starvation period and became unrecogn izable relatively slowly, especially the least preferred brown algae E cklonia radiata and Phyllospora comosa, which have high polyphenol con tents. Thus, the gut contents of starved abalone in the field contain recognizable fragments of less preferred species for long periods, whe reas well-fed abalone retain recognizable fragments of preferred speci es only for short periods.