An improved whole life cycle culture protocol for the hydrozoan genetic model Clytia hemisphaerica

Abstract

The jellyfish species Clytia hemisphaerica (Cnidaria, Hydrozoa) has emerged as a new experimental model animal in the last decade. Favorable characteristics include a fully transparent body suitable for microscopy, daily gamete production and a relatively short life cycle. Furthermore, whole genome sequence assembly and efficient gene editing techniques using CRISPR/Cas9 have opened new possibilities for genetic studies. The quasi-immortal vegetatively-growing polyp colony stage provides a practical means to maintain mutant strains. In the context of developing Clytia as a genetic model, we report here an improved whole life cycle culture method including an aquarium tank system designed for culture of the tiny jellyfish form. We have compared different feeding regimes using Artemia larvae as food and demonstrate that the stage-dependent feeding control is the key for rapid and reliable medusa and polyp rearing. Metamorphosis of the planula larvae into a polyp colony can be induced efficiently using a new synthetic peptide. The optimized procedures detailed here make it practical to generate genetically modified Clytia strains and to maintain their whole life cycle in the laboratory.

Muscle systems and motility of early animals highlighted by cnidarians from the basal Cambrian

“…Two-week-old Clytia hemisphaerica medusae, newly released Eirene sp . medusae, one-month-old Chrysaora colorata and Pelagia noctiluca metaephyrae were raised in the laboratory (Villeranche-sur-mer) following Lechable et al (2020) and Ramondenc et al (2017) culture protocols. Fixation followed by Phalloidin (actin) and Hoechst (nuclei) staining were performed on the four species as described for Clytia hemisphaerica in Sinigaglia et al (2020).…”

Feeding Behavior, Shrinking, and the Role of Mucus in the Cannonball Jellyfish Stomolophus sp. 2 in Captivity

“…Our system was designed specifically to avoid physical damage to the umbrella of medusae. This was done as an alternative to the relatively expensive Kreisel tank, commonly used to maintain live medusae because of the laminar flow it produces (e.g., [42,43]). The system consisted of an 8 L cylindric plastic bucket placed inside a 20 L plastic bucket.…”

“…live medusae because of the laminar flow it produces (e.g., [42,43]). The system consisted of an 8 L cylindric plastic bucket placed inside a 20 L plastic bucket.…”

Functional modules within a distributed neural network control feeding in a model medusa

“…Culture of the Clytia life cycle was carried out in accordance with published protocols (Lechable et al, 2020), with the exception of the culture tank design. Our circulating system at Caltech uses the same overall flow design as in Lechable et al, 2020, but uses modifications of zebrafish tanks (Pentair) to provide either high flow for polyp slides held in glass slide racks (Fisher, cat#02-912-615) in small tanks, or low flow for jellyfish maintained in large tanks. Jellyfish tanks use a curved plastic insert with a large nylon mesh near the back overflow outlet to keep jellyfish in the tank; a constant speed 5rpm DC motor (Uxcell) attached to a dimmer switch (to tune the rotation speed) is then used to create a constant circular current.…”