Dining Out: Laboratory Observation of Feeding in the Invasive Crustacean, Hemimysis anomala
Mentor 1
John Berges
Start Date
10-5-2022 10:00 AM
Description
Hemimysis anomala, is a mysid crustacean from the Ponto-Caspian region that invaded the Great Lakes in 2006. H. anomala feeds on detritus, phytoplankton and zooplankton, thus competing with native species and potentially altering food webs. Thus, it is critical to understanding what they eat and how quickly material moves through their gut, so gut contents can be related to prey abundance. H. anomala were collected using lighted traps from shoreline breakwalls over summer-autumn 2021. To estimate gut passage time, individuals were placed in 50 mL beakers in ambient light at 20 °C and monitored for gut clearance. Gut passage time was 3.5 (± 0.8) h, with a range of 2 – 5 h. Phytoplankton feeding experiments were conducted providing individual H. anomala with different concentrations of Chlamydomonas reinhardtii allowing grazing for 4 hours. Cells were counted using flow cytometry before and after, and algal pigments in guts determined fluorometrically. Due to high variability, accurate grazing estimates were not obtained, but gut pigments varied with feeding level: 45.9 (± 31.4) µg l-1 for 0 cells mL-1; 118 (± 96.9) µg l-1 for 1.39 x 105 cell ml-1 and 120 (± 38.7) µg l-1 for 3.29 x 105 cells ml-1. Zooplankton feeding experiments were also conducted providing individual H. anomala with different numbers of Daphnia pulex allowing grazing for 4 hours. Only 3 out of 8 H. anomala consumed any zooplankton, making accurate grazing estimates impossible. We hypothesize that either unfavorable lab conditions (temperature, light), inadequate acclimation of animals, or simply that C. reinhardtii and D. pulex are not favored prey might explain results. Future experiments should use extended acclimation, try a wider range of phytoplankton and zooplankton prey and be repeated in different seasons.
Dining Out: Laboratory Observation of Feeding in the Invasive Crustacean, Hemimysis anomala
Hemimysis anomala, is a mysid crustacean from the Ponto-Caspian region that invaded the Great Lakes in 2006. H. anomala feeds on detritus, phytoplankton and zooplankton, thus competing with native species and potentially altering food webs. Thus, it is critical to understanding what they eat and how quickly material moves through their gut, so gut contents can be related to prey abundance. H. anomala were collected using lighted traps from shoreline breakwalls over summer-autumn 2021. To estimate gut passage time, individuals were placed in 50 mL beakers in ambient light at 20 °C and monitored for gut clearance. Gut passage time was 3.5 (± 0.8) h, with a range of 2 – 5 h. Phytoplankton feeding experiments were conducted providing individual H. anomala with different concentrations of Chlamydomonas reinhardtii allowing grazing for 4 hours. Cells were counted using flow cytometry before and after, and algal pigments in guts determined fluorometrically. Due to high variability, accurate grazing estimates were not obtained, but gut pigments varied with feeding level: 45.9 (± 31.4) µg l-1 for 0 cells mL-1; 118 (± 96.9) µg l-1 for 1.39 x 105 cell ml-1 and 120 (± 38.7) µg l-1 for 3.29 x 105 cells ml-1. Zooplankton feeding experiments were also conducted providing individual H. anomala with different numbers of Daphnia pulex allowing grazing for 4 hours. Only 3 out of 8 H. anomala consumed any zooplankton, making accurate grazing estimates impossible. We hypothesize that either unfavorable lab conditions (temperature, light), inadequate acclimation of animals, or simply that C. reinhardtii and D. pulex are not favored prey might explain results. Future experiments should use extended acclimation, try a wider range of phytoplankton and zooplankton prey and be repeated in different seasons.
