''Euglandina rosea'', the rosy wolfsnail or cannibal snail, is a species of medium-sized to large predatory air-breathing land snail, a carnivorous terrestrial
pulmonate
Pulmonata or pulmonates, is an informal group (previously an order, and before that a subclass) of snails and slugs characterized by the ability to breathe air, by virtue of having a pallial lung instead of a gill, or gills. The group includ ...
gastropod
The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda ().
This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...
mollusk
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is e ...
in the family
Spiraxidae
Spiraxidae is a family of predatory air-breathing land snails, terrestrial pulmonate gastropods in the superfamily Testacelloidea (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005).
Distribution
The distribution of th ...
.MolluscaBase eds. (2020). MolluscaBase. Euglandina rosea (Férussac, 1821). Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=1289331 on 2020-11-09
This species is a fast and voracious predator, hunting and eating other snails and slugs.Clifford, Kavan T., Liaini Gross, Kwame Johnson, Khalil J. Martin, Nagma Shaheen, and Melissa A. Harrington. (2003)."Slime-trail Tracking in the Predatory Snail, Euglandina Rosea." Behavioral Neuroscience 117.5:1086-095. The rosy wolfsnail was introduced into
Hawaii
Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...
in 1955 as a biological control for the invasive African land snail, ''
extinction
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
of an estimated eight native snail species in Hawaii.Kurt Auffenberg & Lionel A. Stange (November 2001). "Snail-eating snails of Florida, Gastropoda". University of Florida. EENY251. Retrieved October 7, 2012. This has caused the snail to be added to the IUCN’s top 100 most invasive species.
Description
The rosy wolfsnail lives around 24 months. The snail takes 30–40 days to hatch and is then considered young (before sexual maturity). Sexual maturity begins between 4 and 16 months after hatching. The snail is relatively fast moving at about 8 mm/s. The snail has a light grey or brown body, with its lower tentacles being long and almost touching the ground. The shell has usual dimensions of 76 mm long and 27.5 mm in diameter. The shape of the shell tapers to a point at both ends (
fusiform
Fusiform means having a spindle-like shape that is wide in the middle and tapers at both ends. It is similar to the lemon-shape, but often implies a focal broadening of a structure that continues from one or both ends, such as an aneurysm on a b ...
) with a narrow oval- to crescent-shaped opening and a shortened axis of the spiral shell near the opening (truncated columella). The shell has a brownish pink color. The full-grown adult snail ranges in size from 7–10 cm in length.
Ecology
This species is found naturally in the Southern United States, usually in hardwood forests and urban gardens.Hubricht L. (1985). "Distributions of the native land mollusks of the eastern United States". Fieldiana: Zoology (new series) No. 24: i-viii, 1-191. It is a fast and voracious predator, hunting and eating other snails and slugs. The smaller prey species are ingested whole or sucked out of their shells. This gives it the nickname "the cannibal snail". Rosy wolfsnails use slime trails to track their prey and potential mates, resulting in rosy wolfsnails following these trails more than 80% of the time they are alive. The rosy wolfsnail prefers to consume smaller snails because these are quicker and easier to eat.Cook, Anthony. (1989). "Factors Affecting Prey Choice And Feeding Technique In The Carnivorous Snail Euglandina Rosea Ferussac." Journal of Molluscan Studies 55.4: 469-77.
The rosy wolfsnail is specialized for carnivory, its
buccal mass
The digestive system of gastropods has evolved to suit almost every kind of diet and feeding behavior. Gastropods (snails and slugs) as the largest taxonomic class of the mollusca are very diverse: the group includes carnivores, herbivores, scaven ...
being totally contained within a beak-like rostrum that can be extended, thus allowing the toothed
radula
The radula (, ; plural radulae or radulas) is an anatomical structure used by molluscs for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food ...
to be ejected past the mouth and into the snail's prey. The radula is enlarged and has teeth specialized into elongated cones.
The four main mammalian predators for the rosy wolfsnail are rats,
tenrec
A tenrec is any species of mammal within the afrotherian family Tenrecidae endemic to Madagascar. Tenrecs are wildly diverse; as a result of convergent evolution some resemble hedgehogs, shrews, opossums, rats, and mice. They occupy aquatic, a ...
s, pigs, and mongooses. The rats consume the snail by chewing the top of the shell off. The tenrecs crack the shell into large pieces. The pigs have a tendency to crush the shell completely. The mongooses attack the body of the snail. Cannibalism among adults has also been seen in the rosy wolfsnail. However, this has only been observed in captive populations and appears to be a rare occurrence.
