Journal of Biosciences

, Volume 36, Issue 1, pp 117–121 | Cite as

Efficiency of wear and decalcification technique for estimating the age of estuarine dolphin Sotalia guianensis

Article

Abstract

Most techniques used for estimating the age of Sotalia guianensis (van Bénéden, 1864) (Cetacea; Delphinidae) are very expensive, and require sophisticated equipment for preparing histological sections of teeth. The objective of this study was to test a more affordable and much simpler method, involving of the manual wear of teeth followed by decalcification and observation under a stereomicroscope. This technique has been employed successfully with larger species of Odontoceti. Twenty-six specimens were selected, and one tooth of each specimen was worn and demineralized for growth layers reading. Growth layers were evidenced in all specimens; however, in 4 of the 26 teeth, not all the layers could be clearly observed. In these teeth, there was a significant decrease of growth layer group thickness, thus hindering the layers count. The juxtaposition of layers hindered the reading of larger numbers of layers by the wear and decalcification technique. Analysis of more than 17 layers in a single tooth proved inconclusive. The method applied here proved to be efficient in estimating the age of Sotalia guianensis individuals younger than 18 years. This method could simplify the study of the age structure of the overall population, and allows the use of the more expensive methodologies to be confined to more specific studies of older specimens. It also enables the classification of the calf, young and adult classes, which is important for general population studies.

Keywords

Age estimation GLG Sotalia guianensis 

References

  1. Borobia M, Siciliano S, Lodi L and Hoek W 1991 Distribution of the South American dolphin Sotalia fluviatilis. Can. J. Zool. 69 1025–1039CrossRefGoogle Scholar
  2. Boyde A 1980 Histological studies of dental tissues of Odontocetes. Rep. Int. Whaling Comm. Special Issue 3 65–87Google Scholar
  3. Flores PAC 2002 Tucuxi – Sotalia guianensis; in Encyclopedia of marine mammals (eds) Perrin WF, Würsig B and Thewissen JGM (San Diego: Academic Press) p. 1414Google Scholar
  4. Geise L and Borobia M 1987 New Bazilian records for Kogia, Pontoporia, Grampus, and Sotalia (Cetacea, Physeteridae, Platanistidae, and Delphinidae). J. Mamm. 68 873–875CrossRefGoogle Scholar
  5. Hohn, AA 1990 Reading between the lines: analysis of age determination in dolphins; in The bottlenose dolphin (eds) S Leatherwood and RR Reeves (San Diego: Academic Press) p. 653Google Scholar
  6. Hohn AA 2009 Age estimation; in Encyclopedia of marine mammals 2nd edition (eds) WF Perrin, B Würsig and JGM Thewissen (London: Academic Press) p. 1316Google Scholar
  7. Hohn AA, Scott MD, Wells RS, Sweeney JC and Irvine AB 1989 Growth layers in teeth from known-age, free-ranging bottlenose dolphins. Mar. Mamm. Sci. 5 315–342CrossRefGoogle Scholar
  8. Klevezal GA 1980 Layers in the hard tissues of mammals as a record of growth rhythms of individuals. Rep. Int. Whaling Comm. Special Issue 3 89–94Google Scholar
  9. Nishiwaki M and Yagi T 1953 On the age and growth of teeth in a dolphin, Prodelphinus coeruleo-albus. Sci. Rep. Whales Res. Inst. 8 133–146Google Scholar
  10. Pierce VK and Kajimura H 1980 Acid etching and highlighting for defining growth layers in cetacean teeth. Rep. Int. Whaling Comm. Special Issue 3 99–101Google Scholar
  11. Pinedo MC and Hohn AA 2000 Growth layer patterns in teeth from the franciscana, Pontoporia blainvillei: developing a model for precision in age estimation. Mar. Mamm. Sci. 16 1–27CrossRefGoogle Scholar
  12. Ramos RMA 1997 Determinação de idade e biologia reprodutiva de Pontoporia blainvillei e da forma marinha de Sotalia fluviatilis (Cetacea: Pontoporiidae e Delphinidae) no Norte do Rio de Janeiro. Dissertação de mestrado. UENF, Campo dos Goytacazes-RJGoogle Scholar
  13. Ramos RMA and Di Beneditto APM 2005 Guia para estudo de cetáceos. Volume 3: Métodos para determinação de idade em cetáceos odontocetos (Campos dos Goytacazes: Editora da Universidade Estadual do Norte Fluminense Darcy Ribeiro) p. 38Google Scholar
  14. Ramos RMA, Rosas FCW, Simões-Lopes PC, Zanelatto RC, Dans S and Crespo EA 2008 Estimativa de idade; in Biologia ecologia e conservação do boto-cinza (eds) ELA Monteiro-Filho and KDKA Monteiro (São Paulo: Páginas & Letras Editora e Gráfica) pp 193–209Google Scholar
  15. Ricklefs REA 2003 Economia da natureza (Rio de Janeiro: Guanabara Koogan) p. 503Google Scholar
  16. Rosas FCW 2000 Interações com a pesca, mortalidade, idade, reprodução e crescimento de Sotalia guianensis e Pontoporia blainvillei (Cetacea: Delphinidae e Pontoporidae) no litoral sul do Estado de São Paulo e do Estado do Paraná, Brasil. Tese de doutorado. UFPR, Curitiba-PRGoogle Scholar
  17. Rosas FCW, Barreto AS and Monteiro-Filho ELA 2003 Age and growth of the estuarine dolphin (Sotalia guianensis) (Cetacea, Delphinidae) on the Paraná coast, Southern Brazil. Fish. Bull. 101 377–383Google Scholar
  18. Scheffer VB and Myrick AC 1980. A review of studies to 1970 of growth layers in the teeth of marine mammals. Rep. Int. Whaling Comm. Special Issue 3 51–63Google Scholar
  19. Simões-Lopes PC 1988 Ocorrêcia de uma população de Sotalia fluviatilis Gervais 1853, (Cetacea, Delphinidae) no limite sul de sua distribuição, Santa Catarina, Brasil. Biotemas 1 57–62Google Scholar
  20. Slooten E 1991 Age, growth, and reproduction in Hector’s dolphins. Can. J. Zool. 69 1689–1700CrossRefGoogle Scholar

Copyright information

© Indian Academy of Sciences 2011

Authors and Affiliations

  • Nicolle V Sydney
    • 1
  • Emygdio LA Monteiro-Filho
    • 2
    • 3
  1. 1.Instituto de BiociênciasUniversidade de São PauloSão PauloBrasil
  2. 2.Departamento de ZoologiaSetor de Ciências BiológicasCuritibaBrasil
  3. 3.Instituto de Pesquisa em CananéiaCananéiaBrasil

Personalised recommendations