Full text
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| Author(s): |
Bianca de Sousa Rangel
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB) |
| Defense date: | 2018-03-28 |
| Examining board members: |
Renata Guimarães Moreira Whitton;
Carolina Arruda de Oliveira Freire;
Gisele Akemi Oda;
Cristiéle da Silva Ribeiro
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| Advisor: | Renata Guimarães Moreira Whitton; Aline Dal Olio Gomes |
| Abstract | |
The aim of the present study was to investigate the neonatal nutritional strategy adopted by species R. bonasus and R. brasiliensis, related to its trophic interactions and maternal resource dependency during the early stages of life. Lipids, fatty acids (FA) and stable isotope (SI) were assessed in different tissues, as tools to evaluate biomarkers changes during growth in young-of-the-year (YOY) rays, divided into two stages, YOY I (<=50 cm) and YOY II (50-70 cm). The registration of YOY in three consecutive years (2015, 2016 and 2017) and the permanence of the YOY during the year, confirms that the region of Bertioga is a nursery area for R. bonasus and possibly to R. brasiliensis. In R. bonasus the plasma triglycerides and δ-hydroxybutyrate did not differ between YOY I and II. Plasma cholesterol (CHOL) was higher in YOY I than in YOY II. FA profiles were similar in liver, muscle and plasma, with a predominance of polyunsaturated FA (PUFA), followed by saturated FA (SFA) and monounsaturated FA (MUFA). In R. bonasus there was a reduction of C22:6n3 (DHA - docosahexaenoic acid) and C20:4n6 (ARA - arachidonic acid), and an increase in C20:5n3 (EPA - eicosapentaenoic acid) in muscle, with increasing body size, resulting in a decrease in DHA/EPA ratio (used as an indicator of trophic position). In terms of SI, δ15N values decreased with increasing body size with higher δ15N values found in dorsal fin and red blood cells (RBC) of YOY I compared to YOY II animals. In YOY I and II, the δ13C of fin tissue was higher than RBC. Comparing both species, R. bonasus presents higher δ15N and δ13C values in the RBC than R. brasiliensis, suggesting the partition of food resources, at different trophic levels and/or foraging in different locations, despite the two species being sympatric in the region. These combined data demonstrate that cownose rays significantly invest in their young and consequently better nutritional conditions at birth, since the data suggest that the pups did not show essential FA (EFA) deficiency, as observed in placental sharks. High values of DHA, ARA and CHOL in YOY I, and subsequent decrease with increasing body size, confirms the use of these substrates in metabolic processes. In addition, data indicate that larger animals have improved foraging skills, demonstrated by increased plasma levels of EFA, such as DHA, EPA and a decrease of ΣSFA in YOY II. Such metabolic aspects linked to neonatal nutritional strategy are fundamental factors for understanding the patterns of maternal investment and energy resources required in the early life stages of viviparous elasmobranchs (AU) | |
| FAPESP's process: | 16/09095-2 - Lipids and stable isotopes as maternal investment and neonatal nutritional strategies indicators in histotrophic stingrays |
| Grantee: | Bianca de Sousa Rangel |
| Support Opportunities: | Scholarships in Brazil - Master |