Crown jellyfish

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Crown jellyfish
Nausithoe aurea

Nausithoe aurea

Systematics
without rank: Holozoa
without rank: Multicellular animals (Metazoa)
without rank: Tissue animals (Eumetazoa)
Trunk : Cnidarians (Cnidaria)
Class : Umbrella jellyfish (Scyphozoa)
Order : Crown jellyfish
Scientific name
Coronatae
Vanhöffen , 1892

The crown jellyfish (Coronatae) are an order of the umbrella jellyfish (Scyphozoa). There are currently 51 rsp. 57 species described. They occur to very great depths and are also called deep-sea jellyfish .

Geographical occurrence and distribution

The coronates have been detected in the littoral as well as in the deep sea of boreal , subtropical and tropical seas .

features

Most of the species of coronatae are metagenetic , i.e. That is, they have a polyp and a medusa stage . In some species, however, the medusa stage is reduced or the medusa remain at an ephyra-like stage of development throughout their life .

Their polyps, which are characterized by a typical peridermal tube made of chitin , are called Stephanoscyphistomae according to Gerhard Jarms (* 1948/49?). The retractable head part of the soft body of the polyp protrudes from this tube when it is extended. The lower soft body is tetraradially symmetrical and has four perradial gastric pockets, which are formed by four interradial gastric septa. A muscle cord lies against the wall in each septum. The head part carries the tentacles and has an annular channel in its interior, which opens into the gastric pockets perradially via four short radial channels.

In the species that form a medusa stage, the central part of the exumbrella is clearly delimited from the marginal area, which consists of marginal lobes, tentacles, pedals and static organs, by an annular furrow. The medusa generation is formed by a process known as strobilation , in which the transverse division of the soft polyps is used to pinch off discs that are transformed into ephyries. After detaching from the polyp, the ephyries grow into sexually mature medusa in the open water.

In these jellyfish, the surface of the umbrella is constricted by an annular furrow and divided into an upper bell and a rim with lobes. This wreath gives the German name for this order. The screen can be arched high, have the shape of a thimble, or be completely flat. The maximum diameter is 38 centimeters. Deep-sea forms are usually purple, dark red or black-brown in color; the deeper the habitat, the darker their color.

The polyps of the animals are up to nine centimeters long and are surrounded by a peridermal covering made of chitin, which only exposes the polyp head. In the crown jellyfish ( Periphylla periphylla ) the polyp stage is absent.

Way of life

The medusa of almost all species release their germ cells into the free water and then die. The fertilization and the subsequent development up to the planular larva takes place in open water. The larvae look for a suitable substrate and transform into sessile polyps. In addition to the normal metagenetic alternation of generations, development cycles often occur within the Nausithoidae , which are reduced in different ways. In Nausithoe racemosa and Nausithoe eumedusoides , the medusa generation is reduced to short-lived eumedusoids. The germ cells are already placed in the septa of the polyps before the medusoid formation. N. racemosa releases the germ cells directly into the open water, whereas N. eumedusoides takes care of brood care. In the hermaphroditic medusoids, the germ cells develop into the planula. The species Nausithoe aurea, on the other hand, is able to follow two different developmental paths. On the one hand, normal, separate-sex medusas with eight gonads can be formed; on the other hand, vegetative reproduction is possible through the conversion of ephyries to planuloids. An exclusively asexual mode of reproduction is found in the species Nausithoe planulophora . The epiphytes formed by strobilation are converted directly into planuloids. T. zibrowii has a particularly modified development cycle in which no medusa appear; only female individuals appear who reproduce parthenogenetically. The egg cells develop in a structure called the Eisack up to the planula, which then turns back into a polyp after a short planktonic phase. In contrast to the sexual (amphimictic), parthenogenetic mode of reproduction in the animal kingdom generally occurs rather rarely, but is described within many different phyla. A parthenogenetic mode of reproduction is e.g. B. in the rotifers (Rotatoria), abdominal curls (Gastrotricha), molluscs (Mollusca), annelids (Annelida), syringes (Sipunculida), arthropods (Arthropoda), tardigrades (Tardigrada) and echinoderms (Echinodermata). A whole series of parthenogenetic species occur in the cnidarians. Werner described a parthenogenetic mode of reproduction in the anthomeduse Margelopsis haeckeli . Within the Anthozoa, a parthenogenetic mode of reproduction occurs, for example in Alcyonium hiberniculum , Tubastraea and Pocillopora . The sea anemones Cereus pendunculatus and Sagartia troglodytes can produce offspring in a bisexual as well as parthenogenetic way. Parthenogenesis is unisexual reproduction in which the egg cell develops without fertilization. There are a number of different forms of parthenogenesis, and in the laboratory it can also be triggered artificially, through chemical or physical stimuli. A basic distinction is made between the so-called apomictic parthenogenesis, in which no recombination takes place, from the automictic, in which a reduction division occurs and the complete set of chromosomes is then restored by certain upregulation mechanisms. Amphitocia, in which both sexes can arise from the unfertilized egg cells (e.g. annelids), is separated from arrhenotocia, in which only males develop (e.g. bees, mites) and thelytocia, in which only ever Females arise (e.g. daphnia, rotatoria). There is also a distinction between the obligatory parthenogenesis, in which the egg cells remain unfertilized for many generations (e.g. rotifers, ostracods) and the cyclical parthenogenesis (heterogony), in which after several generations with parthenogenetic reproduction, a generation with bisexual reproduction again occurs (e.g. aphids). A geographical parthenogenesis occurs particularly among arthropods, in which an amphimictic and a parthenogenetic race develops within a species (Fioroni, 1987). According to current knowledge, T. zibrowii is a species in which exclusively female animals occur, which reproduce parthenogenetically. So far, nothing was known about the precise processes of this parthenogenesis. Previous observations during the long culture period lead to the hypothesis that it is an obligatory and automictic parthenogenesis. In addition, against the background of the differently reduced development cycles within the Nausithoidae family, the hypothesis can be made that T. zibrowii is the form in which the regressive evolution of the medusa generation has advanced furthest. Based on these hypotheses, this work investigates both the question of whether the biological investigation of the Eisack formation provides evidence of a previously existing medusa generation, and the question of whether evidence of the occurrence of a meiosis in the formation of egg cells can be found.

