Elysia pusilla

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Elysia pusilla
Elysiella pusilla.jpg
Elysia pusilla
Elysia pusilla.png
Elysia pusilla about 1 cm in length
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Subclass: Heterobranchia
Family: Plakobranchidae
Genus: Elysia
Species:
E. pusilla
Binomial name
Elysia pusilla
(Bergh, 1872) [1]
Synonyms

Elysiella pusillaBergh, 1872

Elysia pusilla is a species of small sea slug, a marine gastropod mollusk in the family Plakobranchidae. It is a sacoglossan.

Contents

Elysia pusilla feeds on the calcified green alga Halimeda and incorporates functioning chloroplasts into its body, thus it is known as a solar-powered sea slug. It is found in shallow water in tropical regions of the Indo-Pacific wherever its host species grows.

Elysia pusilla are part of Sacoglossa, also known as the solar powered sea slugs and might be the most common Elysia species. [2] Sacoglossans are marine gastropods that ingest the chloroplast of algae. Sacoglossa has two superfamilies under it: Plakobranchidae and Oxynoace. The distinguishing feature between the two superfamilies is having a shell or being able to store chloroplast. Oxynoacea consists of three shelled families, all of whom don't photosynthesize with the algae they consume. However, they might be able to retain the chloroplast and use it as camouflage. Elysia pusilla is under the superfamily Plakobranchidae. The majority of the organisms in this superfamily are shell less, however, many develop a shell before hatching. Sacoglossa are the only metazoans on earth to exhibit kleptoplasty. [3] The only other organisms known to have this ability are single celled protists. [3]

Elysia pusilla and Elysia stylifera are each other's closest living relative. [3] They are often found together on a calcareous algae called Halimeda. [3] The sea slugs use the chemicals to protect themselves and their eggs. [4]

Description

Elysia pusilla is a cryptic sea slug which grows to about 3 centimetres (1.2 in) long. Its colour and shape both match that of the alga on which it is feeding; on older foliage it is flattened and a mottled pale green, on fresh new growth it is a brighter shade of green and on the cylindrical shoots that sometimes develop, it adopts a more circular cross section. [5]

Elysia pusilla are green in color and are typically 1-3 cm in length. [6] They are a cryptic species whose morphology matches the algae they feed on. Elysia pusilla are found exclusively on calcareous green algae, called Halimeda taenicola. The shape or texture influences the shape of the nudibranch. When living on broader segments of Halimeda, Elysia tends to be more flattened, while cylindrical segments of Halimeda have more cylindrical-shaped Elysia. [5]

This uniform green color is due to the ingested chloroplast that is stored in their tissue. They occasionally have white dots as well. Many of the Elysia species have parapodia, wing-like flaps, that are spread out and flattened to increase surface area and cephalic tentacles. [3] Specifically in Elysia pusilla, the parapodia are partially fused. Because their parapodia are smaller than other species, some scientists place them in a separate genus. [7] Located on top of its head are white, club-shaped sensory organs called rhinophores or cephalic tentacles. [3] The rhinophores may be used to detect chemical stimuli which can act as an indicator to metamorphosize. As part of the mollusca phylum and under the class Gastropod, Elysia pusilla has a soft body, ventralized foot for moving, radula and long guts used for feeding, and  a mantle used for protection. They are also bilaterally symmetrical, with three layers of tissues that allow them to form a body cavity, called a coelom, and have organs independent of the body wall.

