Nest watch – 2

Nests in aquatic environments

Geetha Iyer

Nests of birds are the most visible, easily observable and built by organisms that humans in general like. But nests are built by diverse organisms and for purposes that are sometimes not limited to raising the young. Imagine building in water! It requires a lot more engineering skill than building on land. Animals that live in water have needs similar to those of the avian community. How do they build? What are the materials they use? Is it possible to observe them build? I share with you some of the interesting nests built in watery habitats.

bubblenest-of-male-fighter-fish If nest immediately evokes images of birds, water naturally brings to mind the fish and then perhaps whales and dolphins. But the aquatic medium is home to diversity beyond our imagination. With deep sea submersibles and advance photographic systems, scientists and researchers are beginning to discover a whole new world of organisms deep down in the oceans and equally bizarre structures built for their use. Organisms found in both fresh and marine environments build structures, the largest among them is the coral reefs. Since it is easier to study fish and insect for a classroom project I confine this article to these two groups.

Fish are found in the marine, freshwater and estuarine regions. Each of these habitats present challenges the fish has to deal with and ensure that they are not only able to build but retain the nest till the purpose is achieved. Ocean currents, tides, wind, sand particles, viscosity of the mud are all factors to be taken into account and the only tools they have are their fins and mouths. With the help of the fins they build by excavating, piling or finding ways to glue materials together. One or a combination of these techniques are used. Here are three examples from bizarre to easily observed in homemade aquariums.

Puffer fish
Year 1995. On a seabed at the Amami-Oshima island of Japan, a circular structure approximately 2m in diameter caught the interest of divers and scientists. Divers came across this structure frequently and not knowing its origin named it mysterious circles. The mystery was solved in 2011 by marine scientists from Japan who discovered that it was a nest built by the male puffer fish. A fish which is no bigger than 12 cms long creates a nest that is 2 metres wide. Fascinating! The process of creating a geometric structure in the sands of the sea bed requires talent especially when the tools available for the job are just fins. The blueprint resides within the fish’s brain. Imagine the kind of abstract thinking and spatial reasoning needed for such a venture. This is intelligence of a very high order. How does it manage those circles and radials? Something else is new here. Once the female has inspected the nest and approved it, he then remodels it so that she can lay her eggs and he can fertilize them. Very rare are examples of nest modifications. The entire process is very detailed, too large for this article. Do read the detailed description of how they created this amazing structure in this paper available on the Internet. The video presentation is worth using when you teach reproduction; your class would not only be an instant hit with the students, it will also effortlessly make them think, connect, raise questions, etc.

The male puffer fish is the architect and his work continues much after the female has laid her eggs and left. He fertilizes them and then takes care of them till they hatch, as the nest he built with such care disintegrates slowly around him. There are many other fish architects in the ocean such as the gobies, sticklebacks, etc.

The author is a consultant for science and environment education. She can be reached at

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