The advanced paralarva of G. berryi at 8-10 mm ML has a spherical digestive gland rather than the spindle-shaped, obliquely-oriented digestive gland common to paralarvae of many (all?) other members of the genus.

Figure. Side view of a paralarva of G. berryi, 10 mm ML. Drawing from Young (1972).

The size of the juvenile at which the various hooks first develop is often distinctive of the species.

Figure. Chart of the size ranges over which hooks in juveniles of G. berryi first appear. Chart modified from Young (1972).