Nudibranchs have no gills and breathe through their skin secondary gills using tentacle-looking things, called cerata, on their back. [8] In many nudibranchs, the cerata is a blood-filled tube that acts as an extension of the digestive system and can be used for defense. In another nudibranch species, such as the aeolids, the cerata contain sacs called cnidosacs that store nematocysts, stinging cells from cnidarians which have been acquired from feeding. [8]

Distribution

Sacoglossa are found in temperate and tropical oceans, with most of them living in the Central Pacific. Specific species, such as Elysia pusilla are found in the tropical indo Pacific Ocean, with other species living in the Caribbean. [6] They are found between the depths of 0.5 and 0.9 m. [9]

Ecology

Diet and Feeding

As a member of the class gastropod, Elysia pusilla uses a radula, which is a ribbon of chitinous teeth to feed. In general, the radula is used to scrape algae and slice seaweeds. They have digestive enzymes secreted by the digestive and salivary glands to aid in digestion. Sea slugs extract the green algae by piercing the cell wall and storing the plastids in their digestive glands. [10]

Many nudibranchs are stenophagous, meaning that they only feed on one to two organisms. [11]

Specifically, Elysia pusilla feeds on a green calcareous algae called Halimeda, but can also use the chloroplast and genes from the algae to photosynthesize, thus producing its own energy.

Kleptoplasty

Elysia pusilla and other sea slugs in this superorder are able to take the plastids from the algae they eat and incorporate it into their living tissue in a process called kleptoplasty. This is a special form of parasitic endosymbiosis. The organism uses the chloroplast they eat and store it in their tissues. The chloroplast lines the digestive tract, which allows the organisms to survive for several months solely relying on kleptoplasty. [12] Specifically, the algae is digested, but the plastids are still intact, allowing it to be incorporated into the host organism. The chloroplast from the algae the organisms feed on are kept alive for weeks to months. Many of the proteins in chloroplast are also encoded in the genome of the sea slugs. The proteins synthesized by the sea slugs are moved into the chloroplast, allowing it to survive for long periods in the host cells. Through kleptoplasty, the organisms are able to survive for months just relying on this process. [13]

Life Cycle

Reproduction

The eggs are usually laid in a spiral formation. [11] They usually hatch after 6 days. [14]

The reproduction method poecilogony, [15] an intraspecific reproduction method in which there are two different forms of larvae modes, is quite rare in the animal kingdom. [16] The different egg sizes, or egg dimorphism, are able to produce two kinds of larvae: planktotrophic and lecithotrophic larvae. [17] Lecithotroph, meaning “feeding on yolk” refers to the larvae relying on the yolk sac produced by the mother as they are not able to feed. [18] Planktophic larvae are larvae that must feed on plankton in order to grow and develop. [18] There are only thirteen cases of poecilogony reported in marine organisms, with seven in spionid polychaetes and six in gastropods- five sacoglossan gastropods and littorinimorph gastropod. [19] Elysia pusilla may be the sixth organism in the order sacoglossans to be capable of this. In Elysia pusilla and Elysia zuleicae, the planktotrophic larvae are more common, but some still produce the lecithotrophic larvae. [20] The smaller size of the lecithotrophic larvae in sacoglossans in comparison to other heterobranchs may allow for developmental plasticity in response to the environment. The frequency of the size difference among the eggs allows sacoglossans to get around the one mode reproductive methods. [20]

Hermaphrodites

Fertilization in gastropods is mainly internal. Many are hermaphrodites, [11] either simultaneous hermaphrodites, meaning they gave both female and male sex genitiles or sequential hermaphrodites, meaning they switch between female and male.

Mating between simultaneous hermaphrodites involves the two individuals lining up on the right side since their genitals are on the right side of their body, close to their head. [21] During mating, both individuals are fertilized and involve the transfer of love darts which includes stabbing and hormonal manipulation. In some species, the hook of the love dart will break off.

Larval stage

As Protostomes, under Bilateria, this species’ blastopore formed the mouth first, then the anus. The way the early cells cleaved is a spiral. The coelom is formed by the masses of mesoderms splitting.

Cleavage

The cleavage is spiral and holoblastic. This means that the upper tier of the animal's cells, called micromeres, are situated at a 45° angle to the lower tier of the macromeres. This means that the daughter blastomeres are at a 45° angle. [22]

Movement

Like other gastropods, Elysia pusilla uses their ventral foot to move. They use mucus to aid in gliding. Muscle contractions and expansions cause the mucus to spread out, allowing the animal to glide across the surface.

