Lobatus costatus

This species occurs in the Caribbean Sea; the Gulf of Mexico and the Lesser Antilles; in the Atlantic Ocean from North Carolinato East Brazil. Specifically in Central and South America, Lobatus Costatus have been recorded along the coasts of Paraiba state of northeastern Brazil,[3] Venezuela,[4] Panama,[5] Bermuda, Yucatan Peninsula in Mexico,[4] and Trinidad and Tobago.[2]

Lobatus costatus is composed of a large soft-bodied snail with an exterior of a calcium carbonate shell. The shell of an adult milk conch can be distinguished by the high spire, siphonal canal, and flaring lip.[3] Milk conch gets its common name by the milky, white interior of the aperture and light cream exterior of its shell. In contrast, other conch species, such as Strombus gigas or Strombus pugilis, are known to have various shades of pink and red tones for the aperture and various patterns or colors on the exterior shell.[2] The milk conch eyes have rings that can range in colors of red, orange, yellow, or black.[3] The average Lobatus costatus measures around 20 cm in shell length and are considered to be large gastropods. The maximum recorded shell length is 23.1 cm. However, they are a smaller species of conch compared to the more widely studied Lobatus gigas, the queen conch, which can measure up to 31 cm.[5]

Lobatus costatus prefers shallow-water back reef habitats, such as algal banks, seagrass beds, and patch reefs, which provide them with shelter, protection, and food.[6] The habitat environment of a milk conch changes with its geographical location. In Paraiba, they have been seen at one meter under surface water, in areas of sand between patch reefs.[4] Whereas in Puerto Rico, they are mostly found in algal mats. In Panama, there is an overwhelming abundance of milk conch in seagrass meadows, where turtle and manatee grass dominates the flora.[5]  Milk conch can inhabit depths varying between three meters to twenty meters.[2] Minimum recorded depth is 2 m.[7] Maximum recorded depth is 55 m.[7]

Lobatus costatus has external sex organs. Male milk conchs have a verge, while female milk conchs have an egg groove.[8] Milk conchs are oviparous. These marine gastropods begin to spawn in early November throughout the winter and spring seasons. Spawning comes to an end in May. They have been found to aggregate in groups to spawn in locations of open sand and deeper waters.[2]

Lobatus costatus begins its life developing inside eggs as planktonic larvae. The larvae, known as veligers, feed on different cultures of phytoplankton for nutrition to support growth.[4] Then, as a pelagic veliger, the milk conch reaches metamorphosis to a benthic snail in approximately 26–30 days after hatching.[4][2] The development of the proboscis (contains part of the oral cavity and radula), the loss of velar lobes, and the eyes migrating outwards occur provide morphological evidence of metamorphosis.[2] Juvenile milk conchs have a distinguished conical shaped shell with tight whorls and green-colored proboscis. At this stage, they begin grazing on algae via their proboscis.[2] Crustaceans, such as crabs and lobsters are their main predators when they are juvenile.[2]

Lobatus costatus is a herbivorous marine gastropod.[2] As veligers, they consume phytoplankton. As adult snails, they feed mostly on algae.[2]

Lobatus costatus is fished for its meat and ornamental shell along the tropical Atlantic regions.[6][5] The species has commercial importance, especially in the Caribbean, but the total catch volume has not been estimated.[4] It is believed that Lobatus costatus is overfished.[4] Therefore, there may be a major decline in the species populations. In Panama, there are no current regulations on the harvesting of milk conch.[5] The conservation status of the species is unknown, due to lack of research.

• Rosenberg, G., F. Moretzsohn, and E. F. García. 2009. Gastropoda (Mollusca) of the Gulf of Mexico, Pp. 579–699 in Felder, D.L. and D.K. Camp (eds.), Gulf of Mexico–Origins, Waters, and Biota. Biodiversity. Texas A&M Press, College Station, Texas

• "Lobatus (Macrostrombus) costatus costatus". Gastropods.com. Retrieved 21 March 2011.
• Photos of Lobatus costatus on Sealife Collection