Biodiversity & Conservation

St John’s jellyfish - Lucernariopsis cruxmelitensis

Lucernariopsis cruxmelitensis

Image Steve Trewhella - Lucernariopsis cruxmelitensis with distinctive maltese cross. Image width ca XX cm.
Image copyright information

  • #
  • #
Distribution map

Lucernariopsis cruxmelitensis recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

Why do the maps differ?

Sightings Have you seen Lucernariopsis cruxmelitensis?
If so please submit your record.

  • UK_BAP
Taxonomy icon Taxonomy Taxon English term
Phylum Cnidaria Sea anemones, corals, sea firs & jellyfish
Authority (Corbin, 1978)
Recent synonyms None
Map icon Recorded Distribution in Britain and Ireland The distribution of Lucernariopsis cruxmelitensis appears to be limited to the south-west of England, from Swanage to north Devon, and the Atlantic coasts of Ireland.
Habitat information icon Habitat information Lucernariopsis cruxmelitensis inhabits moderately-exposed rocky shores in the low intertidal and shallow sub-littoral zones. In contrast to most species of Stauromedusae it is rarely attached to Zostera spp. but, is often found on the algae Chondrus crispus and Mastocarpus stellatus.
Text page icon Description This stalked jellyfish is the smallest member of its family. Lucernariopsis cruxmelitensis has a translucent, maroon, broad funnel-shaped bell that can reach 1.2 cm in diameter and 0.8 cm in height. The bell is divided by hollow septa. The reproductive gonads are thick and linear, and arranged inside the bell in halves which join at the base and extend in a linear fashion to the arms. The 8 arms are arranged in a circle and well-developed with up to 35 tentacles each. Each of the tentacles has a rounded head. Unique to the Lucernariopsis cruxmelitensis is the arrangement of the nematocyst organs, which appear as white spots in the shape of a maltese cross. A distinguishing feature of Lucernariopsis cruxmelitensis is its stalkless appearance due to the base of the bell involuting around the stalk that is 0.8cm in height and attached to the substratum by a broad basal disc. Tentacle anchors are absent in Lucernariopsis cruxmelitensis compared to Haliclystus salpinx.
Identifying features
  • Stalk-less appearance.
  • 8 arms.
  • Up to 35 tentacles on each arm.
  • Translucent, maroon colour.
  • White spots on surface of bell form a distinctive maltese cross.
  • No tentactle anchors.
Additional information icon Additional information Individuals of Lucernariopsis cruxmelitensis are gonochoristic and reproduce through external fertilization whereby gametes are shed into the water from the gonads situated on the sepal walls. Once fertilized, the zygotes develop into vermiform planula larvae. The planula larvae attach to the substratum and undergo a period of encystment followed by development into the adult form via a small larval polyp.

This review can be cited as follows:

Saskiya Richards 2008. Lucernariopsis cruxmelitensis. St John’s jellyfish . Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 19/05/2013]. Available from: <http://www.marlin.ac.uk/speciesinformation.php?speciesID=3734>