See also

Related Research Articles

<span class="mw-page-title-main">Sea slug</span> Group of marine gastropods

Sea slug is a common name for some marine invertebrates with varying levels of resemblance to terrestrial slugs. Most creatures known as sea slugs are gastropods, i.e. they are sea snails that over evolutionary time have either completely lost their shells, or have seemingly lost their shells due to having a greatly reduced or internal shell. The name "sea slug" is most often applied to nudibranchs, as well as to a paraphyletic set of other marine gastropods without obvious shells.

<span class="mw-page-title-main">Sacoglossa</span> Clade of gastropods

Sacoglossa, commonly known as the sacoglossans or the "solar-powered sea slugs", are a superorder of small sea slugs and sea snails, marine gastropod mollusks that belong to the clade Heterobranchia. Sacoglossans live by ingesting the cellular contents of algae, hence they are sometimes called "sap-sucking sea slugs".

<span class="mw-page-title-main">Kleptoplasty</span> Form of algae symbiosis

Kleptoplasty or kleptoplastidy is a process in symbiotic relationships whereby plastids, notably chloroplasts from algae, are sequestered by the host. The word is derived from Kleptes (κλέπτης) which is Greek for thief. The alga is eaten normally and partially digested, leaving the plastid intact. The plastids are maintained within the host, temporarily continuing photosynthesis and benefiting the host.

<i>Elysia subornata</i> Species of gastropod

Elysia subornata is a species of small sea slug, a marine opisthobranch gastropod mollusk in the family Plakobranchidae.

<i>Elysia chlorotica</i> Species of gastropod

Elysia chlorotica is a small-to-medium-sized species of green sea slug, a marine opisthobranch gastropod mollusc. This sea slug superficially resembles a nudibranch, yet it does not belong to that clade. Instead it is a member of the clade Sacoglossa, the sap-sucking sea slugs. Some members of this group use chloroplasts from the algae they eat for photosynthesis, a phenomenon known as kleptoplasty. Elysia chlorotica is one species of such "solar-powered sea slugs". It lives in a subcellular endosymbiotic relationship with chloroplasts of the marine heterokont alga Vaucheria litorea.

<i>Elysia viridis</i> Species of gastropod

Elysia viridis, the sap-sucking slug, is a small-to-medium-sized species of green sea slug, a marine opisthobranch gastropod mollusc in the family Plakobranchidae.

<span class="mw-page-title-main">Plakobranchidae</span> Family of gastropods

Plakobranchidae is a family of sea slugs, marine opisthobranch gastropod mollusks in the superfamily Plakobranchoidea. They superficially resemble nudibranchs but they are sacoglossans, members of the clade Sacoglossa within the Opisthobranchia.

<i>Elysia</i> (gastropod) Genus of gastropods

Elysia is a genus of sea slugs, marine gastropod molluscs in the family Plakobranchidae. These animals are colorful sea slugs, and they can superficially resemble nudibranchs, but are not very closely related to them. Instead they are sacoglossans, commonly known as sap-sucking slugs.

<i>Elysia crispata</i> Species of gastropod

Elysia crispata, common name the lettuce sea slug or lettuce slug, is a large and colorful species of sea slug, a marine gastropod mollusk.

<i>Elysia timida</i> Species of gastropod

Elysia timida is a species of sacoglossan sea slug, a marine opisthobranch gastropod mollusk. Found in the Mediterranean and nearby parts of the Atlantic, it is herbivorous, feeding on various algae in shallow water.

<i>Elysia maoria</i> Species of gastropod

Elysia maoria is a species of marine gastropod mollusk in the family Plankobranchidae. It is found off of New Zealand.

<i>Plakobranchus ocellatus</i> Species of gastropod

Plakobranchus ocellatus is a species of sea slug, a sacoglossan, a marine opisthobranch gastropod mollusk in the family Plakobranchidae. It is found in shallow water in the Indo-Pacific region.

