{
  "id": 3761705,
  "title": "Can an original be found? Mitochondrial species identity does not predict nuclear genome similarity in the photosymbiotic jellyfish Cassiopea andromeda and C. xamachana",
  "url": "https://urgent.news/2026/08/27/can-an-original-be-found-mitochondrial-species-identity-does-not",
  "topic": "science",
  "section": "Science",
  "published": "2026-08-27T00:00:00.000Z",
  "source": {
    "name": "bioRxiv",
    "slug": "biorxiv",
    "url": "https://www.biorxiv.org/content/10.64898/2026.08.26.747389v1?rss=1"
  },
  "original_language": "en",
  "account": "The Upside-Down Jellyfish, Cassiopea, is a popular subject in cnidarian photosymbiosis research. Two closely related species, C. xamachana and the introduced C. andromeda, are commonly utilized in laboratory research across America and Europe. Researchers have now sequenced the genomes of 21 Cassiopea medusae from the Florida Keys, Bocas del Toro in Panama, and a laboratory line in Europe to determine if assigning mitochondrial species predicts nuclear genome similarity.\n\nSurprisingly, medusae from Florida carrying either C. xamachana or C. andromeda mitochondria types cannot be distinguished from one another based on their nuclear genomes, and geographic location is the primary factor influencing nuclear genetic structure. A population tree that groups the Floridian mitotypes as a single interbreeding unit is strongly supported, while a tree that respects mitochondrial species boundaries is rejected. The European C. andromeda laboratory line, however, clusters with Panamanian C. xamachana rather than with Floridian C. andromeda-mitotype animals.\n\nThe study also reveals evidence of variability in the symbiont communities of the hosts in Panama and presents two nearly-complete genomes of the Tenacibaculum and Endozoicomonas organisms. Collectively, these findings suggest that the hybridization zone between C. andromeda and C. xamachana may span across ocean basins, making it difficult to find a pure representative of either species. The researchers recommend that Cassiopea researchers establish new laboratory lines with well-documented genomes to avoid this issue.",
  "summary": "The Upside-Down Jellyfish, Cassiopea, has become a mainstay of cnidarian photosymbiosis research. Two nominal sister species, C. xamachana and the globally introduced C. andromeda, supply most of the medusae used in American and European laboratory research within this genus. As founder identity can shape experimental outcomes, here we utilize whole genome resequencing of 21 Cassiopea medusae…",
  "key_points": [],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}