Genome evolution Abstract Jellyfish medusae are a distinctive life-cycle stage of medusozoan cnidarians. They are major marine predators, with integrated neurosensory, muscular and organ systems. The genetic foundations of this complex form are largely unknown. We report the draft genome of the hydrozoan jellyfish Clytia hemisphaerica and use multiple transcriptomes to determine gene use across life-cycle stages. Medusa, planula larva and polyp are each characterized by distinct transcriptome signatures reflecting abrupt life-cycle transitions and all deploy a mixture of phylogenetically old and new genes. Medusa-specific transcription factors, including many with bilaterian orthologues, associate with diverse neurosensory structures.
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Select Page Clytia hemisphaerica by Anna Ferraioli Jan 25, The life cycle of a jellyfishe from a cell-type perspective , Animal life cycles , people 0 comments Clytia hemisphaerica is a hydrozoan of the Campanulariidae family. This species was chosen some years ago as a promising model for molecular and cellular studies in development and evolution thanks to its phylogenetic position, the ease of culturing all life cycle stages under laboratory condition and its accessibility to different experimental techniques.
Furthermore, this tiny jellyfish represents an important potential contribution to the understanding of fundamental scientific questions about animal complexity possessing significant features such as a complex nervous system, sensory organs and striated muscle which characterize the medusa form.
Fertilization is external and follows the simultaneous release of gametes from males and females medusae. Around three days after the fertilization the planula is ready to undergo metamorphosis and to give rise to a primary feeding polyp. The polyp propagates on the sea bed forming a colony within two polyp types coexist: the gonozooid, specialized for medusa budding and the feeding form, gastrozooid.
Newly released baby medusa reach maturity after weeks and the entire life cycle can be completed in a minimum of weeks. Houliston, T. Momose and M. Manuel Clytia hemisphaerica: a jellyfish cousin joins the laboratory. Trends Genetics Author.
Clytia hemisphaerica has emerged as a promising model organism as its life cycle, small size, and relatively easy upkeep make it conducive to experimental manipulation and maintenance in a laboratory setting. Ovulated eggs are fertilized externally and take approximately 24 hours to develop into planula. The ciliated planula will swim freely until the proper external cues, for instance, experimental treatment with CsCl,  trigger the metamorphic process. The planula can undergo its metamorphosis into a polyp as soon as three days after fertilization. Once the proper external cue is received, the planula stops swimming and attaches itself to a substrate via its aboral or aboral-lateral pole what was previously the front end of the swimming planula. After attaching itself to a substrate, the planula contracts along its oral—aboral axis and so forms a flattened holdfast to anchor itself to the substrate.