Lucernaria janetae

Lucernaria janetae is an exceptionally large stalked jellyfish discovered on deep-sea hydrothermal vents on the East Pacific Rise in 2003 and described in 2005.[1]

Lucernaria janetae
Scientific classification
Kingdom: Animalia
Phylum: Cnidaria
Class: Staurozoa
Order: Stauromedusae
Family: Lucernariidae
Genus: Lucernaria
Species:
L. janetae
Binomial name
Lucernaria janetae
Collins and Daly, 2005[1]

Name

This species was named after Dr Janet Voight of the Field Museum of Natural History in Chicago "in recognition of her commitment to discovering and describing deep-sea invertebrates".[1]

Description

L. janetae is an exceptionally large stalked jellyfish. It has eight distinct arms which are tipped with clusters of about 100 secondary tentacles. Small juvenile forms of this species sometimes have small, ovate primary tentacles but these are always absent in the adult organism. This species does not have anchor tentacles. The 'umbrella' (calyx) of this organism is goblet-shaped and creamy white with a hint of green or orange. It is up to 100mm wide and 50mm deep, a significantly larger calyx size than those of other members of this genus. The 'stalk' (peduncle) is the same colour as the calyx. Unlike the peduncles of many Stauromedusae, which often have 4 chambers, the peduncle of L. janetae only has a single chamber.[1]

Distribution and habitat

It is the only known species of Lucernaria from the Pacific Ocean.[1] All other members of this genus inhabit the Atlantic Ocean.[1] It is the first and currently the only known Stauromedusan described as living near a hydrothermal vent.[1] L. janetae has been found at depths ranging between 2500-2700m.[1][2] When originally described it was believed to be the second deepest-living member of the genus Lucernaria,[1] the deepest living known Stauromedusan was then Lucernaria bathyphila, recorded at a depth of 2800m.[3] However a recent study found organisms which could be L. janetae at 3001m.[4] As of 2006, these organisms are, the deepest living known Stauromedusae. Unlike most Stauromedusae, which are solitary organisms, L. janetae forms large populations and, where it occurs, is the dominant macrofauna.[1]

Feeding

L. janetae eats small pelagic crustaceans[1] which probably include amphipods, a common prey of Stauromedusae, since amphipods (Halice hesmonectes) were found in the same region as a possible population of L. janetae.[2]

Lifecycle

L. janetae has 8 gonads which are shaped like lances and arranged in pairs extending from the centre of the calyx to the base of the arms.[1] They give the organism an orange/pink colour when reproductively active. The scientists who originally identified L. janetae have speculated that this species may also be capable of asexual reproduction.[1] This had not been shown for any Stauromedusan at the time the paper was written, although it has subsequently been suggested for Haliclystus antarcticus.[5] Stauromedusae are believed to be sessile, except in the larval stage. The larvae are able to move by crawling but are believed not to migrate large distances. It is therefore presently unclear as to how L. janetae is able colonise multiple unconnected vents.[2][4]

References
  1. A. G. Collins & M. Daly (2005). "A New Deepwater Species of Stauromedusae, Lucernaria janetae (Cnidaria, Staurozoa, Lucernariidae), and a Preliminary Investigation of Stauromedusan Phylogeny Based on Nuclear and Mitochondrial rDNA Data". The Biological Bulletin. 208 (3): 221–230. doi:10.2307/3593154. JSTOR 3593154. PMID 15965127.
  2. Lutz, Richard A.; Desbruy?res, Daniel; Shank, Timothy M.; Vrijenhoek, Robert C. (1998). "A deep-sea hydrothermal vent community dominated by Stauromedusae". Deep-Sea Research Part II: Topical Studies in Oceanography. 45 (1–3): 329. doi:10.1016/S0967-0645(97)00047-7. NB. The Stauromedusan population described in this paper can not be definitively identified due to a lack of retrieved specimens, however, Collins and Daly tentatively identify this population as L. janetae.
  3. Deep Sea News - "From The Desk of Zelnio: Lucernaria janetae" Archived 2011-09-07 at the Wayback Machine
  4. Lutz, R; Collins, A; Annis, E; Reed, A; Bennett, K; Halanych, K & Vrijenhoek, R (2006). "Stauromedusan populations inhabiting deep-sea hydrothermal vents along the southern East Pacific Rise" (PDF). Cahiers de Biologie Marine. 47: 409–413.
  5. Vollmer, Steve; Miranda, Lucília S.; Collins, Allen G.; Marques, Antonio C. (2010). Vollmer, Steve (ed.). "Molecules Clarify a Cnidarian Life Cycle – The "Hydrozoan" Microhydrula limopsicola Is an Early Life Stage of the Staurozoan Haliclystus antarcticus". PLoS ONE. 5 (4): e10182. doi:10.1371/journal.pone.0010182. PMC 2854716. PMID 20418959.
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