Systematics

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literature

Web links

Commons : Common Jellyfish  - Collection of images, videos and audio files
  • Integrated Taxonomic Information System: Coronatae

Individual evidence

  1. ↑ Marymegan Daly, Mercer R. Brugler, Paulyn Cartwright, Allen G. Collin, Michael N. Dawson, Daphne G. Fautin, Scott C. France, Catherine S. McFadden, Dennis M. Opresko, Estefania Rodriguez, Sandra L. Romano & Joel L. Stake: The phylum Cnidaria: A review of phylogenetic patterns and diversity 300 years after Linnaeus. Zootaxa, 1668: 127-182, Wellington 2007 ISSN  1175-5326 Abstract - PDF
  2. ^ World Register of Marine Species
  3. ↑ a b c d B. Werner; H.-E. Gruner (Ed.): Cnidaria . P. 305. In: Textbook of special zoology . Volume 1: Invertebrates  - Part 2: Cnidaria, Ctenophora, Mesozoa, Plathelmithes, Nemertini, Entoprocta, Nemathelminthes, Priapulida . Fischer, Jena 1984
  4. ↑ G. Jarms, U. Båmstedt, H. Tiemann, MB Martinussen, JH Fosså: The holopelagic life cycle of the deep-sea medusa Periphylla periphylla (Scyphozoa, Coronatae) . Sarsia, 1999. 84, pp. 55-65
  5. ↑ B. Werner: Contribution to the evolution in the genus Stephanoscyphus (Scyphozoa, Coronatae) and ecology and regeneration qualities of Stephanoscyphus racemosus Komai . Publs. Seto Mar. Biol. Lab., 1970. 18, pp. 1-20
  6. ↑ B. Werner: Stephanoscyphus (Scyphozoa, Coronatae) and its direct descent from the fossil Conulata . Helgoland scientific marine studies, 1966. 13, pp. 317-451
  7. ↑ B. Werner: Stephanoscyphus (Scyphozoa, Coronatae) and its direct descent from the fossil Conulata. Helgoländer wiss. Meeresunters., 1966. 13, pp. 317-451
  8. ↑ a b B. Werner: Stephanoscyphus eumedusoides n. Spec. (Scyphozoa, Coronatae), a cave polyp with a new evolution mode. Helgoland scientific marine survey. 1974. 26, pp. 434-463
  9. ↑ B. Werner: New investigations on systematics and evolution of the class Scyphozoa and the phylum Cnidaria . Publs. Seto Mar. Biol. Lab. 20, pp. 35-61
  10. ^ A b F. Lang da Silveira, AC Morandini: Nausithoe aurea n. Sp. (Scyphozoa: Coronatae: Nausithoidae), a species with two pathways of reproduction after strobilation: sexual and asexual. Contributions to Zoology, 1997. 66, pp. 235-246
  11. ^ F. Lang da Silveira, AC Morandini: Asexual reproduction in Linuche unguiculata (Swartz, 1788) (Scyphozoa: Coronatae) by planuloid formation through strobilation and segmentation . Proc. Biol. Soc. Washington, 1998. 111, pp. 781-794
  12. ^ A b B. Werner, CE Cutress, JP Studebaker: Life cycle of Tripedalia cystophora Conant (Cubomedusae) . Nature, 1971. 232, pp. 582-583
  13. ↑ a b I. Sötje, G. Jarms: Detailed description of Thecoscyphus zibrowii Werner, 1984 (scyphozoa Coronatae) with remarks on the life cycle . Mitt. Hamb. zool. Mus. Inst., 1999. 96, pp. 5-13
  14. ^ A b C. M. Lively, SG Johnson: Brooding and the evolution of parthenogenesis: stratigy models and evidence from aquatic invertebrates . Proc. R. Soc. Lond. (Ser. B), 1994. 256, pp. 89-95
  15. ↑ B. Werner: About the reproduction of the anthomeduse Margelopsis haeckeli Hartlaub by subitan and permanent eggs and the dependence of their formation on external factors . Verh. Dt. Zool. Ges., Zool. Anz., Suppl., 1955. 18, pp. 124-133
  16. ↑ RN Hughes: A functional biology of clonal animals . Chapman and Hall, London 1989