Late Pleistocene and Holocene chitons (Mollusca, Polyplacophora) from Uruguay: Palaeobiogeography and palaeoenvironmental reconstruction in mid latitudes of the southwestern Atlantic

Here we present a revision of the fossil record of chitons (Mollusca, Polyplacophora) of Late Pleistocene and Holocene marine deposits of Uruguay and discuss their potential for palaeoenvironmental reconstruction. Chitons were recorded as isolated valves in bivalve- and gastropod-rich assemblages. They are represented by the species Chaetopleura angulata (Spengler), C. isabellei (d’Orbigny), C. asperrima (Gould) and Ischnochiton striolatus (Gray). The last two species are recorded for the first time as fossils not only in Uruguay but also in South America. Exclusively recorded for the Late Pleistocene is the warm water species I. striolatus, whose current southern range limit is located in Santa Catarina, Brazil. Higher temperatures than at present are inferred for the Uruguayan coast during the Late Pleistocene, probably driven by the southward influence of the warm Brazilian Current along the eastern margin of South America. Chitons from Holocene deposits show a wider geographic distribution along the Uruguayan coast in comparison to current distributions. They are recorded where an estuarine and eurihaline fauna lives today, which suggests the former existence of marine conditions. This is explained by the westward displacement of the marine front in the Uruguayan coast during the Holocene transgressive events. Chitons have proven to be useful palaeoenvironmental proxies for the reconstruction of salinity and temperature trends in the Uruguayan coast during the climatic oscillations of the Late Pleistocene and Holocene epochs. As such, their patterns of distribution are related to the recent physical evolution of the Southwestern Atlantic Ocean.     

Detection of chronic bee paralysis virus and acute bee paralysis virus in Uruguayan honeybees

Chronic bee paralysis virus (CBPV) causes a disease characterized by trembling, flightless, and crawling bees, while Acute bee paralysis virus (ABPV) is commonly detected in apparently healthy colonies, usually associated to Varroa destructor. Both viruses had been detected in most regions of the world, except in South America. In this work, we detected CBPV and ABPV in samples of Uruguayan honeybees by RT-PCR. The detection of both viruses in different provinces and the fact that most of the analyzed samples were infected, suggest that, they are widely spread in the region. This is the first record of the presence of CBPV and ABPV in Uruguay and South America.     

Seabird bycatch in the Southwest Atlantic: interaction with the Uruguayan pelagic longline fishery

This paper analyzes the spatiotemporal variation and the causes of seabird bycatch by the Uruguayan pelagic longline fleet in a region of the Atlantic Ocean where the world’s highest historical rates of seabird bycatch were recorded. The study is based on data obtained by the Uruguayan Observers Program in 29 trips, conducted from 1998 to 2004, totalling about 648,000 hooks. The bird capture per unit of effort (BCPUE) for the studied period was 0.42 birds/1,000 hooks. The highest BCPUE values were recorded in the period May–November. Three zones were identified, with BCPUEs of 2.50 birds/1,000 hooks (very high); 0.78 birds/1,000 hooks (high) and 0.04 birds/1,000 hooks (low). Though these BCPUE values are lower than those historically reported, some are still high in global terms. Night setting was found to be effective in reducing seabird bycatch, but it is necessary to implement additional measures as seabirds have access to bait also by night, especially during the more luminous moon phases.     

Toward a global database for the molecular typing of Saccharomyces cerevisiae strains

Most of the yeast strains used in fermented beverages and foods are classified as Saccharomyces cerevisiae. However, different strains are suitable for different fermentation processes. The purpose of this work is the proposal of a standardized methodology for the molecular genotyping of S. cerevisiae strains based on polymorphisms at microsatellite loci and/or single nucleotide polymorphisms (SNPs). Single nucleotide variants in the coding region of FLO8, a key regulator of flocculation and pseudohyphae formation, were analyzed in a subset of Uruguayan wine strains. Polymorphism analysis at nine microsatellite loci (selected from 33 loci tested) was performed in a collection of 120 strains, mostly wine strains, from different origins. From a total of 184 different alleles scored, 50 were exclusive alleles that could identify 29 strains. Four selected microsatellite loci are located within or near genes of putative enological interest. The Uruguayan strains are highly diverse and evenly distributed in the phylogenetic reconstructions, suggesting an evolutionary history previous to human use. The Saccharomyces cerevisiae Microsatellites and SNPs Genotyping Database is presented (www.pasteur.edu.uy/yeast). Comparison of standardized results from strains coming from different settings (industrial, clinical, environmental) will provide a reliable and growing source of information on the molecular biodiversity of S. cerevisiae strains.     

