Reproductive biology of an amphidromous goby, Sicyopterus lagocephalus, in La Réunion Island

In the Indo-Pacific region, rivers are inhabited by amphidromous gobies. They are often subjected to a heavy fishing pressure, highlighting the urgent need to acquire knowledge on their biology for management purposes. This study investigated the reproductive strategy of Sicyopterus lagocephalus, a widespread amphidromous goby, in two rivers of La Réunion Island. Histological observations of ovarian samples and oocyte-size frequency distributions revealed that females had a group-synchronous ovarian follicle development (i.e., two cohorts of oocytes were distinguished simultaneously in ovaries). Females laid an entire clutch in a unique event (from 14,304 to 232,475 eggs) and then another batch of oocytes was recruited, showing that the annual fecundity is indeterminate. Ovarian growth was isometric at all oocyte development stages showing that the gonadosomatic index (GSI) is a good proxy of reproductive condition. The main reproductive season of S. lagocephalus spanned from early February to May with a narrower range upstream and a wider one downstream. Reproduction activity is mainly restricted by water temperatures in upstream areas, whereas it is likely influenced by female body condition and competition in downstream areas. The variability of reproductive traits leads to size structure variation in stocks of spawning females throughout the year.     

Spectrum of CFTR mutations on Réunion Island: impact on neonatal screening

The large heterogeneity in the cystic fibrosis (CF) gene is the main difficulty for genotype characterization. Numerous studies have reported considerable variations in frequencies of CF transmembrane conductance regulator (CFTR) mutations in different populations, such as African, Asian, or European populations. To completely characterize the spectrum of mutations in the CFTR gene in the Réunion Island population, we screened 228 CF chromosomes using denaturing high-pressure liquid chromatography and denaturing gradient gel electrophoresis following by direct sequencing. We identified 27 mutations, accounting for 93% of CF chromosomes. They included three novel mutations (M1T, 3121-3C-->G, and L1324P), which are described in this paper. The detection of such a high proportion of Réunion Island CFTR mutations is important for improving neonatal screening of CF on Réunion Island.     

Admixture and sexual bias in the population settlement of La Réunion Island (Indian Ocean)

La Réunion, one of the three Mascarene islands located in the Indian Ocean, remained devoid of inhabitants until it was first colonized by the French in the middle of the 17th century. The continuous flow of foreign-born slaves and immigrant workers from Africa, India, Southeast Asia, and China to work on coffee and sugar cane plantations led to the island becoming a melting pot of people of multiple ethnic origins. To establish the impact of the different incoming ethnic groups on the present Reunionese gene pool, we have sequenced both hypervariable regions I and II of the mitochondrial DNA molecule, the 9 bp COII/tRNA(Lys) deletion, and four SNPs located in the coding region in a total of 41 samples of the general population, and a further 18 STRs and 35 SNPs on the Y chromosome in 26 of these samples. Our results show that there was a strong sexual bias (asymmetrical gene flow) in the peopling of La Réunion, where admixture events were mainly between male settlers and females from the incoming slave groups. Most of the Y-chromosome gene pool is of European/Middle Eastern ancestry (85%), whereas the mtDNA gene pool is mainly of Indian and East Asian ancestry (70%). The absence of genetic diversity within these two major components of the mtDNA gene pool suggests these populations may have witnessed strong founder effects during the colonization process.     

Prospective Study of Chikungunya Virus Acute Infection in the Island of La Réunion during the 2005–2006 Outbreak

Background

Chikungunya virus (CHIKV) is a recently re-emerged arthropod borne virus responsible for a massive outbreak in the Indian Ocean and India, and extended to Southeast Asia as well as Italy. CHIKV has adapted to Aedes albopictus, an anthropophilic mosquito species widely distributed in Asia, Europe, Africa and America. Our objective was to determine the clinical and biological features of patients at the acute phase of CHIKV infection.

