Current Projects
My lab explores fish-focused questions in the marine and freshwater realm. New College Students (or students from the Sarasota area in general) are welcome to contact me about project ideas you may have. This page has information about some of the projects our lab is working on that I would be happy to discuss more. Whether you want to get involved in hands-on research for the first time, or you are ready to plan your thesis, I am happy to help facilitate fish-focused research.
Stress Physiology & Adaptation
Previous research has shown that Heterandria formosa, a small, placental livebearing fish (pictured above), adjusts offspring size and number when living in high vs. low social densities (Leatherbury and Travis 2019), and that these characteristics are heritable (Levell and Travis 2023). However, it is unknown whether these treatments are physiologically stressful for them. My lab is expanding on these experiments to investigate environmental effects of crowding and food restriction in Heterandria formosa.
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My lab is also investigating other adaptive responses to difficult conditions. These include potential adaptive responses to inbreeding depression as a result of low densities in nature, and differences in external sensory organs resulting from predation risk in nature.
The warmouth sunfish, Lepomis gulosus, a common predator of lake-dwelling H. formosa (Photo via FLMNH)
Male Reproductive Characters
Males of the Eastern Mosquitofish, Gambusia holbrooki, have two color morphs, silver and melanic; melanic scales containing patches of black pigmentation. Melanic males are relatively rare in nature, comprising 1-7% of males in most populations (Regan 1961). Melanic males experience less predation than silver males (Horth 2004), but females tend to avoid them, as they are more aggressive (Horth 2003). Melanic males are typically larger than silver males and have relatively large gonopodia, which is a modified anal fin to deliver sperm to females (Horth et al., 2010). It is not yet known whether sperm traits (or testosterone level) differ between silver and melanic males, though sperm number is positively correlated with male size (Locatello et al. 2008; O'Dea et al. 2014).
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This project also explores how male reproductive characters may vary in other poeciliid species (namely Heterandria formosa, pictured to the right) based on population traits like density, maternal investment, and predation.
This figure from Lisa Horth shows the coloration of melanic vs. silver Gambusia holbrooki
Life History
The Eastern Mosquitofish, Gambusia holbrooki, belongs to the same genus as the Western mosquitofish Gambusia affinis, a highly invasive species around the world. Pior work shows that G. affinis is capable of invading marine environments involving changes in life history characters (Alcaraz and Garcia-Berthou 2007; Peterson and Peterson 1990), physiology (Tsai et al. 2017; Uliano et al. 2010), but little work has been done on G. holbrooki.
Photos via EmeraldKing-Aquatics
Gambusia affinis vs. holbrooki (Page and Burr 1991)
Gambusia affinis: six dorsal fin rays, male lacks teeth on the third ray of the gonopodium
Gambusia holbrooki: 7-8 rays, males have a toothed gonopodium
These two species also have different sex chromosomes (Black and Howell 1979)
Sexual Selection & Sexual Conflict in Syngnathids
Syngnathids are "ideal for studies of the evolution of reproductive complexity, because they exhibit multiple parallel origins of complex reproductive phenotypes" (Whittington and Friesen 2020).
Seahorses and pipefish in the family Syngnathidae have incredibly diversity and varying complexity of pouch morphology and thus paternal allocation potential. Syngnathids have historically been regarded as lecithotrophic, meaning offspring receive all nutrients from the egg’s yolk. Two pipefish species that are found in Florida, Syngnathus fuscus and S. floridae have been found to transport labelled amino acids to developing embryos (Kvarnemo et al. 2011; Ripley and Foran 2009). Transporting amino acids from the parent to offspring are considered to be an incipient pathway to direct provisioning of resources from parent to offspring (Morrison et al. 2017). A 2020 paper by Skalkos et al. found that the seahorse Hippocampus abdominalis is apparently patrotrophic, meaning the father provides the developing embryos with nutrients that go beyond what is contained in the original egg yolk, resulting in an offspring whose mass is larger than the initial egg.
We are currently investigating questions related to sexual selection in syngnathids in terms of potential hybridization among Syngnathus species.
Biodiversity Succession at Midnight Pass
Midnight Pass represented a natural opening into the Gulf until 1983 when it was closed for a homeowner. It is part of "Little Sarasota Bay", a southern portion of the main bay.
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Tales of clear water and a thriving fishery were converted to a "dead bay" that couldn't "breathe". However, the closed section of Little Sarasota Bay became a nursery, having higher fish counts than any other part of the bay according to fisheries-independent monitoring by the Florida Wildlife Research Institute (FWRI). After a series of hurricanes in Fall 2024, the pass was naturally reopened, bringing flow back to Little Sarasota Bay, but destroying the thriving seagrass beds in the process. In collaboration with Dr. Samuel Bedgood at NCF and Dr. Emily Lancaster at Eckerd, we are monitoring biodiversity changes as a result of the pass reopening with special attention to seagrass, sediment/meiofauna, fish and invertebrates, and environmental DNA.
2025 - Credit: Sarasota Bay Estuary Program
Shrimp phenotypes & microbiomes
In collaboration with New College Faculty Dr. Kent Hatch, Dr. Jose Moscoso, and Dr. Samuel Bedgood, we are exploring how shrimp phenotype influences microbiome diversity using four local species.
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Pictured to the left: Tozeuma green and clear phenotypes
Pictured to the right: Hippolyte green and brown/clear phenotypes
Red tide effects on fish behavior
Red tide is a colloquial term for blooms of Karenia brevis algae. These algae release brevetoxins, which are neurotoxins that affect other organisms in their environment. Humans also suffer from respiratory complications due to the blooms. Many animals in our bay are unable to escape these blooms, leading to questions and experiments about the tolerance of local animals to the brevetoxins.
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Pictured to the right: A red tide bloom via NOAA
