Purpose
The evolutionary process of the animal kingdom is a key area of study by modern developmental biologists. The empirical research study presented by Yano and Tamura (100) attempts to explore the relationship between fins and limbs as well as their morphological distinctions. The functional and morphological nature of organs in a fish is also instrumental in this study. The authors argue that the evo-devo era massively contributed to the evolution of fish. In this particular research study, the authors purpose to investigate how tetrapod limbs evolved with time and equally relate the same to the development of fins in fish. It is suspected that homologous organs exist in the body of fish.
Methods
The process of investigating the evolution of limbs and fins in fish was carried out using “In situ” hybridization. Before initiating this method, a Prx1-GFP transgenic fish was investigated by the researchers. T7 RNA polymerase was used in preparing RNA antisense. In addition, it is vital to mention that the substance known as SpeI was used during the linearization procedure. Delicate cryosections were also prepared for the experiment. Since fish gelatin was crucial in the quantitative procedures, a gelatin-embedded solution was used to soak fixed embryos. The final solution obtained consisted of 30% sucrose.
Results
The findings indicate that the autopod, zeugopod, and stylopod are the three main domains under which tetrapod limbs can be classified. A single long bone is clearly seen in the case of a stylopod. It is the pelvic girdle that supports this bone. In the case of zeugopod, there are two similar outstretched bones. The latter can further be classified into two main groups namely the phalanges and metatarsal bones. When the anatomy of tetrapod taxa is keenly studied, it can be affirmed that there are differences in the number of bones.
Moreover, the endoskeletal domains are not complete in the structure of some species of fish. A case in point is the sarcopterygian fish. It is a clear indication that fish as a species is still undergoing major evolutionary processes. In other words, unsettled skeletal patterns can be observed in species that belong to Tiktaalik, Panderichthys or Eustenopteron. Besides, they lack digits and fin rays. As a result, these species are well endowed with a mixture of patters that comprise of finlimbs. The latter is a vivid evidence of the relationship that exists between fins and limbs in the developmental and evolutionary stages of fish. From the empirical study, actinopterygian fins exist independently from sarcopterygian appendages. This explains why two proximal domains are formed. Second, when the sarcopterygian fish evolves, the autopod region is formed. Third, both digit and bone numbers have the tendencies of being formed and finally, the tetrapod limb experiences gradual disappearance of fin rays. It is also interesting to learn that the sarcopterygian fish appendage is not affected by the loss of fin rays. Similar findings on the evolution of fish have been affirmed in other theoretical and quantitative studies (“Fish with fingers” par. 5). In a study conducted by Hogenboom (par. 1), there are conclusive pieces of evidence on how fins gradually evolved into limbs in several terrestrial species. The author observes that genetic machinery exists in fish and that is why this aquatic animal is capable of generating limbs in form of fingers.
Conclusion
From the above studies, it is vivid that several land animals are believed to have systematically evolved into terrestrial animals over millions of years. Although experimental procedures differ in each case, the results are the same. The desire to navigate swampy wetlands is probably the main reason why most four legged animals (tetrapods) evolved from aquatic species.
References
Fish with fingers 2001. Web.
Hogenboom, Melissa. Genetic clue to how limbs evolved from fins. 2014. Web.
Yano, Tohru, and Koji Tamura. “The Making of Differences between Fins and Limbs.” Journal of Anatomy 222.1 (2013): 100-113. Print.