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Brief Summary

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This is a very small Class, comprising a few species of curious structure. They are all of diminutive size, and all swim in the open ocean, rarely approaching the shore, except when washed thither by accident. They are all characterised by having a membranous expansion, resembling a large fin, on each side of the head. By means of these organs, the little Pteropod rows itself about in the open sea perpetually; being unfurnished with any means of crawling, or of affixing itself to any solid body. Some of these animals, as the genera Hyalæa and Cleodora for example, have the body enclosed in a shell of elegant form, and of a texture resembling the thinnest glass, for delicacy and transparency. The Cleodora pyramidata, one of the species of the latter genus, is of extreme delicacy and beauty. The shell is glassy and colourless; very fragile; nearly in the form of a triangular pyramid; with an aperture at its base, from which proceeds a long and slender glassy spine; and a similar spine projects from each side of the middle of the shell. The hinder part of the animal is globular and pellucid, and in the dark vividly luminous, presenting a singularly striking appearance, as it shines through its perfectly transparent lantern. Both of these are found floating in great numbers on the surface of the tropical sea.

Others are entirely destitute of a shelly covering, as is that little species which occurs in enormous profusion in the Arctic Seas, and which we now proceed to describe.

Genus Clio("Whale-food.")

These little creatures have an oblong membranous body, without a mantle; a head formed of two rounded lobes, each of which is furnished with three long tentacles, capable of being withdrawn into a fold of skin, or protruded at pleasure. The mouth, which is terminal, has two small fleshy lips; and two eyes, of elaborate structure, are placed at the back of the neck.

The species best known is that which is commonly called by our northern voyagers, Whale-food (Clione limacina). Though not more than an inch in length, it occurs in such countless millions as to form the principal part of the nourishment required by the most gigantic of living creatures. The Clio bears some slight resemblance to a butterfly just emerged from the chrysalis, before the wings are expanded. Near the head there is on each side a large fin or wing, by the motions of which it changes its place.These motions are amusing; and as the little creatures are so abundant, they make the dreary sea quite alive with their gambols as they dance merrily along. In swimming, the Clio brings the tips of its fins almost into contact, first on one side, then on the other. In calm weather they rise to the surface in myriads, for the purpose of breathing; but scarcely have they reached it before they again descend into the deep. Mr. Scoresby kept several of them alive in a glass of sea-water for about a month, when they gradually wasted away and died. The head of one of these little creatures exhibits a most astonishing display of the wisdom of God in creation. Around the mouth are placed six tentacles, each of which is covered with about three thousand red specks, which are seen by the microscope to be transparent cylinders, each containing about twenty little suckers, capable of being thrust out, and adapted for seizing and holding their minute prey.

Thus, therefore, there will be three hundred and sixty thousand of these microscopic suckers upon the head of one Clio: an apparatus for prehension perhaps unequalled in the creation.

-Philip Henry Gosse

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Gosse, P.H. Natural history, Mollusca. London, 1854.
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Jennifer Hammock (jhammock)
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Pteropoda

provided by wikipedia EN

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.

Taxonomy

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]

Evolutionary history

Pteropods are estimated to have originated during the Early Cretaceous, around 133 million years ago, with the diversification into the major lineages occurring during the mid-late Cretaceous. The oldest known fossil pteropod is a member of Limacinidae from the early-middle Campanian deposits of the San Juan Islands.[9][10]

Phylogeny

Cladogram of genera and species of pteropods. Pteropoda Gymnosomata

Clione antarctica

     

Pneumodermopsis spe

   

Spongiobranchaea australis

Pneumoderma violaceum

        Thecosomata Pseudothecosomata

Cymbulia sibogae

   

Peracle reticulata

    Euthecosomata Limacinoidea

Heliconoides inflatus

     

Limacina retroversa

   

Limacina antarctica

     

Limacina lesueurii

   

Limacina trochiformis

Limacina bulimoides

          Cavolinioidea

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).[11]

Vulnerability to ocean acidification

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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.[12] Limacina helicina was used to test the sensitivity to decreasing pH.[12] This species of pteropod is potentially vulnerable to the corrosive waters associated with ocean acidification due to their calcium carbonate shell.[13] 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.[12]

Distribution

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.[14]

References

  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 (2020-10-13). "The origin and diversification of pteropods precede past perturbations in the Earth's carbon cycle". Proceedings of the National Academy of Sciences. 117 (41): 25609–25617. doi:10.1073/pnas.1920918117. PMC 7568333. PMID 32973093.
  10. ^ A. W. Janssen, J. L. Goedert, Notes on the systematics, morphology and biostratigraphy of fossil holoplanktonic Mollusca, 24. First observation of a genuinely Late Mesozoic thecosomatous pteropod. Basteria 80, 59–63 (2016)
  11. ^ 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. 117 (41): 25609–25617. doi:10.1073/pnas.1920918117. ISSN 0027-8424. PMC 7568333. PMID 32973093.
  12. ^ 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.
  13. ^ 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.
  14. ^ 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". Earth System Science Data. 4 (1): 167–186. doi:10.5194/essd-4-167-2012. hdl:20.500.11850/60379. Retrieved 18 June 2018.{{cite journal}}: CS1 maint: multiple names: authors list (link)

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Pteropoda: Brief Summary

provided by wikipedia EN

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. Current consensus, guided by molecular studies, leans towards interpreting the group as monophyletic.

Pteropoda encompasses the two clades Thecosomata, the sea butterflies, and Gymnosomata, the sea angels. The Thecosomata (lit. "case-body") 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.

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Wikipedia authors and editors
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