Table 1.

Synaptic morphology and synaptic connectivity (HC hair cell, Fib fiber, LF low frequency, HF high frequency, Syn synapse, ND not determined). The table summarizes part of the available information obtained in the various preparations. The references are examples from which information was obtained, but which do not represent a complete list. Data were obtained by electron microscopy except for those obtained by immunofluorescence (Khimich et al. 2005)

Species/Organ	Hair cell	Ribbon: shape, size (nm), and number	Afferent connectivity	References
Mammalian cochlea	Inner hair cells	Ellipsoid; 3 axes: 55, 100–200, 200–600; 5–30	1 HC: 5–30 Fib; 1 Fib: 1 HC; 1 Fib: 1 Syn	Liberman 1980; Francis et al. 2004; Khimich et al. 2005
	Outer hair cell (apex)	Elongate; 100–200; 8–10		Liberman et al. 1990
Avian papilla	Tall hair cells:	Round; 120 (apex), 210 (base); 15	1 HC: 1–3 Fib; 1 Fib: 1(−3) HC*; 1 Fib: several Syn	Fischer 1992; Martinez-Dunst et al. 1997
	Short hair cells	0 (HF) −10 (LF)
Mammalian crista ampullaris	Type I hair cell	Spheroid: 90, Rod: 200–300. ~17	1 HC: 1 Fib; 1 Fib: 1–5 HC; 1 Fib: 1–5 Calyces with 15 Syn each	Goldberg et al. 1990
	Type II hair cell	Barrel: 200 Elongate 150–300. ~18	1 HC: 3–6 Fib; 1 Fib (bouton): −30 HC; 1 Fib (bouton): 50–80 Syn	Lysakowski and Goldberg 1997 Fernandez et al. 1988
Avian crista ampullaris	Type I hair cell type II hair cell	Spheroid; rod ND	1 Fib: up to 12 HCs	Lysakowski 1996
Turtle crista ampullaris	Type I hair cell type II hair cell	Spheroid; ND	1 Fib: up to 8 HCs	Lysakowski 1996; Brichta and Peterson 1994
Frog crista ampullaris	Type II hair cell	Spheroid; ND		Lysakowski 1996
Fish crista ampullaris	Type II hair cell	Spheroid 15–25 central; 4–5 peripheral		Wegner 1982; Chang et al. 1992; Lysakowski 1996