Atlantic Coast Of South America Research Articles

Evolutionary morphology of haptoral anchors in monogenoids (Dactylogyridae) of marine catfish (Siluriformes: Ariidae) from the Atlantic coast of South America.

Exploring the phylogenetic signal of morphological traits using geometric morphometry represents a powerful approach to assess the relative weights of convergence and shared evolutionary history in shaping species' forms. We evaluated the phylogenetic signal in shape and size of ventral and dorsal haptoral anchors of 10 species of monogenoids (Hamatopeduncularia, Chauhanellus and Susanlimocotyle) occurring in marine catfish (Siluriformes: Ariidae) from the Atlantic coast of South America. The phylogenetic relationships among these species were mapped onto the morphospaces of shape and size of dorsal and ventral anchors. Two different tests (squared change-parsimony and Kmult) were applied to establish whether the spatial positions in the phylomorphospace were influenced by phylogenetic relationships. A significant phylogenetic signal was found between anchor form and parasite phylogeny. Allometric effects on anchor shape were non-significant. Phylogenetically distant species on the same host differed markedly in anchor morphology, suggesting little influence of host species on anchor form. A significantly higher level of shape variation among ventral anchors was also found, suggesting that the evolutionary forces shaping ventral anchor morphology may operate with differing intensities or exhibit distinct mechanisms compared to their dorsal counterparts. Our results suggest that phylogenetic relationships were a key driver of changes in shape (but not size) of anchors of monogenoids of South American ariids. However, it seems that the emergence of the digitiform haptor in Hamatopenducularia and in some species of Chauhanellus played an important role in the reduction in anchor size and may cause secondary losses of anchors in other groups of monogenoids.

Status of the invasion of Carpobrotus edulis in Uruguay based on citizen science records

Carpobrotus edulis, a highly invasive plant species repeatedly introduced along the Atlantic coast of South America, poses a significant threat to the ecological integrity of coastal dune ecosystems in Uruguay. This study used 15 years of iNaturalist records to assess the magnitude of Carpobrotus invasion, focusing on its distribution, abundance, and reproductive phenology. Through the analysis of georeferenced and dated data, we determined that Carpobrotus has spread extensively, covering a 10-km-wide coastal area and occupying approximately 220 km along the Atlantic coast and the outer Rio de la Plata estuary. Records have increased in the last three years, with a summer prevalence of 52.9%, due to higher activity on the platform. The species exhibited two flowering peaks in spring and autumn, suggesting an extended reproductive period. The widespread presence of this species in both natural and urbanized areas highlights the urgent need for effective management strategies to mitigate its impact on native biodiversity. Utilizing citizen science platforms like iNaturalist has been instrumental in monitoring and documenting processes of invasion. However, further investigations are necessary, particularly in less sampled regions, to fully understand the extent of Carpobrotus invasion. To protect the country’s coastal ecosystems, it is crucial for local authorities to reassess current practices related to non-native species ornamental planting. By addressing the invasion of C. edulis, the ecological integrity of coastal dune ecosystems can be preserved, ensuring the survival of native flora and fauna along Uruguay’s Atlantic coast.

Marine pollution between gyres: plastic debris in marine turtles and dolphins in French Guiana, Equatorial Atlantic

Plastic pollution has not raised much attention until the 2000s, despite being manufactured for about a century. It is now considered one of the most substantial environmental issues. Here we investigate the presence of plastic contamination in 34 stranded animals on the coast of French Guiana, South America. Here we present information highlighting the magnitude of plastic contamination in marine coastal and pelagic tropical marine vertebrates on the Equatorial Atlantic coast of South America. All four species studied here are protected and emblematic vertebrates of the region, with a fragile conservation status, including the olive ridley turtle Lepidochelys olivacea, the green turtle Chelonia mydas and the leatherback turtle Dermochelys coriacea, and a small cetacean, the Guiana dolphin Sotalia guianensis. Macroplastics (polypropylene, polyethylene, terephthalate, and polystyrene) were detected in four juvenile green turtles. Microplastics (polypropylene, polyethylene, terephthalate, polystyrene, nylon, acrylates, polycarbonates) were found in 13 individuals (two dolphins, six olive ridleys, four green turtles, and the leatherback turtle). The sampled species have different diets, distribution patterns, and ages, suggesting widespread plastic pollution. The study area is located far from the oceanic gyres. However, they are influenced by the North Brazilian Current, the Amazon River, and other rivers of the Guianas.