Mitochondrial DNA in Basque descendants from the city of Trinidad, Uruguay: Uruguayan- or Basque-like population?

Like other countries in the Americas, during its colonization Uruguay was the recipient of immigrants from several ethnic groups from Europe, as well as of enslaved Africans. After its independence in 1830, Basques were the first group of Europeans to arrive in the country. In this paper, we aim to contribute to the understanding of the process of integration of these migratory waves into the Uruguayan society. For that purpose, individuals of Basque origin from the city of Trinidad, Uruguay, were chosen to participate in this study. Particularly, we wanted to determine if Basque descendants in Uruguay remained relatively isolated or if they mixed with other ethnic groups. Mitochondrial DNA (mtDNA) of 60 self-identified Basque descendants, taken from a larger sample of subjects with Basque ancestors, was analyzed. The origin of mtDNA haplogroups was 77.8% European, 20.4% Amerindian, and 1.8% African, showing similar frequencies to other Uruguayan regions. Very few sequences showed a clear Basque origin, although other sources such as the Canary Islands are likely. Moreover, genetic distances clearly show that Basque descendants are genetically closer to other Uruguayan groups than to European populations, including Basques. It is possible to conclude that Basques and their descendants in the region of Trinidad did not remain isolated and that their marriage behavior was similar to that of other Uruguayan populations. However, to have a more accurate picture of the way Basques intermarried with other populations in Uruguay, new analyses are needed that take into account paternal lineages as well as biparental genetic markers.     

Population genetic structure and social kin associations of franciscana dolphin, Pontoporia blainvillei

We investigated population and social structure of the franciscana dolphin, Pontoporia blainvillei, an endemic and the most endangered cetacean of the southwestern Atlantic Ocean. We analyzed samples from the Rio de la Plata estuary obtained in Uruguayan waters and from the Atlantic Ocean obtained in both Uruguayan and Brazilian waters. Mitochondrial and microsatellite DNA markers were used to study differentiation between the estuary and the ocean and the association between kinship and social group structure. Although multilocus analyses suggested that franciscanas are structured into 2 subpopulations (K = 2, divergence among clusters: F(ST) = 0.06, P = 0.002; R(ST) = 0.3, P = 0.001), mitochondrial markers did not support such divergence (F(ST) = 0.02, P = 0.12; Ф(ST) = 0.06, P =0.06). However, these units are not entirely segregated geographically. Regarding social structure, some groups are composed by first-order related individuals (R ≥ 0.5, P < 0.5). Overall, the data suggest that matrilines could be the social unit in this species. We argue that the divergence found could be associated to local adaptation and social structure, resulting from either feature leading to a recent divergence or reflecting equilibrium between local differentiation and gene flow. This evidence supports considering franciscanas from the Rio de la Plata estuary a discrete management unit.     

COEVOLUTION AND AVIAN BROOD PARASITISM: COWBIRD EGGS SHOW EVOLUTIONARY RESPONSE TO HOST DISCRIMINATION

The Rufous Hornero (Furnarius rufus) is an important host of the brood parasitic Shiny Cowbird (Molothrus bonariensis) in Uruguay, but not in nearby Buenos Aires Province, Argentina. Eggs of the Shiny Cowbird are extremely variable in size, and horneros eject cowbird eggs with widths less than about 88% of the widths of their own eggs. Uruguayan cowbird eggs are, on average, 12% larger than those from Buenos Aires, a geographic pattern in egg size that corresponds to the pattern of successful host use. Uruguayan cowbird eggs are also wider per unit volume than eggs from Buenos Aires. Allometric analyses of egg width and volume indicate that this shape change is apparently an evolutionary response to selection exerted by the hornero. Such a response is absent in Buenos Aires because interactions between the cowbird and the hornero are probably of recent origin there.     

