In these myriads of living beings, different animals have adapted with different features for survival. It not only mesmerizes the layperson but also puzzles curious scientists as to how it works. As an illustration, at the brink of a quiet pond, a frog rests motionless on a lily pad—still as a shadow at noon. In a sudden, precise motion, its tongue lashes out, snatching an insect mid-air. Moments later, a fish bursts from the water, seizing a fly before disappearing below the surface. These instinctive actions, so different yet so alike, reflect nature’s ingenuity: survival strategies shaped by a common force—evolution.
Evolution: life-sustaining adaptations.
Organisms are evolving according to the needs and conditions they must survive in. But what exactly is evolution?
As stated in Princeton’s Guide to Evolution, evolution refers to “change through time as species become modified and diverge to produce multiple descendant species” (1). Most of us are familiar with the concept of “survival of the fittest,” proposed by Charles Darwin, which highlights the importance of evolution for survival. A chameleon’s ability to change colour to blend with nature, a spider’s ability to spin intricate webs to catch prey, or birds imitating various sounds are a few progressions developed in the course of time.
Many birds have evolved an extraordinary ability to mimic a wide range of sounds they hear in their environment. But why do they do this? It’s not to mock their surroundings, as it might seem. Instead, this skill is an evolutionary adaptation—used to attract mates and sometimes even to deter predators. One such fascinating example of this is the lyrebird, known for its extraordinary ability to imitate not just other birds, but also artificial sounds. Our evolutionary history is evident, but many other lesser-known fascinating adaptations are cited here.
Lyrebirds: Masters of Mimicry
Found in southeast Australia and the moist forests and woodlands of eastern New South Wales and Victoria, these birds are ground-dwelling by nature. They feed on small insects like cockroaches, ticks, and beetles and are known for their striking plumage and remarkable ability to mimic natural and artificial sounds.
They can imitate the calls of other birds, as well as environmental sounds like chainsaws and camera shutters, showcasing their extraordinary adaptability and intelligence.
With this inborn ability, during the mating season, males try to impress females by singing the most complex song they can manage (2)—often trying to out-sing rivals. Some can imitate the calls of over 20 different species, doable due the presence of a special vocal organ called the syrinx, situated below their windpipe. So, the next time you hear a camera shutter deep in the forest but are unable to spot a human—it’s probably just a lyrebird showing off!
Extreme Survival: Wood Frogs
Most frog species are generally seen during monsoons, but have you ever thought about where they go during winters? They hibernate! Just like bears. Wood frogs are one of them.
These small-sized frogs, found from the Arctic Circle in Alaska to the midwestern and northeastern US, and south along the Appalachians to Georgia and Alabama, freeze themselves in winter at temperatures as low as –16°C and thaw in spring (3). Astonishingly, they freeze both externally and internally—i.e., the water between their cells freezes as well, but not the organs (4). They accumulate and retain urea in their tissues during overwintering, while glycogen is broken down into glucose when internal ice begins to form. Together, glucose and urea function as cryoprotectants, enabling them to endure freezing and harsh environments. (5)
Spawning Strategies in Sea Cucumbers: Insights into External Fertilization
Sea cucumbers are benthic marine organisms—meaning they live on the ocean floor. Generally found in the Asia-Pacific region, they resemble a cucumber with elongated bodies and branched gonads. Despite their odd appearance, sea cucumbers are crucial for nutrient recycling and breaking down detritus and organic matter.
They exhibit external fertilization, observed in less than half of the animal species in the world (6). During the spawning season, males arch their bodies into a “cobra” position and release sperm into the water, which then fuses with the eggs released by females. The first larval stage is called Auricularia, followed by Doliolaria, before eventually maturing into adults.
Sea cucumbers have evolved various mechanisms for floating and swimming. Some have umbrella-like skirts that help them move with breaststroke-like motions; others use water-powered tube feet or oral tentacles to navigate.
The Art of Self-Renewal: The Axolotls
Another interesting organism is the axolotl—a fully aquatic amphibian rooted only in Lake Xochimilco in Mexico. They can breathe air but primarily breathe underwater using their gills (7). Growing up to 23 cm long and available in a variety of colors, they are kept as pets by many.