How does invasive Spartina densiflora respond to contrasting environmental conditions in its native region?

Coastal salt marshes are recognized worldwide as diverse and productive environments, providers of many ecosystem services, and as places where a wide variety of taxa live, nest, nurse, and/or feed. Along the Atlantic coast of South America, the austral cordgrass Spartina densiflora displays great phenotypic variations that may favor it to thrive on a wide range of substrates, inhabiting not only the typical soft bottom marshes, but also on cobble beaches and rocky shores. These Patagonian rocky salt marshes, unlike other salt marshes, develop predominantly on top of wave-cut platforms made of sedimentary rock, highly exposed to wave action, and with a dwarf Patagonian phenotype of S. densiflora commonly dominating the vegetation. In this work we evaluate experimentally the hypothesis that this phenotype is a plastic response that maximizes the survival of S. densiflora on rocky bottom environments exposed to wave action. Our results strongly suggest that the austral cordgrass S. densiflora is able to adjust its morphological characteristics in relation to contrasting environmental changes, allowing it to survive in a broad spectrum of coastal environments, including rocky shores with little accumulation of mud and high wave exposure. The typical plants transplanted from the muddy marsh to the rocky marsh exhibited lower height (80%) than the typical control in muddy marsh and than the Patagonian plants in rocky marsh (38%), additionally the typical transplants in the rocky marsh showed no visible damage to their leaves or stems. Our research provides new evidence to understand the success of this species across non-native regions worldwide where it is considered an aggressive invasive bioengineer.

Surveillance of avian malaria and related haemoparasites in common terns (Sterna hirundo) on the Atlantic coast of South America.

Haemosporidia (Apicomplexa, Haemosporida) are protozoa that infect vertebrate blood cells and are transmitted by vectors. Among vertebrates, birds possess the greatest diversity of haemosporidia, historically placed in 3 genera: Haemoproteus, Leucocytozoon and Plasmodium, the causative agent of avian malaria. In South America, existing data on haemosporidia are spatially and temporally dispersed, so increased surveillance is needed to improve the determination and diagnosis of these parasites. During the non-breeding season in 2020 and 2021, 60 common terns (Sterna hirundo) were captured and bled as part of ongoing research on the population health of migratory birds on the Argentinian Atlantic coast. Blood samples and blood smears were obtained. Fifty-eight samples were screened for Plasmodium, Haemoproteus and Leucocytozoon, as well as for Babesia parasites by nested polymerase chain reaction and by microscopic examination of smears. Two positive samples for Plasmodium were found. The cytochrome b lineages detected in the present study are found for the first time, and are close to Plasmodium lineages found in other bird orders. The low prevalence (3.6%) of haemoparasites found in this research was similar to those reported for previous studies on seabirds, including Charadriiformes. Our findings provide new information about the distribution and prevalence of haemosporidian parasites from charadriiforms in the southernmost part of South America, which remains understudied.

Cross-Hemispheric Genetic Diversity and Spatial Genetic Structure of Callinectes sapidus Reovirus 1 (CsRV1).

The movement of viruses in aquatic systems is rarely studied over large geographic scales. Oceanic currents, host migration, latitude-based variation in climate, and resulting changes in host life history are all potential drivers of virus connectivity, adaptation, and genetic structure. To expand our understanding of the genetic diversity of Callinectes sapidus reovirus 1 (CsRV1) across a broad spatial and host life history range of its blue crab host (Callinectes sapidus), we obtained 22 complete and 96 partial genomic sequences for CsRV1 strains from the US Atlantic coast, Gulf of Mexico, Caribbean Sea, and the Atlantic coast of South America. Phylogenetic analyses of CsRV1 genomes revealed that virus genotypes were divided into four major genogroups consistent with their host geographic origins. However, some CsRV1 sequences from the US mid-Atlantic shared high genetic similarity with the Gulf of Mexico genotypes, suggesting potential human-mediated movement of CsRV1 between the US mid-Atlantic and Gulf coasts. This study advances our understanding of how climate, coastal geography, host life history, and human activity drive patterns of genetic structure and diversity of viruses in marine animals and contributes to the capacity to infer broadscale host population connectivity in marine ecosystems from virus population genetic data.

