------------------------------------------------- avoid predation by evolution

by
Joseph Yang
April 13, 2015

by
Joseph Yang
April 13, 2015

Evolution is a change in the gene frequency in a population through time. Evolution causes an organism’s ability to survive to increase. In many cases, predators evolve to catch their prey more efficiently. Evolution is not one sided. The prey also evolves to avoid predation. In this paper, I will discuss three researches done on a prey’s evolution to survive against predation. I will discuss the tail autonomy in Tokay gecko (Sanggaard et al. 2012), the odorous and non-fatal secretion in Wrinkled frog (Yoshimura and Kasuya 2013), and the avoidance response in Brownbanded bamboo shark embryos (Kempster et al. 2013). Together, these studies show the effectiveness and vital impact of evolution to the survival of prey. Sanggaard et al. (2012) researched evolution in Tokay gecko (Gekko gecko) to investigate the mechanism of their tail autonomy by facilitating autonomy. The geckos were euthanized by pentobarbital and the tails were removed by induced autonomy. Moisture from the exposed end of the tail was collected and subjected to Gel Electrophoresis and Mass Spectrometry and analyzed using MS-BLAST. The tails’ structure was analyzed through multiple methods. Through Magnetic Resonance Imaging, a Micro Imaging 5 probe, a Great 60 Imaging system, a saddle coil, and a gradient cooling temperature of 20°C was utilized. Electron Microscopy and 3D Fast Low-Angle Shot sequence were utilized. Scanning Electron Microscopy was utilized and the tails were observed through a FEI NOVA NanoSEM 600. The analysis showed that there was a fat layer around the vertebra and the muscle was between the fat layer and dermis. The autonomy septum divided the fat and muscle regions in each fracture planes. A dorsal median septum, a ventral median septum, and a horizontal septum divided the tail into four individual longitudinal segments. Each segment formed two wedge-shaped extensions. The collagen layer thickened and condensed at the intervals corresponding to the distance between fracture planes. Cells in a radiated pattern was shown in the collagen condensation and in the dermis going towards an epidermal indentation between scales. The SDG polyacrylamide gel electrophoresis analysis showed that the proteins of the proximal and distal parts of the tail were similar. Protein esterase was identified and there was no sign of proteolytic enzymes or proteolytic fragments. Of the identified proteins, there was a high quantity of cytosolic. The wedge-shaped muscle extension was analyzed through scanning electron microscopy, which showed mushroom shaped structures at the cranial margins of the muscle termini. A magnetic resonance imaging of the tail showed the muscle fiber terminations in the fracture planes and fiber interaction in the intact fracture plane. This likely facilitates adhesion by the large surface area interaction. There was a lack of structures going through the fracture planes which supports adhesion. The termini of the muscle fibers and the interdigitation of tail- segments supports adhesion as the main factor of contact between tail segments.
Sanggaard et al. (2012) concluded that the tail autonomy did not involve proteolysis but rather, it is a biological friction and adhesion based phenomenon generated by the large surface area of interaction from the wedges. The mushroom structures facilitate the release of the tail by reducing the adhesion between tail segments. The tail has pre-formed score lines at fracture planes that allow for a fast autonomy without the use of a slow protease-based degradation.
Yoshimura and Kasuya (2013) researched evolution in Rana rugosa, Wrinkled frog, to investigate the effectiveness of their odorous and non-fatal secretion for the evasion of predation by snakes. The research was conducted using Rana rugosa, Fejervarya limnocharis, Rana japonica, and Elaphe quadrivirgata. 34 Fejervarya limnocharis snakes were chosen and divided into two groups of 17 snakes. They conducted two separate experiments. For Experiment 1, group 1 was experimented with R. rugosa frogs on the first day and F. limnocharis frogs on the second day. Group 2 was experimented with F. limnocharis frogs on the first day and R. rugosa frogs on the second day. They recorded the number of times the snakes bit, swallowed, and showed gaping behavior for the frogs. Experiment 2 was conducted the same way but with different frogs and a different number of snakes. Of the 34 snakes, 16 were chosen randomly. R. japonica frogs was used. Group 1 snakes were experimented on with R. japonica frogs coated R. rugosa secretion on the first day and F. limnocharis secretion on the second day. Group 2 snakes were experimented on with R. japonica frogs coated with F. limnocharis secretion on the first day and R. rugosa secretion on the second day.
