''Macrostrombus costatus'', formerly known as ''Strombus costatus'' and ''Lobatus costatus'', or commonly known as the milk conch, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of large

sea snail Sea snails are slow-moving marine (ocean), marine gastropod Mollusca, molluscs, usually with visible external shells, such as whelk or abalone. They share the Taxonomic classification, taxonomic class Gastropoda with slugs, which are distinguishe ...

, a marine

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Strombidae Strombidae, common name, commonly known as the true conchs, is a Taxonomy (biology), taxonomic family (biology), family of medium-sized to very large sea snails in the superfamily (zoology), superfamily Stromboidea, and the Epifamily Neostromboid ...

, the true conchs. They are an edible species and important food source for the inhabitants of where they are found. Conchs are most notable for their medium to large-sized ornamental shells. Milk conchs are dispersed among the tropical waters of the Atlantic Ocean, along the coasts and islands of North, Central, and South America.

Distribution

This species occurs in the

Caribbean Sea The Caribbean Sea is a sea of the Atlantic Ocean, North Atlantic Ocean in the tropics of the Western Hemisphere, located south of the Gulf of Mexico and southwest of the Sargasso Sea. It is bounded by the Greater Antilles to the north from Cuba ...

; the

Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...

and the

Lesser Antilles The Lesser Antilles is a group of islands in the Caribbean Sea, forming part of the West Indies in Caribbean, Caribbean region of the Americas. They are distinguished from the larger islands of the Greater Antilles to the west. They form an arc w ...

; in the Atlantic Ocean from

North Carolina North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...

East East is one of the four cardinal directions or points of the compass. It is the opposite direction from west and is the direction from which the Sun rises on the Earth. Etymology As in other languages, the word is formed from the fact that ea ...

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

. Specifically in Central and South America, ''Macrostormbus costatus'' have been recorded along the coasts of

Paraíba Paraíba ( , ; ) is a states of Brazil, state of Brazil. It is located in the Brazilian Northeast, and it is bordered by Rio Grande do Norte to the north, Ceará to the west, Pernambuco to the south and the Atlantic Ocean to the east. Paraíba i ...

state of

northeastern Brazil The Northeast Region of Brazil ( ) is one of the five official and political regions of the country according to the Brazilian Institute of Geography and Statistics. Of Brazil's twenty-six states, it comprises nine: Maranhão, Piauí, Ceará, R ...

, Venezuela, Panama, Bermuda, Yucatan Peninsula in Mexico, and

Trinidad and Tobago Trinidad and Tobago, officially the Republic of Trinidad and Tobago, is the southernmost island country in the Caribbean, comprising the main islands of Trinidad and Tobago, along with several List of islands of Trinidad and Tobago, smaller i ...

Anatomy and morphology

''Macrostrombus costatus'' is a large species of sea snail with a thick shell. The shell of an adult milk conch can be distinguished by the high spire and flaring lip. Te common name milk conch is derived from the milky, white interior coloration of the aperture and light cream exterior of its shell. In contrast, other conch species, such as ''

Aliger gigas ''Aliger gigas'', originally known as ''Strombus gigas'' or more recently as ''Lobatus gigas'', common name, commonly known as the queen conch, is a species of large sea snail, a marine gastropod mollusc in the family (biology), family of true c ...

'' or ''

Strombus pugilis ''Strombus pugilis'', common names the fighting conch and the West Indian fighting conch, is a species of medium to large sea snail, a marine gastropod mollusk in the family Strombidae, the true conchs. ''S. pugilis'' is similar in appearance t ...

'', are known to have various shades of pink and red tones in the aperture and various patterns or colors on the external surface. Milk conch eyes have rings that can range in colors from red, orange, yellow, to black. An average ''M. costatus'' shell measures around 20 cm in length. The maximum recorded shell length is 23.1 cm. However, they are a smaller conch species compared to the more widely studied ''Aliger gigas'', the queen conch, which can measure up to 31 cm.

Habitat

''Macrostrombus costatus'' prefers shallow-water back reef habitats, such as algal banks, seagrass beds, and patch reefs, which provide them with shelter, protection, and food. 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. Whereas in Puerto Rico, they are mostly found in algal mats. In Panama, there is an overwhelming abundance of milk conch in

seagrass meadow A seagrass meadow or seagrass bed is an underwater ecosystem formed by seagrasses. Seagrasses are marine (saltwater) plants found in shallow coastal waters and in the brackish waters of estuaries. Seagrasses are flowering plants with stems and ...

s, where turtle and manatee grass dominates the flora. Milk conch can inhabit depths varying between three meters to twenty meters. Minimum recorded depth is 2 m.Welch J. J. (2010). "The "Island Rule" and Deep-Sea Gastropods: Re-Examining the Evidence". '' PLoS ONE'' 5(1): e8776. . Maximum recorded depth is 55 m.

Reproduction

''Macrostrombus costatus'' has external sex organs. Male milk conchs have a verge, while female milk conchs have an egg groove. 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.

Life cycle

''Macrostrombus 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. Then, as a pelagic veliger, the milk conch reaches metamorphosis to a benthic snail in approximately 26–30 days after hatching. 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. 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. Crustaceans, such as crabs and lobsters are their main predators when they are juvenile.

Feeding

''Macrostrombus costatus'' is a herbivorous marine gastropod. As veligers, they consume phytoplankton. As adult snails, they feed mostly on algae.

Threats

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

References

External links

* * {{Taxonbar, from1=Q126924027, from2=Q10681939, from3=Q6663568 Strombidae Gastropods described in 1791 Taxa named by Johann Friedrich Gmelin