Current and paleoclimate models for an Atlantic Forest kissing bug indicate broader distribution outside biome delimitations

IntroductionRhodnius domesticus is a kissing bug with known occurrence around the Atlantic coast of South America and is considered to be the only endemic species of the Atlantic Forest for the Rhodniini tribe. In this study, we aimed to indicate the species trends in possible distribution in the current and paleoclimate scenarios from the last glacial maximum (LGM).MethodsWe revised R. domesticus distribution information and created ecological niche models (ENMs) between the current time and Pleistocene end scenarios for the study regions. Models were built and validated using Maxent, KUENM, and ENMeval packages in R and ArcMap. We considered the models' uncertainty when calculating the average model variance and using mobility-oriented parity (MOP) analyses to indicate extrapolation risk areas in transfer scenarios.ResultsWe found 44 different geographical species records, and our current time models indicate suitable areas in coastal regions of the Atlantic and surrounding locations in higher and lower latitudes. Paleoclimate models indicate general suitability in coastal regions and change in suitability in the interior region through time.DiscussionOur revision and ENMs indicate two main points: Despite the fact that R. domesticus records are spatial and time concentrated in some coastal regions of the Atlantic Forest, species could have a broader distribution area, including regions outside the biome delimitations in northeast and southwest areas of South America. Paleodistribution models indicate species broader distribution in Atlantic Forest-related areas in LGM and northern interior regions of South America from late Pleistocene to the current times. In glaciation scenarios, continental shelf distribution was relevant and species' different connectivity routes with other biomes may be developed after LGM.

Can hyper/hypo-osmoregulating fiddler crabs from the Atlantic coast of South America mobilize intracellular free amino acids as osmotic effectors during salinity challenge?

Weakly osmoregulating crustaceans use intracellular free amino acids (FAA) to attenuate cell volume changes consequent to alterations in hemolymph osmolality. Whether semiterrestrial, strong hyper/hypo-osmoregulators exhibit this ability is unknown. We investigate FAA mobilization in muscle tissue of 10 fiddler crabs from the genera Minuca, Leptuca, and Uca distributed along the Atlantic coast of South America. Crabs were subjected to severe hypo- or hyper-osmotic challenge at their lower or upper critical salinity limits for 5 days; reference crabs were held in isosmotic media. Hemolymph osmolality was measured, chela muscle FAA were identified and quantified, and percent contribution to intracellular osmolality (%FAA) was calculated. At isosmoticity, total FAA were nominally twofold higher in Minuca species (≈116 mmol/kg wet mass) compared to Uca (≈60 mmol/kg wet mass). Glycine, alanine, arginine, and taurine constituted >80% of the total FAA pool. On hyperosmotic challenge, hemolymph osmolalities ranged from 843 to 1282 mOsm/kg H2 O. FAA increased, although %FAA remained unaltered. Hypo-osmoregulating crabs thus can mobilize FAA, likely owing to a lesser ability to secrete salt near their upper critical limits. On hypo-osmotic challenge, osmolalities were regulated more tightly, between 475 and 736 mOsm/kg H2 O. Total FAA and %FAA showed little change, probably due to the crabs' strong hyper-osmotic extracellular regulatory ability, FAA consequently playing a diminished role in isosmotic intracellular regulation (IIR). Total FAA responses to hyper/hypo-osmotic challenge are thus asymmetrical. The lack of phylogenetic signal in FAA mobilization suggests that closely related fiddler crabs do not share similar strategies of IIR.

Morphology and molecular phylogeny of Chauhanellus Bychowsky & Nagibina, 1969 (Monogenoidea) parasitizing marine catfish (Ariidae) from the Atlantic coast of South America: a new species, supplementary taxonomic information and new insights.

