Lung jellyfish
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Lung jellyfish ( Rhizostoma pulmo ) |
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| Rhizostoma pulmo | ||||||||||||
| ( Macrì , 1778) |
The lung jellyfish ( Rhizostoma pulmo ) is one of three species from the genus Rhizostoma in the family of the root-mouth jellyfish (Rhizostomatidae). The scientific name is based on the shape in the medusa stage. On average, the lung jellyfish reaches an umbrella diameter of 60 cm, but in individual cases it can also grow up to 90 cm, which makes it one of the largest species of jellyfish in the Mediterranean. You can easily recognize them by their white to partially pink shade with a blue to purple border. The umbrella has stinging cells, which cannot be dangerous for humans and only in exceptional cases lead to discomfort. Throughout its life, it feeds on plankton in all of its various stages of development, which is caught in its tentacles or arms.
Distribution and occurrence
The lung jellyfish is found on all European Atlantic coasts, in the English Channel as well as in the North and Baltic Seas and is widespread in the entire Mediterranean up to the Black Sea . It is the most common offshore jellyfish species in these areas. It was also the second most frequently sighted jellyfish species on the Catalan coast in the summers from 2007 to 2009. One focus of their distribution is the Mar Menor , a 135 km² sea lagoon in southeastern Spain, in which several 100,000 medusas are counted every year. Medusas can be observed from the beginning of May, but the main time is from July to the end of September.
The number of jellyfish is increasing worldwide and seasonal, massive occurrences of jellyfish in schools, so-called "jellyfish blooms", are observed more and more frequently. This phenomenon has already been observed several times in R. pulmo , for example in the North and South Adriatic Sea and in the Black Sea. Such jellyfish blooms are a huge problem for tourism and commercial fishing as they wash large quantities of dead jellyfish onto the beaches and clog fishing nets. So far it is only possible to speculate about the reasons and conditions for this, but it is assumed that this phenomenon is related to rising water temperatures, as the jellyfish can then develop better and to the decline in predators due to overfishing.
Life cycle and anatomy
The life cycle of the pulmonary jellyfish is characterized by a change from a benthic to a pelagic way of life as well as sexual and asexual reproduction. Adult medusa reproduce sexually by releasing their germ cells into the open water, which forms a fertilized egg cell. This then develops into the so-called planular larva , which has two layers (endo- and ectoderm) and ciliate. This then sticks to a rock, which starts the benthic phase of the life cycle. It develops into a polyp, the scyphostoma. This has an approximate length of 1.7 mm and an average of 16 tentacles, which line the peristome (mouth disk) and are used for nutrition. The scyphostome is able to reproduce asexually, by so-called budding on the calyx (calyx) and stalk and thereby producing other polyps. At this stage the winter is survived and it is also assumed that the polyp can survive more than one winter and is therefore perennial.
The scyphostomas then produce ephyral larvae , the next stage of development, through a process called strobilation . The calyx is lengthened and the mouth disc thickens, whereupon a constriction is created directly under the tentacle crown. Then the Ephyra precursor (Primordia) sits on the Scyphostom. This process can be repeated up to 8 times, with all precursors then sitting on the polyp at the same time. The development of these precursors also takes place simultaneously and they are then released into the open water at the same time. The polyp then takes about two weeks to grow back to adult size with tentacles to produce more ephyries.
Ephyrae are 3.5 mm in diameter, have eight arms and are pelagic. The development to the medusa stage is characterized by eight phases. The gastric system undergoes changes and the characteristic structures at the end of the arms develop. The development time strongly depends on the temperature and the environment. The juvenile medusa then has an umbrella diameter of 5–10 cm and eight arms.
Web links
Individual evidence
- ↑ Divers 'humbled' by Cornwall jellyfish encounter. bbc.com , July 17, 2019, accessed July 16, 2020 .
- ↑ Mills, CE Hydrobiologia (2001) 451: 55. doi: 10.1023 / A: 1011888006302 .
- ↑ Lilley, M., Houghton, J., & Hays, G. (2009). Distribution, extent of inter-annual variability and diet of the bloom-forming jellyfish Rhizostoma in European waters. Journal of the Marine Biological Association of the United Kingdom, 89 (1), 39-48. doi: 10.1017 / S0025315408002439 .
- ↑ a b c Fuentes, V., Straehler-Pohl, I., Atienza, D. et al. Mar Biol (2011) 158: 2247. doi: 10.1007 / s00227-011-1730-7 .
- ↑ Arai, MN Hydrobiologia (2009) 616: 241. doi: 10.1007 / s10750-008-9588-5 .
- ↑ CIESM (Commission Internationale pour l'Exploration Scien-tifique de la mer Méditerranée) (2001) Gelatinous zooplankton outbreaks: theory and practice. CIESM Workshop Series No. 14, Monaco. Available at www. ciesm.org/publications/Naples01.pdf
- ^ A b Mariottini GL, Pane L. Mediterranean jellyfish venoms: a review on scyphomedusae. Mar Drugs. 2010; 8 (4): 1122-52. Published 2010 Apr 4. doi: 10.3390 / md8041122 .
- ↑ Lakkis, S. "Aggregations of the scyphomedusa Rhizostoma pulmo in the Lebanese coastal waters during the summer of 1986." Jellyfish blooms in the Mediterranean, Proceedings of the II Workshop on Jellyfish in the Mediterranean Sea. MAP Technical Reports Series. No. 47th 1991.
- ^ Straehler-Pohl, Ilka, Chad L. Widmer, and Andre C. Morandini. Characterizations of juvenile stages of some semaeostome Scyphozoa (Cnidaria), with recognition of a new family (Phacellophoridae). Zootaxa 2741.1 (2011): 1-37.