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Fig. 4 | Frontiers in Zoology

Fig. 4

From: Morphological and biochemical characterization of the cutaneous poison glands in toads (Rhinella marina group) from different environments

Fig. 4

Morphological characteristics of poison glands of type PAR, typical of parotoids. (a) Part of the syncytium (syn) with low number of nuclei (n) and the typical arrangement in layers. The first more external thin layer (1) is followed by the second intermediate layer (2) containing the nuclei (n) and small poison granules of different sizes (arrowheads). The third inner layer (3) is characterized by the high number of poison granules of different sizes and shapes, without internal subunits, many of them fusing to each other (b-d). (e) Part of the inner layer showing the poison granules (gr) immersed in the syncytial cytoplasm matrix (syn). Insert: higher magnification of a granule resembling a wool ball. (f) The syncytial cytoplasm matrix (syn) with spongy appearance, after removal of the granules. (g) Ultrastructure of syncytial layers 1 and 2. my, myoepithelium; n, nucleus; sy, syncytium. (h) High magnification of the region marked by the rectangle in (g). Layer 1 contains high numbers of organelles (*) such as endoplasmic reticulum, mitochondria and Golgi apparatus. (i) Syncytial layer 2, is devoid of organelles but show small electron lucent poison granules (gr). syn, syncytium. (j) Syncytial layer 3 is full of fusing electron lucent poison granules (gr), without internal subunits. Species: Rhinella icterica (a, e, i), Rhinella schneideri (b), Rhinella marina (c, g, h, j) and Rhinella jimi (d, f). Histological sections stained with toluidine blue-fuchsine (a-d). SEM cryofractures (e-f). TEM (g-j)

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