Neoteny or not? The distribution of the hypophysial duct within the Galaxioidea
The hypophysial duct, a hollow tube of tissue linking the pituitary gland and the buccal cavity, was found in adults of all the galaxiid genera examined except Aplochiton and Paragalaxias. The pituitary structure in these genera, however, indicated that the duct was probably once present and has been subsequently lost. The duct was absent in the other galaxioid families, Retropinnidae and Lepidogalaxiidae. Mapping the distribution of the duct onto a DNA sequence‐based phylogeny suggests that the embryological duct was retained in a galaxiid ancestral to Aplochiton, with subsequent losses in Aplochiton and Paragalaxias.
No Supplementary Data