In this study, a new dactylogyrid species is described from the gills of two ariid fish species of the Brazilian coast, Genidens barbus and Genidens genidens, by combining morphological characters with partial 18S rDNA sequences. The new species can be distinguished from its congeners by the following morphological characteristics: a male copulatory organ (MCO), a coiled tubular shaft of around one counterclockwise ring, base with a sclerotized cap; MCO with tapered distal region; a T-shaped accessory piece; a vagina, a cup-shaped vaginal vestibule, slightly sclerotized; and a pharynx comprising a muscular, glandular bulb. Supplementary taxonomic data for Chauhanellus velum from Sciades couma (type-host) are also presented and new 18S rDNA sequences of Chauhanellus spp. from other ariid fish from South America are provided. Phylogenetic analyses based on partial 18S rDNA gene sequences placed Chauhanellus riograndinensis n. sp. and Chauhanellus velum as two early divergent lineages within Chauhanellus from South America. Finally, a way to test the monophyly of Chauhanellus and Hamatopeduncularia is also discussed, which may be useful for future studies.

Diversification processes between monogenoids (Dactylogyridae) and their marine catfish (Siluriformes: Ariidae) from the Atlantic coast of South America.

Due to their high specificity, monogenoids from fish provide an interesting model to study historical associations of hosts and parasites. High agreement between host and parasite phylogeny is often interpreted as evidence of cospeciation. However, cophylogenetic signal may also arise from other, either adaptive or non-adaptive, processes. We applied the recently developed Cophylospace Framework to better understand the evolutionary relationship between monogenoids and marine catfish from the Atlantic coast of South America. The associations between 12 marine catfish and 10 monogenoid species were assessed. Molecular data of host and parasite species were used for phylogenetic reconstruction. We used anchor morphology based on Procrustes coordinates to evaluate whether closely related hosts are associated with morphologically similar parasites. To assess the association between parasite phylogeny and host morphology, we produced a distance matrix based on morphological characters of catfishes. Agreement between phylogenies and between phylogeny and morphology was measured using Procrustes R2 computed with PACo. The parasite phylogeny obtained in this study represents the first complete phylogenetic hypothesis of monogenoids parasitizing ariids from South America. The Cophylospace analysis suggested that phylogenetic and morphological distance of monogenoids contributes similarly to explain the pattern of host–parasite associations, whereas parasite phylogeny is more strongly associated with the morphological traits of the hosts than with host phylogeny. This evidence suggests that cospeciation is not a major force accounting for diversification in the monogenoids studied. Rather host morphological traits seem to be a more important driver, which conforms with evidence from other host‒monogenoid systems.

Odara, a new genus to Edessinae (Hemiptera, Pentatomidae) with Eleven New Species

Abstract The genus Odara gen. n. is here described and composed exclusively of new species: Odara ori sp. n., Odara amazonica sp. n., Odara caribensis sp. n., Odara dracula sp. n., Odara maculatus sp. n., Odara osaensis sp. n., Odara peruensis sp. n., Odara rondoniensis sp. n., Odara tambopatensis sp. n., Odara umbabarauma sp. n. and Odara variegata sp. n. The new genus is characterized by the dorsal coloration green, humeral angles tooth-like generally with black apices, corium dark brown to black with yellow veins, parameres spearhead-shaped, and the sclerotized swelling of the ductus receptaculi in the female internal genitalia. The species are distributed from Central America to the Atlantic coast of South America, from Costa Rica to Rio de Janeiro [Brazil]. Diagnosis, keys to the species, and distributional maps are provided. Photographs of dorsal and ventral view, pygophore, female genital plates, male and female internal genitalia are also provided.

