Meeting Abstract
12.5 Tuesday, Jan. 4 It’s not what you make; it’s what you keep: Biochemical “taxation” helps explain the gap between laboratory and field measurements of sea urchin larval growth GINSBURG, DW*; MANAHAN, DT; University of Southern California dginsbur@usc.edu
Many studies have defined the growth of marine invertebrate larvae under controlled laboratory conditions. Predicting growth rates under natural conditions, however, remains a challenge. Larvae of the sea urchin Lytechinus pictus were reared in the field off Santa Catalina Island and compared to similar cohorts cultured under routine conditions in the laboratory (n = 5 cohorts). Our goal was to understand the biochemical basis for differential growth rates under field and laboratory conditions. For all cohorts examined, field-reared larvae grew at maximal rates as defined by measurements of protein growth in laboratory cultures fed-to-excess. Surprisingly, for all sets of protein synthesis measurements (n = 17), field-reared larvae had protein synthesis rates that were ~50% less than those in the laboratory. A comparison of protein (P) synthesis and growth revealed the mechanism using the conceptual equation: Pgrowth = Psynthesis – Pdegradation. Mean protein depositional efficiency (Pgrowth/Psynthesis) of field-reared larvae was 60%, compared to 39% for laboratory-reared cultures. Observations of larval growth rates in the field and under laboratory conditions are potentially reconcilable by knowing what an organism “keeps” (protein accretion) compared to what it “makes” (synthesis). In the field, larvae had 2-fold lower synthesis rates, yet had comparable growth rates to those reared in the laboratory. We suggest that this energy savings in synthesis per unit growth might be attained through better food quality in the field, resulting in more efficient biochemical growth even under food-limited conditions.
