Margarita Island Research Articles

N. 6 Fuel Oil Effects on Antioxidant Enzymes and Immunological Responses in the Fish Thalassophryne maculosa (Pisces: Batrochoididae)

With the aim of investigate the acute effects of two concentrations (25 and 100%) of N. 6 fuel oil-water-accommodated fraction (OWAF) on antioxidant enzyme activities and immunological responses, fishes Thalassophryne maculosa were sampled from the La Restiga Lagoon, Margarita island, in eastern Venezuela. The antioxidant enzymes, catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR) and glutathione-S-transferase (GST) were measured in liver and gills. The macrophagic phagocytosis and antibacterial lysozyme activity of anterior kidney were the immune parameters examined. Increases in gill GST activity and hepatic GR activity were observed after the exposure to 25 and 100% OWAF, respectively. GPX, CAT and immune responses were not affected by the experimental treatments. Our results demonstrated that among the antioxidant enzymes tested, GR and GST activities were the most sensible to the acute treatment with fuel oil, indicating changes in the redox cellular state that may result in oxidative stress in T. maculosa.

Karyological characterization of <i>Mugil trichodon</i> Poey, 1876 (Pisces: Mugilidae)

Cytogenetic studies were conducted on Mugil trichodon from Margarita Island, Venezuela. The species showed a karyotype 2n=48 with entirely acrocentric chromosomes (Arm number, NF=48). Chromosomes gradually decreased in size and did not allow a clear distinction of homologues, except for one marker pair, which showed a conspicuous secondary constriction. C-banding showed heterochromatic blocks restricted at the centromeric regions of all the chromosomes. Some were more obvious than others, with the exception of the chromosome pair that had a secondary constriction with entirely heterochromatic short arms. Sequential staining with Giemsa and AgNO3 demonstrated the conspicuous secondary constrictions corresponding to the NORs, and these had significant intraindividual size variations between both homologous chromosomes. The data obtained here support the contention that Mugilidae have a conservative chromosome macrostructure and reinforce the hypothesis that small structural chromosome rearrangements involving active NOR sites are the main cause of the karyotypic diversification seen in this group.

Cell adhesion molecules in the CNS

Cell-cell adhesions are important for brain morphology and highly coordinated brain functions such as memory and learning ([Sanes and Yamagata, 1999][1]; [Yamagata et al., 2003][2]; [Washbourne et al., 2004][3]). During early development of the nervous system, neurons elongate their axons towards

Nutritional quality of Metamysidopsis insularis Brattegard (Crustacea: Mysidacea)

In natural conditions the mysid Metamysidopsis insularis is commonly found in the littoral lagoon of Margarita Island (Venezuela). It is used as live food in the marine fish culture. However, its nutritional quality is not well documented. In the present study we analysed the nutritional value (total protein, carbohydrate and lipids profile) of M. insularis. The mysids were collected in La Restinga lagoon (Margarita Island, Venezuela). Levels of total proteins, lipids and carbohydrates were 700 ± 28.5, 160 ± 13.9 and 20 ± 0.90 gk g )1 respectively. The lipids classes were 427 ± 2, 106 ± 98, 287 ± 113 and 179 ± 87 for phospholipids, triglycerides, cholesterol and cholesterol esters respectively. The fatty acids profile, determined by gas chromatography, showed important concentration of fatty acids for the metabolism of marine organism, such as 16:0, 18:0, 18:2n-6, 18:3n-3, 18:4-3, 20:5n-3 and 22:6n-3; attaining levels of 27.49% in PUFA n-3 and 2.92% in n-6. The relation of eicosapentaenoic acid/docosahexaenoic acid was 2.1 ± 0.15. The results support the use of M. insularis as food for species of fish and crustaceans under culture conditions.

