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Sea angel.jpg
Scientific classification e
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Subclass: Heterobranchia
Informal group: Opisthobranchia
Informal group: Pteropoda

Pteropoda (common name pteropods, from the Greek meaning "wing-foot") are specialized free-swimming pelagic sea snails and sea slugs, marine opisthobranch gastropods. Most live in top 10 m of the ocean and are less than 1 cm long. The monophyly of Pteropoda is the subject of a lengthy debate; they have even been considered as paraphyletic with respect to cephalopods.[1] Current consensus, guided by molecular studies, leans towards interpreting the group as monophyletic.[2]

Pteropoda encompasses the two clades Thecosomata, the sea butterflies, and Gymnosomata, the sea angels. The Thecosomata (lit. "case-body"[3]) have a shell, while the Gymnosomata ("naked body") do not. The two clades may or may not be sister taxa; if not, their similarity (in that they are both pelagic, small, and transparent, and both groups swim using wing-like flaps (parapodia) which protrude from their bodies) may reflect adaptation to their particular lifestyle.


The group Pteropoda was established by Georges Cuvier as "ptéropodes" in 1804.[4] François Péron and Charles Alexandre Lesueur thought the group to be larger, and so they also included the opisthobranch taxa (Phyllirhoë and Glaucus), the heteropoda taxa (Carinaria and Firola), and even the Ctenophora (Callianira). In 1810 these authors divided the whole group in two separate groups: those with a shell and those without a shell.

In 1824 Henri Marie Ducrotay de Blainville named these two groups Gymnosomata and Thecosomata and named the combining order Aporobranchia instead of Pteropoda.[5] He rejected the additional genera, except Phyllirhoë which he upgraded to a third group that he called Psilosomata. Only much later was Phyllirhoë classified within the order Nudibranchia.

Other attempts were made to describe the Pteropoda. John Edward Gray divided the Pteropoda into Dactylobranchia (with just the genus Cavolinia) and Pterobranchia (including all the other genera).[6] Cuvier (and his followers) did not accept the classification by de Blainville; they preferred the original classification as described in Le Règne Animal.

In 1829 Paul Rang followed the Cuvierian classification, but tried to include the character of having a distinct head or not.[7] The German naturalist Lorenz Oken went one step further and, for the sake of symmetry, wanted each order to contain four families and each family to contain four genera.[8] Pierre André Latreille divided the Pteropoda according to the size of their fins: "Macroptérygiens" (including only Pneumonoderma) and "Microptérygiens" (including all the others). In 1851 William Bullock Clark treated the Pteropoda as a family and emended the spelling to Pteropodidae (a name now used for a family of fruit bats)

Finally all these attempts were abandoned and, as more and more species were described as a result of several scientific expeditions, the classification of the Pteropoda into Thecosomata and Gymnosomata was generally adopted. Many of these new species were first described by French zoologists, for example Jean René Constant Quoy and Joseph Paul Gaimard, Paul Rang, Alcide d'Orbigny and Louis François Auguste Souleyet.

The relationship between these two clades is not unequivocally established, but it seems that they are sister taxa.[2]


Cladogram of genera and species of pteropods.

  Clione antarctica

  Pneumodermopsis spe


  Spongiobranchaea australis


  Pneumoderma violaceum


  Cymbulia sibogae

  Peracle reticulata


  Heliconoides inflatus


  Limacina retroversa

  Limacina antarctica


  Limacina lesueurii


  Limacina trochiformis


  Limacina bulimoides


  Creseis acicula

  Creseis virgula


  Styliola subula


  Hyalocylis striata


  Clio pyramidata

  Cuvierina atlantica


  Clio cuspidata


  Diacavolinia longirostris

  Cavolinia inflexa


  Diacria danae


  Diacria trispinosa

The phylogenetic tree has been inferred from 2,654 nuclear proteins (representing 834,394 concatenated amino acid positions).[9]

Vulnerability to ocean acidification[edit]