Dendrochronological dating and provenance determination of a 19th century whaler in Patagonia (Puerto Madryn, Argentina)

Dendrochronological methods have been widely used to determine the date of construction and provenance of shipwrecks. Despite a large number of shipwrecks, the application of dendroarchaeological techniques is relatively incipient in the coasts of South America. This paper presents the results of a dendroarchaeological study conducted at the shipwreck site "Bahía Galenses" (BG), located in the western sector of Golfo Nuevo, on the Patagonian coast of the South Atlantic Ocean. Based on previous archaeological research, two hypotheses were tested in this study. First, the wreck described in the BG 2 sub-site corresponds to a mid-19th-century whaler built in the northeastern US. Second, these remains correspond to the Dolphin, a northeastern American whaler built in Warren (Rhode Island) in 1850 and shipwrecked in the Atlantic coast of Patagonia in 1859. Using dendroarchaeological provenance methods and a novel approach based on the gridded North American Drought Atlas, we found highly significant correlations between the wreck's tree-ring width series and white oak and yellow pine tree-ring reference chronologies from the eastern US. The latest non-cutting dates obtained in this analysis correspond to the year 1849. To our knowledge, our study pioneered the use of dendrochronological methods for dating and establishing the provenance of a whaler's remains on the Atlantic coast of South America and encourages the feasibility for future dendroarchaeological research based on the large number of wooden shipwrecks that occurred in the region.

Convergence of virulence and resistance in international clones of WHO critical priority enterobacterales isolated from Marine Bivalves

The global spread of critical-priority antimicrobial-resistant Enterobacterales by food is a public health problem. Wild-caught seafood are broadly consumed worldwide, but exposure to land-based pollution can favor their contamination by clinically relevant antimicrobial-resistant bacteria. As part of the Grand Challenges Explorations: New Approaches to Characterize the Global Burden of Antimicrobial Resistance Program, we performed genomic surveillance and cell culture-based virulence investigation of WHO critical priority Enterobacterales isolated from marine bivalves collected in the Atlantic Coast of South America. Broad-spectrum cephalosporin-resistant Klebsiella pneumoniae and Escherichia coli isolates were recovered from eight distinct geographical locations. These strains harbored blaCTX-M-type or blaCMY-type genes. Most of the surveyed genomes confirmed the convergence of wide virulome and resistome (i.e., antimicrobials, heavy metals, biocides, and pesticides resistance). We identified strains belonging to the international high-risk clones K. pneumoniae ST307 and E. coli ST131 carrying important virulence genes, whereas in vitro experiments confirmed the high virulence potential of these strains. Thermolabile and thermostable toxins were identified in some strains, and all of them were biofilm producers. These data point to an alarming presence of resistance and virulence genes in marine environments, which may favor horizontal gene transfer and the spread of these traits to other bacterial species.

Macrofaunal assemblages structure three decades after the first report of the invasive Crassostrea gigas reefs in a soft-intertidal of Argentina

The macrofaunal assemblages of a soft-bottom intertidal area invaded by the Pacific oyster Crassostrea gigas (Thunberg, 1793) were studied at the site where reef formation was first reported for the Atlantic coast of South America (Los Pocitos; 40° 25′ 59.5″ S, 62° 25’ 23.2” W). Seasonal random sampling (winter, spring and summer) was conducted on oyster reefs and the nearby bare sediment and cordgrass areas. The habitat showed different structures with a wide size range of available spaces for macrofaunal colonization. Fifty-three macrofaunal species were recorded. Thirty-five percent of them were native, 3% were cryptogenic, 5% were exotic, and 54% need further taxonomic determination. All of the exotic species were found in reefs; though the amphipod Monocorophium insidiosum (Crawford, 1937) also settled on soft and cordgrass sediments. Species assemblages changed across seasons. Diversity was higher in reefs than in cordgrass or bare sediments during the warm season. There were no differences in the proportion of trophic groups. Our results suggest that C. gigas restructures the macrofaunal species assemblages and that this effect is driven by seasonality. In Los Pocitos, oyster reefs currently show a primary role as a suitable habitat for many species, but the net impacts of the invasion of this ecosystem engineer, including the cascading effects on the food web or the facilitation of further invasions remain unclear. The mechanisms and net effects of this restructuring force need further attention.

