PMC

(A), utricle of a cave fish (male, SL = 35 mm) in dorsal view displaying the lapillus, otolithic membrane, macula utriculi, non-sensory epithelium, and the basal lamina. (B), Utricle and rostral most part of the saccule in caudal view. The black arrowhead labels the thickened part of the basal lamina that dorsally surrounds the rostral most region of the macula sacculi. (C), macula utriculi and the rostral most part of the macula sacculi in lateral view illustrating the closeness of the two maculae to each other. (D), macula utriculi and lapillus in dorsal view illustrating the three parts of the macula utriculi, namely the striola, lacinia, and cotillus and the amount of the macula overlain by the otolith. (E), Orientation pattern of ciliary bundles on the macula utriculi of a surface fish female (Río Oxolotán, SL = 34 mm) and (F), and on the lacinia of the right macula utriculi of a cave fish male (SL = 30 mm). Note that the orientation pattern of the lacinia was inferred from other surface fish individuals. The dashed line in (E) and (F) shows the change of the orientation pattern with ciliary bundles revealing the opposing orientation of ciliary bundles in the striola region and labels the change of the orientation in the lacinia. BL, basal lamina; d, dorsal; la, lateral; lap, reconstruction based on organic remains of the lapillus; NSE, non-sensory epithelium; me, medial; Msa, macula sacculi; Mu, macula utriculi; OM, otolithic membrane; r, rostral. Scale bars = 100 µm.

The macula utriculi and macula sacculi were transfected with Cy3-siRNA/TAT-DRBD through the RWM and stained with Alexa 488 Phalloidin (green) and To-Pro-3 (blue). Cy3-siRNAs are shown in the hair cells of the macula utriculi after 24 h with a stronger signal in peripheral dark cells (a). Cy3 fluorescence was also visible in hair cells of the macula sacculi after 24 h, but a weaker signal was present in the peripheral supporting epithelium than in the macula utriculi (d). This can be explained by the absence of dark cells in the macula sacculi. siRNAs were present everywhere in the hair cells of the macula utriculi and macula sacculi after 72 h (b, e) and still existed after 7 days (c, f), but the siRNA signal in the dark cells of the macula utriculi eliminated quickly than supporting cells region in the macula sacculi.

Phalloidin-labeled macula utriculi, macula sacculi and macula lagenae of the three investigated cichlid species. E. maculatus shows a distinctly broader lacinia of the macula utriculi (A), a larger macula lagenae (D), and a wider ostium (see explanation in Figure ) of the macula sacculi (G) than H. guttatus(C, F, I) and S. tinanti(B, E, H). The red squares indicate the patches on the macula lagenae and the macula sacculi chosen for ciliary bundle counts. a, anterior; d, dorsal; me, medial. Scale bars, 100 μm (A-C, G-I), 50 μm (D-F).

Projection of the 2D orientation patterns of ciliary bundles onto the 3D models of the macula utriculi. (A-B) Macula utriculi of S. tinanti in dorsal (A) and medial (B) views. (C) Macula utriculi of the black molly in medial view. Especially the strongly curved lacinia illustrates the value of orientation patterns shown in 3D. a, anterior; d, dorsal; l, lateral.