Meeting Abstract

P3.74  Sunday, Jan. 6  THE INDETERMINATE GROWTH CONUNDRUM: How do fishes continue to grow throughout their lives? FROEHLICH, JM*; FOWLER, ZG; REMILY, EA; ROMERO AROCHA, SR; GALT, NJ; BIGA, PR; UNIVERSITY OF ALABAMA AT BIRMINGHAM; NORTH DAKOTA STATE UNIVERSITY; NORTH DAKOTA STATE UNIVERSITY; NORTH DAKOTA STATE UNIVERSITY; UNIVERSITY OF ALABAMA AT BIRMINGHAM; UNIVERSITY OF ALABAMA AT BIRMINGHAM jmfroehlich@uab.edu

It is well established that terrestrial vertebrates, namely mammals and birds, reach a growth plateau during ontogeny, resulting in highly restrictive growth potentials as adults. For decades, however, most teleost fishes have been recognized as indeterminate growers, possessing the ability to increase overall somatic size well into adulthood. The nonasymptotic growth potential of these animals begs the question: how do fishes continue to grow throughout their lives? Using skeletal muscle as a model, we present data supporting our hypothesis that teleosts rely on adult stem cells, termed myogenic precursor cells (MPCs) in this tissue, of increased proliferative and regenerative capacity to maintain “endless” growth. Consistent with this hypothesis, skeletal muscle of smaller, determinate-like fishes (~0.3-0.5 g) contains three- to seven-fold more MPCs than larger, indeterminate fishes (>1.5 g). Further, MPCs isolated from large danionins (Devario aequipinnatus and Danio dangila) and salmonids (Oncorhynchus mykiss) appear to proliferate to generate several-fold more progeny and express genes associated with self-renewal of the MPC niche, namely paired-box (Pax) and processivity factors (PCNA), than those of the determinate-like zebrafish (Danio rerio). Taken together, it appears that a small population of less committed, Pax-expressing MPCs affords most teleosts indeterminate growth in skeletal muscle, although it remains to be determined if this mechanism is conserved among agnathans, chondrichthyans, chondrosteans and other neopterygiians.