Unhealthy pteropod showing effects of ocean acidification

A study was conducted on the West Coast of the United States to see ocean acidification’s effects on pteropods.[10] Limacina helicina was used to test the sensitivity to decreasing pH.[10] This species of pteropod is potentially vulnerable to the corrosive waters associated with ocean acidification due to their calcium carbonate shell.[11] The shell of a pteropod was immersed in ocean water with the projected pH level that the water will reach by the year 2100. After a month and a half in the water, the shell had almost completely dissolved.[10]


Pteropods are found in all major oceans, usually 0–10 metres (0–33 ft) below the ocean surface and in all levels of latitude. Pteropods can be found lower than 10 meters, but in less amounts in terms of biomass, however pteropod distribution is more spread out deeper based on findings. This can be explained as Pteropods from tropical areas become more common in deeper areas. They are not found commonly in the deep sea, in fact, few live lower than 500 meters below sea level. Continental shelves, areas containing many opportunities for nutrients, and productivity are locations in which Pteropods are usually populous, according to patterns in data. Springtime is a peak season for pteropoda, as they reach higher populations, though data shows that pteropoda south of the equator are less abundant seasonally. In addition, current data suggests that, 93% of the world's pteropods are part of the Thecosomata family, while the 7% are Gymnosomata.[12]


  1. ^ Wägele, Heike; Klussmann-Kolb, Annette; Verbeek, Eva; Schrödl, Michael (2013). "Flashback and foreshadowing—a review of the taxon Opisthobranchia". Organisms Diversity & Evolution. 14: 133–149. doi:10.1007/s13127-013-0151-5.
  2. ^ a b Klussmann-Kolb, A.; Dinapoli, A. (2006). "Systematic position of the pelagic Thecosomata and Gymnosomata within Opisthobranchia (Mollusca, Gastropoda) - revival of the Pteropoda". Journal of Zoological Systematics and Evolutionary Research. 44 (2): 118. doi:10.1111/j.1439-0469.2006.00351.x.
  3. ^ "theco-". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  4. ^ Mémoire sur l'Hyale et Ie Pneumoderme; Ann. Mus. Hist. Nat. Paris., 4 p. 232)
  5. ^ Diet. d. Sci. Nat., t. xxxii. p. 271.
  6. ^ London Medical Repository, p. 235, 1821.
  7. ^ Manuel de l’histoire naturelle des mollusques et leurs coquilles
  8. ^ Description d'un genre nouveau de la classe des Ptéropodes, Ann. d. &i. Nat., ser. 1, t. V. p. 284, 1825.
  9. ^ Peijnenburg, Katja T. C. A.; Janssen, Arie W.; Wall-Palmer, Deborah; Goetze, Erica; Maas, Amy E.; Todd, Jonathan A.; Marlétaz, Ferdinand (2020-09-24). "The origin and diversification of pteropods precede past perturbations in the Earth's carbon cycle". Proceedings of the National Academy of Sciences. doi:10.1073/pnas.1920918117. ISSN 0027-8424. PMID 32973093.
  10. ^ a b c Bednaršek, N.; Feely, R. A.; Reum, J. C. P.; Peterson, B.; Menkel, J.; Alin, S. R.; Hales, B. (2014). "Limacina helicina shell dissolution as an indicator of declining habitat suitability owing to ocean acidification in the California Current Ecosystem". Proc. R. Soc. B. 281 (1785): 20140123. doi:10.1098/rspb.2014.0123. ISSN 0962-8452. PMC 4024287. PMID 24789895.
  11. ^ Comeau, S.; Gorsky, G.; Jeffree, R.; Teyssié, J.-L.; Gattuso, J.-P. (2009-09-04). "Impact of ocean acidification on a key Arctic pelagic mollusc (Limacina helicina)". Biogeosciences. 6 (9): 1877–1882. doi:10.5194/bg-6-1877-2009. ISSN 1726-4189.
  12. ^ N. Bednaršek, J. Možina, M. Vogt, C. O'Brien, and G. A. Tarling (10 Dec 2012). "The global distribution of pteropods and their contribution to carbonate and carbon biomass in the modern ocean". 4 (1): 20. Retrieved 18 June 2018. Cite journal requires |journal= (help)CS1 maint: multiple names: authors list (link)

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