Methods and Findings

A prospective study enrolled 274 consecutive patients with febrile arthralgia recorded at the Emergency Department of the Groupe Hospitalier Sud-Réunion between March and May 2006. Three groups were defined: one group of 180 viremic patients (positive CHIKV RT-PCR), one group of 34 patients with acute post-viremic infection (negative CHIKV RT-PCR, positive anti-CHIKV IgM and negative IgG), and one group of 46 uninfected patients (negative CHIKV RT-PCR, anti-CHIKV IgM and IgG). Bivariate analyses of clinical and biological features between groups were performed. Patients with CHIKV viremia presented typically with asymmetrical bilateral polyarthralgia (96.5%) affecting the lower (98%) and small joints (74.8%), as well as asthenia (88.6%), headache (70%), digestive trouble (63.3%), myalgia (59%), exanthems (47.8%), conjunctival hyperhemia (23%) and adenopathy (8.9%). Vertigo, cutaneous dysesthesia, pharyngitis and haemorrhages were seldom observed. So far unreported symptoms such as chondrocostal arthralgia (20%), entesopathies (1.6%), talalgia (14%) were also noted. Prurit was less frequent during the viremic than post-viremic phase (13.9% vs. 41.2%; p<0.001), whereas lymphopenia was more frequent (87.6% vs. 39.4%; p<0.001). Others biological abnormalities included leukopenia (38.3%), thrombocytopenia (37.3%), increased ASAT and ALAT blood levels (31.6 and 7.3%, respectively) and hypocalcemia (38.7%). Lymphopenia <1,000/mm³ was very closely associated with viremic patients (Yule coefficient 0.82, positive predictive value 92.3%). Age under 65 was associated with a benign course, as no patients younger than 65 had to be hospitalized (Yule coefficient 0.78).

Conclusions

The diagnosis of CHIKV infection in acute phase is based on commonly accepted clinical criteria (fever and arthralgia), however clinical and biological diffrences exist in acute phase depending on whether or not the patient is within the viremic phase of the infection.     

First record of troglobitic Hemiptera (Fulgoromorpha: Cixiidae) from La Réunion Island

A new species of troglobitic Cixiidae (Hemiptera: Fulgoromorpha), Brixia briali n. sp. is described from a lava tube on La Réunion Island. Information on its ecology, distribution, and comments on its tentative systematic placement into the genus Brixia is provided. The new discovery from La Réunion is placed into the context of cavernicolous Fulgoromorpha of the world, their zoogeography, ecology and biology.     

Aedes albopictus in Sardinia: reappearance or widespread colonization?

The Asian tiger mosquito Aedes albopictus (Skuse, 1894) was first discovered in the South of Sardinia in October 1994, in a tyre depot not far from Cagliari-Elmas airport. Insecticide treatment was thought to have successfully eradicated the mosquito, but in 1996 and 1997 new breeding sites were discovered, a few at some distance from the first. More recently two sites have been reported in the heart of the city of Cagliari. It is not known whether the mosquito has spread from the first breeding place discovered, where treatment may not have been definitive, or whether they have been newly introduced. The recent sighting of Ae. albopictus in Olbia in the Northeast of the island tends to suggest the latter. Cagliari and Olbia are actually Sardinia's two largest sea ports of entry.     

The Chikungunya epidemic on La Réunion Island in 2005-2006: a cost-of-illness study

Background

This study was conducted to assess the impact of chikungunya on health costs during the epidemic that occurred on La Réunion in 2005–2006.

Methodology/Principal Findings

From data collected from health agencies, the additional costs incurred by chikungunya in terms of consultations, drug consumption and absence from work were determined by a comparison with the expected costs outside the epidemic period. The cost of hospitalization was estimated from data provided by the national hospitalization database for short-term care by considering all hospital stays in which the ICD-10 code A92.0 appeared. A cost-of-illness study was conducted from the perspective of the third-party payer. Direct medical costs per outpatient and inpatient case were evaluated. The costs were estimated in Euros at 2006 values. Additional reimbursements for consultations with general practitioners and drugs were estimated as €12.4 million (range: €7.7 million–€17.1 million) and €5 million (€1.9 million–€8.1 million), respectively, while the cost of hospitalization for chikungunya was estimated to be €8.5 million (€5.8 million–€8.7 million). Productivity costs were estimated as €17.4 million (€6 million–€28.9 million). The medical cost of the chikungunya epidemic was estimated as €43.9 million, 60% due to direct medical costs and 40% to indirect costs (€26.5 million and €17.4 million, respectively). The direct medical cost was assessed as €90 for each outpatient and €2,000 for each inpatient.