<i>Elysia catulus</i> Species of gastropod

Elysia catulus is a small species of sea slug, a marine gastropod mollusc in the family Plakobranchidae. This sea slug resembles a nudibranch, but it is not closely related to that order of gastropods, instead it is a sacoglossan. The specific name "catulus" comes from the Greek and means "little cat", referring to the superficial resemblance that the head of this slug bears to the head of a cat.

<i>Elysia australis</i> Species of gastropod

Elysia australis is a species of sea slug, a marine gastropod mollusc in the family Plakobranchidae. This sea slug resembles a nudibranch, but it is not closely related to that order of gastropods, instead it is a sacoglossan. It occurs in Australia.

<i>Elysia diomedea</i> Species of gastropod

Elysia diomedea is a species of sea slug, a marine gastropod mollusc in the family Plakobranchidae.

<i>Elysia trisinuata</i> Species of gastropod

Elysia trisinuata is a species of sea slug, a marine gastropod mollusc in the family Plakobranchidae. This sea slug resembles a nudibranch but is not closely related to that order of gastropods, instead belonging to another clade, Sacoglossa, the "sap-sucking" sea slugs.

Elysia rufescens is a species of sea slug, a marine gastropod mollusc in the family Plakobranchidae. This sea slug resembles a nudibranch but is not classified in that order of gastropods, instead belonging to a closely related clade, Sacoglossa, the "sap-sucking" sea slugs. This species was first described by Pease from Tahiti in 1871.

Elysia serca, the seagrass elysia or Caribbean seagrass elysia, is a species of sea slug, a marine gastropod mollusc in the family Plakobranchidae. Although this sea slug resembles a nudibranch, it is not a nudibranch; it belongs to the clade, Sacoglossa, the "sap-sucking" sea slugs. It was first described by Marcus in 1955 from specimens found in Brazil.

<i>Costasiella ocellifera</i> Species of gastropod

Costasiella ocellifera is a small (5–13 mm) species of sea slug, a shell-less marine gastropod mollusk in the family Costasiellidae. Costasiella ocellifera, and other members of the Costasiellidae family are often mistakenly classified as nudibranchs because they superficially resemble other species of that group, but they are actually a part of the Sacoglossa superorder of sea slugs, also known as the “sap-sucking sea slugs,” "crawling leaves" or the "solar-powered sea slugs." C. ocellifera was discovered by Simroth in 1895, and was initially classified as Doto ocellifera. The Brazilian species, Costasiella liliana, is a synonym of C. ocellifera.Costasiella ocellifera shows long-term retention of functional kleptoplasty.

<i>Elysia marginata</i> Species of sea slug

Elysia marginata is a marine gastropod in the family Plakobranchidae. It is known for its ability to regenerate its whole body and heart after autotomizing it from its head.

