Biology of the Queen Conch
Classification and Life Cycle of Strombus gigas
The geographical range of the queen conch is in the Western Atlantic Ocean, from North Carolina to Bermuda.
They are a commercially important species to the Caribbean fisheries. Harvesting of the queen conch is prohibited in much of the U.S. and is restricted in the Caribbean; they can only be harvested on they become sexually mature adults, which can be identified by the lip on their shell.
Classification of the Queen Conch
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Order: Sorbeoconcha
Family: Strombidae
Genus: Strombus
Anatomy and Reproduction of the Queen Conch
The queen conch is protected by a spiral shell that is lined in pink. They can 'lock' themselves in their shell by pulling a horny claw in to seal the opening. This claw is called the operculum, and is also used in locomotion. The pointed operculum is anchored in the sand and then used to pull the conch forward.
The queen conch has two eyes, on the end of eyestalks, and two sensory tentacles, also located on the eye stalks. These can all be retracted, along with the tube-like mouth, called a proboscis into the shell if the conch is threatened.
It takes up to 3 years for the queen conch to reach sexual maturity. Once maturity is reached the mating will take place; the males have a verge which will deposit spermatozoa at the entrance of the egg groove. The female will use the sperm to fertilise the eggs later and will lay an egg mass which can contain up to 400,000 eggs.
Life Cycle of the Queen Conch
There are 8 stages in the life cycle of the conch:
- Benthic Eggs: Crescent in shape and camouflaged on the seafloor by a coating of sand grains. Ready to hatch in 3–5 days.
- Newly Hatched Veliger: The newly hatched conch, know as veligers have lobes on them, the purpose of which is to supply the veliger with oxygen and obtain food, in the form of microscopic algae from the water column in which it floats.
- Four Lobed Veliger: As the veliger increase in size it grows more lobes to supply it with oxygen and food.
- Six Lobed Veliger: By 21–30 days the veliger will have 6 lobes and will be ready metamorphose and enter the benthic stage of the life cycle.
- Post larva: The conch now resembles the adult form although it is only 1 mm long. Ctendium (gills) have elongated during metamorphosis to take over the job of respiration. They also have a proboscis that they will use for feeding, and the operculum has started to form. The conch will settle, instead of floating in the water column, in shallow seagrass beds or sand flats. The change in environment will be sensed and the final stage of metamorphosis, to lose the lobes, will take place.
- Infaunal Juvenile: At this stage the conch is between 5 and 10 months old and up to 60 mm in length. At this stage the juvenile conch will live buried under the sand it settled in
- Epifaunal Juvenile: The conch is now 1 to 3 years in age and can be 180 mm in length. They will emerge from their nursery habitat and start to migrate to deeper waters in search of food. Conch feed on algae and bacteria on seaweed.
- Adult: The conch is now about 3 years old and is sexually mature. As an adult the conch will no longer increase in size but it will form the 'lip' that identifies it as an adult. For the remainder of its life the conch will add shell to this 'lip'.
There is currently only one well established commercial queen conch fishery. It is based in Turks and Caicos, and has been in operation since 1984. According to the Conch Heritage Network, research is underway in the United States, Mexico and Guadaloupe, with the aim of developing successful breeding techniques for queen conch in captivity to help replenish the oceans.
A Juvenile Queen Conch
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