Conomurex luhuanus

Conomurex luhuanus, commonly known as the strawberry conch or tiger conch, is a species of medium-sized sea snail, a marine gastropod mollusk in the family Strombidae, the true conchs.^[1] C. luhuanus is found in sandy habitat among corals in the Indopacific region. They feed on algae or detritus, move with a modified foot, and have complex eyes compared to other gastropods.^[2]

Strawberry conch
Five views of a shell of the Strawberry conch, Conomurex luhuanus
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Subclass:	Caenogastropoda
Order:	Littorinimorpha
Superfamily:	Stromboidea
Family:	Strombidae
Genus:	Conomurex
Species:	C. luhuanus
Binomial name
Conomurex luhuanus (Linnaeus, 1758)
Synonyms
Strombus luhuanus Linnaeus, 1758

Shell description

Some shells of Conomurex luhuanus. The two smaller shells to the right have been cut open to reveal the coloration of the parietal wall

The shell of C. luhuanus ranges from a more common length of 5 cm, to a maximum length of 8 cm.^[3]

C. luhuanus is often mistaken for a cone snail, mainly because of the conoidal outline of its shell, which is relatively unusual among the Strombidae. Its stromboid notch, though not as conspicuous as observed in many species that used to belong to Strombus (such as Lentigo lentiginosus), is deep and easily distinguished. The interior may be slightly lirate.

The external color of the shell can be either white with an orange, brown/tan pattern of blotches, or completely brown/white. The interior is usually colored strong orange, red or pink, and the inner lip border is black or chocolate brown.^[3]

Phylogeny

The phylogenetic relationships among the Strombidae have been mainly accessed on two occasions, by Simone (2005)^[4] and Latiolais (2006),^[5] using two distinct methods. Simone proposed a cladogram (a tree of descent) based on an extensive morpho-anatomical analysis of representatives of Aporrhaidae, Strombidae, Xenophoridae and Struthiolariidae, which included C. luhuanus.^[4]

Strombidae Terebellum terebellum Canarium urceus Conomurex luhuanus Tricornis raninus Lambis lambis Strombus Eustrombus Aliger

Phylogeny and relationships of Strombidae according to Simone (2005)[4]

With the exception of Lambis and Terebellum, the remaining taxa were previously allocated within the genus Strombus, including C. luhuanus. However, according to Simone, only Strombus gracilior, Strombus alatus and Strombus pugilis, the type species, remained within Strombus, as they constituted a distinct group based on at least five synapomorphies (traits that are shared by two or more taxa and their most recent common ancestor).^[4] The remaining taxa were previously considered as subgenera, and were elevated to genus level by Simone in the end of his analysis. The genus Conomurex, in this case, only included C. luhuanus.^[4]

In a different approach, Latiolais et al. (2006) proposed a cladogram based on sequences of nuclear histone H3 gene and mitochondrial cytochrome-c oxidase I (COI) gene showing phylogenetic relationships of 32 species that used to belong to the genus Strombus and Lambis, including Conomurex luhuanus (= Strombus luhuanus).^[5] All species in this cladogram are still given under their original names in Strombus and Lambis.

Regeneration

Another remarkable feature of the eyes of Strombus luhuanus is that they are capable of regeneration following amputation. The first step of regeneration following severance of the optic nerve is the formation of an eye cup as the epithelium adjacent to the cut folds inward. This occurs within a day after the optic nerve is cut. The eye cup is closed by day three, and at this stage it resembles an embryonic eye. The diameter of the eye continues to increase, and meanwhile the cells of the eye differentiate to form the different layers in the retina. When the diameter of the eye reaches about 0.8 mm (after about 15 days), the retina looks like a mature adult eye. The eye will continue to grow until it becomes fully sized, with a diameter of 2 mm, which can take several months. Size, age, sex, nutritional state, or whether the left or right eye is amputated does not have a substantial influence on the regenerative prospects of the eye.^[16]

Tiger conch (C. luhuanus)

In gastropod eye regeneration, the degenerating nerve is important for the formation of the new eye. New axons leave the eye cup and bundle together to form the optic nerve. The new nerve fibers seem to be attracted to the previous optic nerve, and grow down it until they make contact with the cerebral ganglion.^[17]

Electroretinograms (ERGs) have been used to monitor neuron activity in the developing eye of C. luhuanus over the course of the eye's development. The ERGs of the regenerating C. luhuanus eye grow increasingly complex as the eye matures. During the first week of regeneration, a simple "on" peak was recorded, and steady-state potentials were observed in response to prolonged illumination. When the eye reached about 0.4 mm in diameter, an "off" response was observed occasionally. At a diameter of 0.6 mm, rhythmic ERG "off" responses were detected. By 0.8 mm in diameter, the ERGs of the regenerated eye resembled that of a mature adult eye, with two distinct cornea-negative "on" potentials and rhythmic "off" potentials.^[16]