Acus sive belone unus piscium dehiscente propter multitudinem utero parit.
The pipefish (acus, or belone) is the one fish that gives birth by its womb splitting open, due to its great number [of young].
The family of the garfish are referred to generally as needlefish, which name directly corresponds to the Latin acus and the Greek βελόνη. However, that fish does not appear to be the one referred to here. The other, toothless fish called belone is identified with the greater pipefish (Syngnathus acus).
Pliny reports that the wound caused by the splitting womb grows back together after the birth (a partu coalescit vulnus) suggesting to us that perhaps a natural opening is meant, not merely one caused by injury to the animal.
Now, the pipefish is related to the seahorse and, as with the seahorse, the males carry the eggs till the young have hatched. This pipefish has a pouch in which the developing young are carried and which, apparently, has here been taken for the creature’s womb.