Journal of the World Aquaculture Society
Volume 35 Issue 1 Page 46-54, March 2004
Artificial Propagation and Induction of Triploidy in Largemouth Bass Micropterus salmoides and Ploidy Discrimination using Erythrocyte Length
J. Wesley Neal11Department of Zoology, North Carolina State University, Campus Box 7617, Raleigh, North Carolina 27695-7617 USA, Diana M. Neal11Department of Zoology, North Carolina State University, Campus Box 7617, Raleigh, North Carolina 27695-7617 USA, Richard L. Noble11Department of Zoology, North Carolina State University, Campus Box 7617, Raleigh, North Carolina 27695-7617 USA, Michael V. McGee22Caribe Fisheries, HC-03 Box 22972, Lajas, Puerto Rico 00667 USA1Department of Zoology, North Carolina State University, Campus Box 7617, Raleigh, North Carolina 27695-7617 USA 2Caribe Fisheries, HC-03 Box 22972, Lajas, Puerto Rico 00667 USA
Abstract
We describe an artificial propagation procedure and simple ploidy discrimination techniques using erythrocyte major axis length for largemouth bass Micropterus salmoides. Hormonal treatments of 5 mg/kg of carp pituitary and 50 μg/kg of leutinizing hormone-releasing hormone (LHRH) produced viable gametes in 21-24 h, and triploidy was induced using a pressure treatment of 563 kg/cm2 on embryos for a 1-min duration exactly 5 min following fertilization. We produced about 500 fingerling triploids and about 500 diploid controls, and verified genetic status of a subset of each group using flow cytometry. Erythrocyte length was measured for 10 known diploid and 10 known triploid individuals. Remaining fish were internally microtagged with group-specific tags and mixed to test the model. We developed ploidy discrimination intervals based on the 99% confidence limits of mean erythrocyte length (MEL, N = 25 erythrocytes) for individual fish, which were 14.43-16.66 μ.m for triploids, and 10.23-13.62 μm for diploids. Logistic regression provided the discrimination model: Ploidy status (�) = -196.16 + 13.97 x MEL, with positive (+) outcomes considered triploid. Both discrimination techniques were 100% effective at differentiating ploidy of the 22 microtagged largemouth bass recollected from the mixed population. We did not observe a significant change in erythrocyte length as fish size increased, indicating that erythrocyte length is an accurate predictor of ploidy for all sizes of largemouth bass.