Conclusions/Significance

The medical management of chikungunya during the epidemic on La Réunion Island was associated with an important economic burden. The estimated cost of the reported disease can be used to evaluate the cost/efficacy and cost/benefit ratios for prevention and control programmes of emerging arboviruses.     

Mitochondrial DNA heteroplasmy maintained in natural populations of Drosophila simulans in Réunion

Mitochondrial DNA (mtDNA) variation in Drosophila simulans was studied to determine whether the cytoplasmic state of mtDNA heteroplasmy persists in natural populations in Réunion. For this purpose, 172 isofemale lines, newly collected from two local populations, were examined, among which three types of mtDNA (siII, siIII and siIII') were found, based on the Hpa II restriction pattern. Ten of the lines were heteroplasmic for a combination of siII and siIII, as determined by autoradiography. The same type of heteroplasmy had been noted in one of the two local populations 8 years before (Satta et al. 1988). The present results suggest that the heteroplasmic state occurs recurrently in natural populations of D. simulans in Réunion.     

Is Switzerland Suitable for the Invasion of Aedes albopictus?

Background

Over the last 30 years, the Asian tiger mosquito, Aedes albopictus, has rapidly spread around the world. The European distribution comprises the Mediterranean basin with a first appearance in Switzerland in 2003. Early identification of the most suitable areas in Switzerland allowing progressive invasion by this species is considered crucial to suggest adequate surveillance and control plans.

Methodology/Principal Findings

We identified the most suitable areas for invasion and establishment of Ae. albopictus in Switzerland. The potential distribution areas linked to the current climatic suitability were assessed using remotely sensed land surface temperature data recorded by the MODIS satellite sensors. Suitable areas for adult survival and overwintering of diapausing eggs were also identified for future climatic conditions, considering two different climate change scenarios (A1B, A2) for the periods 2020–2049 and 2045–2074. At present, the areas around Lake Geneva in western Switzerland provide suitable climatic conditions for Ae. albopictus. In northern Switzerland, parts of the Rhine valley, around Lake Constance, as well as the surroundings of Lake Neuchâtel, appear to be suitable for the survival at least of adult Ae. albopictus. However, these areas are characterized by winters currently being too cold for survival and development of diapausing eggs. In southern Switzerland, Ae. albopictus is already well-established, especially in the Canton of Ticino. For the years 2020–2049, the predicted possible spread of the tiger mosquito does not differ significantly from its potential current distribution. However, important expansions are obtained if the period is extended to the years 2045–2074, when Ae. albopictus may invade large new areas.

Conclusions/Significance

Several parts of Switzerland provide suitable climatic conditions for invasion and establishment of Ae. albopictus. The current distribution and rapid spread in other European countries suggest that the tiger mosquito will colonize new areas in Switzerland in the near future.     

Household-Level Expenditure on Protective Measures Against Mosquitoes on the Island of La Réunion,France

Background

For decades La Réunion has experienced a number of epidemics that have resulted in efforts to control the density of Aedes species on this Island. This study was conducted to assess household-level expenditure on protective measures against mosquito nuisance on the Island of La Réunion in 2012.

