Kirsten Work

Benthic fish exhibit more plastic crypsis than non-benthic species in a freshwater spring

Cryptic coloration reduces the ability of predators to detect prey, but the plasticity of this defense varies. Some organisms possess static and permanent cryptic coloration, whereas in other species color changes may be induced. Depending upon the species, induced color changes may be reversible or irreversible. In this study, we examined a subtle, rapid, and reversible crypsis in which small fish exhibit muted changes in brightness to match varying substrates in clear spring water. In the laboratory, we visually measured the changes in brightness, using a ten-point brightness scale, of five abundant small species in our study spring. Two species, Lucania goodei and Heterandria formosa, exhibited no change, but the other three species exhibited changes in brightness to match background brightness. Two species, Gambusia holbrooki and Poecilia latipinna, exhibited only slight shifts, whereas Lucania parva exhibited relatively large shifts in brightness and color pattern—from virtually white to tan interspersed with dark-brown bands. In the field, L. parva also exhibited significant shifts in brightness and color pattern, both when swimming freely and when enclosed in an open-bottomed cage. These results suggest that rapid cryptic changes in brightness may augment other forms of defense in small vulnerable fish.

Fish Assemblage Variability in a Florida Spring

Abstract Florida springs are generally characterized as static ecosystems with unique faunal and floral assemblages that persist under relatively stable physical and chemical conditions. We sampled the fish fauna of Volusia Blue Spring to determine whether this presumption would withstand scrutiny at a higher temporal resolution and over time. We sampled by seining or snorkeling at five stations along the 320-m run weekly or bimonthly from October 2000 to September 2004. This four-year study consisted of 1152 samples that produced approximately 164,000 observations of 30 species of fish on 72 sampling trips. Concurrent water quality samples were collected at 14 sites along the center of the run and at each of the seine sites. Virtually anoxic water discharged from the spring head, but this water accumulated oxygen as it traveled the run. Fish density and species composition also changed dramatically along the length of the run. Species that tolerate low oxygen concentrations, such as poeciliids, dominated the assemblage at the spring head. Species that use patches of algae or small backwater areas, such as fundulids, were prominent in the middle reach of the run. Larger species, such as centrarchids and Lepisosteus spp., were abundant in the lower reach of the run. Within these broad patterns, most species exhibited great variability in density, probably due to the influence of variable emigration of potential predators, and also perhaps smaller species, from the St. Johns River.

The Immune System Game

Abstract We describe a card game that helps introductory biology students understand the basics of the immune response to pathogens. Students simulate the steps of the immune response with cards that represent the pathogens and the cells and molecules mobilized by the immune system. In the process, they learn the similarities and differences between the immune responses to viral and bacterial pathogens and why the primary and secondary responses differ.