A robust flow‐cytometric protocol for assessing growth rate of hatchery‐reared barramundiLates calcariferlarvae

Abstract

In this study, a flow-cytometric cell cycle analysis method to assess instantaneous growth rate of whole larvae of the Australian barramundi Lates calcarifer was developed and validated. High-resolution DNA measurements of either fresh, frozen or RNAlater-preserved larvae (gap0-gap1, G(0) -G(1), coefficient of variation (c.v.) < 3, 4 and 5%, respectively) enabled the deconvolution of the DNA histogram and assignment of the proportion of nuclei into cell cycle compartments G(0) -G(1), S (DNA synthesis) and G(2) -M (Gap2-Mitosis). This technique can be also used for individual fish tissues such as brain, liver, fin and muscle. For the first time, the combined proportion of replicating nuclei (into S and G(2) -M phases) of whole fish larvae and absolute growth rate in length (mm day(-1)) has been correlated in commercial aquaculture conditions. Fast growing L. calcarifer larvae had an overall hyperplasia advantage as indicated by a greater proportion of cells in the S+G(2) -M phase compared with slow growing larvae, which might explain the increasing differences in size during culture. In a fasting trial, larvae ceased growth while maintaining the constant initial rates of cell division throughout a 6 day period. For a highly fed fast growing control group, cell division rates significantly increased after day 4. Flow-cytometric cell cycle analysis of whole fish larvae may provide fish biologists and aquaculturists with a better understanding of how cell division rates influence early growth in natural and artificial environments.

Using measurements of muscle cell nuclear RNA with flow cytometry to improve assessment of larval condition of Walleye Pollock (Gadus chalcogrammus)

“…Specifi c tissue types (e.g., Theilacker and Shen, 1993b;González-Quirós et al, 2007;Porter and Bailey, 2011) or individual whole larval homogenates (Domingos et al, 2012) have been used with this method, and fl ow-cytometric cell-cycle analysis is as responsive to starvation as the RNA:DNA ratio in that it is able to detect starvation within a few days of no feeding (Porter and Bailey, 2011).…”

“…Previous studies have assessed the condition and growth of fi sh larvae with fl ow-cytometric cell-cycle analysis, which is a technique that measures the DNA content of individual cells in a population to determine the proportion of cells in different phases of the cell cycle (Theilacker andShen, 1993b, 2001;Bromhead et al, 2000;González-Quirós et al, 2007;Porter and Bailey, 2011;Domingos et al, 2012). Cells that are in the process of dividing can have up to twice the amount of DNA as cells that are not dividing.…”