Parasites as biological tags for stock discrimination of the Brazilian flathead Percophis brasiliensis in the south-west Atlantic

Three stocks of the Brazilian flathead Percophis brasiliensis were identified on the coast of Argentina and Uruguay using parasites as biological tags. A total of 177 fish were examined and 23 parasite species were found. Fish were caught in four zones: north of the Argentine–Uruguayan Common Fishing Zone (34°30′–36°30′ S; 53°30′–56°00′ W), south of the Argentine–Uruguayan Common Fishing Zone (38°08′ S 57°32′ W), El Rincón zone (39–41° S; 60–62° W) and San Matías Gulf (41°40′–42°10′ S; 63°50′–65°00′ W). Discriminant analyses allowed the identification of three discrete stocks in the four zones (86·44% of classified samples were correctly identified), with P. brasiliensis from both north and south of the Argentine–Uruguayan Common Fishing Zone clumping together, as a single stock. Some species were important in discriminating among groups, Anisakis simplex was related to southern areas, while Grillotia sp., Corynosoma australe and Hysterothylacium sp. were important in determining the position of fish from the Argentine–Uruguayan Common Fishing Zone. These results were corroborated by comparing parasite prevalence and abundance among zones. The main differences were observed in those comparisons involving fish from the San Matías Gulf. Fish from the Argentine–Uruguayan Common Fishing Zone were characterized by higher infections of Grillotia sp., C. australe, Corynosoma cetaceum and Hysterothylacium sp., while the samples from El Rincón and San Matías Gulf showed higher infections of A. simplex. Samples from San Matías Gulf were characterized by lower levels of parasitism for all other species. Differences in environmental factors and their influence on the distribution of zooplankton and other hosts in the food web may be differentially shaping the parasite community structure in each zone, resulting in identifiable stocks of the P. brasiliensis. The present study confirmed the existence of regional biological tags that delineated fish assemblages.     

Gametogenesis, histological gonadal cycle and in vitro fertilization in the whitemouth croaker (Micropogonias furnieri, Desmarest, 1823)

The whitemouth croaker (Micropogonias furnieri) is a demersal teleostean fish inhabiting the Atlantic Ocean from northern Venezuela to southern Argentina. In terms of biomass, the whitemouth croaker is the dominant sciaenid in the Río de la Plata and constitutes an important renewable resource for the Uruguayan and Argentinean fisheries. In the present study, analyzed were the gametogenesis and histological gonadal cycle in female and male whitemouth croakers collected at the Uruguayan coast of the Río de la Plata, between March 1997 and February 1998. In addition, the experimental conditions required to obtain mature viable gametes and achieve in vitro fertilization in this species were investigated. These studies indicate that the whitemouth croaker inhabiting the Río de la Plata is a multiple spawner, which reproduces on the Uruguayan coast between October and February. In vitro studies showed that following activation, sperm remain motile for up to 40 min, and under optimal dilution conditions that they retain a high fertilization capability for 15 min. Taken together these results could support future aquaculture research and exploitation of this species.     

FATTY ACID COMPOSITION OF FATS FROM THE URUGUAYAN FUR SEAL (ARCTOCEPHALUS AUSTRALIS ZIMMERMANN)

The composition and properties of commercial oil collected from Uruguayan fur seals ( Arctocephalus australis Zimmermann) during 1985, 1986 and 1987 are reported. Oil recovered from some organs (kidney, heart, liver) and blubber were also analyzed. All have compositions similar to oils from other marine animals in commercial use, containing high percentages of long chain and polyunsaturated fatty acids.     

