Ratio-dependent functional responses-tests with the zooplanktivore Mysis mixta

• Published in: Marine ecology. Progress series (Halstenbek) 2001-07, Vol.216, p.181-189
• Main Authors: HANSSON, Sture, DE STASIO, Bart T, GOROKHOVA, Elena, MOHAMMADIAN, M. Ali
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Animals; Artemia; Autoecology; Biological and medical sciences; Brackish; Copepoda; Daphnia magna; Fundamental and applied biological sciences. Psychology; Marine; Mysis mixta; Protozoa. Invertebrata
• ISSN: 0171-8630; 1616-1599
• DOI: 10.3354/meps216181

The response of a consumer to varying densities of its food resources is essential to consumer-resource interactions, yet the proper way to describe this interaction (the functional response) has been intensively debated. Traditionally, consumption has been assumed to be solely a function of resource abundance (prey dependent). However, it has lately been suggested that consumption depends on the ratio between resource and consumer abundances (ratio-dependent functional responses). In this paper, we experimentally tested if the consumer density influences food consumption rates. As the consumer, we used a dominant Baltic Sea zooplanktivore, the mysid shrimp Mysis mixta. The prey used were of 3 types; the large but slow Daphnia magna, the small and slow Artemia sp., and a natural assemblage of Baltic Sea copepods that exhibit strong escape responses. Our results show that intraspecific interactions occurred among the consumers, supporting the hypothesis that a functional response can be dependent on the consumer density.