Meeting Abstract

25.5  Monday, Jan. 4  Effects of load and reproduction on locomotor performance in the lizard Iguana iguana BUTLER, MA*; SCALES, JA; University of Hawaii mbutler@hawaii.edu

One demand placed exclusively on females is maintaining locomotor performance during the large increase in mass as females produce offspring or eggs (gravidity). Since the females of many taxa carry large reproductive loads, often repeatedly throughout life, this is a widespread and potentially important selective pressure that has received comparatively little study. Are females designed for the gravid state, implying that their musculoskeletal systems are overengineered for the majority of the year? Or alternatively, do they suffer a great performance decline when they are gravid? In addition, what happens when they are immediately post-gravid if their body wall is greatly stretched during reproduction? Reproduction sometimes results in reduced locomotor performance, but it is unclear whether performance is affected by load (mass) or the physiological changes associated with carrying an internal load. Green iguanas (Iguana iguana) are excellent runners and carry very large clutches ranging from 31% to 63% of their nongravid mass. We compared performance in gravid and post-gravid iguanas experiencing natural reproductive cycles with iguanas implanted with artificial loads. The implants were filled with saline, mimicing pregnancy (volume + mass), with air (volume) or empty (no mass, reduced volume). We report the changes in performance in velocity, acceleration, and force production.