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Postnatal development of franciscana's ( Pontoporia blainvillei ) biosonar relevant structures with potential implications for function, life history, and bycatch
Author(s) -
Frainer Guilherme,
Huggenberger Stefan,
Moreno Ignacio Benites
Publication year - 2015
Publication title -
marine mammal science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.723
H-Index - 78
eISSN - 1748-7692
pISSN - 0824-0469
DOI - 10.1111/mms.12211
Subject(s) - bycatch , biology , mandible (arthropod mouthpart) , cetacea , anatomy , zoology , fishery , fish <actinopterygii> , genus
Franciscana dolphins ( Pontoporia blainvillei ) are the most endangered species of the western South Atlantic Ocean. The major cause of their vulnerability is incidental bycatch in fishery gill nets. Ontogenetic changes of biosonar relevant structures in Pontoporia were analyzed in five specimens (one female neonate, two male neonates and two male adults) using digital imaging technology ( MRI , CT ) and macroscopic dissections to compare structures involved in sound production and reception. These data were compared to an ontogenetic series of 69 macerated skulls of Pontoporia in order to elucidate the correlation between soft tissue structures and bones of the epicranial complex and to describe the development‐related changes in the mandible. Postnatal developmental shape changes of the posterior part of the right vestibular air sac followed bone formation and the melon with its right branch elongated, paralleling the flatter facial depression of adults. Minor postnatal developmental modifications were verified in the tympano‐periotic complex but a shape change of the mandible was visible by a ventral deviation of the posterior part of the mandible in adults. These results reveal postnatal changes in allometry and shape of biosonar relevant structures that may be one of the causes that increase bycatch of neonate and young Pontoporia individuals.