Onchidiidae

Onchidiidae are a family of small, air-breathing sea (and land) slugs. They are shell-less marine (except for 2 species)[2] pulmonate gastropod molluscs. Onchidiidae is the only family within the superfamily Onchidioidea.

Onchidiidae
A live but partially retracted individual of Onchidella sp.
A live and active individual of Onchidella nigricans
Scientific classification
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Subclass: Heterobranchia
Superorder: Eupulmonata
Order: Systellommatophora
Superfamily: Onchidioidea
Rafinesque, 1815
Family: Onchidiidae
Rafinesque, 1815[1]
Genera

See text

Synonyms
  • Hoffmannolidae Starobogatov, 1976
  • Onchidinidae Starobogatov, 1976
  • Onchidellidae Labbé, 1934
  • Peroniidae Keferstein, 1865
  • Peroninidae Starobogatov, 1976
  • Platevindecidae Starobogatov, 1976
  • Quoyellidae Starobogatov, 1976
  • Scaphidae Labbé, 1934

These animals are quite unusual in that they are emphatically not opisthobranchs with gills, as are almost all of the sea slugs. Instead these creatures are pulmonates. They are more closely related to air-breathing land and freshwater snails and slugs than they are to most other sea snails and sea slugs.

This family has no subfamilies (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005).

143 species names were created within the Onchidiidae,[2] but until recently few species could be identified. In the late 1920s Hoffmann revised the family (based on the descriptions), and classified the described species into genera.[3] Labbé later continued the revision and named many new genera in his classification of onchidiid slugs.[4] Labbé also made mistakes in describing the anatomy of some species,[5] and the Onchidiidae was not revised again for over 80 years. Finally, in 2016, the genus Onchidium was revised based on natural history, comparative anatomy, and DNA sequences.[6] This was followed by a revision of the genus Onchidina, and the descriptions of onchidiid species in several new genera.[7][8][9][5]

Anatomy

Adult onchidiids lack a shell, although a shell[10] and operculum is present at the larval stage. The mantle cavity is reduced to the point of absence, correlating with a loss of gills, raphes, and other characters usually found in the mantle cavity. The organism is completely detorted.[11]

Slugs in this family make and use love darts made of chitin.[12]

Genetics

In this family, the number of haploid chromosomes lies between 16 and 20 (according to the values in this table).[13]

Habitat

Most of the species in this family are marine and are found in the intertidal zone. Many species live on rocky coasts, while others live in mangrove forests which may be marine or brackish.[6] Onchidium stuxbergi (as E. ajuthiae, synonym in literature) was previously described as being collected from fresh water, but recent research has shown that the species has only been collected from brackish water.[6]

Remarkably, some onchidiid species are completely terrestrial.[14] Semperoncis montana (synonym in literature: Platevindex apoikistes and Semperella montana) and Platevindex ponsonbyi are the only known terrestrial species in the Onchidiidae.[2] They live in high-elevation rainforests in Borneo and the Philippines.[2]

Life habits

All these slugs breathe air. The marine ones breathe and move around and feed during low tide, when the water recedes and the slugs are exposed to the air.

Genera

Genera in the family Onchidiidae include:[15]

Synonymized genera
  • Arctonchis Dall, 1910: synonym of Onchidella J. E. Gray, 1850
  • Elophilus Labbé, 1935: synonym of Labbella Starobogatov, 1970
  • Eudrastus Gistel, 1848: synonym of Peronia Fleming, 1822
  • Lessonia Labbé, 1934: synonym of Lessonina Starobogatov, 1976
  • Lessonina Starobogatov, 1976: synonym of Peronia Fleming, 1822[5]
  • Occidentella Hoffmann, 1929: synonym of Onchidella J. E. Gray, 1850
  • Onchis Férussac, 1821: synonym of Peronia Fleming, 1822
  • Oncidiella P. Fischer & Crosse, 1878: synonym of Onchidella J.E. Gray, 1850
  • Oncidina Plate, 1893: synonym of Onchidina Semper, 1882
  • Oncidium Agassiz, 1846: synonym of Onchidium Buchannan, 1800
  • Oncis Plate, 1893: synonym of Platevindex H. B. Baker, 1938[17]
  • Paraoncidium Labbé, 1934: synonym of Onchidina Semper, 1882[9]
  • Peronella Mörch, 1863: synonym of Onchidella J.E. Gray, 1850
  • Peroniella Starobogatov, 1976 : synonym of Onchidella J. E. Gray, 1850
  • Quoya Labbé, 1934: synonym of Peronia J. Fleming, 1822
  • Quoyella Starobogatov, 1976: synonym of Quoya Labbé, 1934
  • Semperella Labbé, 1934 synonym of Semperoncis Starobogatov, 1976
  • Watsoniella Hoffmann, 1928: synonym of Hoffmannola Strand, 193

