Species Description: Aliger gigas is one of the largest and most commercially important gastropod molluscs in the Caribbean Sea, Bermuda, and Bahamas (Stoner et al. 1988). It is a member of the family Strombidae and one of seven species that occur in the western Atlantic Ocean. Queen conch adults have a widely flaring lip, while the lip of the juveniles is sharp and un-flared. The color of the adult shell is pale to bright pink with hues of yellow, peach and cream. A. gigas is coated with a moderately thick and horny periostracum protecting the shell from erosion. The periostracum begins to chip off when the animal dies.
Regional Occurrence: Aliger gigas is native to north and Central America. It is encountered along the Atlantic coast from South Carolina to the Florida Keys and in the Caribbean Sea and the Bahamas islands at depths from 0.3 to 18 m. A. gigas migrates en masse in offshore directions moving in a flood tide direction (Stoner et al. 1988, Stoner and Lally 1994). Juvenile queen conch are found in shallow, inshore seagrass meadows whereas adults are found in deeper algal plains and seagrass meadows distinct from juveniles (Stoner 1989). Juveniles move in large aggregations that most likely afford them protection from predation (Stoner and Lally 1994).
IRL Distribution: Juvenile Aliger gigas occur in the shallow seagrass beds of the Indian River Lagoon.
Age, Size, Lifespan: Queen conch reach sexual maturity at approximately 3 1/2 to 4 years reaching a shell length of at least 180 mm and up to 5 pounds (Stoner 1989). Juvenile shells reach a length of 50 to 70 mm in the first year before they emerge from the sand (Stoner et al. 1988). The maximum reported size is 352 mm. Aliger gigas are recorded to live 6 to 7 years and as long as 20-30 years in deeper waters.
Abundance: Densities of juvenile queen conch are usually 1 conch per meter square but have been recorded as high as 2.1 per meter square (Stoner et al. 1988). In southern Exuma Cay in the Bahamas, the average density of the conch was reported to be 1.72 per meter square in 1984 (Wicklund et al. 1991). Two-year-old queen conch have been observed to aggregate in even greater densities during periods of heavy wave action (Stoner 1989).
Locomotion: Aliger gigas moves by a unique shell-thrusting motion called "leaping" (Hesse 1980). The queen conch uses its claw-like operculum to dig into the sand and then "pole" forward by extending the foot (Rupert and Barnes 1994). This is a very different mode of transportation from other gastropods.
Reproduction: Adult queen conch migrate to shallow, warmer inshore waters to mate and lay their eggs (Stoner et al. 1988). The peak reproduction period is from April to August. Queen conch lay between 180,000 - 460,000 eggs in gelatinous strings, some as long as 50 - 75 feet. Females may spawn many times during a reproductive season (Stoner et al. 1996).
Embryology: Planktotropic (feeding) larvae emerge and travel long distances in the water column (Davis et el. 1993). At approximately 18 days, the swimming veliger shifts to a swimming/crawling stage that allows it to move along the substratum and find an appropriate place to settle and metamorphose (Davis 1994). Metamorphosis occurs in response to environmental cues from algae and seagrasses (Davis 1994). After larval recruitment, metamorphosis, and settlement of plantonic larvae, the juveniles live in the sand for the first year until they reach 5-10 cm (Stoner et al. 1988, Stoner 1989). Once the juveniles emerge, they move to the seagrass beds to feed on plant detritus and algae, staying there for the next 2 years (Stoner et al. 1988, Stoner 1989).
Temperature: Increases in the metamorphosis of Aliger gigas veliger larvae are observed at elevated seawater temperatures of 37-38°C (Boettcher 2005).
Salinity: There are no reports specifically addressing the affects of salinity fluctuations on adults, juveniles, or larvae of the queen conch.
Trophic Mode: Aliger gigas is an herbivore, feeding on detritus, macroalgae, and epiphytes (Ray and Stoner 1995). The green macroalga Batophora oerstedi appears to be a preferred food.
Associated Species: Small cardinal fish can sometimes be found living within the mantle of the conch.
Special Status: Fishery species.
Economic Importance: Aliger gigas has been historically used by the Mayans, Arawak and Florida Indians for food and tools (Stoner et al. 1988). They are still highly valued as an inexpensive and nutritious food source in the Caribbean. Queen conchs are also highly prized for their shells and are the target of heavy fishing in tourist areas. In addition, they are cultured in western Montana for medicinal purposes.
Queen conch populations are declining throughout their geographic range and, in some regions stocks have collapsed. In the United States, fishing for A. gigas is illegal and in Puerto Rico and the Virgin Islands the fishery is regulated by the Caribbean Fishery Management Council. In the Caribbean, the queen conch commercial fishery is estimated at 60 million U.S. dollars wholesale.
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Davis M, Bolton CA, and AW Stoner. 1993. A comparison of larval development, growth, and shell morphology in three Caribbean Strombus species. Veliger 36:236-244.
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Stoner AW, Ray M, Glazer RA, and KJ McCarthy. 1996. Metamorphic responses to natural substrata in gastropod larvae: decisions related to postlarval growth and habitat preference. Journal of Experimental Marine Biology and Ecology 205:229-243.
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