Morphology of the franciscana (<i>Pontoporia blainvillei</i>) off southeastern Brazil: sexual dimorphism, growth and geographic variation

Abstract

Variations in body and skull morphology may exhibit geographic differences evidencing distinct population stocks. The objectives of the present study were to analyze such variation to test the hypothesis of a disjunct distribution of the franciscana (Pontoporia blainvillei) off the southeastern coast of Brazil. Body length and 39 cranial variables were measured from bycaught animals to considered sexual, ontogenetic and geographic variations. The areas studied were Espírito Santo (ES) (18º30S-19º40S), northern Rio de Janeiro (NRJ) (21º35S-22º25S) and São Paulo (SP) (23º30S-25º30S). Franciscanas from NRJ and SP presented significant sexual dimorphism, with the means for the metric characters larger for females than for males. Sexual dimorphism for franciscanas from ES was not examined due to limited sample size. The growth pattern for body and skull did not indicate clinal variation. The asymptotic values obtained for franciscanas from SP were smaller than the values obtained for franciscanas from NRJ and ES. Canonical discriminant analysis of the cranial metric characters indicated significant differences among the three geographic areas. Differences between areas ES and NRJ accounted for 85% of the variation (axis 1). The remaining 15% (axis 2) was due to difference between the area SP from the others. The geographic variation supports the hypothesis stock division in southeast Brazil; allopatry might be present. Therefore, three franciscana stocks from the southeastern coast of Brazil should be considered distinct for conservation and management actions.Resumo Variações no padrão morfológico do corpo e do crânio podem apresentar diferenças geográficas evidenciando estoques populacionais distintos. O objetivo do presente estudo foi estudar tais variações para testar a hipótese de distribuição disjunta para a toninha (Pontoporia blainvillei) na costa sudeste do Brasil. Para tanto, o comprimento do corpo e 39 caracteres cranianos foram determinados, considerando-se as variações morfológicas sexual, ontogênica e geográfica. As áreas estudadas foram Espírito Santo (ES) (18º30S-19º40S), norte do Rio de Janeiro (NRJ) (21º35S-22º25S) e São Paulo (SP) (23º30S-25º30S). Toninhas do NRJ e SP, apresentaram dimorfismo sexual significativo, com as médias obtidas para os caracteres métricos maiores para as fêmeas do que para os machos. O dimorfismo sexual não pode ser testado para o ES devido a problemas amostrais. Os padrões de crescimento para o tamanho corpóreo e craniano indicaram que não há uma variação clinal para a espécie. Os valores assintóticos obtidos foram menores para os espécimens do SP em relação aos valores obtidos para os espécimens do NRJ e ES. A análise discriminante canônica para os caracteres métricos do crânio indicou diferença significativa entre as três áreas geográficas, sem sobreposição para os estoques analisados. Diferenças entre as áreas ES e NRJ foram explicadas por 85% da variação (eixo 1). O 15% restantes da variação (eixo 2) foram responsáveis pela diferença entre a área SP das demais áreas. A ...

Morphometric relationships of franciscana dolphin, Pontoporia blainvillei (Cetacea), off Rio Grande do Sul coast, southern Brazil

“…This suggested a model based upon a single sample of both sexes, with its increased precision due to larger sample size, may be preferable. Several morphometric and genetic studies (Pinedo, 1991(Pinedo, , 1995Secchi et al, 1998Secchi et al, , 2003aOtt et al, 2002;Ramos et al, 2002;Lázaro et al, 2004;Barreto and Rosas, 2006) have established the existence of three franciscana morphotypes/genotypes: one found in FMA I (Rio de Janeiro and Espírito Santo states, Brazil); a second one in FMA II (from São Paulo to Santa Catarina states, Brazil) and the third in FMA III and IV (from Rio Grande do Sul state, Brazil down to Buenos Aires Province, Argentina). Animals inhabiting FMA I are smaller than animals from FMA III and IV but larger than those from FMA II.…”

“…Franciscanas inhabiting the southern end of this range are larger than the individuals from the northern end. Conversely, individuals from the central area of distribution are the smallest of all (Pinedo, 1991(Pinedo, , 1995Ramos et al, 2002;Barreto and Rosas, 2006). Body size affects all aspects of an organism's physiology and morphology, thereby influencing life history traits (e.g.…”

Patterns of Skull Variation ofBrachydelphis(Cetacea, Odontoceti) from the Neogene of the Southeastern Pacific

“…Generally, the variation within P. blainvillei has been attributed to a north-south disjunction in geographic distribution resulting in 2 subpopulations (Pinedo 1991;Ramos et al 2002;Secchi et al 1998). However, this distributional hiatus, often mentioned for Santa Catarina State (Brazil), cannot be supported because regular records of the species (Cherem et al 2004) and a resident population have been recently reported (Cremer and Simões-Lopes 2005).…”

What is the colour of the franciscana (Pontoporia blainvillei)? a review and a proposed assessment method

“…Fortunately other approaches including morphological and molecular analyses have been used successfully for determining stock units (e.g. Pinedo, 1991;Secchi et al, 1998;Higa et al, 2002;Ramos et al, 2002;Secchi et al, 2003;Lázaro et al, 2004).…”

“…Previous research based on morphological (Pinedo, 1991;Higa et al, 2002;Ramos et al, 2002) and genetic data (Secchi et al, 1998;Lázaro et al, 2004) have suggested the existence of at least two clearly defined stocks of franciscana, one to the north of Santa Catarina (~29°S), Brazil and the other to the south. Furthermore, a phylogeographic analysis by Secchi et al (2003) (combining mtDNA data, morphometrics, and lifehistory parameters) provided evidence for separating the species into four management stocks: two inhabiting coastal waters of Brazil, the third occurring in Rio Grande do Sul state (southern Brazil) and Uruguay, and the fourth in coastal Argentinean waters.…”