title: Hydrozoan insights in animal development and evolution.
abstract: The fresh water polyp Hydra provides textbook experimental demonstration of positional information gradients and regeneration processes. Developmental biologists are thus familiar with Hydra, but may not appreciate that it is a relatively simple member of the Hydrozoa, a group of mostly marine cnidarians with complex and diverse life cycles, exhibiting extensive phenotypic plasticity and regenerative capabilities. Hydrozoan species offer extensive opportunities to address many developmental mechanisms relevant across the animal kingdom. Here we review recent work from non-Hydra hydrozoans - hydromedusae, hydroids and siphonophores - shedding light on mechanisms of oogenesis, embryonic patterning, allorecognition, stem cell regulation and regeneration. We also highlight potential research directions in which hydrozoan diversity can illuminate the evolution of developmental processes at micro- and macro-evolutionary time scales.
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), 181 chemin du Lazaret, 06230, Villefranche-sur-mer, France. Electronic address: leclere@obs-vlfr.fr.
authors.forename: Lucas
authors.initials: L
authors.lastname: Leclère
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), 181 chemin du Lazaret, 06230, Villefranche-sur-mer, France.
authors.forename: Richard R
authors.initials: RR
authors.lastname: Copley
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), 181 chemin du Lazaret, 06230, Villefranche-sur-mer, France.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Momose
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), 181 chemin du Lazaret, 06230, Villefranche-sur-mer, France.
authors.forename: Evelyn
authors.initials: E
authors.lastname: Houliston
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000235:genetics; D019143:Evolution, Molecular; D006829:Hydra / Q000235:genetics* / Q000254:growth & development; D037402:Hydrozoa / Q000235:genetics* / Q000254:growth & development; D008018:Life Cycle Stages / Q000235:genetics; D009866:Oogenesis / Q000235:genetics; D010802:Phylogeny; D012038:Regeneration / Q000235:genetics*; D013234:Stem Cells / Q000378:metabolism