Large-scale connectivity of the sandy beach clam Mesodesma mactroides along the Atlantic coast of South America, and climate change implications

The yellow clam Mesodesma mactroides is a cool-water species that typifies sandy beaches of the Southwestern Atlantic Ocean (SAO), which embraces one of the strongest ocean warming hotspots. The region is influenced by the Rio de la Plata (RdlP), which represents a zoogeographic barrier that restricts its larval exchange. We investigated yellow clam larval connectivity patterns using an individual based model (IBM). The IBM combined outputs from a 3D hydrodynamic model with a clam submodel that considered salinity- and temperature-dependent mortality for the planktonic larvae. Connectivity across the RdlP estuary occurred only for larvae released in spring during a strong La Niña event. Mortality due to freshwater precluded larval transport across the RdlP, whereas larval mortality induced by warmer waters reduced connectivity, leading to self-recruitment in most areas. Warming acceleration in this hotspot could further restrict larval connectivity between populations in the SAO, with conservation implications for this threatened species.

Not going with the flow: Ecological niche of a migratory seabird, the South American Tern Sterna hirundinacea

Defining a species’ ecological niche is not a trivial task particularly for marine taxa, since physical and biological constraints are not easily perceived in these environments. Yet, coastal habitats are divided into provinces, influenced by different environmental conditions, such as superficial marine currents, causing seasonality in marine productivity and biomass. The South American Tern Sterna hirundinacea is a poorly known, migratory seabird distributed along the Pacific and Atlantic coasts of South America, including the Malvinas/Falkland Islands, and occurring in most of the South American coastal provinces. Limited knowledge on the migratory behaviour of the species points to differential habits between southern and northern populations. The species’ breeding season also varies with latitude and season, occurring during spring in the south and in the fall in northern areas of the species occurrence. These observations point to putatively ecologically distinct populations along the species range that seem to be coincident with coastal provinces. To test our hypotheses, we estimated full-range ecological niche models per season, and we used coastal provinces to model ecological niches for each of the known breeding areas/seasons. We also tested for environmental space differentiation between seasons and breeding and non-breeding areas. Overall, the species does not seem to occupy significantly different ecological niches throughout the year, except during the breeding season, particularly between the Warm Temperate Southeastern Pacific and Warm Temperate Southwestern Atlantic provinces in fall. This suggests that the South American Tern migratory behaviour, the selection of different microhabitats and reproductive areas or distinct biological interactors might be influencing the species environmental space. Nonetheless, our models reinforce the gradual migration of this tern species towards the south, spending the summer mostly in the Malvinas/Falkland Islands. Interestingly, the species seems to be resident in Peru coastal area. Thus, despite the absence of ecological divergence, population structure should be tested and demographic trends assessed along the species range.

Ecology, evolution, and epidemiology of zoonotic and vector-borne infectious diseases in French Guiana: Transdisciplinarity does matter to tackle new emerging threats.

French Guiana is a European ultraperipheric region located on the northern Atlantic coast of South America. It constitutes an important forested region for biological conservation in the Neotropics. Although very sparsely populated, with its inhabitants mainly concentrated on the Atlantic coastal strip and along the two main rivers, it is marked by the presence and development of old and new epidemic disease outbreaks, both research and health priorities. In this review paper, we synthetize 15 years of multidisciplinary and integrative research at the interface between wildlife, ecosystem modification, human activities and sociodemographic development, and human health. This study reveals a complex epidemiological landscape marked by important transitional changes, facilitated by increased interconnections between wildlife, land-use change and human occupation and activity, human and trade transportation, demography with substantial immigration, and identified vector and parasite pharmacological resistance. Among other French Guianese characteristics, we demonstrate herein the existence of more complex multi-host disease life cycles than previously described for several disease systems in Central and South America, which clearly indicates that today the greater promiscuity between wildlife and humans due to demographic and economic pressures may offer novel settings for microbes and their hosts to circulate and spread. French Guiana is a microcosm that crystallizes all the current global environmental, demographic and socioeconomic change conditions, which may favor the development of ancient and future infectious diseases.

Description of Leurocyclus tuberculosus (Decapoda, Brachyura) for northern Chilean Patagonian inner seas (41°S, Puerto Montt, Chile)

Abstract The brachyuran crab, Leurocyclus tuberculosus (H. Milne Edwards & Lucas, 1842) is widely distributed along the Atlantic coast of South America, but there are no precise records about its occurrence on the Chilean Pacific coast. The present study is a description of four juvenile specimens of L. tuberculosus collected from an intertidal prairie of Gracilaria sp. in an inner sea in Chile (41°S, Puerto Montt). According to existing literature, the specimens would be juvenile individuals belonging to L. tuberculosus that, in accordance with the literature, was described as probably inhabiting the Chilean coasts without more details. The literature revealed that this species is widely distributed along the Atlantic coasts of South America, and can also, probably due to dynamic oceanographic processes, be present on the southern Pacific coast.