A Single-Use Site Selection Technique, Using GIS, for Aquaculture Planning: Choosing Locations for Mangrove Oyster Raft Culture in Margarita Island, Venezuela

Oyster culture has a potential to generate income for coastal communities and to lessen pressure on natural overexploited populations. A project to transfer mangrove oyster Crassostrea rhizophorae raft culture technology to selected coastal communities in Margarita Island, Venezuela is being developed, and an optimum location selection technique was devised. To pick the variables or factors that determine site suitability, a bibliographic database was made, aspects of interest chosen, and the most comprehensive ones singled out, eliminating redundant ones. Twenty variables were grouped in criteria based on the way they influence the project. Variables were classified as intrinsic environmental, environmental extrinsic, logistic, and socioeconomic criteria. Thirty-five experts were asked to evaluate the factors and to score each according to their suitability weight. Logistic criterion received the highest values, followed by environmental extrinsic issues. A Geographic Information System using a base map compiled from 1:25,000 scale maps was developed. A thematic map for each factor was completed, dividing graphically the 3896-km2 study area into polygons of equal weight for each factor. The Multi-Criteria Evaluation (MCE) was used to combine the variables. Resultant vectors in thematic maps were added to obtain smaller polygons with the same value sum. Finally, MCE was used to generate a final output: the optimum sites for oyster aquaculture resulting from the added values of over 3000 polygons in the maps, for the 20 criteria. Higher scores were reached in 13 areas covering 4.1 km2, those places having the optimum conditions for oyster raft aquaculture in the region. Additional locations meeting 75% to 70% of the demanded criteria for a final suitable selection cover 137 sites encompassing 37.5 km2.

A highly efficient oyster spat collector made with recycled materials

This study presents data from over 7 years on the numbers of spat settling onto plastic bottles (2l soda bottles). The bottles were cut longitudinally into two halves and suspended in a series from 0.10 to 2.00m in depth in the “Laguna de la Restinga” on Margarita Island, Venezuela. The surface area of one entire collector was 1.8m2 (formed by 20 bottles halves) and the average number of oysters attaching after a deployment period of 1 month was 326spat/m2 (and the monthly average ranged from 42 to 1496 over 7 years). Plastic bottles used in this way provided an efficient and cost-effective means of collecting oyster spat, and the spats were easily detached because of the flexibility of the plastic surfaces.

Desarrollo embrionario y larval de Lytechinus variegatus (Echinoidea: Toxopneustidae) en condiciones de laboratorio en la isla de Margarita-Venezuela

Embrionary and larval development of Lytechinus variegatus (Echinoidea: Toxopneustidae) in laboratory conditions at Isla de Margarita-Venezuela. The sea urchin Lytechinus variegatus is a promissory species for aquaculture activities in tropical countries. In Venezuela, this species has some economical importance but their embryonic and larval development had not been studied. We collected specimens from seagrass beds in Margarita Island (Venezuela) and kept them in the laboratory, where they spawned naturally. With filtered sea water (temperature 28oC, salinity 37 psu) and moderate aeration, the eggs and sperm were mixed (relation 1:100) and reached a 90% fertilization rate. The fertilization envelope was observed after two minutes, the first cellular division after 45 minutes and the prism larval stage after 13 hours. The echinopluteus larval stage was reached after 17 hours and metamorphosis after 18 days of planktonic life, when the larvae start their benthic phase. Rev. Biol. Trop. 53(Suppl. 3): 313-318. Epub 2006 Jan 30.

Crecimiento y supervivencia de larvas de Echinometra lucunter (Echinoidea: Echinometridae) alimentadas con las microalgas Chaetoceros gracilis e Isochrysis galbana

