The sociable and graceful dolphin displays playfulness and athleticism as it leaps from the marine waters.
Onlookers may see these dolphins’ bodies glimmering in the sun which may cause them to wonder if they are covered with tiny scales. However, they do not.
Dolphins do not have scales and are classified as mammals. Dolphins give live births to calves with a small amount of hair. These babies nurse milk from their mothers. Dolphins breathe air with their lungs by rising to the surface for oxygen. They also have three layers of skin, which includes blubber, helping them to maintain their warm-blooded functions.
This article explores how these aquatic creatures survive with mammalian characteristics and thick skin in the cold oceanic waters.
Topics
Dolphins Are Aquatic Mammals
Not all creatures in the ocean are fish, crustaceans, or reptiles. The ocean also has mammals, which include dolphins, whales, and porpoises.
These creatures do not have hard outer layers made of scales like sharks or crustacean exoskeletons.
Marine Mammal Characteristics
Dolphins are cetaceans, in a group of over 70 different species that are entirely aquatic, spending all of their lives in the water.
This table shows that the dolphin has the following common mammalian characteristics:
| Characteristics | Dolphin Information |
|---|---|
| Warm-blooded |
|
| Breathe air through the lungs |
|
| Have hair |
|
| Mammary glands |
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| Birth live young |
|
Dolphin Skin: 3 Layers And Their Functions
The skin of a dolphin functions to allow it to survive as a mammal in marine waters.
It has three layers of varying thicknesses with different features, as follows:
| Layer | Thickness (Inches) | Features |
|---|---|---|
| Epidermis (top layer) | 1.57 to 1.97 | The epidermis (outer layer) is up to 20 times thicker than a human’s epidermis. A dolphin’s skin sheds, flakes, and peels very quickly to replace old skin cells with new ones. For example, the bottlenose dolphin sheds its outermost layer of skin every 2 hours. This smooth, rubber, outer layer does not have hair (as adults) or sweat glands. The color of the skin can vary depending upon species, but is typically a mixture of black, white, and gray, often with a fading effect along the body. |
| Dermis (middle layer) | 2.36 to 6.30 | Underneath the epidermis is the dermis, which contains connective tissue, blood vessels, and nerves. |
| Hypodermis (bottom layer) | 6.30 to 19.69 | Then, underneath the dermis is the hypodermis, the layer of blubber (fat) with fibrous connective tissue. |
Each of these three layers serves a functional purpose, as described below.
1. Epidermis
The outer layer serves several essential functions for hydrodynamics, camouflage, and protection from infection.
Hydrodynamics
Dolphins’ bodies are streamlined for optimal hydrodynamics.
Close inspection of the skin will reveal that there are minute cutaneous ridges on the surface. These run around the body’s front trunk and in varying directions past the dorsal fin and other areas.
This layer sheds quickly, maintaining a smooth surface. This helps with sensory function in the water, speed, and drag reduction when swimming.
The dolphin’s anatomy of a streamlined body shape with flippers, flukes (tails), and fins helps it navigate waters swiftly and effectively as well.
Some dolphins can maintain speeds up to 25 miles per hour (mph), diving to depths of 10,000 feet.
Camouflage: Countershading
The dolphin’s skin coloring is a type of camouflage called countershading, with a dark back and fading to white on the lower jaw and underbelly.
The dark back blends in with the dark depths of the ocean when seen from above. The underbelly blends in with the bright sea surface when viewed from underneath.
Some species of dolphins have light streaking or spotting, which also aids in the creature blending in with the oceanic surroundings.
Countershading helps to conceal a dolphin from predators, such as Orcas and large sharks.
Dolphins are opportunistic carnivores of aquatic creatures such as fish, jellyfish, octopuses, and squid. Countershading helps the dolphin to be less detectable as they approach prey.
Protection From Infection
Scientists study the epidermal layer of dolphins to see the effects, if any, of infection and pollution on their overall health.
The constant shedding of their epidermal skin helps to eliminate diseased cells, protecting their innermost layers.
2. Dermis
The dermis is a connecting middle layer between the epidermis and hypodermis.
It strengthens the construction of the skin, providing elasticity with collagen and elastin fibers. There is perivascular concentration controlling blood flow and distribution.
3. Hypodermis
The deepest layer of skin is the hypodermis, the blubber layer. This layer is lipid-rich, collagen fibers, of adipose (fat) tissue with a vascular system.
It covers the entire body except for the appendages (flippers, fins, and flukes/tails). Their appendages have arteries and veins to circulate blood to conserve or dissipate heat to protect these parts in the absence of blubber.
Blubber is highly important for the survival of dolphins in cold marine waters. It insulates them to maintain body heat, stores energy (calories), and increases buoyancy.
This thick layer also protects vital organs from predator attacks. Often, scars can be seen on dolphins, and due to the high level of blubber protection, the dolphin is still thriving.
The thickness of blubber can change with seasons and abundance of food supplies, as well as a result of overall body size and health.
In Conclusion
Dolphins are mammals, and therefore do not have scales like other ocean creatures. Dolphins present characteristics of mammals which include hair (at birth), warm-blooded bodies, live births, mammary glands, and oxygen-accessing lungs.
Dolphins have three layers of skin: epidermis, dermis, and hypodermis (blubber). These layers exist to allow the dolphin to swim quickly and efficiently, camouflage, thermoregulate, and protect against predators and illness.