EPISYMBIOTIC INFECTION ON CYCLOPOID COPEPODS DURING THE STAGNATION PERIOD OF 2018-2022 IN LAKE BIWA, JAPAN

Epibionts impact the biology and ecology of host zooplankton, and therefore, more information is necessary on these associations to better understand lake ecosystems. In this study, we investigated the morphological characteristics of the epibionts to identify the species and the year-to-year and seasonal variations of their infection rates on crustacean zooplankton in Lake Biwa. Zooplankton samples were collected monthly with a vertical net haul from the bottom to the surface in the north basin of Lake Biwa from January 2018 to December 2022. Temperature, dissolved oxygen, and chlorophyll-a were simultaneously measured throughout the water column. Two epibiont species were identified, i.e., epizoic flagellate Colacium vesiculosum and peritrich ciliate Epistylis anastatica, throughout the study period. Both the epibionts just infested adult and copepodites of Cyclopoida spp. No such infections were found in any other crustacean zooplankton species. The lake water was stratified from June to October every year. An oxygen-minimum layer was formed below the thermocline from July to September, just after the massive phytoplankton bloom in June. Episymbiotic infestation was generally found from May to December every year but not from January to April. The infestation prevalences were high from August to November. The infestation prevalence was positively correlated with temperature or host abundance while negatively with dissolved oxygen, suggesting a stable interaction between abiotic and biotic ecological processes related to the stratification of the lake water.

Presentation Preference: Oral

Primary Presenter: Taiabur Rahman Tuhin, The University of Shiga Prefecture (tuhin.rahman78@gmail.com)

Authors:

Taiabur Rahman Tuhin, The University Of Shiga Prefecture  (taiabur.t@ses.usp.ac.jp)

Most Fahima Ahmed Anny, The University of Shiga Prefecture/ Jahangirnagar University  (mfa.anny81@gmail.com)

Xin Liu, The University of Shiga Prefecture/ Guangxi Key Laboratory of Aquatic Biotechnology and Modern Ecological Aquaculture  (liuxin.rk@gmail.com)

Shoko Hosoi-Tanabe, The University of Shiga Prefecture  (tanabe.sh@ses.usp.ac.jp)

Syuhei Ban, The University Of Shiga Prefecture  (ban@ses.usp.ac.jp)