Lunar Cycle Triggers Reproduction

Biological Strategy

Pacific palolo worm

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Regulate Reproduction or Growth

Reproduction and growth are two physiological processes that occur in all living systems. There are situations when conditions are right for both, and other situations when continuing either harms the living system because both have a very high energy cost. Reproduction and growth are unique in that both can stop until conditions improve, although stopping either for an extended time can cause problems. An example of regulating reproduction is a process called delayed implantation or embryonic diapause found in some mammals, such as otters. An otter’s embryos sometimes temporarily cease developing and won’t develop further until the female senses that conditions are suitable.

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Sense Time and Day Length

Being aware of time and day length is important for living systems to appropriately time such activities such as flowering or releasing seeds, migrating, and reproducing. When these activities are done at the wrong time it wastes energy, and resources, and may even jeopardize survival. To determine time, living systems sense light signals. Processing these signals goes beyond simply sensing light; it entails determining whether there is enough light (in quantity or duration) to support a given activity. The rockcress plant, for example, uses light as an environmental cue to time flower development. Delaying blooming protects its reproductive parts from freezing or from blooming before enough pollinators are active.

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Animals

Kingdom Animalia (“having breath or soul”): Mammals, reptiles, sponges, corals, insects, birds

This kingdom captures a staggering variety of life—from the smallest coral polyp to the largest elephant. Although animal body shapes and life histories vary, there are a few defining characteristics. Animals are heterotrophs, meaning they gain energy from eating other organisms, and have developed from single-celled ancestors to highly diversified and coordinated multicellular forms. Unlike plant and fungi cells that have rigid cell walls, animal cells are bound by more flexible combinations of proteins. Most animals have cells organized into tissues and are able to move within their environment.

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The reproductive cycle of the Pacific palolo worm is synchronized via lunar cycle detection.

“The Pacific palolo worm (Eunice viridis) and its West Indian relative (E. fucata) exhibit one of the most incredible examples of reproductive behavior on record, which is intimately linked to the lunar cycle. These two annelid species are polychaete worms, and normally remain secure within tubes excavated by them in coral or under rocks, with their heads at the open end of their tubes – until the breeding season, that is.

“When this period approaches, the rear half of each worm transforms dramatically, developing fast-growing reproductive organs. The worm itself reverses its position within its tube, so that it is now pointing head-down, with its highly modified posterior half-projecting out of the tube. Once the reproductive organs are fully developed, the posterior body half breaks off from the rest of the worm (which remains inside its tube but realigns itself so that its head is at the tube’s open end again), and swims up toward the sea’s surface – almost as if it were a separate animal in its own right. Indeed, it has even developed a pair of eyes to assist it in locating the surface.

“As it swims, the worm’s posterior body half undergoes a further transformation, its internal structures and segmentation breaking down, so that when it reaches the surface it is nothing more than a writhing bag of either sperm or eggs (the sexes are separate in these species). At the surface, the bag bursts, releasing its contents – and, bearing in mind that millions of palolo worms have all undergone this radical metamorphosis at precisely the same time, the sea is soon awash with a mass of sperm and eggs, yielding a vast bout of communal, random fertilization. What makes these worms’ reproductive behavior even more extraordinary is the exact nature of this event’s timing. It occurs twice a year on the neap tides of the last quarter moon in October and November for the Pacific species, and the third quarter moon in June and July for the West Indian species of palolo worm.” (Shuker 2001:94-95)

Last Updated August 18, 2016

References

Book

The Hidden Powers of Animals: Uncovering the Secrets of Nature

26/02/2021 | Dr. Karl P. N. Shuker

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