Finding. The fan sponge everyone called Phakellia robusta is at least three species once you read mitochondrial cox1. Gracia-Sancha, Riesgo, Diaz and colleagues add nuclear 28S and morphology and name two of them: Phakellia pallida and Phakellia pusilla. Spicules will not save you; the forms overlap. The molecules do not. The two new species live together in the Northeast Atlantic and the Mediterranean, with P. pallida tending deeper. A group I intron already known from P. robusta cox1 shows up in some P. pusilla individuals, not others, and not in P. pallida. Old Mediterranean and southern Northeast Atlantic "P. robusta" records need a second look.
Why this paper matters
On a mitochondria desk this is a barcode-and-intron note. Cox1 still delimits sponges when morphology lies, and the intron is a reminder that animal mtDNA is not a closed, intron-free circle in every phylum. If you maintain poriferan mitochondrial references, the polymorphism matters: presence of that intron is not a species badge.
It is not a paper about OXPHOS, mitophagy, or disease. The score says so.
What they actually measured
Integrative taxonomy. cox1 and 28S trees. Depth and range tables. Intron presence at the previously reported P. robusta insertion site, scored per individual. A warning that the historical distribution of P. robusta is contaminated by the new names.
How to read the score
High 50s. Real mtDNA character (cox1 plus a group I intron), thin organelle biology. Confidence is high for the three-species molecular split as stated.
Caveats
Two loci. No complete mitogenomes in the abstract. Historical re-identification is a suggestion. Intron mechanism is not pursued.
What to do with it
Update sponge cox1 databases and do not assume a cox1 intron means P. robusta. If you do not curate poriferan mtDNA, skip it.