Did you know that animals also have growth rings, but they are hidden deep inside?

You must have heard of tree rings, which are concentric circles formed during the growth of trees, with each ring representing a year's growth period. By counting the tree rings, we can know the age of the tree and the environment in which it grew. But did you know that animals also have growth rings, but they are not as easy to see as trees, but are hidden in certain parts of the animal, such as teeth, scales, shells, etc. These parts are the products of calcification in the animal's body, and they are also affected by seasonal changes and growth rates, forming different layers and patterns. Today, let's take a look at several animals with growth rings, where their growth rings are hidden, and what they can tell us.

1. Tortoises: Rings on the carapace shields

Turtles are long-lived animals. There are many concentric rings on their carapace scutes, and each ring represents a year's growth period. These rings are formed due to the different growth rates of turtles in summer and winter. In summer, turtles grow fast, and the cells on their carapace scutes are larger and lighter in color; in winter, turtles grow slowly, and the cells on their carapace scutes are smaller and darker in color. By counting the rings on the carapace scutes of turtles, we can know the age of the turtle. However, it should be noted that some turtles have a certain number of growth rings at birth, so these certain number of growth rings should be subtracted when calculating the age of such turtles.

2. Whales: Stripes on earwax

Whales are the largest animals in the ocean, and their annual rings are on their earwax. The outer ear of a whale is S-shaped, and earwax cannot fall out of the external auditory canal, but accumulates in the ear canal. The number of alternating light and dark stripes on the longitudinal section of the earwax is the age of the whale, and the reason for its formation is similar to that of trees. In summer, due to the rich nutrition, there are more lipids and bright stripes; winter is the breeding period of whales, and the nutrition intake is less, so the stripes are darker. By analyzing the earwax stripes of whales, we can know the whale's age, gender, reproduction, food source and other information.

3. Shellfish: Growth lines on shells

Shellfish are one of the most common animals in the ocean, and their growth rings are on their shells. Shells are functional organs built by shellfish using calcified tissue to protect the soft tissue of their bodies and regulate the water balance in the body. There are different forms of rings or growth lines on the shells, such as concentric circles, radials, or waves. Each ring or growth line represents a layer of calcified tissue added to the shell in different time units such as a year, a season, a day, or a month. By counting the rings or growth lines on the shells, we can know the age, growth rate, growth environment, and other information of the shellfish.

4. Fish: Concentric circles on scales

Fish are aquatic vertebrates, and their annual rings are on their scales. Scales are a keratinized structure on the skin of fish. They have functions such as protecting the body, reducing water flow resistance, and regulating body temperature. There are concentric circles on the scales, and each circle represents a growing season. Summer is a period when fish take in a lot of nutrients. At this time, fish grow very quickly, so the concentric circles on the scales will grow faster, and the concentric circles will eventually appear wider, which is called "summer rings". Winter is a period when fish lack food. At this time, the growth rate of fish becomes slow or even stagnant, so the concentric circles on the scales will grow slower, and the concentric circles will eventually appear narrower, which is called "winter rings". "Summer rings" and "winter rings" are separated from each other and cycle once a year, thus forming annual rings. By counting the annual rings on the scales of fish, we can know the age, growth rate, living habits and other information of the fish.