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| Author(s): |
Thiago Silva Loboda
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB) |
| Defense date: | 2010-10-08 |
| Examining board members: |
Marcelo Rodrigues de Carvalho;
Ulisses Leite Gomes;
Mônica de Toledo Piza Ragazzo
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| Advisor: | Marcelo Rodrigues de Carvalho |
| Abstract | |
Originally described from Parana-Paraguay basin since the middle of XIX century, Potamotrygon motoro (Müller & Henle, 1841), one of the first discovered species of Potamotrygonidae family, presents the major distributional range between the neotropical freshwater stingrays, including the three major basins of South America, Amazon, Parana-Paraguay and Orinoco, and also the minor Mearim river basin, in the Maranhão state, Brazil. Since the discoveries of P. motoro in other basins systems rather than Paraná-Paraguai basin, this species always had give doubts in many authors taxonomically, if it can be represent just one specific unity or if can be subdivided in another new forms, mainly because the great chromatic variety in its dorsal disc coloration (the principal diagnostic character in this species). Thus, the principal point in the present study is concerned this question through the morphological revision of P. motoro with specimens of many locallities of Amazon basin, also to complement a inicial taxonomic revision with the species in Parana-Paraguay basin made in 2006. Therefore, it was obtained in many national museums collections and also some field works more than 250 specimens from at least 23 principal rivers located in peruvian and brazilian Amazon regions, besides some photographs and radiographs taken from some type-specimens of nominal species attributed to P. motoro in Amazon basin, such as Trygon (Taenura) mülleri Castelnau, 1855, Potamotrygon ocellata (Engelhardt, 1912), P. laticeps Garman, 1913 and P. circularis Garman 1913. Besides some morphological characters showed variations, the specific unity of P. motoro is well corroborated and a possible subdivision of this species in others new forms is rejected here. A principal and diagnostic pattern of the various morphological characters, as skeleton, dentition, ventral canals of lateral line system, squamation, even so coloration had showed a stable condition in all populations analysed and can be easily identified in the species. It was also possible to see that the few morphological differences found to some characters can provide a visualization of the biogeographic distribution of P. motoro through of the similarities between some of these different morphological patterns, which it is possible identify some vias of communication between the basins where the species occur, such as Negro/Branco system plus Orinoco basin or Peruvian Amazon plus Parana-Paraguay basin. It was also certificated that the distribution of P. motoro follow a well-known pattern called by lowlands of foreland basins, which can help to understand the great distribution of this species through the basin where it occur, besides been a common verified pattern to another many species of freshwater bony fishes. Moreover, a variety of dorsal coloration disc pattern found just in adult male specimens of many populations could be identified. Finally, three possible new forms of Potamotrygon were identified, and the next nominal and valid species were synonymized to P. motoro in Amazon basin: nominal species Trygon garrapa Schomburgk, 1843, Trygon (Taenura) mülleri and Potamotrygon circularis Garman, 1913 (in part, just the MCZ295-S specimen) and the valid species Potamotyrgon ocellata (Engelhardt, 1912). (AU) | |