Larval growth and survival of Echinometra lucunter (Echinoidea: Echinometridae) fed with microalgae Chaetoceros gracilis and Isochrysis galbana. Thirty sexually mature sea urchins (Echinometra lucunter; diameter 45.8 ± 17.5 mm) were collected at Macanao, Margarita Island, Venezuela (11°48’29” N / 64°13’10” W). They were injected potassium chloride (50 M) directly into the celomic cavity. After two minutes 90% spawned (17 females and 10 males), the others never spawned. Fertilization was 87.0 ± 12.6% (1:100 oocytes/sperm) at 29 ± 2oC. The fertile eggs were placed in three treatment gropsu with nine containers (18 liters; 2 eggs/ml) each, all with bottom aeration. Treatments were: Chaetoceros gracilis; Isochrysis galbana, and a mixture of both microalgae (respectively: 20 000 and 60 000 cell/ml for each microalgae, 1:1 for the mixture). Salinity, pH, temperature and larval survival were determinated daily. The study ended when the post-metamorphic phase was completed. The embryonic development time was 16.3 ± 0.2 h until the prism stage at pH 8.4 ± 0.1; 38 ± 1 psu and 28 ± 1.4°C. The two-arms larval stage was reached at 24 h: 33 min, with a total length of 190 ± 16.3 μm fed on C. gracilis, 152 ± 19.0 μm with I. galbana and 182.4 ± 14.1 μm with the mixture. The larvae next to metamorphosis reabsorbed the arms and had the characteristic shape of juvenile urchins at 12 days with 670.2 ± 22.2 μm fed on C. gracilis, 665 ± 12.1 μm fed on I. galbana and 670 ± 14.1 μm fed on the mixture. The accumulated survival to the juvenile stage was 14.7 ± 3.8% when fed on C. gracilis, higher than the other treatments (5.4 ± 1.2; 14.0 ± 2.6). E. lucunter is an excellent prospect to be commercially cultured because of its short embryonic (16 hours) and larval development time (12 days) and good survival rate when fed on monoculture (C. gracilis and I. galbana) or mixed diet (we recommend C. gracilis). Rev. Biol. Trop. 53(Suppl. 3): 337-344. Epub 2006 Jan 30.

"Primor con fuerza". Trayectoria de Bernardo de Vargas Machuca

Se presenta un esbozo de la interesante biografía del capitán baquiano -europeo americanizado a partir de una larga estancia en el nuevo mundo- Bernardo de Vargas Machuca (Simancas, hacia 1555 - Madrid, 1622), cuya actividad guerrera la llevó a cabo sobre todo en Nueva Ganada y que luego fuera alcalde mayor de Portobelo y gobernador de la isla Margarita. Fue autor de varios libros sobre temas relacionados con las conquistas indianas y la caballería de la jineta.

Ciclo reproductivo de Lytechinus variegatus (Echinoidea: Toxopneustidae) en el sur de Isla Margarita, Venezuela

Reproductive cycle of Lytechinus variegatus (Echinoidea: Toxopneustidae) in the south of Margarita Island, Venezuela . The sea urchin Lytechinus variegatus is of some commercial importance on the Southern coast of Margarita Island (Venezuela), where artisan women fishers process and sell the roe. The reproduction cycle of this species had not been fully studied. We collected these sea urchins in two stations from November 1997 through October 1998. The samples were transported fresh to the laboratory to determine weight, diameter and height. The sexual stage was established with a macroscopic scale and the gonadosomatic index (GI). Maturity is achieved when the animals reaches a diameter of 22 mm, although 50% of the population reaches sexual development at diameters of 43 mm (males) and 45 mm (females) at Station 1, and 35 mm for both sexes at Station 2. Mature individuals, in a sexual proportion of 1:1 were collected every month. According to the monthly GI variation and frequency (%) of the development stages, on the southern beaches the main reproductive period begins in April and continues through October, and it is most intensive from May to July, when gonads reach the greatest growth. Rev. Biol. Trop. 53(Suppl. 3): 305-312. Epub 2006 Jan 30.

