Andrew W. Thompson, Ph.D.
Research
I am an evolutionary biologist studying Eco-Eco-Devo in Extreme Fishes. My research attempts to understand the links between environment, development, and genomic evolution. Currently, I am using comparative genomics to understand the evolution of seasonality and hatching in aplocheiloid killifishes.
Keywords: Eco-Evo-Devo, comparative genomics, phylogenomics, molecular evolution, delayed hatching, diapause.
Introduction:
Fishes are the most diverse vertebrates on the planet with at least 28,000 species (Helfman et al. 2009). They have colonized every major body of water from caves, toxic environments, the deepest oceans, to temporary pools (Helfman et al. 2009; Riesch et al. 2015). Some species in these extreme environments belong to a group of fishes known as Cyprinodontiformes (Riesch et al. 2015). Often popular pets, Cyprinodontiformes contain over 1,000 species (Helfman et al. 2009) and are known to many aquarists as livebearers or killifishes. But these small, modest fish can be found in habitats inhospitable to all other species of fishes. For example, members of the genus Poecilia can be found in highly acidic caves (Kelley et al. 2016), and Fundulus killifish are well studied as an ecotoxicology model as some members of this genus are pollution tolerant (Whitehead et al. 2010).
Perhaps one of the best examples of extremophile Cyprinodontiformes are the annual killifishes in the suborder Aplocheiloidei. These fish inhabit seasonal pools that dry up, resulting in the death of all adults in the pond. Their progeny survives as dormant embryos in the soil that can hatch when the rains return and the pond refills. The suborder contains over 700 valid species (Eschmeyer and Fong 2016) classified into three families: Rivulidae, native to the Neotropics from the Florida Keys to central Argentina; Nothobranchiidae, native to the tropics of Africa; and Aplocheilidae native to Madagascar, Seychelles, India, and Southeast Asia (Parenti 1981; Murphy and Collier 1997). Members of Nothobranchiidae and Rivulidae inhabit seasonal, ephemeral pools in tropical regions of Africa and the Neotropics (Figures 1 and 2).
Overall, my research offers an extensive investigation into the molecular aspects of dormancy, desiccation tolerance/resistance, and hatching in killifishes. With studies on egg structure, delayed hatching, and diapause genetics along with phylogenomic datasets, I hope to provide insight into the evolution of annualism in this remarkable group of "fish-out-of-water."
Figure 1. Life cycle of the Rio Pearlfish, Nematolebias whitei, a biannual killifish from Rio de Janeiro, Brazil.
Figure 2. A seasonal killifish pool in the Ribeira de Iguape region of São Paulo, Brazil. The annual fish species Leptopanchax aureoguttatus was collected at this locality.
References:
Eschmeyer WN, Fong JD. 2016. Catalog of fishes: Species by Family/Subfamily.
Helfman GS, Collette BB, Facey DE, Bowen BW. 2009. Diversity of Fishes. 2nd ed. John Wiley and Sons.
Kelley JL, Arias-rodriguez L, Martin DP, Yee M, Bustamante D, Tobler M. 2016. Mechanisms underlying adaptation to life in hydrogen sulfide rich environments. Mol Biol Evol 33:1419–1434.
Murphy WJ, Collier GE. 1997. A Molecular Phylogeny for Aplocheiloid Fishes (Atherinomorpha, Cyprinodontiformes): The Role of Vicariance and the Origins of Annualism. Mol Biol Evol 14:790–799.
Parenti LR. 1981. A Phylogenetic and Biogeographic Analysis of Cyprinodontiform Fishes (Teleostei, Atherinomorpha). Bull Am Museum Nat Hist 168:335–557.
Riesch R, Tobler M, Plath M eds. 2015. Extremophile Fishes: Ecology, Evolution, and Physiology of Teleosts in Extreme Environments. Springer.
Whitehead A, Triant DA, Champlin D, Nacci D. 2010. Comparative transcriptomics implicates mechanisms of evolved pollution tolerance in a killifish population. Mol Ecol 19:5186–5203.