Summary of the Papers(s) Topics

One of the primary goals of modern biology and research is to fathom the cause and mechanisms of morphological evolutions. In the article by Xiong et al. (2018), the authors conducted an experimental morphology using fish to show that animals adapt to varying and challenging environments by constantly changing their morphology, physiology and behavior. The experiment, which compared the visceral adipose tissue (VAT) of surface fish and three derived cavefish, Tinaja, Pachon, and Molino, revealed that cavefish, Tinaja and Pachon display more VAT than surface fish. Cavefish generally have more body fat levels than surface fish.

The adaptation helps them to avoid starvation (Xiong et al., 2018). Most cavefish have high hyperphagia, which is characterized by the desire for more food. They feed mostly on small fish, snails, aquatic worms, and insects, translating into excess fat depot acquisition, which also helps resist starvation. Practically, different species of organisms have distinct morphological characteristics resulting from a combination of neutral drifts, adaptation, and various biological and physical constraints, just like cavefish have fat deposits to control their high appetitive for food, accompanied by high rates of starvation. The differences in morphological features are often subtle in closely related species but more diverse in species from divergent lineage.

Kim, Kerr and Min (2000) also conducted an experiment to study the evolution of development or developmental biology, also known as heterochrony. The researchers adopted In Situ Hybridization (ISH) technique, which allows for localization of nuclei acid segment within a histologic section. The experiment reveals varying hairy expressions in Drosophila at different times, starting with no expression at the embryo stage to full expression, separated by strips, and cephalic furrow formation (Kim, Kerr & Min, 2000). Morphologically just as revealed by the experiment to establish fat deposit in the fish for adaptation mechanism, the regulatory gene hairy is essential at early embryogenesis for adaption in Drosophila species. It effectively controls segmentation gene expressions. At larvae and pupal stages of development, hairy expressions help control sensory structures in adult Drosophila species. Hence, explaining the morphological observation in Kim, Kerr and Min, (2000)’s experiment.

References

Kim, J., Kerr, J. Q., & Min, G. S. (2000). Molecular heterochrony in the early development of Drosophila. Proceedings of the National Academy of Sciences, 97(1), 212-216.

Xiong, S., Krishnan, J., Peuß, R., & Rohner, N. (2018). Early adipogenesis contributes to excess fat accumulation in cave populations of Astyanax mexicanus. Developmental biology, 441(2), 297-304.