Activity ofLutzomyia pseudolongipalpisandL. longipalpis s.l.(Diptera: Psychodidae) in Venezuela

The nocturnal activity of the phlebotomine sandfly Lutzomyia pseudolongipalpis and two populations of L. longipalpis s.l. from different American visceral leishmaniasis foci in Venezuela was studied using collection bottle rotator traps. The activity of L. pseudolongipalpis from Lara State was continuous throughout the night, while that of L. longipalpis s.l. from El Layero, Guárico State and from Santa Ana del Valle, Margarita Island, was greatest before 23:00 h. The activity of sandflies of both populations and sexes steadily decreased thereafter. These different patterns seem to correlate with genetic data that indicate the presence in Venezuela of at least two sibling species in the L. longipalpis complex. The advantages of the bottle rotator trap for this type of study are discussed.

Paralytic shellfish poisoning (PSP) in Margarita Island, Venezuela.

A severe outbreak of Paralytic Shellfish Poisoning (PSP) occurred in Manzanillo and Guayacán, northwestern coast of Margarita Island, Venezuela, between August and October 1991. A bloom of dinoflagellates including Prorocentrum gracile, Gymnodinium catenatum and Alexandrium tamarense seemed to be responsible for this outbreak. Levels of PSP toxins in mussels (Perna perna) exceeded the international safety limit of saxitoxin, 80 microg STX/100 microg meat. PSP toxin values varied between 2548 and 115 microg STX/100 g meat in Manzanillo, and between 1422 and 86 microg STX/100 g meat in Guayacán. At both locations, the highest levels were detected in August, when 24 patients exhibited typical symptoms of PSP toxicity after consuming cooked mussels (16 required hospitalization). A high pressure liquid chromatographic (HPLC) procedure was recently used on the 1991 samples. The major toxin detected in samples of both locations was decarbamoyl saxitoxin (dcSTX), but low concentrations of saxitoxin were also found in Manzanillo samples. Gonyautoxins GTX1, GTX2 and GTX3 were detected only at Guayacán, while in both locations, decarbamoylgonyatouxin (dcGTX2,3) toxins were detected. These findings represent the first time that causative toxins of PSP in Venezuela have been chemically identified, and confirm the presence of dcSTX and dcGTX in mussels from the Caribbean Sea. The presence of dcSTX and dcGTX in shellfish is indicative that Gymnodinium catenatum was a causative organism for outbreak of PSP.

Clinical and genetic linkage analysis of a large Venezuelan kindred with Usher syndrome

Objective: To undertake a comprehensive investigation into the very high incidence of congenital deafness on the Macano peninsula of Margarita Island, Venezuela. Methods: Numerous visits were made to the isolated island community over a 4-year-period. During these visits, it became apparent that a significant number of individuals complained of problems with hearing and vision. Socioeconomic assessments, family pedigrees and clinical histories were recorded on standard questionnaires. All individuals underwent thorough otolaryngologic and ophthalmologic examinations. Twenty milliliters of peripheral venous blood was obtained from each participant. A Genome-wide linkage analysis study was performed. Polymorphic microsatellite markers were amplified by polymerase chain reaction and separated on polyacrylamide gels. An ABI 377XL sequencer was used to separate fragments and LOD scores were calculated by using published software. Results: Twenty-four families were identified, comprising 329 individuals, age range 1–80 years, including 184 children. All families were categorized in the lower two (least affluent) socioeconomic categories. A high incidence of consanguinity was detected. Fifteen individuals (11 adults, 4 children) had profound congenital sensorineural hearing loss, vestibular areflexia and retinitis pigmentosa. A maximum LOD score of 6.76 (Linkage >3.0), between markers D11s4186 and D11s911, confirmed linkage to chromosome 11q13.5. The gene myosin VIIA ( MYO7A) was confirmed in the interval. Clinical and genetic findings are consistent with a diagnosis of Usher syndrome 1B for those with hearing and vision problems. Conclusions: We report 15 Usher syndrome 1B individuals from a newly detected Latin American socio-demographic origin, with a very high prevalence of 76 per 100,000 population.

