Meeting Abstract
Suction is used as a primary mode of prey capture by the vast majority of aquatic-feeding vertebrates, and fishes exhibit a myriad of morphologies for suction feeding. Yet, even in radically divergent species, such as the cichlids of the African rift lakes, suction is still used to capture midwater prey. Under what circumstances is suction lost in the aquatic realm? Two categories of morphologies reflect a departure from suction as a key component of prey acquisition: 1) enlarged oral apertures that reduce wake phenomena and 2) structurally reinforced heads that resist ventro-lateral expansion. Species with enlarged oral apertures fall into two foraging guilds: ram filter-feeders and long-jawed piscivores. Ram filter-feeders are characterized by enlarged oral apertures and a food capturing mechanism that is located at the posterior end of the oropharyngeal cavity; this location facilitates laminar flow anterior to the particle collection sites. In piscivores, an elongated jaw is coupled with a deep V-shaped mouth opening that channels turbulent flow to the corners of the mouth, and behavioral limitation of gape size. In contrast, fish species with reinforced heads largely represent biting and scraping foraging guilds that remove their food as fragments of large or attached food sources. Although biters and scrapers can use suction to mobilize detatched particles, species that are characterized by reduction in the number of mobile elements in the skull/suspensorium seemingly cannot. Based on these behavioral and morphological characteristics, we define a suction-feeding morphospace and identify the physical parameters that are associated with a shift from suction feeding and a reliance on other modes of moving prey into the oral cavity.
