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ANATOMY
ANATOMY
Blue whales are slender-bodied baleen whales, meaning they have long plates of baleen they use to filter food out of the water. A blue whale's mouth cavity is so vast that it can engulf a volume of water equivalent to its own body mass. The cetacean has a broad U-shaped head, and thin, elongated flippers. Their skin has a grayish-blue coloration, but appears deep blue underwater.
Figure 4. The Anatomy of a Blue Whale, Whale Watch Western Australia.
Figure 5. Blue Whale Anatomy, Uko Gorter.
Each side of the upper jaw features a filter-feeding system of 260 to 400 bristle-like keratin plates called baleen.
Weighing roughly 4,400 pounds, the tongue assists in feeding by controlling water flow and trapping food in the baleen.
The parts of the brain that are associated with the sense of hearing are very highly developed in cetaceans, however, whales have a relatively small hippocampus.
The lungs are closer to the vertebral column than to the sternum. Due to the size of their lungs and the ability to store oxygen in red blood cells, blue whales can hold their breathe for up to one hour.
The four-chambered heart is set fully forward in the rib cage, and depending on energy expenditure, it can pump between 3-12 bpm.
Like other mammals, the vertebral column mostly moves up and down by pressing the tail flukes against the water to move forward. The muscle running from the dorsal fin to the fluke is known as the peduncle, and it's the most powerful muscle in the entire animal kingdom.
PHYSIOLOGY
PHYSIOLOGY
DIGESTION
Blue whales have a three-chambered stomach that assists not only in the breakdown of food, but with other materials like small rocks. When substances enter the esophagus, they are stored in the first compartment, known as the fore-stomach, where they are broken down by contractions of massive muscular walls and anaerobic bacteria.
KIDNEYS
Blue whales have multilobed kidneys that filter blood and enable them to release excess salt. Baleen whales have a high metabolic rate and oxidize fats more than carbohydrates or proteins. This causes them to lose even more water through waste, which is also why a functional and efficient way of expelling excess salt is necessary.
MOTION
Similar to otters, baleen whales use using their flippers for steering, while their tail fluke is used to propel themselves forward through vertical motion.
Several cerebellum mechanisms prevent water from flowing into their blowholes even while the blue whale sleeps.
REPRODUCTION
REPRODUCTION
Unlike other baleen whales, blue whales typically travel alone. However, from late July to early August, males begin to follow a female around for weeks on end.
While blue whale mating has never been documented, they are believed to be polygynous, as males compete for females to reproduce.
The species mates from fall to winter, and sexually reproduce via meiosis. The male and female each produce haploid gametes, and a single sperm and egg fertilize to form a diploid zygote. They fertilize internally, where semen is deposited inside the female.
Once female blue whales reach sexual maturity - around 5 to 15 years old - they can give birth every two to three years. Blue whales are roughly 23 feet long and can weigh up to 6,000 pounds at birth.
Blue whale mothers cannot stop swimming for the first several weeks of a newborn's life, so they sleep while swimming. Young blue whales rest, eat, and sleep in what is known as echelon swimming, where their mother tows them along in her slipstream. If the mother whale stops swimming for any length of time, the calf will begin to sink as it is not born with enough body fat or blubber to float easily.
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