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

The significance of this research is multifaceted. At the 8^th 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:

1. Cavefish develop pigmentation across their body when exposed to UV light.
2. Cavefish exhibit behavioral and physiological pre-adjustments to high CO₂ (low pH) water.
3. Surface fish lose pigmentation across their body and labor during respiration in high CO₂ (low pH) water.
4. The adults of cavefish and surface fish respond to experimental conditions within weeks of treatment. Their responses are not limited to multigenerational genetic inheritance.

The first result implies that UV light may stimulate melanosome production in adult cavefish through biochemical induction of a latent melanin synthesis pathway. Second, pre-acclimation to acidic water chemistry likely reflects conditions within their native cave environments. Third, the comparative loss of pigmentation and associated respiratory challenges in adult surface fish exposed to darkness and high CO₂ (low pH) suggest they actively self-adjust. And in contrast to cavefish, non-acclimated surface fish indicate they are outside of their native environment. Importantly, both cavefish and surface fish respond rapidly and adaptively, without enduring repeated cycles of death and survival over long time periods. These results have directed us to begin a new series of experiments specifically designed for statistical analyses. Mating pairs of genetically identified cavefish will be maintained in replicate tanks under variable light intensities (UV or ambient light) while controlling for biostable pH levels. Simultaneously, multiple pairs of surface fish will be maintained in total darkness at high CO₂ (low pH) levels. Photographic and statistical measures of change in pigmentation, anatomy and behavior will be recorded and presented at the 9^th ICC in 2023.

Our initial experiments and the predictions listed above do not support the conventional view that beneficial adaptations arise from random mutation, unregulated genomic recombination, or an incremental accumulation of unguided genetic variation regardless of time scales. In our view, CET proposes that organisms are the agents in control of adaptation and diversification and thus nature is not the agent of control. If correct, then hypotheses that attribute the exquisite fit of organisms to their environments through the agency of nature are mistaken. Here, we present a new direction in experimental science for the ICR, and a vital new approach for Creation Science that sees every organism as a divinely engineered creation with innate capacity to rapidly adapt to multiple environmental conditions. Our research will confirm that life is thoughtfuly and intentionally prepared by the infinite wisdom of our Creator, “in whose hand is the life of every living thing, and the breath of all mankind” (Job 12:10).