Browsing by Author "Regalla, Aissa"
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- Fibropapillomatosis and the chelonid Alphaherpesvirus 5 in green turtles from West AfricaPublication . Monteiro, Jessica; Duarte, Margarida; Amadou, Kidé; Barbosa, Castro; El Bar, Nahi; Madeira, Fernando M.; Regalla, Aissa; Duarte, Ana; Tavares, Luís; Patrício, Ana RitaFibropapillomatosis (FP) is a tumorigenic panzootic disease of sea turtles, most common in green turtles (Chelonia mydas). FP is linked to the chelonid alphaherpesvirus 5 (ChAHV5) and to degraded habitats and, though benign, large tumours can hinder vital functions, causing death. We analyse 108 green turtles, captured in 2018 and 2019, at key foraging grounds in Guinea-Bissau and Mauritania, West Africa, for the presence of FP, and use real-time PCR to detect ChAHV5 DNA, in 76 individuals. The prevalence of FP was moderate; 33% in Guinea-Bissau (n = 36) and 28% in Mauritania (n = 72), and most turtles were mildly affected, possibly due to low human impact at study locations. Juveniles had higher FP prevalence (35%, n = 82) compared to subadults (5%, n = 21), probably because individuals acquire resistance over time. ChAHV5 DNA was detected in 83% (n = 24) of the tumour biopsies, consistent with its role as aetiological agent of FP and in 26% (n = 27) of the ‘normal’ skin (not showing lesions) from FP turtles. Notably, 45% of the asymptomatic turtles were positive for ChAHV5, supporting multifactorial disease expression. We report the first baselines of FP and ChAHV5 prevalence for West Africa green turtles, essential to assess evolution of disease and future impacts of anthropogenic activities.
- Fibropapillomatosis and the chelonid alphaherpesvirus 5 in green turtles from West AfricaPublication . Monteiro, Jessica; Duarte, Margarida; Amadou, Kidé; Barbosa, Castro; El Bar, Nahi; Madeira, Fernando M.; Regalla, Aissa; Duarte, Ana; Tavares, Luís; Patrício, Ana RitaFibropapillomatosis (FP) is a tumorigenic panzootic disease of sea turtles, most common in green turtles (Chelonia mydas). FP is linked to the chelonid alphaherpesvirus 5 (ChAHV5) and to degraded habitats and, though benign, large tumours can hinder vital functions, causing death. We analyse 108 green turtles, captured in 2018 and 2019, at key foraging grounds in Guinea-Bissau and Mauritania, West Africa, for the presence of FP, and use real-time PCR to detect ChAHV5 DNA, in 76 individuals. The prevalence of FP was moderate; 33% in Guinea-Bissau (n = 36) and 28% in Mauritania (n = 72), and most turtles were mildly affected, possibly due to low human impact at study locations. Juveniles had higher FP prevalence (35%, n = 82) compared to subadults (5%, n = 21), probably because individuals acquire resistance over time. ChAHV5 DNA was detected in 83% (n = 24) of the tumour biopsies, consistent with its role as aetiological agent of FP and in 26% (n = 27) of the ‘normal’ skin (not showing lesions) from FP turtles. Notably, 45% of the asymptomatic turtles were positive for ChAHV5, supporting multifactorial disease expression. We report the first baselines of FP and ChAHV5 prevalence for West Africa green turtles, essential to assess evolution of disease and future impacts of anthropogenic activities.
- Nutrient input from green turtle eggs and hatchlings in a west Africa Island and its nearshore environmentPublication . Ferreira Raposo, Cheila Sofia; Patrício, Ana Rita; Catry, Paulo; Barbosa, Castro; Camará, Assana; Regalla, Aissa; Rebelo, RuiSea turtle nesting brings marine-derived nutrients into sandy beach ecosystems, potentially influencing their dynamics. We investigated nutrient input from green turtle Chelonia mydas eggs and hatchlings into coastal habitats in Guinea-Bissau, West Africa. We assessed two islands within the João Vieira-Poilão Marine National Park (‘JVPMNP’), with contrasting sea turtle nesting density: very low (João Vieira) and very high (Poilão). On each island, we analyzed stable isotopes of carbon and nitrogen in one pair of plant species (coinvine Dalbergia ecastaphyllum bush/baobab Adansonia digitata tree) and two pairs of predator species (tufted ghost crab Ocypode cursor/African rainbow crab Cardisoma armatum and sea catfish Carlarius spp./crevalle jack Caranx hippos). The first species in each pair is distributed closer to nesting sites, while the second is found further inland or offshore. Stomach content analysis was also conducted for fishes. Results supported nutrient input from turtle clutches benefiting the species living near nesting sites. Shoreline coinvines at Poilão had higher δ15N (5.1 ± 3.2‰) compared to João Vieira (≈0‰), suggesting assimilation of turtle-derived 15N. Shoreline tufted ghost crabs at Poilão had enriched δ15N (15.2 ± 0.7‰ vs. João Vieira’s 12.2 ± 1.1‰) and δ13C (− 13.4 ± 0.7‰ vs. João Vieira’s − 18.7 ± 1.4‰), likely reflecting predation upon eggs and hatchlings. Sea catfishes at Poilão frequently consumed unhatched turtle eggs washed into the sea (17% frequency of occurrence) and hatchlings (up to 27%). This study suggests that nutrient availability from turtle nests influences and supports shoreline plants and consumers at JVPMNP.
