Testing the Cavefish Model: An Organism-Focused Theory of Biological Design

The significance of this research is multifaceted. At the 8th ICC, Guliuzza and Gaskill (2018) introduced a novel paradigm: Continuous Environmental Tracking (CET). This theory infers that organisms actively and continuously track conditions within their specific environments to self-adjust through internal mechanisms that integrate molecular, biochemical, physiological and behavioral functionality of the whole organism. These mechanisms are predicted to operate by the same integrative principles that govern human-engineered control systems, suggesting that fish and other animals make highly-regulated responses in order to compensate for changes in external conditions that may exceed their routine efforts to maintain homeostasis. Moreover, the theory also predicts that organisms can modify the course of their development; that adaptive larval and adult traits are sometimes reversible; that epigenetic modifications are heritable across multiple generations; and that phenotypic traits will trend toward convergence among a diversity of organisms living within similar environments. Our predictions are testable. The Institute for Creation Research (ICR) is performing controlled experiments to test the response of an organism to different environmental conditions. Our model is Astyanax mexicanus (Mexican tetra), a freshwater fish with well-differentiated, interfertile morphotypes: eyed surface-dwelling fish (surface fish) with a distinct pigmentation pattern, and eyeless cave-dwelling fish (cavefish) with minimal pigmentation. Each morphotype exhibits a unique set of anatomical, physiological and behavioral traits, while possessing nearly identical genomes. Conventional timeframes estimate the divergence of Astyanax cavefish from ancestral surface-fish to have occurred between 8.1 million and 20,000 years ago. These estimates align with the evolutionary premise that differential success in the reproduction of heritable genetic variation produced Mexican tetras and their extant morphotypes. Hypothetical frameworks of ecological diversification over eons cannot be replicated or verified, and are thus not falsifiable by rigorous scientific methodologies. We have established a modern laboratory with reproductive populations of A. mexicanus cavefish and surface fish. Aquaria within the laboratory contain breeding pairs of cavefish exposed to either (A) cyclical light/dark patterns of high-intensity UV light, or (B) minimal light combined with low pH levels by the regulation of CO2 gas diffusion into water. These parameters are predicted to simulate several of the native surface conditions in (A) and subterranean conditions within limestone cave systems in (B). Preliminary results from controlled experiments with mature adult A. mexicanus include the following: Cavefish develop pigmentation across their body when exposed to UV light. Cavefish exhibit behavioral and physiological pre-adjustments to high CO2 (low pH) water. Surface fish