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Elizabeth Wurdak


The rotifer Asplanchna herricki (A. herricki) is an integral predatory species impacting rotifer and algae populations of fresh water lake habitats. In order to determine the feeding behavior and mechanism of A. herricki, stomach content analysis was performed and predator/prey interactions were observed. A. herricki encountered prey randomly, only attacking after physical contact of the prey with the corona. It was found that A. herricki prefers small rotifer prey as opposed to algae. Algae such as Volvox and Pediastrum appeared to deter ingestion due to size or shape. Rotifers such as Keratella cochlearis, Brachionus patulus, and Ploesoma are preferred items, generally eliciting the highest overall frequencies of attack, capture, and ingestion, corresponding to trends seen in similar species. The polymorphic defense mechanisms of Keratella and Brachionus were found to be somewhat effective, yet these prey were highly preferred food items. Polyarthra was not capable of being captured due to its jumping defense. Trophi analysis showed that A. herricki possesses both numerous small teeth-like serrations, along with a moderately sized midramal tooth on each rami, suggesting a mixed diet of both rotifer and algae, corresponding to stomach content analysis. According to these results, A. herricki has the strongest impact on populations of Keratella, Brachionus, and Ploesoma; however, further studies questioning prey item nutritional content, prey size, and the effect of prey density on Asplanchna consumption are needed in order to more clearly determine prey preference.

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