Larval Development of Pachycheles Serratus (Decapoda: Anomura: Porcellanidae) under Laboratory Conditions, with Notes on the Larvae of the Genus

Abstract Larval stages and the megalopa of Pachycheles serratus are fully described and illustrated on the basis of laboratory-reared materials collected from Margarita Island, Venezuela. Complete development of P. serratus includes two zoeal stages and the megalopal (decapodid) stage, cultured at a water temperature of 25°C and salinity of 37‰. The first zoea lasts 5–6 days and the second lasts 8–10 days. A diagnostic character of the present species is the existence of a short mesial spine on the maxillular endopodite, unique among known zoeae of the genus Pachycheles. In addition, they can be distinguished from the first zoeae of P. laevidactylus and P. monilifer (western Atlantic congeners for which larval morphology is well-described) by size and ornamentation of the rostral spine, disposition of lateral spines on the abdominal somites, and setation of the maxilliped 3 in the second zoea. A comparative summary of zoeal morphology is provided for members of the genus Pachycheles.

Insular species of Neotropical freshwater crabs (Crustacea: Brachyura)

One species of Trichodactylidae and four species of Pseudothelphusidae are present on continental islands in three areas of Central and South America. (1) Trinidad and Margarita Island have, in common with the Venezuelan mainland, the pseudothelphusid Eudaniela garmani (Rathbun, 1898); additionally, Trinidad shares with the mainland the trichodactylid Dilocarcinus dentatus (Randall, 1839). These disjunct distributions can be attributed to changes in sea level during the Quaternary, but the presence of the endemic pseudothelphusid Microthelphusa odaelkae (Bott, 1970) in Trinidad probably reflects an older connection with the continent. (2) A new species, Potamocarcinus roatensis, was found on Roatan Island, off the coast of Honduras. A cladistic analysis of the genus Potamocarcinus (H. Milne Edwards, 1853) revealed a close association of P. roatensis with P. magnus (Rathbun, 1896), a widely distributed Central American pseudothelphusid. Possibly both species originated in a pre-Quaternary vicariant event. (3) Another pseudothelphusid, Hypolobocera gorgonensis von Prahl, 1983, inhabits disjunct areas on Gorgona Island, off the Pacific coast of Colombia, and on the mainland of Ecuador, reflecting either a wider distribution before the last Holocene transgression or accidental dispersal through natural rafts.

Un caso de malformación en Pachycheles serratus (Decapoda: Porcellanidae)

An adult male of Pachycheles serratus with a malformation on the right cheliped was found during a collection of anomuran crabs in coastal waters of the peninsula de Macanao, Margarita island, Venezuela. The specimen was found at La Carmela beach (11 degrees 04'N-64 degrees 20'W), and featured a bifurcated fixed finger on the right cheliped.

Epidemiological aspects of human and canine visceral leishmaniasis in Venezuela.

To report recent data on the distribution of human and canine visceral leishmaniasis (VL) in Venezuela, and to highlight problems associated with effective control measures. We report the number of cases, incidence rate, age and sex distribution, and mortality rates for human VL (HVL) for the period of 1995 through 2000, based on National Registry of Leishmaniasis data. We carried out serological studies on a total of 3 025 domestic dogs from the 12 states in Venezuela reporting cases of human VL in this 1995-2000 period and also from the state of Yaracuy, where cases were reported earlier during the decade of the 1990s. From 1995 through 2000, 242 cases of HVL were reported from 12 states, in various sections of Venezuela. There was a relatively stable national incidence rate of 0.2 cases per 100 000 persons per year. Of the 242 cases, 26.0% were from Margarita Island, one of the three islands that make up the state of Nueva Esparta (Margarita Island was the only one of the Nueva Esparta islands that had HVL cases). Over the 1995-2000 period, the annual incidence rates for Nueva Esparta ranged from 1.7 to 3.8 cases per 100 000 population. Males in Venezuela were more frequently affected (59.5%) than were females (40.5%). In terms of age, 67.7% of the VL patients were </= 4 years of age, and 80.6% were younger than 15 years. The mortality rate among the persons with VL was 7.85% during the 1995-2000 period. Serological screening with rK39 antigen of 1 217 dogs from Margarita Island found a 28.5% positivity rate (testing of dogs was not done on the two other islands of Nueva Esparta). In contrast, the rate was 2.8% in the 1 808 samples from dogs from 12 states on the mainland. Human and canine VL are unevenly distributed in Venezuela. The distribution may reflect such factors as differences among the states in human population density, vector density, and the presence or absence of other trypanosomatidae. Particularly high infection rates in very young children as well as in domestic dogs occur in semiurban communities of Nueva Esparta, where other human-infecting trypanosomatidae have not been reported. Control measures related to limiting canine infection might contribute to disease control where VL infections are frequent. Reducing VL mortality requires increased awareness among medical professionals of the possibility of VL in the differential diagnosis of hepato-splenic syndromes, particularly in children.

