Facetotecta

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Facetotecta
A Y-psigon escaping from its y-cyprid
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Thecostraca
Subclass: Facetotecta
Grygier, 1985
Family: Hansenocarididae
Itô, 1985
Genus: Hansenocaris
Itô, 1985
Species

See text

Facetotecta is a poorly known subclass of

neritic waters around Japan,[3] and the Mediterranean Basin, where they also survive in brackish water.[4]

History

The German zoologist

Cirripedia).[6]

Life cycle

  • Y-nauplius illustration
    Y-nauplius illustration
  • Y-cyprid illustration
    Y-cyprid illustration

Nauplius

Y-nauplii are 250–620 micrometres (0.010–0.024 in) long,

cephalic shield, from which the group derives its name.[7] The abdomen is relatively long, and also ornamented.[2] In common with other thecostracans, Facetotecta pass through five naupliar instars before undergoing a single cyprid phase.[5]

Cyprid

The presence of a distinctive

cyprid larva indicates that the Facetotecta is a member of the Thecostraca. A number of species have been described on the basis of a y-cyprid alone.[8] As in barnacles, the cyprid is adapted to seeking a place to settle as an adult. It has compound eyes, can walk using its antennae, and is capable of producing an adhesive glue.[9]

Juvenile

In 2008, a juvenile form was artificially produced by treating y-larvae with the hormone 20-hydroxyecdysone, which stimulated ecdysis and the transition to a new life phase. The resulting animal, named the ypsigon, was slug-like, apparently unsegmented, and limbless.[9][10]

Adults

While they have never been seen, the adult facetotectans may be

endoparasites of other animals, some of which could be inhabitants of coral reefs.[11]

Species

Eleven species are currently recognised,[3] while one species which is assigned to Hansenocaris – H. hanseni (Steuer, 1905) – is of uncertain affinities:[5]

References

  1. ^ Chan, Benny K. K.; Dreyer, Niklas; Gale, Andy S.; Glenner, Henrik; et al. (2021). "The evolutionary diversity of barnacles, with an updated classification of fossil and living forms". Zoological Journal of the Linnean Society. 193 (3): 789–846.
    hdl:11250/2990967
    .
  2. ^ a b c d Joel W. Martin; George E. Davis (2001). An Updated Classification of the Recent Crustacea (PDF). Natural History Museum of Los Angeles County. p. 132. Archived from the original (PDF) on 2013-05-12. Retrieved 2009-12-14.
  3. ^ a b Daphne Cuvelier (April 4, 2005). "Hansenocaris Itô, 1985". World Register of Marine Species.
  4. S2CID 208372852
    .
  5. ^
    S2CID 2943845
    .
  6. S2CID 84126659
    .
  7. ^ Christopher Taylor (February 23, 2008). "The secret of y-larvae". Catalogue of Organisms.
  8. Raffles Bulletin of Zoology
    . 55 (2): 343–353.
  9. ^
    PMID 18598383
    .
  10. PMID 18492233
    .
  11. ^ Mark Grygier; Jens T. Høeg; Yoshihisa Fujita (July 2004). Introduction to the tremendous diversity of y-larvae (Crustacea: Maxillopoda: Thecostraca: Facetotecta) in inshore coral reef plankton at Sesoko Island, Okinawa, Japan (PDF). 10th International Coral Reef Symposium. Biodiversity and Diversification in the Indo-West Pacific. Okinawa, Japan. Archived from the original (PDF) on 2011-06-11.
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