Extinct and extant sand dollars (Clypeasteroida: Echinoidea) from Uruguay

We summarize information concerning Recent and Pleistocene-Holocene Uruguayan sand dollars (Mellitidae), as well as Miocene taxa (Monophorasteridae). Recent and Pleistocene-Holocene species (Encope emarginata, Mellita quinquiesperforata, and Leodia sexisperforata) are at their southernmost limits of distribution, with only E. emarginata recorded further south than Uruguay. Lower temperatures to the south, and/or the Rio de la Plata salinity barrier are suggested as controlling factors of these distributions. During the Miocene, the sea temperatures were notably higher than at present, and it was at this time that the extinct genera Monophoraster and Amplaster reached their maximum diversity in Uruguay. The family Monophorasteridae is the basal sister group of the Mellitidae.     

Heavy metal distribution in zooplankton from Buenos Aires coastal waters (Argentina)

ABSTRACT

Total Zooplankton samples from Argentinian and Uruguayan Coastal Waters were analysed to determine their heavy metal contents. Zinc, copper, cadmium, iron, lead and manganese concentrations were measured using atomic absorption spectrophotometry and metal content distributions were geographically plotted. Except for cadmium, all the studied metals showed maximum values on the Uruguayan shores, and this was related not only to the location of the potential metal sources, but also to the hydrographical characteristics of the area. Finally, the suitability of zooplankton as an adequate biological indicator of heavy metal pollution in coastal environments is discussed.     

Genetic evidence of two stocks of the whitemouth croaker Micropogonias furnieri in the Río de la Plata and oceanic front in Uruguay

Analysis of the mitochondrial DNA control region resolved two stocks of whitemouth croaker Micropogonias furnieri in Uruguayan waters, one in the Río de la Plata and the other on the Uruguayan shelf. The whitemouth croaker is the most important coastal fishery resource along the coast and has the greatest commercial importance in the Río de la Plata and its oceanic front. The number of pair-wise differences (π) and haplotype diversity ( h ) showed significant differences between the two regions. Frequencies of mtDNA haplotypes did not differ between Río de la Plata from Bahia Blanca M. furnieri . Samples from the oceanic front showed greater genetic variability and a larger effective number of females that were an order of magnitude larger than that in Río de la Plata. Mismatch distributions showed evidence of a recent population expansion in the oceanic region, beginning c. 40 000 b.p. The presence of two stocks of the M. furnieri in the study area should be considered in the management of this species' fishery.     

Prevalence of vitamin D receptor gene polymorphism in a Uruguayan population and its relation to type 1 diabetes mellitus

Vitamin D has important immuno-modulatory properties and it influences insulin secretion. It acts through a vitamin D receptor (VDR), for which several gene polymorphisms have been described. The Uruguayan population presents several epidemiological characteristics that make it different from that of other counties, including other Latin-American countries. It went through miscegenation processes, with a tri-hybrid European, Amerindian and African origin, with no contribution from isolated Amerindian communities. Such differences have important consequences for the relationship between frequencies of several genes in the general population and their association with the diabetes mellitus. We examined the prevalence of VDR gene polymorphisms in the general population and their relation to type 1 diabetes in a parent-case design. One hundred unrelated individuals from the general population and 45 parent-patient triads with a child affected with type 1 diabetes were genotyped for FokI, BsmI and TaqI VDR gene polymorphisms by RFLP-PCR. We used a transmission disequilibrium test to assess preferential transmission of parents to affected offspring. The prevalence of the three VDR polymorphisms was: allele F = 48%, B = 35%, T = 64%. The f, b, T alleles and heterozygous genotypes were found at a high frequency in this population. Among 36 informative heterozygous parental genotypes, 30 transmitted the F allele (probability of transmission = 83%). The other two polymorphisms did not show significant transmission. We suggest that FokI polymorphism indicates susceptibility to type 1 diabetes mellitus in the Uruguayan population.     

Findings from the Peutz-Jeghers Syndrome Registry of Uruguay

Background

Peutz-Jeghers syndrome (PJS) is characterized by intestinal polyposis, mucocutaneous pigmentation and an increased cancer risk, usually caused by mutations of the STK11 gene. This study collected epidemiological, clinical and genetic data from all Uruguayan PJS patients.

