Euglandina rosea

Euglandina rosea
A live individual of Euglandina rosea
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
(unranked): clade Heterobranchia
clade Euthyneura
clade Panpulmonata
clade Eupulmonata
clade Stylommatophora
informal group Sigmurethra
Superfamily: Testacelloidea
Family: Spiraxidae
Genus: Euglandina
Species: E. rosea
Binomial name
Euglandina rosea

Euglandina rosea, common names the rosy wolfsnail or the cannibal snail, is a species of medium-sized to large predatory air-breathing land snail, a carnivorous terrestrial pulmonate gastropod mollusk in the family Spiraxidae. This species is a fast and voracious predator, hunting and eating other snails and slugs.[1] The rosy wolfsnail was introduced into Hawaii in 1955 as a biological control for the invasive African land snail, Achatina fulica. [2] This snail is responsible for the extinction of an estimated eight native snail species in Hawaii.[3] This has caused the snail to be added to the IUCN’s top 100 most invasive species.

Description

Euglandina rosea from NW Florida

The rosy wolfsnail lives for approximately 24 months.[3] The snail takes 30-40 days to hatch and are then considered young (before they reach sexual maturity). Sexual maturity begins between 4-16 months after hatching. After reaching maturity they are considered an adult for the rest of their lives. The snail is relatively fast moving at about 8 mm/s.[2] 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 76mm tall and 27.5 mm in diameter.[3] The shape of the shell tapers to a point at both ends (fusiform) 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 fully-grown adult snail ranges in size from 7-10 cm in length.[3]

Ecology

The rosy wolfsnail lives for approximately 24 months.[3] This species found naturally in the southern portion of the United States, usually in hardwood forests and urban gardens.[4] This species is a fast and voracious predator, hunting and eating other snails and slugs. The smaller species of prey are ingested whole. This gave it the nickname "the cannibal snail". The predatory snail uses slime trails to track its prey and potential mates, resulting in the rosy wolfsnail following these trails more than 80% of the time they are alive.[1] The rosy wolf snail prefers to consume smaller snails because it is quicker and easier to eat the smaller snails.[5] These prey snails include like the O'ahu tree snail and other small snails native to Hawaii and other Polynesian islands.[6] When prey is found the rosy wolfsnail usually consumes the prey snail whole.[7] The snail has also been seen to quickly suck the prey snail out of its shell which is slower than simply swallowing the prey snail whole.[5] The snail is able to do this because it has no jaw plate. The snail is also specialized for carnivory, the mouth of the snail (buccal mass) being totally contained within a beak like structure (rostrum) that can be extended thus allowing the toothed tongue (radula) to be ejected past the mouth and into the snail’s prey. The radula is also adapted to be larger and have specialized the teeth into elongated cones.[2]

There are four main mammalian predators for the rosy wolfsnail; rats, tenrecs, 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 by the rosy wolfsnail. However, this has only been observed in captive populations and appears to be an incredibly rare occurrence. [2]

There are diseases that affect the death rate or mortality of the rosy wolfsnail as well. There is not a tremendous amount of information about the different diseases that affect the rosy wolfsnail. However, one disease that is known to affect the snail is caused by the pseudomonad bacterium or Aeromonas hydrophila. Infection occurs by ingesting the bacteria, if it rests on the snail’s food, or by contact with another individual who is infected. This causes reduced digestive function resulting in emaciation even when there is an abundance of food resources.[2] This finally results in the slow death of starvation.

The rosy wolf snail is a hermaphrodite and is oviparous.[2] This means the snail has both male and female reproductive parts and lays eggs instead of having live birth. 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 snail it was following. Following this mounting, a head waving display occurs were 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.[8] Following this copulation 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. This copulation then lasts for up to four hours.[11] An adult snail lays 25 -35 eggs in a shallow pocket of soil and these eggs then hatch after 30-40 days.[3]

The snail has been known to go into hibernation during winter months and emerge in April/May.[2]

As an Invasive Species

This species is native to Central America.[9] It is also found in the southern portion of the United States, usually in hardwood forests and urban gardens.[4] It has become an invasive species in many other places, including Hawaii. These predatory snails were originally introduced to Hawaii in an attempt to eliminate another invasive species, the giant African land snail, Achatina fulica. The introduction occurred in 1955 when specimens were collected from Florida and sent to Hawaii. During the same year 616 individuals were released on Oahu. Then in 1958 12,000 were taken from Oahu and introduced onto 8 other Pacific islands. This did not however reduce the populations of Achatina fulica but rather caused a decline in native snail populations.[2] The introduced species vigorously attacked the indigenous O'ahu tree snail. 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.[10]

Of all known mollusk extinctions since the year 1500, about 70% are from islands, and it has been estimated that one-third of these were caused by introduced Euglandina rosea. [10] These prey snails were at an increased risk of predation caused extinction because of their extremely low reproduction rates.[11] Overall the rosy wolfsnail has an caused the extinction of an estimated eight native snail species in Hawaii.[3] Due to this the 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 the native snails from the predatory rosy wolfsnail has been to breed the native tree snails in captivity. Then introduce the small population into a predator-proof patch of forest. This predator-proof patch of forest 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.[12] 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 utilized or discussed are collection, chemical and biological control. The use of collection has not been extensively used because it is incredibly labor-intensive and time consuming. The use of chemical poisoning has been utilized extensively in many areas even though it is not very effective in controlling the population of the species. The biological control has been a highly favored option. [2]

Policy/Laws

The rosy wolfsnail is now legally considered to be a “noxious species in French Polynesia”. This means that people cannot bring live individuals to the islands.[13] The IUCN states that the introduction of the rosy wolfsnail is now formally discouraged.

References

  1. 1 2 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.
  2. 1 2 3 4 5 6 7 8 9 Gerlach, Justin. (1994). “THE ECOLOGY OF THE CARNIVOROUS SNAIL EUGLANDINA ROSEA.” Diss. Wadham College, Oxford.
  3. 1 2 3 4 5 6 7 Kurt Auffenberg & Lionel A. Stange (November 2001). "Snail-eating snails of Florida, Gastropoda". University of Florida. EENY251. Retrieved October 7, 2012.
  4. 1 2 Hubricht L. (1985). “Distributions of the native land mollusks of the eastern United States”. Fieldiana, Zoology (new series) No. 24: i-viii, 1-191.
  5. 1 2 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.
  6. ↑ 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.
  7. ↑ Griffiths, O., A. Cook, and Susan M. Wells. (1993)."The Diet of the Introduced Carnivorous Snail Euglandina Rosea in Mauritius and Its Implications for Threatened Island Gastropod Faunas." Journal of Zoology 229.1: 79-89.
  8. ↑ Cook, Anthony. (1985). "THE COURTSHIP OF EUGLANDINA ROSEA FÉRUSSAC." Journal of Molluscan Studies 51.2: 211-14.
  9. ↑ Kolbert, Elizabeth. (2014). The Sixth Extinction: An Unnatural History. New York: Henry Holt and Company, LLC.
  10. 1 2 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.
  11. ↑ Cowie, Robert H., and Robert P. Cook. (2001)."Extinction or Survival: Partulid Tree Snails in American Samoa." SpringerLink. Kluwer Academic Publishers.
  12. ↑ Coote, Trevor, Dave Clarke, Carole Jean Stentz Hickman, James Murray, and Paul Pearce-Kelly. (2004). "Experimental Release of Endemic Partula Species, Extinct in the Wild, into a Protected Area of Natural Habitat on Moorea." Pacific Science 58.3: 429-34.
  13. ↑ 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.
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