SREL Reprint #3409

Mastering Medaka culture: Improved techniques for increasing egg and fry production in Japanese Rice Fish (Oryzias latipes)

Melissa Thompson1,2, Morgan Reed3,2, Melissa A. Pilgrim1,2, Shem D. Unger4,2, and Olin E. Rhodes, Jr.2

1University of South Carolina Upstate, Spartanburg, SC 29303
2University of Georgia, Savannah River Ecology Laboratory, Aiken, SC 29802
3Clemson University, Clemson, SC 29634
4Wingate University, Wingate, NC 28174

Abstract: Aquatic systems are integral to ecosystem function and human health. By trapping sediments and retaining nutrients, wetlands protect our water quality. However, a wetland’s capacity to trap sediments and nutrients also means they can capture many contaminants (e.g., heavy metals and radionuclides) released into the environment due to anthropogenic activities. Both heavy metals and radionuclides have detrimental effects on wildlife at acute dosages. However, little is known regarding underlying biological responses associated with chronic low dose exposure to both ionizing radiation and heavy metals. Our long-term research goal is to work to fill this knowledge gap using Medaka (Oryzias latipes), small fish amenable to experimental manipulation. However, the current study focused on altering the husbandry protocol of a laboratory colony of Medaka in a way that would increase colony size to at least 400 individual fish over a six-week period. At the beginning of our work, we followed a strict cleaning, feeding and egg harvesting protocol. Two weeks into our work, we suspected that food limitations may be negatively impacting egg production and noticed fungal growth on eggs. Thus, we altered the feeding regime and egg harvesting protocol. The altered protocol more than tripled egg production and almost doubled of fry production. By the end of our study the colony had 673 individuals: 191 adults and 482 fry. Our protocol changes resulted in growth of the colony at sufficient numbers to begin experiments related to investigating sub-lethal impacts of heavy metals and radionuclides on Medaka.

SREL Reprint #3409

Thompson, M., M. Reed, M. A. Pilgrim, S. D. Unger, and O. E. Rhodes, Jr. 2015. Mastering Medaka culture: Improved techniques for increasing egg and fry production in Japanese Rice Fish (Oryzias latipes). USC Upstate Student Research Journal 8(Fall): 26-33.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).