Projects

A molecular genetic assay for identifying and quantifying a cryptic marine bioinvader

End Date: 01/31/06

Abstract

Invasive species modify natural ecosystems and cause direct damage to industries and human health. In the United States, the combined costs of invasive species are estimated to be $137 billion/year and invasive species are recognized as a major threat to biodiversity on a global scale. The extent and impacts of invasive species in marine environments have only recently been appreciated but are now recognized as a principal threat to marine biodiversity. Gelatinous zooplankton (including ctenophores & scyphozoans) have gained particular notoriety as invasive species. Introductions of scyphozoans (i.e. jellyfish) have demonstrated the strong controls that they can exert over marine food-webs including commercial fisheries. Anthropocentric modifications of marine habitats appear to be increasing their susceptibility to invasions of scyphozoans and the probability that populations of the medusae life-history stages reach astonishing sizes. Despite the potential for invasions by scyphozoans, the trends towards increasing population sizes, and the controls that they can exert on marine food webs, there is no concerted effort towards understanding their invasive ecology.

Studies into the ecology of invasions by scyphozoans are hampered by their complex bipartite life-history: a highly cryptic benthic, asexually reproducing, scyphistomae (polypoid) stage is followed by a pelagic, sexually reproducing medusae stage. The most likely means by which scyphozoans are transported globally is as scyphistomae attached to the hulls of ships. Nothing is known of the ecology of the scyphistomae in the field because of the lack of techniques for identifying and quantifying this life-history stage. Answers to questions including transport mechanisms, the numbers and frequency with which scyphistomae are transported, and whether persistence in an area is dependent on repeated introductions or whether a population has become established are critical towards understanding the ecology of scyphozoan invasions.

We will develop a rapid quantitative molecular assay for the identification and quantification of scyphozoan scyphistomae at the class and species levels using a powerful emerging technology, Quantitative TaqMan®Polymerase Chain Reaction (PCR). This technology is capable of detecting and quantifying small concentrations of gene sequences specific to target species among genetic material from many other organisms. Our three objectives are: 1) to develop a TaqMan® PCR assay with broad specificity for scyphozoans scyphistomae from homogenates of organisms scraped from the hulls of ships; 2) to develop TaqMan® PCR assay for identifying and quantifying scyphistomae from the invasive scyphozoan Phyllorhiza punctata and the cosmopolitan scyphozoan Aurelia aurita; 3) to test the potential application of the TaqMan® PCR assays for identifying and quantifying scyphozoan scyphistomae in general, andPhyllorhiza punctata and Aurelia aurita in particular, entering a port on the hulls of ocean going ships. Preliminary investigations have successfully designed a TaqMan® system based on ribosomal DNA sequences for P. punctata among DNA from P. punctata, A. aurita, and Cyanea capillata (another common scyphozoan in the Gulf of Mexico).

The project will provide a tool for understanding the ecology of scyphozoan invasions and invasive species in marine environments as a whole. The primary public benefit will be through facilitating greater understanding of bioinvasions in marine environments that underlies every aspect of detecting, preventing, controlling, and eradicating invasive species as well as in educating citizens and stakeholders. The project will bring together the expertise of a biological oceanographer, a reproductive biologist, and molecular biologists specializing in the development of TaqMan® PCR assays and marine invertebrate phylogeny across three institutions, the Dauphin Island Sea Lab (DISL), Alabama, the University of California, Davis and Auburn University, Alabama. Public engagement will be primarily achieved by linking the project to established internet sites run through DISL. The United States Coast Guard will assist in the collection of fouling organisms from ship hulls. Postdoctoral training is an integral component of the project and results of the project will be published in peer-reviewed literature. DNA sequences generated during the project will be lodged in the publicly accessible database, GenBank. Tissue samples will be stored and made available to other researches through existing facilities at DISL.

Objectives

  1. To develop a quantitativeTaqMan® PCR assay with broad specificity scyphozoan polyps from homogenates of organisms scraped from the hulls of ships
  2. To develop a highly specific TaqMan® PCR assay to identify and quantify Phyllorhiza punctata and Aurelia aurita polyps from homogenates of organisms scraped from the hulls of ships.
  3. To test the potential application of theTaqMan® PCR assays for identifying and quantifying scyphozoans in general and Phyllorhiza punctata and Aurelia aurita in particular entering a port on the hulls of ocean going ships. 

Methodology

In year 2, we will test the potential of the two sets of primers and TaqMan® probes for identifying and quantifying scyphozoans in general, and Phyllorhiza punctata and Aurelia aurita in particular, entering a port of Mobile Bay on the hulls of oceangoing ships. Ten samples from each of ten ships will be sampled. Factors which may influence the composition of the fouling community, including the route that the ship has taken and treatments applied to the hulls will be recorded. Fouling organisms remain imbedded to the fibers of the scouring pad and will be transported to the laboratory for further processing. Organisms imbedded in the scouring pads will be rinsed off into separate containers, 
centrifuged, and DNA from all of the organisms will be extracted using standard protocols.

Rationale

: Gelatinous zooplankton (including ctenophores & scyphozoans) have gained notoriety as invasive species and introductions of scyphozoans (i.e., jellyfish) have demonstrated the strong controls that they can exert over marine foodwebs including commercial fisheries. Studies into the ecology of invasions by scyphozoans are hampered by their complex bipartite life-history: a highly cryptic benthic, asexually eproducing, scyphistomae (polypoid) stage is followed by a pelagic, sexually reproducing medusae stage. The most likely means by which scyphozoans are transported globally is as scyphistomae attached to the hulls of ships. Nothing is known of the ecology of the cyphistomae in the field because of the lack of techniques for identifying and quantifying this life-history stage. The project will provide a tool for understanding the ecology of scyphozoan invasions and invasive species in marine environments as a whole. The primary public benefit will be through facilitating greater understanding of bioinvasions in marine environments that underlie every aspect of detecting, preventing, controlling and eradicating invasive species as well as in educating citizens and stakeholders.