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<p>The megamouth shark, <i>Megachasma pelagios</i>, is a rare circumtropical species with a distinctive appearance. To date, only 273 confirmed occurrence records have been documented globally. This study reports the third occurrence of a megamouth shark on the Brazilian coast and provides descriptions of the dermal denticles of all three specimens recorded in the country. On September 10, 2018, a megamouth shark was found floating off Pedra do Sal Beach, Parnaíba, Piauí, Northeastern, Brazil. A mitochondrial ND2 sequence was obtained from this specimen, confirming its identity. Skin samples from this specimen, as well as from the two other previously recorded individuals from Southeastern Brazil (an adult stranded in Arraial do Cabo, Rio de Janeiro, and a juvenile captured off the coast of São Paulo), were analyzed to describe the dermal denticles using scanning electron microscopy and stereomicroscopy. The dermal denticles from the Brazilian specimens exhibited distinct shapes depending on body region. The specimen from São Paulo showed differences in the dermal denticles to those of adults, with an increase in the ridges and a reduction of cusps, particularly in the caudal peduncle, cheek, and pelvic fin regions. Furthermore, the dermal denticles of the two juvenile megamouth sharks exhibit, in general, a distinct arrangement pattern, appearing more closely spaced and slightly imbricated&#xa0;when compared to the adult from Arraial do Cabo and those reported in the literature.</p>

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New occurrence record and dermal denticles of megamouth sharks from the Southwest Atlantic Coast

  • 期刊论文

  • 发表日期：

    2025年1月30日

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  • Lilian G. Xavier,
  • Ana Kamila M. Lima,
  • Emilio de C. Miguel,
  • Salvatore Siciliano,
  • Rachel Ann Hauser-Davis,
  • Patricia do N. Bordallo,
  • Georgia M. de O. Aragão,
  • Jules M. R. Soto,
  • João Eduardo P. de Freitas,
  • Patricia Charvet,
  • Vicente V. Faria

摘要

The megamouth shark, Megachasma pelagios, is a rare circumtropical species with a distinctive appearance. To date, only 273 confirmed occurrence records have been documented globally. This study reports the third occurrence of a megamouth shark on the Brazilian coast and provides descriptions of the dermal denticles of all three specimens recorded in the country. On September 10, 2018, a megamouth shark was found floating off Pedra do Sal Beach, Parnaíba, Piauí, Northeastern, Brazil. A mitochondrial ND2 sequence was obtained from this specimen, confirming its identity. Skin samples from this specimen, as well as from the two other previously recorded individuals from Southeastern Brazil (an adult stranded in Arraial do Cabo, Rio de Janeiro, and a juvenile captured off the coast of São Paulo), were analyzed to describe the dermal denticles using scanning electron microscopy and stereomicroscopy. The dermal denticles from the Brazilian specimens exhibited distinct shapes depending on body region. The specimen from São Paulo showed differences in the dermal denticles to those of adults, with an increase in the ridges and a reduction of cusps, particularly in the caudal peduncle, cheek, and pelvic fin regions. Furthermore, the dermal denticles of the two juvenile megamouth sharks exhibit, in general, a distinct arrangement pattern, appearing more closely spaced and slightly imbricated when compared to the adult from Arraial do Cabo and those reported in the literature.