Overview

• The peer‑reviewed analysis assembled the pygmy seahorse genome and compared it with other seahorses and fish to pinpoint lineage‑specific changes.
• Researchers report 438 genes missing and 635 rendered nonfunctional, alongside losses of nearby regulatory elements affecting growth and development.
• The developmental gene hoxa2b is nonfunctional, and CRISPR–Cas9 tests in zebrafish reproduced a shortened, juvenile‑like head shape consistent with snout suppression.
• The species shows a striking reduction of immune genes, including missing MHC genes, representing the smallest known vertebrate immune‑gene set according to the authors.
• The team argues these losses facilitated tight symbiosis with gorgonian corals and improved camouflage, and they suggest immune reduction may help tolerate embryos during male pregnancy.