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Partula Snails

Partula A. Férussac 1821

Biology

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These fascinating molluscs have captivated scientists for centuries, with an interesting reproductive strategy and a particularly impressive diversification of species. Occupying islands that were previously free of both competitors and predators, the Partula snails were able to fill every available niche, evolving many new species. In common with many other snail families, Partula snails are hermaphrodites, meaning that every individual produces both sperm and eggs, and possesses male and female reproductive organs. However, they do not self-fertilise, but instead court another individual by touching tentacles and lips. As they court, the male and female genitals begin to emerge from the skin behind the head, and the snails circle one another to position themselves for copulation. Before they copulate, these snails perform an extraordinary and unexplained behaviour. In a state of excitement, one of the snails expels a long, thin 'love dart' made of chalk-like calcium carbonate, pushing it into its partner's head. Shortly afterwards, the other snail reciprocates, firing a return love dart – named as an analogy to Cupid's arrow. Copulation follows, and can last for up to eight hours, during which time the mating partners exchange spermatophores (4). Uniquely, both partners give birth to fully formed, shelled offspring two weeks after fertilisation (2). Partula snails are thought to feed on algae and decaying plant matter and are known to live higher in trees as they mature. They are preyed upon by the introduced carnivorous snail, Euglandina rosea (2).
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Conservation

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In a desperate attempt to salvage this genus, many animal collections have joined in efforts to gather sufficient numbers of several Partula species to breed them in captivity. Captive breeding programmes have run at the Shedd Aquarium, Detroit Zoological Park, the Zoological Society of London, and Jersey Zoo amongst others. The Zoological Society of London released captive-bred snails into a protected area on Moorea Island in August 1994. However, extensive release of captive-bred snails is not possible until Euglandina rosea has been exterminated from the islands. This sad loss to global biodiversity serves as a lesson of the ignorance of man and the consequences of the introduction of non-native species. Introduced species remain the second biggest cause of species loss after habitat destruction (2).
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Description

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In a parallel of Darwin's finches on the Galapagos Islands, the Partula snails are known for the diversification of species that has occurred across the range of islands upon which they live. They vary in size, shape and colouration, with grey to brown spiral shells sometimes marked with white. Their bodies are pale to dark brown (2).
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Habitat

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Mainly tree-dwelling, Partula snails are found in densely forested regions in a moist habitat (2).
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Range

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Found only on islands in the Pacific Ocean, ranging over 8,000 km from Palau to the Society Islands in French Polynesia (3).
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Status

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There are 79 species of the genus Partula on the IUCN Red List 2004, 50 of which are classified as Extinct (EX), 14 as Extinct in the Wild (EW), and 15 as Critically Endangered (CR) (1). Around 100 species of the genus Partula have been described (2).
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Threats

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In a tragic and calamitous story, humans are responsible for the extinction, or extinction in the wild, of 64 species of Partula snails in the recent past. In the 1800s a budding snail farmer introduced the large and edible giant African snail (Achatina fulica) to the islands of the Pacific Ocean in an attempt to profit from providing a new source of food to the islands' human inhabitants. His venture failed for economic reasons and the snails were released. They became an agricultural pest, prompting a response from the authorities to introduce the predatory carnivorous snail Euglandina rosea to the islands to control giant African snail numbers. A lack of forethought and contained experimentation is evident, as the carnivorous Euglandina did not prey on the giant African snail as expected, instead consuming and decimating the majority of Partula snail species, rapidly driving 50 species to complete extinction. Habitat destruction has compounded the snails' decline (2).
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The Partula Pages

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A website dedicated to the Partulidae, covering news of their status, the conservation programmes, research into ecology, conservation, genetics, evolution and diversity, and links to the literature.

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Partula (gastropod)

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Black-and-white photo taken in July 1920 in Saipan, showing numerous Partula snails on the underside of a single leaf of Caladium

Partula is a genus of air-breathing tropical land snails, terrestrial pulmonate gastropod mollusks in the family Partulidae.[2][3]

Many species of Partula are known under the general common names "Polynesian tree snail" and "Moorean viviparous tree snail".[4] Partulids are distributed across 5,000 sq mi (13,000 km2) of Pacific Ocean islands, from the Society Islands to New Guinea.

Once used as decorative items in Polynesian ceremonial wear and jewelry, these small snails (averaging about one-half to three-quarters of an inch in length) gained the attention of science when Dr. Henry Crampton (along with Yoshio Kondo) spent 50 years studying and cataloging partulids, detailing their remarkable array of morphological elements, ecological niches, and behavioral aspects that illustrate adaptive radiation.[5][6]

Decline

The partulids of the island of Tahiti act as an example of the possible deleterious effects of attempted biological control. After an infestation of the introduced giant African land snails (Achatina spp.), the carnivorous Florida rosy wolfsnail (Euglandina rosea) was introduced into Tahiti in an attempt to combat the African species.