What makes them unique is that they retain juvenile (tadpole-like form) characteristics throughout their lives in wild populations through a phenomenon called neoteny. However, experimental studies show they can transform into adults when exposed to thyroid hormones (8).
The Axolotls are an exceptional example of four-legged vertebrates that can transform regular cells back into stem cells, granting them the ability to regenerate lost body parts. They can even regrow parts of their brain and spinal cord (9)—a truly remarkable evolutionary feat.
The Mimic Octopus: Copycat of the Ocean?
Just like the lyrebird, which can mimic different sounds, another animal called the mimic octopus can mimic other sea creatures. This animal has a unique ability to look like other sea animals instantly. They can change their shape, texture, and color to closely resemble other organisms. They can change their color because of a specialized pigment called chromatophores, present in sacs below the skin (10). These sacs contain various pigments, like black, brown, orange, yellow, etc. Each sac stretches to give colour when needed.
They do this to avoid predators. They can appear possibly like any marine animal but usually prefer to mimic dangerous, venomous creatures to keep the predators away and fool their prey as well (11).
Nature never fails to surprise us with the unexpected. Nature’s creativity knows no bounds—whether it’s a bird mimicking a chainsaw or a frog freezing itself solid to survive the winter, every adaptation tells a story of resilience. There are many other creatures with such weird—maybe for us—yet fascinating abilities that are yet to be discovered. But one thing’s for sure: these abilities are equally important to us as they are to the organisms themselves. They even contribute a lot to scientific and technological development in our daily lives, as we learn about biomimetics (mimicking nature) from them. From tiny Velcro strips inspired by a cat’s tongue to towering buildings modelled after termite mounds, many such innovations are inspired by nature. It is equally important for us to protect all the organisms with whom we share our only living planet.
References:
- https://www.kokkonuts.org/wp-content/uploads/jennions_kokko_2014_The_Princeton_Guide_to_Evolut.pdf
- Searcy WA, Nowicki S. Song and mate choice in birds: how the development of behaviour helps us understand function. Auk. 2005;122(1):1–14. doi:10.1642/0004-8038(2005)122[0001:SAMCIB]2.0.CO;2.
- Costanzo JP, do Amaral MCF, Rosendale AJ, Lee RE Jr. Wood frog adaptations to overwintering in Alaska: new limits to freezing tolerance. J Exp Biol. 2014;217(Pt 1):229–237. doi:10.1242/jeb.094787
- Storey KB, Storey JM. Anti-apoptotic response during anoxia and recovery in a freeze-tolerant wood frog (Rana sylvatica). PeerJ. 2015;3:e1834. doi:10.7717/peerj.1834
- Storey KB, Storey JM. Molecular physiology of freeze tolerance in vertebrates. Physiol Rev. 2016;96(1):267–311. doi:10.1152/physrev.00016.2016
- Das, Megha & Mishra, Nitesh & Kumar, Sanjeev. (2020). External Fertilization. 10.1007/978-3-319-47829-6_330-1.
- Griffiths HI, Thomas DH. Aquatic oxygen conformity in the Mexican axolotl, Ambystoma mexicanum. Herpetol J. 1992;2(1):1–4.
- Page RB, Voss SR. Induction of metamorphosis in axolotls (Ambystoma mexicanum). Cold Spring Harb Protoc. 2009;2009(8):pdb.prot5268. doi:10.1101/pdb.prot5268.
- Amamoto R, Rizvi TA, Rozzelle C, et al. Regeneration of neurons and functional electrophysiological activity in adult axolotl brain following injury. Elife. 2016;5:e13998. doi:10.7554/eLife.13998
- Gilmore, R., Crook, R. & Krans, J. L. (2016) Cephalopod Camouflage: Cells and Organs of the Skin. Nature Education 9(2):1
- Hanlon RT, Norman MD. The evolution of predator avoidance in cephalopods: a case of Batesian mimicry in the mimic octopus (Thaumoctopus mimicus). Front Mar Sci. 2022; 9:909192.
Written by Ms. Kasturi Vishwas Deshpande
Edited and reviewed byMr. Rushikesh Rajendra Sankpal (Assistant Professor, Department of Biotechnology, MES Abasaheb Garware College, Pune)