Methodology/Principal Findings

Data was collected during a cross-sectional survey of 1024 households and used to determine the relationship between the use of chemically-based protective measures and subjective and objective indicators of the density of Aedes albopictus. The average household expenditure in July 2012 was USD 9.86 and the total household-level expenditure over a one-year period was extrapolated to USD 28.05million (range: USD 25.58 million to USD 30.76 million). Much of this money was spent on measures thought to be relatively ineffective against Aedes mosquitoes. Expenditure on protective measures was not influenced by the level of knowledge on mosquitoes or by the visual nuisance they generated at home, but rather by the perception of risk related to a future epidemic of chikungunya and socioeconomic factors. Most importantly, household spending on protective measures was found to be influenced by a measure of zone-level mosquito density (the Breteau index), but not by objective indicators of the presence of mosquitoes within or around the house.

Conclusions/Significance

Household-level expenditure on chemically-based protective measures is high when compared to the investment made by public entities to achieve vector control, and it is differentially influenced by subjective and objective measures of mosquito density. The current situation could be improved, firstly by ensuring that the public is well-informed about mosquitoes and the effectiveness of various protective measures, and secondly by implementing interventions that could either complement current vector-control strategies and improve their effectiveness on a country-level, or that would steer the population toward the appropriate behaviours.     

Biallelic Mutations of Methionyl-tRNA Synthetase Cause a Specific Type of Pulmonary Alveolar Proteinosis Prevalent on Réunion Island

Methionyl-tRNA synthetase (MARS) catalyzes the ligation of methionine to tRNA and is critical for protein biosynthesis. We identified biallelic missense mutations in MARS in a specific form of pediatric pulmonary alveolar proteinosis (PAP), a severe lung disorder that is prevalent on the island of Réunion and the molecular basis of which is unresolved. Mutations were found in 26 individuals from Réunion and nearby islands and in two families from other countries. Functional consequences of the mutated alleles were assessed by growth of wild-type and mutant strains and methionine-incorporation assays in yeast. Enzyme activity was attenuated in a liquid medium without methionine but could be restored by methionine supplementation. In summary, identification of a founder mutation in MARS led to the molecular definition of a specific type of PAP and will enable carrier screening in the affected community and possibly open new treatment opportunities.     

A Mathematical Model of Chikungunya Dynamics and Control: The Major Epidemic on Réunion Island

Chikungunya is a re-emerging arboviral disease transmitted by Aedes spp. mosquitoes. Although principally endemic to Africa and Asia, recent outbreaks have occurred in Europe following introductions by returning travellers. A particularly large outbreak occurred on Réunion Island in 2006, the published data from which forms the basis of the current study. A simple, deterministic mathematical model of the transmission of the virus between humans and mosquitoes was constructed and parameterised with the up-to-date literature on infection biology. The model is fitted to the large Réunion epidemic, resulting in an estimate of 4.1 for the type reproduction number of chikungunya. Although simplistic, the model provided a close approximation of both the peak incidence of the outbreak and the final epidemic size. Sensitivity analysis using Monte Carlo simulation demonstrated the strong influence that both the latent period of infection in humans and the pre-patent period have on these two epidemiological outcomes. We show why separating these variables, which are epidemiologically distinct in chikungunya infections, is not only necessary for accurate model fitting but also important in informing control.     

Spatial and Temporal Variability in Territoriality of a Tropical Benthic Damselfish on a Coral Reef (Réunion Island)

The relationship between length of individual Stegastes nigricans and size of the territory that they defend, and both the spatial and temporal variation in territoriality were investigated monthly on a fringing coral reef of Réunion Island over the course of one year. Length of individual S. nigricans was correlated positively with size of the territory. Most small individuals were found separate from adults, in areas with low algal turf cover. This is probably due to strong intra-specific competition for access to algal food resources and shelter availability, and/or differences in habitat preference. Both abundance of individuals and surface defended showed seasonal fluctuations. Densities were slightly higher in austral summer than in winter, and the surface defended by individuals larger than 8cm increased in winter. A permanent redistribution of territories also occured between individuals over time.     

