Application of flow cytometric cell cycle analysis to the assessment of condition and growth in larvae of a freshwater teleost Galaxias olidus

Abstract

Through its ability to measure cell DNA content, flow cytometric analysis (FCA) is a technique capable of accurately assessing the position of cells in the cell cycle. Using FCA to measure the proportion of dividing and nondividing cells, an index was created that allows the amount of cell division within larval fish tissues to be quantified. To assess the suitability of the cell division index (CDI) as an indicator of growth and condition in fish larvae, analyses were divided into four parts. These examined the effects of temperature, nutrition, time of day, and geographic location on the CDI of brain tissue from Galaxias olidus larvae. The index was sensitive to, firstly, differences in the brain CDI of larvae reared at 12 and 20°C and, secondly, to significant fluctuations in mean brain CDI from larvae sampled over 24 h. FCA also revealed significant differences in the CDI of starving and fed larvae. Overall, this study indicates that FCA may be suitable as an indicator of growth and condition in both laboratory-reared and wild fish larvae.

Cell cycle analysis of brain cells as a growth index in larval cod at different feeding conditions and temperatures

“…Larvae presented a higher increase in the %S-phase under High-Food conditions, which is in agreement with patterns of S + G 2 -M observed in previous studies Shen, 1993a, b, 2001;Bromhead et al, 2000;Catalan et al, 2007). High %S-phase at High-Food was coincident with high SL and adjusted means from the morphological relationship between MYO and SL (a proxy for individual larval weight).…”

“…Whereas S + G 2 -M may be a better proxy for the total number of cells dividing and it apparently increases the power of statistical analysis, Shankey et al (1993) recommended that only %S should be used as the index of cell division rate. They argued that G 2 -M measurements have greater variability than S-phase due to the arrest of cells in G 2 -phase and aggregates overlying G 2 -M. Our results agree with the argument that %S-phase is a better estimate of cell proliferation than % S + G 2 -M. However, Bromhead et al (2000) reported that including Sphase data in their cell division index (CDI; G 2 -M/G 0 -G 1 ) had little or no effect on the statistical significance of their results. The software used to model cell cycle phases (G 0 -G 1 , S and G 2 -M) calculates the percentage of cells in each phase.…”

“…There was no significant difference in %S-phase for fully-fed larvae at different temperatures (6 and 10ºC), which was in agreement with the absence of significant differences in G 2 -M/G 0 -G 1 observed in larvae of Galaxias olidus reared at 12 and 16ºC (Bromhead et al, 2000). In our case, this result was unexpected as Otterlei et al (1999) showed that growth rate of cod larvae increased at temperatures from 4 to 14ºC, which is in agreement with the pattern observed in our rearing tanks (Fig.…”

“…As in previous studies Shen, 1992a, b, 2001;Bromhead et al, 2000), our study suggests that cell cycle analysis by flow cytometry is appropriate for analyzing growth variability related to food availability. Furthermore, under food deprivation, the observed %S-phase variability was consistent with the effect that temperature has on metabolic costs.…”

“…Shen (1993a, b, 2001) showed significant differences in the percentage of S + G 2 -M in brain cells and muscle nuclei between fed and unfed Theragra chalcogramma larvae, although their analysis was restricted to first-feeding larvae under a homogeneous temperature. Bromhead et al (2000) also observed differences in the (G 2 -M)/(G 0 -G 1 ) ratio in brain cells between fed and unfed Galaxias olidus larvae at two different temperatures. However, the interaction between both factors was not tested.…”