P6 wild type | | |

VCN cell size | Pearson’s *r* = 0.014; *p* = 0.975; *n* = 8 | Pearson’s *r* = 0.393; *p* = 0.335; *n* = 8 |

MNTB cell size | — | Pearson’s *r* = –0.375; *p* = 0.360; *n* = 8 |

P6 Fmr1 KO | | |

VCN cell size | Pearson’s *r* = 0.675; *p* = 0.096; *n* = 7 | Pearson’s *r* = –0.544; *p* = 0.068; *n* = 12 |

MNTB cell size | — | Pearson’s *r* = –0.785; *p* = 0.037; *n* = 7 |

P14 wild type | | |

VCN cell size | Pearson’s *r* = –0.239; *p* = 0.507; *n* = 10 | Pearson’s *r* = 0.655; *p* = 0.008; *n* = 15 |

MNTB cell size | — | Pearson’s *r* = 0.440; *p* = 0.203; *n* = 10 |

P14 Fmr1 KO | | |

VCN cell size | Pearson’s *r* = –0.176; *p* = 0.650; *n* = 9 | Pearson’s *r* = 0.772; *p* = 0.0012; *n* = 14 |

MNTB cell size | — | Pearson’s *r* = 0.048; *p* = 0.902; *n* = 9 |