Population density of the Réunion Grey White-eye Zosterops borbonicus within the summit ecosystems of Réunion,Mascarene Islands

Assessing population density is crucial for studying the ecology and evolutionary biology of species as well as for conservation purposes. Here we used point count methods to infer population density in a single-island endemic passerine bird, the Réunion Grey White-eye Zosterops borbonicus, that displays striking evidence of differentiation at a small spatial scale. Population density was estimated at 5.17 birds ha^?1 (CL 4.85–5.50), a value somewhat higher than previously believed. This estimation provides the first detailed estimation of bird population density in the vulnerable summit ecosystems of Réunion and will possibly allow a better understanding of the evolutionary causes of this plumage colour variation.     

Use of a simple method for the Epstein-Barr virus transformation of lymphocytes from members of large families of Réunion Island

A simple method for the preparation of lymphoblastoid cell lines from small amounts (100 microliter) of frozen whole blood is described. A success score greater than 90% was obtained for EBV transformations using blood samples which had been collected several months before the infection. Due to the simplicity of the technique, up to 80 samples could be processed per day. This technique was used to prepared 242 permanent cell lines from 13 large families from Réunion Island showing blood group H deficiency. These cell lines are now available for genetic studies.     

An Assessment of Habitat Diversity and Transformation on La Réunion Island (Mascarene Islands,Indian Ocean) as a Basis for Identifying Broad-scale Conservation Priorities

Most natural habitat in the Mascarene Islands (Mauritius, La Réunion and Rodrigues) has been transformed. Although urbanisation, agriculture and alien plant invasions have transformed large areas in La Réunion, the island has by far the greatest area of intact habitats in the Mascarenes, but remaining natural areas are under threat. We propose a protocol for defining a system of habitat types and for using these to provide a preliminary assessment of conservation priorities for La Réunion. The protocol draws on existing data and expert knowledge to map habitat types, assesses the extent of habitat transformation, and quantifies heterogeneity between habitat types based on climate, topography and geology. The pattern of habitat transformation was uneven among the nineteen habitat types identified. While three habitats have lost > 95% of their original area, four still retain> 80% of their original extent. Habitat types could be grouped into the following categories: (i) transformed habitats with low levels of plant endemism, (ii) habitats confined to homogenous geology with high levels of plantendemism, and (iii) species-rich heterogeneous habitats on diverse geological types. Priority habitats were also identified using municipalities as a basis for implementation. Urgent action is required for several habitat types where a large part of the original extent has been transformed. Three municipalities which contain more than 10 habitat types should receive conservation priority. The analysis provides the basis for setting conservation priorities in La Réunion at the regional and local scale. Implications of the results are discussed with reference to requirements for finer-scale conservation planning.     

Occurrence of Natural Vertical Transmission of Dengue-2 and Dengue-3 Viruses in Aedes aegypti and Aedes albopictus in Fortaleza, Ceará, Brazil

Background

Aedes aegypti and Aedes albopictus perform an important role in the transmission of the dengue virus to human populations, particularly in the tropical and subtropical regions of the world. Despite a lack of understanding in relation to the maintenance of the dengue virus in nature during interepidemic periods, the vertical transmission of the dengue virus in populations of A. aegypti and A. albopictus appears to be of significance in relation to the urban scenario of Fortaleza.

Methods

From March 2007 to July 2009 collections of larvae and pupae of Aedes spp were carried out in 40 neighborhoods of Fortaleza. The collections yielded 3,417 (91%) A. aegypti mosquitoes and 336 (9%) A. albopictus mosquitoes. Only pools containing females, randomly chosen, were submitted to the following tests indirect immunofluorescence (virus isolation), RT-PCR/nested-PCR and nucleotide sequencing at the C-prM junction of the dengue virus genome.

Results

The tests on pool 34 (35 A. albopictus mosquitoes) revealed with presence of DENV-3, pool 35 (50 A. aegypti mosquitoes) was found to be infected with DENV-2, while pool 49 (41 A. albopictus mosquitoes) revealed the simultaneous presence of DENV-2 and DENV-3. Based on the results obtained, there was a minimum infection rate of 0.5 for A. aegypti and 9.4 for A. albopictus. The fragments of 192 bp and 152 bp related to DENV-3, obtained from pools 34 and 49, was registered in GenBank with the access codes {"type":"entrez-nucleotide","attrs":{"text":"HM130699","term_id":"297515956","term_text":"HM130699"}}HM130699 and {"type":"entrez-nucleotide","attrs":{"text":"JF261696","term_id":"340343903","term_text":"JF261696"}}JF261696, respectively.

