Morfologia do complexo tímpano-periótico de cetáceos

Abstract

The present study aims to describe the morphology of the tympanic-periotic bone complex (T-P) of different species of cetaceans, as well as to investigate the influence of seismic research activities in the strandings of this group. The data analyzed in this work were obtained by the Cetáceos da Costa Branca-UERN Project (PCCB / UERN), in partnership with the Center for Environmental Studies and Monitoring (CEMAM), during the execution of Beach Monitoring Projects, or through actions by the community. Specimens that stranded or died during rehabilitation had their tympanic complexes removed during necropsies or carcass analysis procedures, being identified on the right and left and submitted to the maceration process. For each specimen, data related to the development phase, sex and species were recorded. 57 TP complexes were collected from 31 cetacean individuals, distributed in 6 species: Peponocephala electra (N = 4), Pseudorca crassidens (N = 2), Sotalia guianensis (N = 39), Stenella attenuata (N = 4), Stenella longirostris (N = 4) and Tursiops truncatus (N = 4). Biometrics and morphological description were performed for each complex of each species, and possible ontogenetic and taxonomic variations were evaluated. The six species shared similar morphological characteristics because they belong to the same family (Delphinidae); however, the species S.guianensis, S attenuata and S. longirostris had a greater number of characteristics in common, which may indicate a greater evolutionary relationship between them. No significant ontogenetic variations were observed for the species S. guianensis, P. electra and S. longirostris, which are the species where we had data from several age classess to compare with. It was observed that the most representative morphological characteristics for the identification of the species would be, for the tympanic: the posterior process, the internal and external prominences and the sigmoid process. For the periotic: the cochlear portion and the cochlear and vestibular aqueduct openings and the parabular crest. Still with the data obtained from the monitoring of beaches, a description of the diversity and patterns of cetacean stranding was carried out, in the periods of occurrence of two Seismic Research projects, denounced from PCS01 and PCS02 being compared with the same periods in previous years, without the occurrence of seismic research activities, PSS01 and PSS02. It was possible to observe, during the period of seismic activities 01 and 02, a reduction in the number of stranding records in the areas of greatest impact, concomitant with the increase of these in other less impacted areas. Assuming a possible departure or change of route, due to the impact caused by seismic noise. In addition, three stranding cases were presented that presented morphological changes and signs of gas embolism, compatible with possible impacts caused by the seismic activities.