Understanding Population Structures of Chironex fleckeri

Collaborator

An understanding of population structures is fundamental to understanding threats, where do jellyfish come from and how far do they go? If there is great genetic exchange among local populations then the source of jellyfish may be distant to areas where swimmers are threatened. In contrast, if populations are geographically small and, are not connected to other populations then the ability to make predictions on likely threats would be more robust. Our focus is on the deadly stinger, Chironex fleckeri, the species that poses the greatest threat to humans in tropical waters of Australia. Population connectivity is the exchange of individuals among geographically separated population units. Some local populations may be limited to a small geographic area such as a bay, estuary or island. It is also possible that local populations with little or zero connectivity could contribute to a mosaic of genetic diversity within a stock, and under the right circumstances could become a separate stock (Pineda et al 2007). Jellyfish have historically been classified as plankton. Accordingly, it would be assumed that connectivity would be high among local jellyfish populations and that populations would vary little in both ecological and genetic clade-level differences over broad spatial scales (i.e., hundreds to thousands of km). However, findings on the behavior and swim speeds of jellyfish suggest they may have swimming behaviour that more aligns with nekton (McManus et al. 2012). Nekton can swim to either maximize dispersal or minimize it by remaining close to natal areas and these strategies can spatially broaden or restrict species population structures, respectively. Cubozoans have a number of attributes that assist in restricting the dispersal of medusa from localized areas. Although cubozoans are generally small, they are generally highly mobile. The fifty known species of cubozoans range in size from those with a bell diameter of a few cm to about 20–25 cm and all of the species that have been observed swim well. Chironex fleckeri (size range: 4 to 12 cm IPD) have been measured to swim at speeds of up to 16.6 cm s−1 in the field (Schlaefer et al. 2018). Cubozoans have excellent sensory abilities including vision provided by 24 eyes. More complex behaviours of cubozoans include responding to objects, conspecifics, currents, diel cycles, shadow and light, bioluminescent plankton, habitat type and small-scale geography (Kingsford et al 2021).. Accordingly, predictions for population structures of jellyfish based on passive dispersal are likely to be highly inaccurate. Our objective it to use mitochondrial DNA (mtDNA) to identify intraspecific phylogenetic relationships among local populations along the coast of Queensland. We will use this approach to study the gene flow and connectivity of local populations separated by 10s to 100s of kilometres and this will include multiple locations used by swimmers. Using this approach we will determine scales of connectivity.

01 Aug 2022

N/A