Muscle Fiber Recruitment in Relation to Growth and Swimming Speed in Spadefoot Tadpoles

University Of California-Riverside, Riverside CA

Investigators

Abstract

The proposed research will examine how patterns of muscle growth and development translate into growth and swimming ability in tadpoles of three toad species. Although much is known about the cellular mechanisms of muscle development, remarkably little is known about how this translates into performance of the individual in the real world. Recent work in fish and pilot work for this proposal already suggest one obvious consequence, namely that fast growing individuals are slower swimmers than their slow growing counterparts. This research examines the consequences of a trade-off between growth rate and swimming speed at several levels including: a mechanistic level (how recruitment and growth of muscle cells influences growth and swimming ability), a genetic level (comparing across species), an environmental level (by manipulating temperature and food levels), and an ecological level (in terms of predator avoidance and escaping pond drying). One species being studied breeds in rain pools which dry within weeks. Rapid muscle development in this situation accelerates metamorphosis allowing toadlets to escape the pond before it dries. Another species breeds in permanent ponds where predators are abundant. Rapid growth allows these tadpoles to outgrow potential predators. The third species breeds in ponds of intermediate duration with intermediate predator levels, and is expected to fall mid-way between the other two in terms of both growth rate and swimming speed. Tadpoles are being used because muscle structure is relatively simple and because skeletal development does not interfere with muscle development (unlike other vertebrates, including people, frogs and toads do not begin to form mineralized bones until metamorphosis). This research will forge bridges among developmental biology, physiology, and ecology and has potential applications in agriculture where selection for rapid growth is common, often without considering potential costs of rapid growth. This relates most directly to the proposed research where meat quality (muscle composition) may be compromised to by selection for rapid growth.