BIOL630 TERM PROJECT
REPRODUCTION
Reproduction is an important and unique aspect of the octopus life cycle. Individuals in the Order Octopoda have a lifespan that can range anywhere from 7 months to 5 years (Morse and Huffard, 2019). Because of this somewhat tight window, octopuses have even less time to find an octopus of the opposite sex to reproduce. This also increases in difficulty depending on the location and availability of possible mates.
Figure 1. Life cycle of the
Giant Pacific Octopus. (Courtesy of
Vic High Marine).
Internal egg fertilization is a hallmark of the reproductive cycle for the octopus, with both sexes having specific anatomy to accommodate this. Male octopuses have a specialized arm called the hectocotylus, which is usually the third-right arm. An organ called the ligula is at the end tip of this arm, with tissue inside of the arm leading all the way to the back of the octopus’s head to the testes (Morse and Huffard, 2019). Female octopuses have two oviducts, located an opening on the head called the mantle aperture. A diagram of the copulation process is seen in figure 1, where the male octopus maneuvers his arm through the aperture to pass his spermatophores into the oviduct. The bigger the female octopus, the more eggs she will lay, with the average being about 250,000 eggs over the span of one month (Hill, 2018).
Octopuses are semelparous, which means that physiologically, they can only reproduce once in their whole lives. Shortly after fertilization of the eggs, the female lays eggs and guards them religiously without looking for any food for herself. When the eggs hatch four to eight weeks later, the mother has starved and then dies (Wang and Ragsdale, 2018). The male octopus also does not make it too long after the copulation process and dies a few months later. Semelparity is advantageous to the eggs, since they have a protector in the mother octopus. The mother uses all her resources and energy focused on the eggs to ensure their safety. Even when live prey are within reach in their home den, a study found that the female octopus still will not feed (Wang and Ragsdale, 2018). This same study wanted to find out the physiological cause and determined that when the optic gland was removed from the octopus, the female octopus did not behave in the same way – she fed again and even went on to mate a second time. Researchers are still working to understand what the secretion must be in the optic gland to signal this “suicide”.