Methods

Clinical data were obtained from public and private medical centers and updated annually. Sequencing of the STK11 gene in one member of each family was performed.

Results and discussion

25 cases in 11 unrelated families were registered (15 males, 10 females). The average age of diagnosis and death was 18 and 41 years respectively. All patients had characteristic PJS pigmentation and gastrointestinal polyps. 72% required urgent surgery due to intestinal obstruction. 3 families had multiple cases of seizure disorder, representing 20% of cases. 28% developed cancer and two patients had more than one cancer. An STK11 mutation was found in 8 of the 9 families analyzed. A unique M136K missense mutation was noted in one family. Comparing annual live births and PJS birth records from 1970 to 2009 yielded an incidence of 1 in 155,000.

Conclusion

The Uruguayan Registry for Peutz-Jeghers patients showed a high chance of emergent surgery, epilepsy, cancer and shortened life expectancy. The M136K missense mutation is a newly reported STK 11 mutation.     

Biogeography and Breeding in Gymnotiformes from Uruguay

This study was carried out in Uruguay (30–35°S), South America, with two complementary approaches. First, an extensive exploration of Uruguayan freshwaters allowed us to assess the distribution of the two major species of Gymnotiformes (out of 4) across sites. Gymnotus carapo was uniformly distributed in Uruguayan territory, whereas Brachyhypopomus pinnicaudatus was observed in the northern and eastern part of the country. There was a highly significant negative correlation between the relative abundance of Brachyhypopomus pinnicaudatus and pH and water conductivity. Moreover, these environmental factors are significant contributors to its spatial differences in relative abundance. Second, temperature, conductivity, photoperiod, and the structure of a Brachyhypopomus pinnicaudatus population were analyzed across seasons in a small lake over a two-year period. Water temperature and photoperiod exhibited important seasonal changes, whereas water conductivity remained low and relatively constant. The presence of sexually mature males, females, and the sudden increase of juveniles indicated the occurrence of the breeding season in November, December, and January, coinciding with high mean water temperatures and extreme photoperiod. These results agree with previous data that support the hypothesis of temperature as an important environmental factor for the onset of breeding in Gymnotiformes from the temperate zone.     

HLA gene and haplotype frequencies in Uruguay

A total of 604 individuals living in Montevideo and other places in Uruguay were studied in relation to three I HLA loci. The most common alleles observed (percentages in parentheses) were A2(24), A9(15), A19(11), B12(12), B35(12), and C4(16). The most marked departures from linkage equilibrium (all numbers multiplied by 10⁵) were B35-C4(636), A2-B5(590), A2C3(515), A2B14(494), and A19-B12(485). These findings do not contradict the hypothesis that while most of the Uruguayan population is of Caucasoid origin, significant African and Amerindian genes may exist in its gene pool.     

The initial peopling of South American Plains: An overview on Late Pleistocene and Early Holocene settlers in Uruguay

This paper reviews more than 20 years of research about the Late Pleistocene and Early Holocene occupations of the Uruguayan plains. The aim of this synthesis is to provide an overview of the available information related to early human peopling of Uruguay. Here, we focus on the main issues discussed over the last two decades: early sites characterization and chronology, human response to climate change, cultural diversity, occupations patterns, mobility and technology. The systematic and continuous efforts made have provided new data and new perspectives regarding the earliest human occupations of the region. We have defined an archaeological complex landscape and ongoing research strategy is based on the three main types of site that compose it: residential camps, cave and rock shelters, and raw material sources. This has allowed us to expand and improve our understanding of the record. The new research and data provided by these sites have led us to propose a settlement model for the region and the period. A cultural diversity has been evidenced through in-depth studies of stratified archaeological sites, cultural sequence, a solid chronological database and lithic technology. Finally, we advance in the characterization of objects of social prestige among hunter-gatherers who occupied the plains during the end of the Pleistocene in Southeastern South America.