Meeting Abstract
Highly invasive Asian carp are destroying ecosystems throughout the United States by outcompeting native species. With populations growing at an alarming rate, these fish have proven difficult to control. Their ability to thrive within eutrophic environments is due to their very efficient filter-feeding mechanism. Here we present data from an ontogenetic series of Silver Carp ranging in size from 15-900mm SL detailing how this unique filtering structure is built. Like many filter-feeding species, Silver carp possess an incredibly large epibranchial organ that occupies the majority of the dorsal buccal cavity. Branchial arches 1-5 have greatly modified gill rakers that span both the ceratobranchial ventrally and the epibranchial as it curves into the body of the epibranchial organ. From the earliest ontogenetic stage examined individual gill rakers already show a modified shape as compared to the basal character state for Cypriniformes. As development proceeds the structure of these gill rakers becomes increasingly complex. By early juvenile stages secondary growth of bone stitches together the primary lamellae, forming a screen-like mesh upon which future elaborations of the filtering structures are built. As development proceeds the individual lamellae of gill rakers maintain their shape as they increase in height. These lamellae will later become scaffolding for more complex filtering structures. Gill rakers involved in filtering undergo significant architectural changes during development. However, those curling into the epibranchial organ undergo separate structural changes due to the morphological constraints of the epibranchial organ. Comparisons with the Bighead carp, a congeneric, suggest the Bighead morphology more closely resembles that of the basal cypriniform condition.
