الجمعة، 12 أغسطس 2016

Underwater Architects

Darussalam Publishers & Distributors
Underwater Architects
It is well-known that fish do not usually build homes for themselves, but there are some kinds of fish that behave in a remarkable manner. These freshwater fish build homes for themselves at the bottom of lakes or rivers or stagnant pools, usually in the form of a ditch that they dig between the rocks or sand. Examples of these include the salmon and trout, which leave their eggs in these ditches until they hatch by themselves.
There are other kinds of fish that guard the eggs, with the male and female taking turns when the eggs are exposed to real danger. In most species of fish, the male is responsible for building the den for laying eggs, and also for guarding it.
There are some fish which build more complex homes. One example of that is the stickleback which lives in most river and lake regions of North America and Europe. The male builds dens that are more skilfully constructed than birds’ nests. This kind of fish gathers pieces of aquatic plants and sticks them together using a fluid that it excretes. The male swims around this sticky mixture and rubs himself against it until he gives it a regular, rectangular shape, after which he jumps suddenly into the middle of this mass and works his way through it, until it becomes like a tunnel with an entrance and exit, through which water passes. If a female happens to pass by this tunnel, the male will try to attract her by swimming around her, going to and fro, until he brings her to the entrance of the tunnel, which he tries to point out to her by turning his head. When the female lays eggs inside the tunnel, the male goes in the front and pushes her out through the back. He repeats the same procedure with several females, and his aim in entering the tunnel and expelling the females is to fertilize the eggs. When the tunnel is full of eggs, the male guards it, but he still allows freshwater to flow through it, and he repairs any parts that become worn out. He continues to guard the tunnel until a few days after the eggs have hatched, then he cuts away the upper part of the tunnel but he leaves the lower part as a dwelling place for the young.
[from “Scientific Miracles in the Oceans & Animals” by “Yusuf Al-Hajj Ahmad”, published by Darussalam, 2010]

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