The recorded data for experiment 1 showed on the first day, 3 R. rugosa frogs were bit, 0 were swallowed, and 3 snakes showed gaping behavior. 14 F. limnocharis frogs were bit, 14 were swallowed, and 0 snakes showed gaping behavior. On the second day, 3 R. rugosa frogs were bit, 0 were swallowed, and 3 snakes showed gaping behavior. 10 F. limnocharis frogs were bit, 10 were swallowed and 0 snakes showed gaping behavior. Less R. rugosa frogs were swallowed compared to F. limnocharis frogs. More snakes that bit the R. rugosa frogs showed gaping behavior compared to the F. limnocharis frogs. For experiment 2 of the first day, 5 frogs coated with R. rugosa secretion were bit and 4 were swallowed. 8 frogs coated with F. limnocharis secretion were bit and 8 were swallowed. On the second day, 6 frogs coated with R. rugosa secretion were bit and 5 were swallowed. 8 frogs coated with F. limnocharis secretion were bit and 8 were swallowed. Less of the frogs coated with R. rugosa secretion were bit and swallowed compared to the frogs coated with F. limnocharis secretion.
It was concluded that the secretion of R. rugosa compared to the F. limnocharis frogs helped more of the R. japonica frogs survive. The proportion of frogs coated with R. rugosa secretion to F. limnocharis secretion swallowed were significantly higher than the proportion of R. rugosa to F. limnocharis frogs swallowed. This suggests that there may be another factor contained within the R. rugosa frogs which contributes to the evasion of predation. Yoshimura and Kasuya (2013) concluded that the odorous and non-fatal secretion of R. rugosa frogs is effective in evasion of predation by snakes.
Kempster et al. (2013) researched evolution in Chiloscyllium punctatum shark embryos to investigate their avoidance response to predators. 11 C. punctatum embryos were collected and placed into separate aquatic tanks for the experiment. The embryos were tested during various stages of development from stage 31-34. A sinusoidal stimulus generator was used to stimulate the embryos. The embryos were stimulated three times each at various frequencies from 0-20 Hz and at three different intensities of 0.4-0.6 µV/cm, 0.9-1.1 µV/cm, and 1.9-2.1 µV/cm. Each embryo were stimulated a total of 27 times. The opaque external fibrous layer of the embryos were scraped off to allow for their responses to be recorded by video camera.
Kempster et al. (2013) recorded each embryos’ peak response frequency and average response duration. A stage 32 embryo exposed to 1.9-2.1 µV/cm peaked at 0.5 Hz for 16.7 seconds. A stage 32 embryo exposed to 0.9-1.1 µV/cm peaked at 0.5 Hz for 14.9 seconds. A stage 32 embryo exposed to 0.4-0.6 µV/cm peaked at 0.5 Hz for 0.3 seconds. A stage 33 embryo exposed to 1.9-2.1 µV/cm peaked at 0.75 Hz for 27.7 seconds. A stage 33 embryo exposed to 0.9-1.1 µV/cm peaked at 1.0 Hz for 13.8 seconds. A stage 33 embryo exposed to 0.4-0.6 µV/cm peaked at 0.5 Hz for 3.7 seconds. A stage 34 exposed to 1.9-2.2 µV/cm peaked at 0.5 Hz for 59.4 seconds. A stage 34 embryo exposed to 0.9-1.1 µV/cm peaked at 0.5 Hz for 38.4 seconds. A stage 34 embryo exposed to 0.4-0.6 µV/cm peaked at 0.5 Hz for 15.8 seconds.
The results showed that the embryo at stage 32 responds only to electric fields as low as 0.4 µV/cm and those of earlier stages would not respond to electric fields between 0.4 µV/cm and 2.1 µV/cm. It was concluded that the embryo of stages 32-34 had the greatest avoidance to sinusoidal electric field frequencies between 0.25 Hz and 1.00 Hz with a peak of 0.5 Hz. As the electric field frequencies increased, the embryo’s response duration increased. It was also concluded that although a more developed embryo had a longer response duration, their avoidance of predators is limited by their survival instinct to feed and defend themselves as well as their limit to cease gill movements for long periods of time.
The research on the tail autonomy in Tokay gecko, the odorous and non-fatal secretion in Wrinkled frog, and the avoidance response in Brownbanded bamboo shark embryos investigates three different areas of evolution. Nonetheless these researches show that evolution is effective and vital to the survival of prey. Each individual research shows possible fields of study for research on predation avoidance that does not need to be evolution based.

References
*Kempster, R. M., Hart, N. S., Collin, S. P. (2013) Survival of the Stillest: Predator Avoidance in Shark Embryos. PLoS ONE 8(1): e52551. doi: 10.1371/journal.pone.0052551
*Sanggaard, K. W., Danielsen, C. C., Wogensen, L., Vinding, M. S., Rydtoft, L. M., Mortensen, M. B., Karring, H., Nielsen, N. C., Wang, T., Thogersen, I. B., Enghild, J. J. (2012) Unique Structural Features Facilitate Lizard Tail Autonomy. PLoS ONE 7(12): e51803. doi: 10.1371/journal.pone.0051803
*Yoshimura, Y., Kasuya, E. (2013) Odorous and Non-Fatal Skin Secretion of Adult Wrinkled Frog (Rana rugosa) Is Effective in Avoiding Predation by Snakes. PLoS ONE 8(11): e81280. doi: 10.1371/journal.pone.0081280