References

  1. ↑ Bergh, L.S.R. (1872). Malacologische Untersuchungen. In: C.G. Semper, Reisen im Archipel der Philippinen, Wissenschaftliche Resultate. Band 2, Heft 3: 137-176, Pls. 17-20.
  2. ↑ "Variable larval development". Patrick J. Krug. Retrieved 2022-04-24.
  3. 1 2 3 4 5 6 Phuong, Mark (2010). "Solar Powered Slugs: Biology of Sacoglossans on Mo'orea, French Polynesia" (PDF)– via University of California, Berkeley, California.{{cite journal}}: Cite journal requires |journal= (help)
  4. ↑ "Halimeda slug (Elysia pusilla)". www.wildsingapore.com. Retrieved 2022-04-24.
  5. 1 2 Elysiella pusilla The Sea Slug Forum. Retrieved 2012-01-22.
  6. 1 2 "Elysia pusilla, Flat Elysia". www.sealifebase.ca. Retrieved 2022-04-24.
  7. ↑ "Elysia pusilla – Solar Sea Slug Blog" . Retrieved 2022-04-27.
  8. 1 2 "Jean-Michel Cousteau : Ocean Adventures . Nudibranchs - Splendid Sea Slugs | PBS". www.pbs.org. Retrieved 2022-04-27.
  9. ↑ "Elysia pusilla (Bergh, 1871)". www.gbif.org. Retrieved 2022-04-24.
  10. ↑ Christa, Gregor; Händeler, Katharina; Kück, Patrick; Vleugels, Manja; Franken, Johanna; Karmeinski, Dario; Wägele, Heike (2015-03-01). "Phylogenetic evidence for multiple independent origins of functional kleptoplasty in Sacoglossa (Heterobranchia, Gastropoda)". Organisms Diversity & Evolution. 15 (1): 23–36. doi:10.1007/s13127-014-0189-z. ISSN   1618-1077. S2CID   13591866.
  11. 1 2 3 "Feature: Nudibranchs". Oceana Europe. Retrieved 2022-04-24.
  12. ↑ Laetz; Jerschabek, Elise Marie; Wägele, Heike (2017-10-11). "Chloroplast digestion and the development of functional kleptoplasty in juvenile Elysia timida (Risso, 1818) as compared to short-term and non-chloroplast-retaining sacoglossan slugs". PLOS ONE. 12 (10): e0182910. Bibcode:2017PLoSO..1282910L. doi: 10.1371/journal.pone.0182910 . PMC   5636068 . PMID   29020043.
  13. ↑ Evertsen, Jussi; Burghardt, Ingo; Johnsen, Geir; Wägele, Heike (2007-03-07). "Retention of functional chloroplasts in some sacoglossans from the Indo-Pacific and Mediterranean". ProQuest   208084181 – via Springer Link.{{cite journal}}: Cite journal requires |journal= (help)
  14. ↑ "Elysia pusilla: main page". seaslugsofhawaii.com. Retrieved 2022-04-27.
  15. ↑ Wiggering, Benedikt; Neiber, Marco T.; Gebauer, Katharina; Glaubrecht, Matthias (2020-06-26). "One species, two developmental modes: a case of geographic poecilogony in marine gastropods". BMC Evolutionary Biology. 20 (1): 76. doi: 10.1186/s12862-020-01644-1 . ISSN   1471-2148. PMC   7318368 . PMID   32591013.
  16. ↑ Knott, K. Emily; McHugh, Damhnait (2012-04-11). "Introduction to symposium: Poecilogony--a window on larval evolutionary transitions in marine invertebrates". Integrative and Comparative Biology. 52 (1): 120–127. doi: 10.1093/icb/ics037 . ISSN   1557-7023. PMID   22495287.
  17. ↑ Knott, K. Emily; McHugh, Damhnait (2012-04-11). "Introduction to Symposium: Poecilogony—A Window on Larval Evolutionary Transitions in Marine Invertebrates". Integrative and Comparative Biology. 52 (1): 120–127. doi: 10.1093/icb/ics037 . PMID   22495287.
  18. 1 2 Gienger, Jonathan (2013-05-22). "Invertebrate Embryology: Planktotrophy versus lecithotrophy". Invertebrate Embryology. Retrieved 2022-04-24.
  19. ↑ Wiggering, Benedikt; Neiber, Marco T.; Gebauer, Katharina; Glaubrecht, Matthias (2020-06-26). "One species, two developmental modes: a case of geographic poecilogony in marine gastropods". BMC Evolutionary Biology. 20 (1): 76. doi: 10.1186/s12862-020-01644-1 . PMC   7318368 . PMID   32591013.
  20. 1 2 Vendetti, Jann E.; Trowbridge, Cynthia D.; Krug, Patrick J. (2012-06-01). "Poecilogony and Population Genetic Structure in Elysia pusilla (Heterobranchia: Sacoglossa), and Reproductive Data for Five Sacoglossans that Express Dimorphisms in Larval Development". Integrative and Comparative Biology. 52 (1): 138–150. doi: 10.1093/icb/ics077 . PMID   22659202 – via Oxford Academic.
  21. ↑ True Facts: Freaky Nudibranchs , retrieved 2022-04-24
  22. ↑ "Elysia pusilla (Bergh 1871) - Encyclopedia of Life". eol.org. Retrieved 2022-04-24.

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