The wolfsnail chose instead to hunt and eat members of the nearly 76 species of Partula that were endemic to Tahiti and the nearby islands, devouring all but 12 species in a decade. Several scientists recognized what was going on, and were able to save 12 species prior to their becoming extinct.

Today, the Zoological Society of London runs the Partula Programme Consortium which maintains a captive-breeding programme in the United Kingdom, France, and the United States.

The 2008 IUCN Red List of Threatened Species contains 15 critically endangered, 11 extinct in the wild, and 48 extinct Partula species.[7] The IUCN Red List of Threatened Species version 2009.2 contains 13 critically endangered, 11 extinct in the wild and 51 extinct Partula species.[8] The IUCN Red List of Threatened Species version 2015-4 contains 83 Partula species.[9]

Individuals are being reintroduced to Tahiti from captive breeding programmes since 2014.[10][11] In April 2023, over 5,000 individual snails from zoos in the United States and the United Kingdom were released on Tahiti and Mo'orea.

Species

Species within the genus Partula include: [6]

Cladogram

A cladogram showing the phylogenic relationships of the genus Partula:[12]

Partulidae

Partula

Samoana

Palaopartula

Eua

Sphendone

Ecology

Partula species on Tahiti were usually found on the undersides of the leaves of Caladium and plantain, although in some valleys, they were frequently found on Dracaena and turmeric.[13]

References

This article incorporates public domain text from the reference.[13]

  1. ^ Férussac A. É. d'A. de (June 1821). Journ. de Physique 92: 460; 1821, H.N. g. et p. Moll., Tabl. Limaçons, 23.
  2. ^ Myers, P.; Espinosa, R.; Parr, C. S.; Jones, T.; Hammond, G. S. & Dewey, T. A. (2006). The Animal Diversity Web (online). Accessed at http://animaldiversity.org.
  3. ^ ITIS Standard Report Page: Partulidae
  4. ^ Searching for "Partula". In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.3. . Downloaded on 14 September 2010.
  5. ^ Jung, Younghun, Taehwan Lee, Burch J. B. & Diarmaid Ó Foighil. (2005) "Historical phylogeny of Tahitian Partula". Proc. Joint Conference - American Malacological Society and Western Society of Malacologists.
  6. ^ a b Gerlach, J. (2016) Icons of Evolution - Pacific island tree snails, family Partulidae. Phelsuma Press, Cambridge
  7. ^ IUCN (2008). 2008 IUCN Red List of Threatened Species. . Downloaded on 23 December 2008.
  8. ^ IUCN (2009). IUCN Red List of Threatened Species. Version 2009.2. . Downloaded on 14 November 2009.
  9. ^ IUCN (2016). The IUCN Red List of Threatened Species. Version 2015-4. . Downloaded on 07 June 2016.
  10. ^ Kuta, Sarah (2 May 2023). "Scientists Reintroduce 5,000 Snails to French Polynesian Islands". Smithsonian Magazine. Retrieved 2023-05-27.
  11. ^ Elizabeth Claire Alberts (28 April 2023). "'Extinct' snails return to Tahiti in largest wildlife reintroduction ever". Mongabay. Retrieved 17 May 2023.
  12. ^ Lee, T.; Burch, J. B.; Coote, T.; Pearce-Kelly, P.; Hickman, C.; Meyer, J. Y.; ó Foighil, D. (2009). "Moorean tree snail survival revisited: A multi-island genealogical perspective". BMC Evolutionary Biology. 9: 204. doi:10.1186/1471-2148-9-204. PMC 3087522. PMID 19686604.
  13. ^ a b Mayer A. G. (January 1902). "Some species of Partula from Tahiti. A study in variation". Memoirs of the Museum of Comparative Zoölogy XXVI(2), Cambridge, U.S.A.
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Partula (gastropod): Brief Summary

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Black-and-white photo taken in July 1920 in Saipan, showing numerous Partula snails on the underside of a single leaf of Caladium Partula gibba Partula langfordi

Partula is a genus of air-breathing tropical land snails, terrestrial pulmonate gastropod mollusks in the family Partulidae.

Many species of Partula are known under the general common names "Polynesian tree snail" and "Moorean viviparous tree snail". Partulids are distributed across 5,000 sq mi (13,000 km2) of Pacific Ocean islands, from the Society Islands to New Guinea.

Once used as decorative items in Polynesian ceremonial wear and jewelry, these small snails (averaging about one-half to three-quarters of an inch in length) gained the attention of science when Dr. Henry Crampton (along with Yoshio Kondo) spent 50 years studying and cataloging partulids, detailing their remarkable array of morphological elements, ecological niches, and behavioral aspects that illustrate adaptive radiation.

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