CHAPTER 3
 BIOCHEMICAL INDICES AS CORRELATES OF RECENT GROWTH IN JUVENILE
 GREEN TURTLES (Chelonia mydas)

 Introduction

 The green turtle, Chelonia mydas, is an endangered marine herbivore with a circumglobal

distribution (Seminoff 2002). Overexploitation of this species by humans during the last several

centuries has caused drastic population declines (Jackson et al. 2001). Development of effective

management plans for this species requires knowledge of demographic parameters such as

somatic growth rates. However, assessing growth rates for long-lived and far-ranging green

turtles typically requires time-consuming mark and recapture programs in which recapture

probabilities can be quite low (Limpus 1992). Furthermore, growth rates calculated using

morphometrics represent long-term, cumulative changes and often do not correlate well with

biochemical indices of short-term growth due to differences in the latency of these responses to

environmental influences (Ferron and Leggett 1994, Gilliers et al. 2004). Establishment of

alternative techniques for estimating recent growth rates of individual turtles upon first capture

would substantially improve our ability to evaluate the instantaneous status of C. mydas

populations and therefore to assess progress toward recovery goals for this endangered species.

 Macromolecular indices (RNA concentrations, RNA:DNA ratios, RNA:protein ratios,

and/or protein:DNA ratios) are frequently measured as indicators of protein synthesis potential

and growth in marine fish and invertebrates (Bulow 1970, Carter et al. 1998, Buckley et al.

1999, Dahlhoff 2004, Caldarone 2005, Mercaldo-Allen et al. 2006, Vidal et al. 2006). These

indices are particularly useful for evaluating recent environmental conditions, as they reflect

differences in growth rates over a period of several days (Rooker and Holt 1996, Buckley et al.

1999, Vrede et al. 2002). The use of these indices depends on the assumption that total RNA

content of a cell (including messenger RNA, transfer RNA, and ribosomal RNA) should increase