References
  1. Rafinesque C. S. (1815). Analyse de la nature ou tableau de l'univers et des corps organisés. Palerme, 223 pp., page 142.
  2. Dayrat B. (2009). "Review of the current knowledge of the systematics of Onchidiidae (Mollusca: Gastropoda: Pulmonata) with a checklist of nominal species". Zootaxa. 2068: 1–26. doi:10.11646/zootaxa.2068.1.1. S2CID 4821033., preview.
  3. Hoffmann, H. (1928). "Zur Kenntnis der Oncidiiden". Zoologische Jahrbücher(Jena). 55: 29–118.
  4. Labbé, A. (1934). "Les Silicodermés (Labbé) du Museum d'Histoire Naturelle de Paris. Première partie: Classification, formes nouvelles ou peu connues". Annales de l'Institut Océanographique de Monaco. 14: 73–246.
  5. Goulding, Tricia C.; Khalil, Munawar; Tan, Shau Hwai; Dayrat, Benoît (4 June 2018). "Integrative taxonomy of a new and highly-diverse genus of onchidiid slugs from the Coral Triangle (Gastropoda, Pulmonata, Onchidiidae)". ZooKeys (763): 1–111. doi:10.3897/zookeys.763.21252. ISSN 1313-2970. PMC 5996013. PMID 29896045.
  6. Dayrat, Benoît; Goulding, Tricia C.; Apte, Deepak; Bhave, Vishal; Comendador, Joseph; Quang, Ngô Xuân; Tan, Siong Kiat; Tan, Shau Hwai (24 November 2016). "Integrative taxonomy of the genus Onchidium Buchannan, 1800 (Mollusca, Gastropoda, Pulmonata, Onchidiidae)". ZooKeys (636): 1–40. doi:10.3897/zookeys.636.8879. PMC 5126514. PMID 27917062.
  7. Goulding, Tricia; Khalil, Munawar; Tan, Shau Hwai; Dayrat, Benoit (2018). "A new genus and a new species of onchidiid slugs from eastern Indonesia (Gastropoda: Euthyneura: Onchidiidae)". Raffles Bulletin of Zoology. 66: 337–349.
  8. Dayrat, Benoît; Goulding, Tricia C.; Apte, Deepak; Bhave, Vishal; Ngô Xuân, Quảng (27 July 2017). "A new genus and four new species of onchidiid slugs from South-East Asia (Mollusca: Gastropoda: Pulmonata: Onchidiidae)". Journal of Natural History. 51 (31–32): 1851–1897. doi:10.1080/00222933.2017.1347297. ISSN 0022-2933. S2CID 91153309.
  9. Dayrat, Benoît; Goulding, Tricia C. (29 June 2017). "Systematics of the onchidiid slug Onchidina australis (Mollusca: Gastropoda: Pulmonata)". Archiv für Molluskenkunde. 146: 121–133. doi:10.1127/arch.moll/146/121-133.
  10. Berry, A.J. (2 December 2012). Giese, A (ed.). Reproduction of Marine Invertebrates V4: Molluscs: Gastropods and Cephalopods. p. 220. ISBN 9780323153058.
  11. Morton, Brian (1992). The Marine Flora and Fauna of Hong Kong and Southern China III___ Fouling and pollution, morphology, behavious and physiology, Hoi Ha Wan. Hong Kong University Press. ISBN 978-962-209-295-2.
  12. Chung D. J. D.: Molluscan 'Love darts'? Hawaiian Shell News, 1986 May, Vol 34(5), pages 3–4. http://s190418054.onlinehome.us/HSN/1980/8605.pdf%5B%5D
  13. Barker G. M.: Gastropods on Land: Phylogeny, Diversity and Adaptive Morphology. in Barker G. M. (ed.): The biology of terrestrial molluscs. CABI Publishing, Oxon, UK, 2001, ISBN 0-85199-318-4. 1–146, cited pages: 139 and 142.
  14. Dayrat, Benoît (January 2010). "Anatomical Re-Description of the Terrestrial Onchidiid SlugSemperoncis montana(Plate, 1893)". Malacologia. 52 (1): 1–20. doi:10.4002/040.052.0101. ISSN 0076-2997. S2CID 84799367.
  15. World Register of Marine Species : Onchidiidae; accessed 13 September 2010 (with modifications).
  16. "Onchidella". Integrated Taxonomic Information System., accessed 13 September 2010.
  17. "WoRMS - World Register of Marine Species - Platevindex H. B. Baker, 1938". www.marinespecies.org. Retrieved 18 July 2018.

Further reading
  • Britton K. M. (1984). "The Onchidiacea (Gastropoda, Pulmonata) of Hong Kong with a worldwide review of the genera". Journal of Molluscan Studies. 50 (3): 179–191. abstract.
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