Strombidae

Strombidae, commonly known as the true conchs, is a taxonomic family of medium-sized to very large sea snails in the superfamily Stromboidea. The term true conchs, being a common name, does not have an exact meaning. It may refer generally to any of the Strombidae but sometimes is used more specifically to include only Strombus and Lambis. The family currently includes 23 extant, and 10 extinct genera. Strombid gastropods live mainly in tropical and subtropical waters. These animals are widespread in the Indo-West Pacific, where most species and genera occur. Nearly 40 of the living species that used to belong to the genus Strombus can be found in the Indo-Pacific region. They also occur in the eastern Pacific and Western Atlantic, and a single species can be found on the African Atlantic coast. Six species of strombids are found in the wider Caribbean region, including the queen conch Lobatus gigas, the goliath conch Lobatus goliath, the hawk-wing conch Lobatus raninus, the rooster tail conch Lobatus gallus, the milk conch Lobatus costatus, the West Indian fighting conch Strombus pugilis, and the Florida fighting conch Strombus alatus. Until recently, all of these species were placed in the genus Strombus, but now many species are being moved into new genera. Strombids have long eye stalks. The shell of a strombid has a long and narrow aperture and a siphonal canal. The shell margin has an indentation near the anterior end which accommodates one of the eye stalks. This indentation is called a strombid or stromboid notch. The stromboid notch may be more or less conspicuous, depending on the species. The shells of most species in this family grow a flared lip upon reaching sexual maturity, and they lay eggs in long, gelatinous strands. The genera Strombus and Lambis have many similarities between them, both anatomical and reproductive, though their shells show some conspicuous differences. Strombids were widely accepted as carnivores by several authors in the 19th century, an erroneous concept that persisted for several decades into the first half of the 20th century. This ideology was probably born in the writings of Lamarck, who classified strombids alongside other supposedly carnivorous snails, and was copied in this by subsequent authors. However, the many claims of those authors were never supported by the observation of animals feeding in their natural habitat. Nowadays, strombids are known to be specialized herbivores and occasional detritivores. They are usually associated with shallow-water reefs and seagrass meadows. Unlike most snails, which glide slowly across the substrate on their feet, strombid gastropods have a characteristic means of locomotion, using their pointed, sickle-shaped, horny operculum to propel themselves forward in a so-called leaping motion. Burrowing behavior, in which an individual sinks itself entirely or partially into the substrate, is also frequent among strombid gastropods. The burrowing process itself, which involves distinct sequential movements and sometimes complex behaviors, is very characteristic of each species. Usually, large strombid gastropods, such as the queen conch Eustrombus gigas and the spider conch Lambis lambis, do not bury themselves, except during their juvenile stages. However, smaller species such as Strombus canarium and Strombus epidromis may bury themselves even after adulthood. For a long time, all conchs and their allies (the strombids) were classified in only two genera, namely Strombus and Lambis. This classification can still be found in many textbooks and on websites on the internet. Based on molecular phylogeny as well as a well-known fossil record, both genera have been subdivided into several new genera by different authors. The family Strombidae actually comprises 23 extant genera and 10 extinct genera (marked with a dagger †).