In addition to common cell types, tissues may also contain rare or sparsely- 132 The -4725sox10:Lifeact-mRFPruby construct was generated using the Gateway Tol2 133 kit (Kawakami, 2007; Kwan et al., 2007) . The p5E -4725sox10 promoter (Dutton et 
Zebrafish embryos and larvae were fixed in 4% paraformaldehyde (PFA) in 145 phosphate-buffered saline (PBS) for two hours at room temperature or overnight at 146 4°C. Zebrafish were washed three or more times with PBS, and permeabilised by 147 incubation in PBS-Triton X-100 (0.2% Triton for 32-48 hpf embryos, 1% Triton for 148 later stages) for several hours at 4°C until staining. which was then used for performing statistical analyses and making graphs. 279 As described above, olfactory rods differ from olfactory cilia in terms of size, shape, 280 cytoskeletal composition, and distribution in the OE. We therefore hypothesised that 281 olfactory rod cell projections would not be affected by mutations that disrupt the 282 formation of cilia. To test this, we examined fish mutant for ift88, which codes for a 326 Given the superficial similarity in appearance of the olfactory rod to hair-cell 327 stereocilia in phalloidin stains, and a report of a rare cell type bearing stereocilia-like (Schulte, 1972) . Olfactory rods in the other four species measured 1 µm 454 in diameter and 10 µm in length. Rods were either found to exist solitarily or in a 455 group; interestingly, it was noted that olfactory cilia were sparse in areas where rods 456 occurred in a group (Yamamoto & Ueda, 1978) . images showing no effect of 500 µM neomycin treatment for 60 minutes on olfactory rods, using 751
Alexa-phalloidin as a marker; anterior to the top, lateral to the right. Arrowheads mark olfactory rods. 