Scleromystax barbatus, (Quoy & Gaimard, 1824) (Quoy & Gaimard, 1824)

Dalcin, Roger Henrique & Abilhoa, Vinícius, 2024, Discriminating Scleromystax barbatus (Siluriformes: Callichthyidae) populations from Atlantic Rainforest streams employing otolith shape, Neotropical Ichthyology (e 230129) 22 (1), pp. 1-15 : 6

The lapillus otoliths of

S. barbatus

display an elongation in the superior-inferior axis, with uneven wavy bottom edges, while the gibbus maculae is large, prominent, occupying much of the surface of the otolith and the sulcus is short, wide and contours the inner gibbus maculae region ( Fig. 2 ). The ANOVA-like permutation test for the Fourier/Wavelet coefficients indicated significant differences between otoliths of males of Scleromystax barbatus from southern and southeastern areas in the Atlantic Rainforest biome, and also between otoliths of males from southeastern areas and females of southern areas of the Atlantic Rainforest biome ( Tab. 2 ).

The Fourier and Wavelet reconstructions showed differences among the mean otolith outlines between the southern and southeastern areas ( Fig. 3 ). The highest variation was observed for the extremum anterior, the posterior region and medial regions of the sulcus. Otoliths from the southeastern areas are more elongated in these portions, mainly in the Wavelet reconstruction. Conversely, high overlaps in the lateral sulcus and in the lateral and medial gibbus maculae regions were observed.

The CAP assessments indicated that otolith shape was not homogeneous among the southern and southeastern regions, for both coefficients (ANOVA-like, P <0.01). The first two principal coordinates axes explained 94.4% of the total Fourier coefficient variation and 94.3% of the Wavelet coefficient variation ( Fig. 4 ).

Figures

FIGURE 2 | Ventral view of the left lapillus otoliths of Scleromystax barbatus from streams in the southern (VR, GR, DM, CU, and PE) and southeastern (AR, PM, and AE) regions of the Atlantic Rainforest biome. A (Anterior), M (Medial).

FIGURE 3 | Mean otolith shape based on the Fourier (above) and Wavelet (below) reconstructions for males and females of Scleromystax barbatus from southern and southeastern regions in the Atlantic Rainforest biome. Lines represent the groups: SeFe (Females from the southeastern region), SeMa (Males from the southeastern region), SFe (Females from the southern region), SMa (Males from the southeastern region).

FIGURE 4 | Otolith shapes of males and females of Scleromystax barbatus from southern and southeastern regions in the Atlantic Rainforest biome employing a Canonical Analysis of Principal Coordinates (CAP) applied to Fourier (above) and Wavelet (below) coefficients. Bold letters represent the mean canonical coordinates surrounding the standard error for each population. Lines represent the groups: SeFe (Females from the southeastern region), SeMa (Males from the southeastern region), SFe (Females from the southern region), SMa (Males from the southeastern region).