- Red, gold and green: Microbial contribution of Rhodophyta and other algae to green turtle (Chelonia mydas) Gut MicrobiomePublication . Díaz-Abad, Lucía; Bacco-Mannina, Natassia; Madeira, Fernando Miguel; EA, Serrao; Regalla, Aissa; Patrício, Ana R.; Frade, Pedro R.The fitness of the endangered green sea turtle (Chelonia mydas) may be strongly affected by its gut microbiome, as microbes play important roles in host nutrition and health. This study aimed at establishing environmental microbial baselines that can be used to assess turtle health under altered future conditions. We characterized the microbiome associated with the gastrointestinal tract of green turtles from Guinea Bissau in different life stages and associated with their food items, using 16S rRNA metabarcoding. We found that the most abundant (% relative abundance) bacterial phyla across the gastrointestinal sections were Proteobacteria (68.1 ± 13.9% “amplicon sequence variants”, ASVs), Bacteroidetes (15.1 ± 10.1%) and Firmicutes (14.7 ± 21.7%). Additionally, we found the presence of two red algae bacterial indicator ASVs (the Alphaproteobacteria Brucella pinnipedialis with 75 ± 0% and a Gammaproteobacteria identified as methanotrophic endosymbiont of Bathymodiolus, with <1%) in cloacal compartments, along with six bacterial ASVs shared only between cloacal and local environmental red algae samples. We corroborate previous results demonstrating that green turtles fed on red algae (but, to a lower extent, also seagrass and brown algae), thus, acquiring microbial components that potentially aid them digest these food items. This study is a foundation for better understanding the microbial composition of sea turtle digestive tracts.
- Satellite tracking and field assessment highlight major foraging site for green turtles in the Banc d'Arguin, MauritaniaPublication . Catry, Paulo; Senhoury, Cheibani; Sidina, Ebaye; El Bar, Nahi; Samba Bilal, Abdellahi; Ventura, Francesco; Godley, Brendan; Pires, António A.; Regalla, Aissa; Patrício, Ana RitaThere is a remarkable paucity of estimates of the numeric importance of sea turtles at foraging grounds. The Banc d'Arguin (BA) is a vast shallow marine area off the coast of Mauritania, known as a site of world importance for coastal migratory birds and other biodiversity, including extensive seagrass beds. We sampled foraging green turtles on the BA, and extensively tracked adult female green turtles from the Bijagós archipelago, the only significant nesting aggregation within 3000 km of the BA, to estimate the abundance of this foraging aggregation. Additionally, we used a demographic simulation to support our findings. Based on satellite tracking of adult females (n = 46), we estimate that 50 % of the nesting population from the Bijagós migrate to the BA post-nesting. We combine data on numbers nesting in the Bijagós with information on proportion migrating to the BA in the same years to conservatively estimate that 8285 adult female green turtles forage at this site. We also estimate that adult females represent only 5.6 % of the green turtles in the BA, implying that the number of turtles there is of the order of 150,000 individuals. Most of the BA enjoys effective protection as part of the Parc National du Banc d'Arguin where significant fisheries regulations are well enforced by a marine surveillance program. We show that the BA is one of the major foraging sites for green turtles nesting in the Bijagós and a site of critical importance for immature and adult green turtles in a global context.
- Seagrass connectivity on the west coast of Africa supports the hypothesis of grazer-mediated seed dispersalPublication . Tavares, Ana I; Assis, Jorge; Patrício, A. R.; Ferreira, Rogério; Cheikh, Mohamed Ahmed Sidi; Bandeira, Salomao; Regalla, Aissa; Silva Dos Santos, Iderlindo Jorge; Potouroglou, Maria; Nicolau, Suzana; Teodosio, MA; Almada, Carmen; Santos, Rui; Pearson, Gareth Anthony; Serrao, Ester A.Population connectivity influences the distribution of genetic diversity and divergence along a species range, as the likelihood of extinction or differentiation increases in isolated populations. However, there is still poor understanding of the processes mediating interpopulation dispersal in marine species that are sessile and lack planktonic life stages. One such case is the seagrass species Halodule wrightii, which produces basal seeds, although detached plants can drift. Along the tropical western coast of Africa, this species occurs in distant discontinuous habitats, raising the question of how interpopulation dispersal is mediated. The species is a key source of ecosystem functions including feeding large migratory grazers. This study aims to infer whether genetic differentiation of the seagrass H. wrightii along the western coast of Africa supports a hypothesis of predominant transportation of rafting seagrass by ocean currents, versus the hypothesis of biotic vectors of dispersal. Additional hypotheses were addressed concerning range-wide clonality and genetic diversity, assessed with microsatellite markers on populations of the west coast of Africa from Mauritania to Angola. Population genetic diversity and structure were compared with predictions from biophysical models of dispersal by oceanographic currents. The genetic data revealed low divergence among most populations, in strong contrast with predictions of very low probability of connectivity mediated by currents along the western African coastline. Moderate to high genotypic diversity showed important seed recruitment, but genetic and genotypic diversities were lower at range edges. Populations north and south of the equator were differentiated, and remarkably, so were neighboring equatorial populations despite their proximity. These results reveal independent sources of colonization of meadows in these islands, which are major habitat for migratory grazing green turtles, also supporting the hypothesis of biotically mediated seed transport. The importance of seagrass for conservation of endangered macrofauna has been widely reported; here we report evidence supporting the reciprocal role, that macrofauna protection can also plays a role in long-term survival and reproductive success of seagrass.