Diseases affect the survival of the rosy wolfsnail, as well. One disease known to affect the snail is caused by the pseudomonad bacterium '' Aeromonas hydrophila''. Infection occurs by ingesting the bacteria, if they contaminate the snail's food, or by contact with another individual that is infected. This causes reduced digestive function, resulting in emaciation even when food is abundant. This finally results in a slow death by starvation.
The rosy wolf snail is a
hermaphrodite
In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes.
Many Taxonomy (biology), taxonomic groups of animals (mostly invertebrate ...
and is
oviparous
Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, most reptiles, and all pterosaurs, dinosaurs (including birds), and ...
. The courtship rituals for the snail begin with one following the trail of another snail. The pursuing snail then mounts the rear side of the shell of the snail it was following. Following this mounting, a head-waving display ensues, where the pursuing snail vigorously shakes its head for 15 minutes. This ultimately ends with a short period of inactivity, where the mounted snail turns its head to face its own shell. Following this,
copulation
Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetrat ...
occurs, with the one snail still mounted on the shell of the other, the two heads are brought together, and then twisted around each other's necks, enabling genital contact. This copulation then lasts up to four hours. An adult snail lays 25–35 eggs in a shallow pocket of soil and the eggs hatch after 30–40 days.
The snail has been known to go into
hibernation
Hibernation is a state of minimal activity and metabolic depression undergone by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It most ...
during winter and emerge in April/May.
Distribution and habitat
The rosy wolfsnail is native to the Southeastern United States, including Florida and Georgia. Other species of the genus are native to South and Central America.
As an invasive species
The rosy wolfsnail has become an invasive species in many areas outside its native range, including in Hawaii. These predatory snails were originally introduced to Hawaii in an attempt to eliminate another invasive species, the giant African land snail, ''
Achatina fulica
''Lissachatina fulica'' is a species of large land snail that belongs in the subfamily Achatininae of the family Achatinidae. It is also known as the Giant African land snail. The
introduced species
An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived there ...
vigorously attacked the endemic
O'ahu tree snail
''Achatinella'' is a tropical genus of colorful land snails in the monotypic Achatinellidae subfamily ''Achatinellinae''. Species are arboreal pulmonate gastropod mollusks with some species called Oʻahu tree snails or kāhuli in the Hawaiian la ...
. As a result, many tree snail species were hunted to extinction within the first year. These predatory snails continue to represent a threat to the local snail fauna.Claire Régnier, Benoît Fontaine & Philippe Bouchet (2009). "Not knowing, not recording, not listing: numerous unnoticed mollusk extinctions". Conservation Biology. 23 (5): 1214–1221. doi:10.1111/j.1523-1739.2009.01245.x. PMID 19459894.
Of all known mollusk extinctions since 1500, about 70% are from islands, and an estimated one-third of these were caused by introduced ''E. rosea''. These prey snails were at an increased risk of predation-caused extinction because of their extremely low reproduction rates. The rosy wolfsnail has caused the extinction of an estimated eight native snail species in Hawaii. Due to this, the
International Union for Conservation of Nature
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
(IUCN) has placed the rosy wolfsnail on the list of the top 100 worst invasive alien species in the world.
Control strategies
One strategy to protect native snails from the predatory rosy wolfsnail has been to breed the native tree snails in
captivity
Captivity, or being held captive, is a state wherein humans or other animals are confined to a particular space and prevented from leaving or moving freely. An example in humans is imprisonment. Prisoners of war are usually held in captivity by a ...
, then introduce the small population into a predator-proof patch of forest. This forest patch consists of a galvanized iron barrier; at the base of the iron barrier, a plastic trough was attached and filled with salt and then a pair of electric wires connected to a battery. This created a protected enclosure with both chemical and electrical defenses. The enclosure allows the native snails to breed in a safe location, but does not allow them to travel outside of the protected area.
Other forms of control for the rosy wolfsnail have been investigated. The three main methods of control being used or discussed are collection and chemical and biological control. The use of collection has not been extensively used because it is too labor-intensive and time-consuming. Chemical poisoning has been used extensively in many areas, though it is not very effective in controlling the ''E. rosea'' population. Biological control has been a favored option.
Policy and laws
The rosy wolfsnail is now legally considered to be a "noxious species in French Polynesia". This means that live individuals cannot be brought to the islands.Meyer, Jean-Yves. (1998)."Observations on the Reproductive Biology of Miconia Calvescens DC (Melastomataceae), an Alien Invasive Tree on the Island of Tahiti (South Pacific Ocean)1." Biotropica 30.4: 609-24. The IUCN states that the introduction of the rosy wolfsnail to non-native habitats is now formally discouraged.