Morphological and Genetic Variation Among Populations of the Fiddler Crab Minuca burgersi (Holthuis, 1967) (Crustacea: Brachyura: Ocypodidae) from Shores of the Caribbean Basin and Western South Atlantic Ocean.

For this study, in addition to museum vouchers, 1437 specimens of Minuca burgersi (Holthuis, 1967) were collected from crab colonies at 105 locations in the western Atlantic Ocean to examine diversity in a species with a large geographic range. Both allometric and geometric morphometry were coupled with the molecular analysis of DNA to give a broader perspective of intraspecific variability in this species. A total of 1153 specimens from the Caribbean Sea and the Atlantic coast of South America demonstrated that M. burgersi from both regions are very similar in their pattern of growth. The average carapace width (CW) for Caribbean is larger than the average for South American males and females. However, size distribution based on CW is unimodal in Caribbean and bimodal in South American populations. The carapace length-width ratio is about 0.68 in females and 0.66 in males. South American males express asymmetric elongation of the cheliped in smaller CW intervals than Caribbean males. In a sample of 259 females, carapace shape is distinct between South American and Caribbean populations. Caribbean populations have less swelling in the branchial regions than South American populations. The swelling correlates primarily with geographic region and to a lesser degree with substrate and salinity. Molecular data from the 16S rDNA and cytochrome c oxidase subunit I (COI) reveal three clades within Minuca burgersi. Two clades are distributed in the Caribbean and the third in eastern South America. The timing of divergence between Caribbean and South American clades is coincident with an increased rate of water and sediment outflow from the Amazon as inferred from the geologic record. Current patterns and associated gene flow within the Caribbean were subsequently influenced by the closing of the Isthmus of Panama. We speculate that various populations may employ different larval dispersion mechanisms resulting in genetic heterogeneity. Consequently, there is considerable biological divergence among populations of M. burgersi in the Caribbean and South America.

Miocene heterozoan carbonate systems from the western Atlantic equatorial margin in South America: The Pirabas formation

Outcrops of Neogene carbonates of the North Brazilian platform occur exclusively along the equatorial coast and represent some of the few existing examples of Neogene carbonate systems of the Atlantic coast of South America. The Pirabas Formation (early-middle Miocene) is the northernmost part of this platform. Although onshore mainly consists of small and scattered outcrops, it considerably extends in the subsurface keeping record of relevant geological and paleontological episodes of tropical South American history. Intending to improve the knowledge of South American carbonate and providing a solid basis for future comparisons between the Pirabas Basin and other, largely subsurface, Cenozoic basins, this research investigates the Aricuru outcrops by combining a standard petrographical and paleontological approach with advanced microCT analyses. The Aricuru area is characterized by mixed siliciclastic-carbonate sand-sized deposits, which probably deposited after the early Miocene according to the palynological assemblage. The bioclastic fraction of the rock is dominated by benthic foraminifera (mostly soritids, amphisteginids, small rotaliids, and small miliolids, typical of marginal marine environments), bryozoans, calcareous algae (Halimeda), echinoderms and mollusks. The abundant siliciclastic fraction together with the taxonomic composition of the foraminiferal, echinodermal, crustacean, ichnofossil and fish assemblages indicates deposition in a tropical coastal environment featuring both protected and more exposed sectors. The carbonate system probably developed under abundant nutrient supply, which fostered heterotroph suspension feeders over hermatypic corals. The demise of this system was most likely caused by a growth in siliciclastic input due to increased rainfall in the coastal area. The sedimentary evolution of the Pirabas Formation is similar to the one of the Foz do Amazonas Basin, and fits well with the general evolutionary trend of Cenozoic carbonate factories of the region, indicating the potential of the Pirabas subsurface record for understanding other Cenozoic basins, their paleoenvironmental significance, and their potential as oil, gas and water reservoirs.