stricted melanophores are spread widely across the body presenting the overall appearance of a semi-transparent, orange-colored cavefish morphotype, distinct from the SF. Both morphotypes are genetically interfertile. This CF, as in all other known A. mexicanus CF, does not have a functional eye, or any of the major components of eye anatomy observed in the SF (Fig. 1B). Differences between functional anatomy and appearance of SF and CF morphotypes provide a foundation for the design and implementation of preliminary and experimental treatments, and for the direct comparison of results in this study. Observations from the first preliminary experiment reveal an increase in spatial coverage of melanic pigmentation across all body regions of CF (Florida) where melanin is expressed in SF (Fig. 5A– C). These areas include sides and center line of the dorsum, at the bases of dorsal, adipose and caudal fins, on posterior flanks of the body, on the head, olfactory pits and gill opercula. Distinct patches of melanin pigment align with the positions of scales along both sides of the dorsum in the adult CF, and also in their F1 progeny, although less distinctly (Fig. 5D–F). The distribution of melanic pigmentation in F1 CF (Florida) is increased, with a comparatively broader spatial pattern of melanophores than in parent fish. Additionally, melanophores are concentrated along ventral undersides of the F1 (Fig. 5D, E), but do not show similar expression in the analogous ventral regions of their adult form. In both the adult and F1, melanophores are expressed in a semi-circular pattern around the areas where functional eyes are located in SF (Fig.5A, D). Another observable chromatophore pigment includes iridophores that are expressed along the dorsal side of the pigmented lateral stripe and along sides of the dorsum in the adult (Fig. 5A, B). Iridophores are noticeable where the lateral stripe meets the caudal fin, and on lateral sides of the head and opercula in F1 cavefish. Xanthophores and iridophores are both observed along fin rays of the caudal fin in the adult and F1. Among the F1 progeny, there is a noticeable range in the amount, distribution and overall expression level of melanophores, as also observed with the xanthophores and iridophores. Observations from the second preliminary experiment show that when surface fish (SF) are exposed to conditions of lower oxygen and pH levels, their behavior and morphology are altered. Behaviorally, these experimental SF exhibit comparatively rapid movements of mouth and gill opercula, they appear disoriented, and at times collide with walls of aquarium (see Discussion, Pleiotropy and genetic integration). Morphologically, there is noticeable reduction of melanic pigmentation along the dorsum, lateral stripe, head, and posterior flanks of the body (Fig. 6A, B). Xanthophoric pigments are visibly less pronounced compared to levels observed in non-treated SF (Fig. 6A). Pigmentation also appears uniform and considerably lighter around the surface of the iris, which surrounds the lens region (Fig. 6B). Results of the third preliminary experiment were not photographed. After 6 weeks of treatment under high levels of dissolved CO2 (pH 5.3–5.5), melanic pigment in these CF (Florida) was clearly reduced from non-treated CF stocks. The expression of melanin in all regions of the head, along the dorsum, posterior flanks of the body, and within rays of the caudal fin, was undetectable without a microscope. Additionally, there were no observed indications of stress, accelerated respiratory activity, agitated swimming or complications with behavioral navigation within the aquarium (see Discussion, Pleiotropy and genetic integration). D. Controlled experiments Results of the first controlled experiment show an increase in the expression of melanic pigmentation. After 45 days of light treatments, the distribution, densities and expression levels of melanic chromatophores is higher in all regions where melanin was observed in the same CF at the start of the treatments (Fig. 4A, B). Notable areas of melanin concentration include the head (olfactory pits, gill opercula), dorsum (bases of dorsal and adipose fins), and posterior dorsal midlines and flanks. The same contrasting pattern of pigmentation is observed when comparing the treated fish directly with untreated CF (Florida) in our stock tanks. After 72 days, the pattern of melanin expression is similar but more intense in the same adult cavefish as observed after 45 days of light treatment (Fig. 4B–C). In general, the underlying orange coloration of CF was diminished over the duration of treatment. All other adult CF (Florida) in this experiment showed a similar increase in chromatophore expression. The general positions of iridophores along the body line are similar after 45 days, and after 72 days, although the amounts or levels of these iridescent chromatophores appear to have increased in those positions. Melanophore and xanthophore distributions along rays of the caudal fin are visually similar from day 1 to day 72. Quantitative differences in pigment expression have not been measured. Results of the second controlled experiments show that pigment levels and distributions have increased in all three CF groups (Molino, Arizona, Florida). In particular, iridescent chromatophores (iridophores) show an increase in level of expression and spatial distribution across the bodies of Molino cavefish, relative to their untreated stocks. And, xanthophore numbers and distributions in the head, body and fins of Molino CF exhibit increases (Fig. 3H–L; see discussion). Melanic pigmentation on and within tissues of the other cavefish (Florida, Arizona) models also increased. When compared to the overall coverage prior to the combined illumination treatments, and specifically in comparison with previous 72d light treatments, there was high contrast in pigment expression across the body and head. The level and pattern of increased melanic pigmentation in treated fish was substantially different from their respective stocks. IV. DISCUSSION How creatures adapt and diversify through time are central questions about the origins of animals on earth. As with Darwin’s celebrated theory, On the Origin of Species by Means of Natural Selection (1859), Neo-Darwinian Theory (NDT, 1895) and the Modern Synthesis (MS, 1942) share a common perspective: adaptation can be, and is, caused by natural selection. All of the iterations of Darwinism promote environmental (natural) selection of mutation-derived trait differences as the primary driver of adaptation in all animals. Because of this, externalism has become the fundamental interpretive framework for all mainstream biology (Lewontin 1983; Gould 2002). And although the Extended Evolutionary Synthesis (EES, 2010) amends externalism with newer “organism-centered” predictions that include ‘epigenetic inheritance’, ‘ecological inheritance’ and ‘non-Mendelian inheritance’, natural environments are ultimately given agency as the inducers of adaptation, speciation and diversification. In direct contrast to conferring transformative agency upon natural, environmental or external resources, we continue to advocate for recognition of the only known creative power – Jesus! As introduced above, ICR’s model of continuous environmental tracking (CET) infers that all organisms were created with purpose and intention, and are therefore divinely ‘engineered’ to adapt rapidly and appropriately to every environmental condition they encounter. If and when those conditions change, they are prepared to respond. Here, we discuss preliminary results of testing the cavefish model of adaptation, consider BOYLE, ARLEDGE, THOMAS, TOMKINS, AND GULIUZZA Testing the cavefish model 2023 ICC 130
RkJQdWJsaXNoZXIy MTM4ODY=