Rapana venosa

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Rapana venosa
A live individual of Rapana venosa retracted into the shell, with the operculum closing the aperture
Five views of a shell of R. venosa
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Subclass: Caenogastropoda
Order: Neogastropoda
Family: Muricidae
Genus: Rapana
Species:
R. venosa
Binomial name
Rapana venosa
(Valenciennes, 1846)
Synonyms[1]

Purpura venosa Valenciennes, 1846 (basionym)
Rapana marginata Valenciennes, 1846
Rapana pechiliensis Grabau & King, 1928
Rapana thomasiana Crosse, 1861

Rapana venosa, common name the veined rapa whelk or Asian rapa whelk, is a

mollusc or whelk, in the family Muricidae
, the rock shells.

This large sea snail has become an invasive species in many different localities around the world.

Shell description

Ventral (left) and dorsal (right) views of a shell of Rapana venosa
Apical view of the shell of Rapana venosa
stamp of the Soviet Union

The shell of Rapana venosa is globose (rounded) and heavy, possessing a very short spire, a large body whorl, a strong columella and a deep umbilicus. The aperture is large and roughly ovate. Ornamentation is present externally as axial ribs, smooth spiral ribs ending in blunt knobs at both the shoulder and body whorl, and internally as small elongated teeth disposed along the outer lip margin. The external color varies from gray to reddish-brown, with dark brown dashes on the spiral ribs. Some specimens may have distinctive black/dark blue vein-like coloration patterns throughout the inner portions of the shell, usually originating from each individual tooth at the outer lip. A diagnostic feature for this species is the deep orange color found in the

columella. The height of the shell can reach up to 180  mm (about 7 in).[2][3]

Distribution

This species is native to the marine and estuarine waters of the western Pacific, from the Sea of Japan, Yellow Sea, East China Sea and the Bohai Sea.[2]

Rapana venosa is included in Russia's Red Book as threatened with extinction. The original known habitat for this species was the Far East, but since 1947 it has been found in the Black Sea, and its shell became a popular souvenir in Crimea. Recently this species has been found as an exotic in the Chesapeake Bay, on the eastern coast of the United States.

Nonindigenous distribution

According to some authors, it appears to be the case that the spreading of this species outside its natural range has been made possible by the planktonic larval stage being transported along with

ballast water in the hulls of ships, or that egg masses may have been transported with products of marine farming.[4]

Rapa whelks were first found in the

Samborombon Bay), and in Argentina.[6][7] In the United States the first specimen discovered was in August 1998 by members of the Virginia Institute of Marine Science (VIMS) Trawl Survey Group in Hampton Roads, Virginia. The species is now widely distributed and established in Chesapeake Bay.[2]

Rapana venosa is considered among the 100 worst alien species in Europe in the DAISIE European Invasive Alien Species Gateway,[8] one of two marine gastropods on the list.[8] It is considered as about the 52nd the worst alien species in Europe.[9]

Ecology

Habitat

Veined rapa whelks favor compact sandy bottoms, in which they can burrow almost completely. The native habitat of this species is a region of wide annual temperature ranges, comparable to other localities. Fleeing cold waters in the winter, this species may migrate to warmer, deeper waters, thereby evading cool surface waters. This fertile sea snail is extremely versatile, tolerating low salinities, water pollution and oxygen deficient waters.[2]

Feeding habits

Veined rapa whelks are

biotoxins to weaken the prey.[12] Shell drilling, however, is also not unknown in this species.[13]

Life cycle

A shell of Veined rapa whelk, side by side with its egg case

Rapana venosa is

bivalve mollusks)[15] then hatch, persisting in the water column for 14 to 80 days[11] and feeding primarily on plankton.[8] They eventually settle on the ocean floor where they develop into hard-shelled snails. Growth is rapid over the first year of life, and reproduction occurs from the second year onwards. Large specimens may be over ten years old.[2]

Reasons for the survival of this invasive species

It is known that the abundance of prey, the lack of competition from other gastropod species, as well as the absence of direct predators of R. venosa may be some of the factors that contributed to the successful establishment of new populations of this sea snail outside its native range.[3] The thick strong shell of the rapa whelk is arguably its strongest advantage over native whelks, because rapas can easily prey on local whelks, whereas local whelks are unable to successfully attack rapas. The thick shell also means that predators such as sea turtles are unable to feed on the invasive species, and can only feed on local whelk populations. It is suggested that once the rapa whelk reaches adulthood, it exists unchecked in the local population, and can consume and reproduce freely.[3] The Veined rapa whelk is also highly tolerant to wide variations in salinity and oxygen concentration,

ecosystems. In its native range Rapana venosa shows high temperature tolerance, being able to withstand temperatures varying from 4 to 27 °C (39.2 - 80.6 °F).[3]

Impact of introduction

Veined rapa whelks have caused significant changes in the

bottom-dwelling organisms, and have become marine pests in the Black Sea. Although scientists are not completely aware of the impacts of the whelk, they are very concerned about its potential impact on native Bay species. Studies are currently under way to help determine the whelk's spread in Chesapeake Bay, so that scientists can develop a model that will define potential impacts to the Bay's ecosystem.[2]

Imposex

The

docking areas, consequently exposing the nearby marine life to its possibly harmful effects.[17] This unnatural development of male reproductive organs, however, has shown no negative effects on populations of this species, and no loss of reproductive capabilities of female R. venosa as a consequence of Imposex has been observed so far.[16]

References

This article incorporates public domain text (a

work of the United States Government) from reference [2]

  1. ^ Rapana venosa (Valenciennes, 1846). Retrieved through: World Register of Marine Species on 2 April 2010.
  2. ^ a b c d e f g h Myriah Richerson. 2008. Rapana venosa. USGS Nonindigenous Aquatic Species Database, Gainesville, FL. <https://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=1018> Revision Date: 4/24/2006
  3. ^
    ISBN 978-87-7482-010-9. Archived from the original
    (PDF) on 2011-12-13. Retrieved 2012-01-31.
  4. ^ Harding, J. M. (2001). Rapana venosa veined rapa whelk, Asian rapa whelk (PDF). Guide to Marine Invaders in the Gulf of Maine. Salem Sound Coastwatch.
  5. ISSN 1126-7801
    .
  6. ISSN 0730-8000
    .
  7. hdl:1834/1572
    .
  8. ^ a b c d DAISIE European Invasive Alien Species Gateway. Rapana venosa. Last updated 30 October 2006, accessed 3 April 2010.
  9. ISSN 1387-3547
    .
  10. S2CID 86752900
    .
  11. ^
    ISSN 1438-3888
    .
  12. ^ a b "Rapana venosa (Valenciennes, 1846) (Mollusca, Gastropoda, Muricidae" (in Italian). Santa Croce, Venezia: Museo di Storia Naturale di Venezia. Archived from the original on 22 July 2011. Retrieved 2 April 2010.
  13. ^ "Global Invasive Species Database". Rapana venosa (mollusc). National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG). 2006. Retrieved 2 April 2010.
  14. S2CID 86797777
    .
  15. ISBN 978-0-87893-097-5
    .
  16. ^
    doi:10.3354/meps310129
    .
  17. ISSN 1516-8913
    .

Further reading

External links

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