Conclusions

This study recorded the first natural evidence of the vertical transmission of the dengue virus in populations of A. aegypti and A. albopictus collected in Fortaleza, Ceará State, Brazil, opening a discuss on the epidemiological significance of this mechanism of viral transmission in the local scenario, particularly with respect to the maintenance of these viruses in nature during interepidemic periods.     

Elver Invasion, Population Structure and Growth of Marbled eels Anguilla marmorata in a Tropical River on Réunion Island in the Indian Ocean

Winter skates, Leucoraja ocellata, exposed to 80% and 50% seawater (SW) exhibited rapid and significant weight gains followed by a slight recovery to new steady state levels within 8 days. Skates were acclimated at each salinity (100% SW [N = 16], 80% SW [N = 8], 50% SW [N = 8]), anesthetized (MS222) and bled from the caudal vein. In 100% SW, skate plasma (930mOsm/kg) was slightly hyperosmotic to the external medium (922mOsm/kg). Plasma osmolality decreased with seawater dilution, but became increasingly hyperosmotic to the bathing media. The environmental dilutions resulted in significant, but disproportionate changes in plasma Cl^–, P^–, Na⁺, Ca⁺, Mg⁺, trimethylamine oxide (TMAO) and urea concentrations. Mean corpuscular [Hb] and milliliter RBC water measurements suggest that skate red cells swelled less at each dilution than predicted for a passive erythrocyte osmometer. Concentrations of the major RBC solutes K⁺, urea, TMAO and Cl^– decreased by 8, 25, 5 and 21%, respectively in 80% SW. In 50% SW, K⁺, urea, TMAO and Cl^– concentrations decreased by 9, 47, 36 and 15%, respectively. Quantitatively, the other measured intracellular electrolytes (Mg⁺, Na⁺, P^– and Ca⁺) also exhibited disproportionate changes in concentration. Our results indicate that L. ocellata is a euryhaline elasmobranch that can tolerate significant reduction in the external salinity through the release of both ions and urea from the extracellular compartments while retaining electrolytes at the expense of urea in the intracellular compartment.     

Swimming medusoid gonophores in two species of Sertularella (Cnidaria,Hydrozoa, Sertulariidae) from Réunion Island,Indian Ocean

Summary

Two life cycle patterns predominate in thecate hydroids, those with alternating polyp and medusa stages, and those with fixed gonophores. Relatively few species release short-lived medusoids, also called swimming gonophores, that carry the gametes. In the family Sertulariidae, with its large number of taxa, this mode of metagenesis has been documented previously for only two species. It is described here for two others, Sertularella diaphana (Allman, 1885) and Sertularella n. sp., from the coastal waters of Reunion Island. Freshly collected fertile male and female colonies released medusoids near dawn, one per gonotheca. Strong contractions of the bell in the swimming movements induced the shedding of gametes. Once gametes were shed, medusoids quickly degenerated and died. The medusoids were similar morphologically in these two related species, and no obvious sexual dimorphism was noted. They were ovoid in shape, the spadix was eccentric, and a velum was present; but they lacked a mouth, tentacles, sense organs, and radial and circular canals as described earlier in Amphisbetia operculata (Linneus, 1758) and Sertularia marginata Kirchenpauer, 1864. However, the medusoids described here lacked exumbrellar nematocysts. Moreover, the spadix with its dense mass of gametes was different from all other described in being stuck from base to top on one side of the subumbrella in spite of hanging freely in the subumbrellar cavity. The hypothesis that this unusual reproductive mode in sertulariids has been underestimated is confirmed by these findings.