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Phylum Mollusca > Class Gastropoda > sea slugs > Order Sacoglossa
Volvatella slugs
Family Volvatellidae
updated Jun 2020
Where seen? These tiny slugs with very fragile shells are sometimes seen among seaweeds on some of our shores.

Features: Fragile, thin shell about 1cm long, that looks like a poorly folded cone that tapers into a spout at the end. The rhinophores are flattened, rounded and the animal has a pair of rounded oral lobes and a short foot. When disturbed, it secretes a white fluid. The egg mass is a flattened disk laid on seaweed.

It is difficult to tell apart the species in the field, but in general, Volvatella vigourouxi (0.2-1cm long) is orange or yellowish, shell with fine darker orange-black spirals; Volvatella ventricosa (about 0.5cm long) is greenish; Volvatella maculata (about 0.5cm long) is white to pale yellowish.

Another kind of Volvatella has a white shell with transparent spots and it has yet to be identified to species.

Sentosa, Jun 12

Smaller 'males' on top of a larger
hermaphrodite snail.
Sentosa, Jun 12
What do they eat? They have been seen on Caulerpa green seaweeds (Caulerpa sp.) as well as other kinds of green seaweeds including Hairy green seaweeds (Bryopsis sp.).

Baby volvatellas: Often one or more smaller slugs are seen 'riding' on top of a larger one. Those on the edge of the shell lip may be mating, with the smaller one inserting its penis into the larger one. According to Bill Rudman, although the slugs are hermaphrodites with both male and female reproductive parts, in smaller slugs, the male parts are developed while the female parts are not yet active. Both are developed in larger ones. Thus smaller slugs may be acting as males on larger slugs which act as females.

Produces a white fluid when disturbed.
Pasir Ris, Aug 11

Volvotella sp. is white with transparent spots.
St. John's Island, May 10
Photo shared by Loh Kok Sheng on flickr.

Volvatella slugs on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores


Pulau Ubin, Dec 17
Photo shared by Loh Kok Sheng on facebook.


Chek Jawa, Jul 18
Photo shared by Marcus Ng on flickr.

Chek Jawa, Jun 17
Photo shared by Toh Chay Hoon on facebook.


Pulau Sekudu, Jul 09

Photo shared by Marcus Ng on his flickr.

Pulau Sekudu, May 10
Photo shared by Toh Chay Hoon on her blog.


Chek Jawa, Oct 10
Photo shared by Neo Mei Lin on her blog.

Changi, May 11
Photo shared by Loh Kok Sheng on his blog.

Changi, May 14
Photo shared by Toh Chay Hoon on facebook.


Cyrene Reef, Jul 14
Photo shared by Loh Kok Sheng on flickr.

Terumbu Semakau, May 17
Photo shared by Toh Chay Hoon on facebook.
 

Family Volvatellidae recorded for Singapore
from Tan Siong Kiat and Henrietta P. M. Woo, 2010 Preliminary Checklist of The Molluscs of Singapore.
^K. R. Jensen. Sacoglossa (Mollusca: Gastropoda: Heterobranchia) from northern coasts of Singapore.

*Cornelis (Kees) Swennen. Large Mangrove-dwelling Elysia species in Asia, with descriptions of two new species (Gastropoda: Opistobranchia: Sacoglossa)

**from WORMS

  Family Volvatellidae
  ^Ascobulla fischeri

^Volvatella ventricosa
Volvatella vigourouxi
(Volvatella slug)
^Volvatella maculata
Volvatella
sp.


Links

References

  • Kathe Jensen & Rene S. L. Ong . 30 Sep 2016. Shelled sacoglossa from Lazarus and Saint John’s Islands. Singapore Biodiversity Records 2016: 120-121.
  • K. R. Jensen. Sacoglossa (Mollusca: Gastropoda: Heterobranchia) from northern coasts of Singapore. 10 July 2015. The Comprehensive Marine Biodiversity Survey: Johor Straits International Workshop (2012) The Raffles Bulletin of Zoology 2015 Supplement No. 31, Pp. 226-249.
  • Kathe R. Jensen. 30 Dec 2009. Sacoglossa (Mollusca: Gastropoda: Opisthobranchia) from Singapore. The Raffles Bulletin of Zoology, Supplement 22: 207-223.
  • Tan Siong Kiat and Henrietta P. M. Woo, 2010 Preliminary Checklist of The Molluscs of Singapore (pdf), Raffles Museum of Biodiversity Research, National University of Singapore.
  • Gosliner, Terrence M., David W. Behrens and Gary C. Williams. 1996. Coral Reef Animals of the Indo-Pacific: Animal life from Africa to Hawaii exclusive of the vertebrates Sea Challengers. 314pp.
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