Estimación de la profundidad de trabajo de anzuelos de un palangre atunero prototipo de la flota de altura de Isla de Margarita (Venezuela)

Based on two fishing trips carried out in the Caribbean Sea in May 1997 and in June 1998, on board of deep sea tuna longline fishing boat, from Chacachacare, Margarita Island, Venezuela, the shape and tension of the longline were determined under working conditions, and the operational depth of hooks were estimated by mechanical simulation method. Lineal scale factor for simulation of a prototype section of six hooks (C L ) was 150 and force scale factor (C R ) was 370.9. Vessel speed during the operations and sections sagging rate, for trial on test panel, ranged from 4.9 knots (55.3%) to 7.1 (80.5%). The angles of incidence at the ends of the main line of prototype ranged between a mean value of 10.4o (± 0.97 SD) and 29.75o (± 1.59 SD), with a mean value of tension between 2.42 kgf (±. 0.46 SD) and 5.35 (± 1.10 SD). The hooks No1 and No6, in a range of vessel speeds, reached depths between 63.9 and 70.4 m, the No2 and No5 reached depths between 89.8 and 103.8 m, and the hooks No3 and No4 reached depths between 103.2 and 133.1 m. The estimated hook depths showed an inverse relation with the speed at which the main line is set (V L ), the sagging rate (k) and the angles of incidence at the end sections of main line (joint between the buoy line and two longline sections). The estimation of horizontal tensions shows a direct relationship with k and V L.

Epidemiological and immunological aspects of human visceral leishmaniasis on Margarita Island, Venezuela.

Sixty-five patients were diagnosed with visceral leishmaniasis (VL) on Margarita Island in the decade from 1990 to1999; 86.2% were <= 3 years old. All were leishmanin-negative at diagnosis. Evaluation of 23 cured patients in 1999 revealed that 22/23 had converted to leishmanin-positive; five had persisting antibodies to rK39 antigen, with no clinical evidence of disease. Leishmanin tests were positive in 20.2% of 1,643 healthy individuals from 417 households in endemic areas. Of the positive reactors, 39.8% were identified in 35 (8.4%) of the households, 15 of which had an antecedent case of VL, a serologically positive dog or both. Weak serological activity to rK39 antigen was detected in 3 of 488 human sera from the endemic areas. The presence of micro-foci of intense peri-urban transmission and the apparent absence of other Trypanosomatidae causing human disease offer a unique opportunity for the study of reservoirs, alternative vectors and evaluation of control measures on the Island.

Isolation of Leishmania infantum, zymodeme MON-1 from canine and human visceral leishmaniasis on Margarita Island, Venezuela.

An increase in the incidence of human visceral leishmaniasis (HVL) has been detected in recent years on Margarita Island, located off the NE coast of Venezuela. Recent studies have revealed reactivity to rK39 antigen (Leishmania chagasi) in 20% of 541 sera from domestic dogs in endemic communities; PCR reactions were positive using primers for the L. donovani complex. Here we report that isolates from human and canine infection, identified by isoenzyme analysis, correspond to L. infantum, zymodeme MON-1. This appears to be the first isolation and identification of an isolate from HVL on Margarita Island and demonstrates the presence of this zymodeme in the canine population.