Clytia photograph by Peter Schuchert

Study of Cnidarians can help to understand animal evolution, as they diverged very early in evolution from the more familiar "Bilaterians" such as vertebrates and insects.

There is a wide diversity of cnidarian species.

Clytia hemisphaerica is a hydrozoan, and member of the order Leptomedusae. Other cnidarians currently used in laboratories around the world include two anthozoans (the sea anemone Nematostella and the coral Acropora), and three other hydrozoans: Hydra, Hydractinia and Podocoryne.

Houliston's team are developing the cnidarian Clytia hemisphaerica as an experimental model for studies in cell and developmental biology.   
Various species of Clytia, including C. hemisphaerica, are found widely throughout the world.
The laboratory colonies were generated from adults collected in the Bay of Villefranche-sur-mer.

This species has a life cycle in three phases, with free swimming sexual medusae and planula larvae, and vegatatively propagating polyp colonies.

All stages can be conveniently maintained in the laboratory.

In our set-up,  Adults (up to 30 individuals) and polyp colonies are maintained in 5l glass beakers containing 3.5l sea water.

Medusae and polyps  are fed artemia (2-5 days after hatching) once or twice a day.  Avoid adding too many artemia at a time, otherwise the dead artemia rot and encourage growth of bacteria and fungi.

Sex determinantion is influenced by temperature. While some colonies produce medusae of only one sex, others will produce male medusae when kept at low temperatures (around 16 °C) and mainly females  at 18- 24°C (Carré & Carré, 2000*).
Baby medusae develop to maturity in about 2 weeks at 20°C if well fed.

Males and females can be easily distinguished by their gonads.

Clytria hemisphaerica gonads

We keep a 8h/16h dark/light cycle. The adults spawn 2h after the light stimulus.

Eggs and sperm can be collected following spawning into small dishes . Depending on maturity, feeding and age, female medusae will produce 5-20 eggs per day. Thus, a dish of 6-7 females should provide around  50- 100 eggs every day.

Good fertilisation rates are obtained if gametes are mixed withi 1 -1 1/2 hours of spawning, whioch gives time for microinjection before fertilisation.


The main research aim is to understand how the body plan is established during embryogenesis in Clytia, with particular emphasis on the role of localised maternal determinants, and studying oogenesis, oocyte maturation and genomics (transcriptome and genome sequencing).


Genetic resources: 

Available data

Data Experiment Size Version


Available individuals