Commercial Fisheries News - September 2000

Why are eggs turning orange?

This summer, lobstermen have been wondering why they have been seeing orange and red lobster eggs. While it’s not clear what’s causing this phenomenon, we do know that orange or red eggs are dead eggs.

In general, trap-caught sized lobsters lay their eggs when the shell becomes hardened after molting. Although female lobsters can store sperm in a receptacle for at least three years and fertilize more eggs without mating again, they cannot keep the sperm through a molt. Lobsters shed the lining of the reproductive track when they molt, including any sperm left in the receptacle.

Given a chance, the female will then mate again to get more sperm. However, if, for some reason, the female doesn’t have the chance to mate, she will lay the eggs anyway.

One by one, these unfertilized eggs eventually die, turn orange or red, and gradually fall from the female lobster’s swimmerets. The entire brood does not turn orange simultaneously. They die one by one.

In addition to lack of fertilization, lobster egg death can also be caused by disease and neglect. Why orange eggs are currently appearing in nature is not well understood. The prevalence and consequences of the lobster egg death needs further careful study.

Midsummer observations of egg-bearing lobsters reveal eggs in three other conditions: hatching, hatched, and new.

Some female lobsters have just finished hatching eggs and are still carrying the remnants of egg cases, as well as the long hairs that held them to the swimmerets for many months.

Others are holding eggs that are hatching. Eggs hatch into “pre-larvae” and hang onto the females’ swimmerets until a couple hundred are ready to be released. Then, the female lobster stretches out her abdomen and flutters her swimmerets in rhythmic waves that send her brood up into the water column.

The hatchling lobsters molt into a first larval stage as they are being released. The next day, the female lobster releases a couple hundred more eggs and so on until her thousands of tiny hatchlings have drifted away. Large, black eyes of the fully developed embryos are easily seen through the transparent eggs when held up to the light.

Finally, freshly extruded eggs are appearing on female lobsters in the traps. These dark, opaque eggs are thick with yolk and appear a deep forest green when held up to the light.

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