Table 1 Comparison of main and accessory olfactory system components in rodent, frog, zebrafish and lamprey *note – teleost fish do not have a recognized vomeronasal organ nor an accessory olfactory bulb

Peripheral

Cell Type

Pseudostratified Ciliated Columnar [29]

Ciliated [30, 31]

Pseudostratified Ciliated Columnar [32, 33]

Pseudostratified Ciliated Columnar and Microvillous [34]

Pseudostratified Ciliated Columnar [35]

Microvillous [31]

Simple Ciliated Cuboidal [23, 24, 36]

Peripheral

Genes

OR, TAAR [10]

OR [37], V1R [9]

OR, TAAR, V1R [22]

OR [38], TAAR [39], V1R, V2R [17]

OR, V1R, V2R [10]

V2R [40]

OR, TAAR, V1R [15, 22]

Peripheral

Projections

To MOB [41]

To MOB and AOB [31, 42]

To MOB and DTN

To MOB [34]

To AOB [43]

To MOB and AOB [31, 44]

To MOB and DTN

Central

Cell Type

Mitral cells [45]

Mitral cells [42, 46]

Mitral cells [24, 33]

Mitral cells [47, 48]

Mitral cells [49]

Mitral cells [44, 50]

Mitral cells

Central

Glomeruli

Yes [51]

Yes, [42, 50]

Yes, loosely defined [52]

Yes [34, 47, 53, 54]

Yes [43]

Yes [44]

Yes, loosely defined [52]

Central

Secondary Projections

To olfactory cortex [55]

To olfactory amygdala [56]

To pallial areas and hypothalamus [26, 27]

To habenula/limbic system output pathway [54]

To amygdala (limbic area) and hypothalamus [57]

To piriform cortex [58]

To pallial areas and hypothalamus