Figure - available from: Journal of Fish Biology
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PIV analysis of a burying event, anterior view, showing direction and relative speed of sediment granules. Every second vector is shown for clarity. Orange vectors indicate data interpolated from neighbouring vectors. (a, b) From a resting position, the fish pressed its body downwards. (c, d) The rostrum and then body lift upwards as the fins folded up and over. (e) The rostrum subsequently pressed towards the substrate as the body pushed downwards and the fins recovered towards the original position. (f, g) Again, the rostrum and then the body lift upwards, as the fins folded up and over, suspending and directing vortices of fluidized sediment along the ventral surface of the fins. (h–j) The vortices of sediment move towards the midline, as the body presses downwards. (k–m) The vortices collided along the midline, as another set of vortices were formed by subsequent finbeat and directed towards the midline. (n) The second set of vortices collided over the midline. (o) The sediment dissipated and settled onto the fish
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Particle image velocimetry and video analysis were employed to determine the pectoral‐fin mechanism used by the stingray Potamotrygon motoro to bury into sand. Rapid oscillations of the body and folding motions of the posterior portion of the pectoral fin suspended sediment beneath the pectoral disc and directed vortices of sediment onto the dorsal...
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Citations
... In the ventral region, these cells were AB + and PAS + , indicating neutral and acidic mucosubstances (Fig. 2e, f). Acidic mucins are known to have antimicrobial (Bosi and Dezfuli 2015) and antiparasitic functions (de Matos et al. 2017), which may explain their presence in this area, considering that the ventral region is susceptible to mechanical wear due to the friction and abrasion caused by the substrate (Seamone and Syme 2021). ...
... In the integument lining the edge of the pectoral fin of P. wallacei, the ventral epidermis (60.35 ± 2.31 µm) was thicker (P < 0.05) when compared to the epidermis in the dorsal region (48.44 ± 3.84 µm). This difference in thickness is related to the friction of the pectoral fin of potamotrygonins when in contact with the sand and plant litter of the riverbed (Carvalho et al. 2016b;Seamone and Syme 2021). ...
The cururu stingray (Potamotrygon wallacei) is an endemic species from the Negro River basin, Brazil. There are only a few studies describing the integument morphology and tissue repair in potamotrygonins. Therefore, this study aimed to describe the integument morphology of P. wallacei in different body portions and report the tissue repair in an injury observed on the edge of the pectoral fin in one individual. Four specimens of P. wallacei were collected in the Mariuá Arquipelago, near to the municipality of Barcelos, Amazonas. Samples of the integument were taken from the dorsal, tail and ventral region and from the edge of the pectoral fin. Subsequently, these samples were submitted to histological processes and stained with hematoxylin–eosin, PAS and Alcian Blue 2.5. In all the body portions, the epidermis comprises a non-keratinized stratified squamous epithelium with mucous and sacciform cells that secrete mucosubstances. In the epidermis, chromatophores are responsible for the brown coloration of this species. The epidermis is thickest in the dorsal region. The dermis comprises two strata: the stratum laxum, with thin collagen fibers, which is thicker on the ventral surface. The stratum compactum, dense in thick collagen fibers, is thicker in the tail region. The repaired pectoral fin showed a thin epidermis with a reduced number of mucous cells and restored cartilaginous radials. The integument of P. wallacei is similar to that described for other elasmobranchs and our findings suggest that this species has the ability to regenerate its integumentary tissues after a potential injury.
Batoids differ from other elasmobranch fishes in that they possess dorsoventrally flattened bodies with enlarged muscled pectoral fins. Most batoids also swim using either of two modes of locomotion: undulation or oscillation of the pectoral fins. In other elasmobranchs (e.g., sharks), the main locomotory muscle is located in the axial myotome; in contrast, the main locomotory muscle in batoids is found in the enlarged pectoral fins. The pectoral fin muscles of sharks have a simple structure, confined to the base of the fin; however, little to no data are available on the more complex musculature within the pectoral fins of batoids. Understanding the types of fibers and their arrangement within the pectoral fins may elucidate how batoid fishes are able to utilize such unique swimming modes. In the present study, histochemical methods including succinate dehydrogenase (SDH) and immunofluoresence were used to determine the different fiber types comprising these muscles in three batoid species: Atlantic stingray (Dasyatis sabina), ocellate river stingray (Potamotrygon motoro) and cownose ray (Rhinoptera bonasus). All three species had muscles comprised of two muscle fiber types (slow-red and fast-white). The undulatory species, D. sabina and P. motoro, had a larger proportion of fast-white muscle fibers compared to the oscillatory species, R. bonasus. The muscle fiber sizes were similar between each species, though generally smaller compared to the axial musculature in other elasmobranch fishes. These results suggest that batoid locomotion can be distinguished using muscle fiber type proportions. Undulatory species are more benthic with fast-white fibers allowing them to contract their muscles quickly, as a possible means of escape from potential predators. Oscillatory species are pelagic and are known to migrate long distances with muscles using slow-red fibers to aid in sustained swimming.
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