Zootecnia Tropical Instituto Nacional de Investigaciones Agrícolas Venezuela ISSN: 0798-7269 Vol. 19, Num. 2, 2001, pp. 165-172

Zootecnia Tropical, Vol. 19, No. 2, 2001, pp. 165-172

NOTA TÉCNICA

Vanadium levels in gonads of white mullet (Mugil curema) in the Cariaco Gulf, Venezuela

Nivel de vanadio en gónadas de lisa (mugil curema) en el Golfo de Cariaco, Venezuela

Alicia Arias de Díaz^1*, Neira Gamboa² and José García¹

¹Toxicology Laboratory, Instituto Nacional de Investigaciones Agrícolas (INIA).
CIAE-Sucre, Cumaná, 6101. Venezuela. ^*Correo electrónico: alidiza@cantv.net
Biochemistry Laboratory, Faculty of Pharmacy. UCV. Caracas

Recibido: 27/3/01 Aceptado: 6/7/01

Code Number: zt01015

SUMMARY

The content of vanadium in gonads of white mullet (Mugil curema) in the Cariaco Gulf, Venezuela, was determined to asses the significance and possible impact of this metal in the biota of this area. Samples were analyzed using atomic absorption spectrometry. Results showed that concentration of vanadium was 5.91 µg/g wet weigh which is relatively elevated, compared to others species of fish and others kinds of foods, and it can be discussed on the possibility of genotoxic effect on this species and their correlation with the marine pollution, besides the effects on human health through the food chain. This is the first report providing information about this metal, among a number of toxic chemical compounds in the fishing zones from Venezuelan oriental region.

Key words: Vanadium, Heavy metal, Fish, Marine, Gonads, Pollution

RESUMEN

En este estudio se determinó el contenido de vanadio en las gónadas de la lisa Mugil curema, en el Golfo de Cariaco, Venezuela, con la finalidad de evaluar el posible impacto de este metal en la biota de esta área. Las muestras fueron analizadas usando Espectrometría de Absorción Atómica. Los resultados señalaron que concentraciones de vanadio a niveles entre 5,91+- 0,7 µg/g de peso húmedo son relativamente elevados, en comparación con otras especies de peces y otros tipos de alimentos. Esto puede ser discutido en base a la posibilidad de efectos genotípicos en la misma especie y su relación con la contaminación marina, además de los efectos nocivos sobre la salud humana a través de la cadena alimenticia. Este estudio, es el primer reporte que contiene información sobre este metal entre otros compuestos tóxicos presentes en las zonas pesqueras de la región oriental venezolana.

Palabras Clave: Vanadio, Metal pesado, Peces, Marino, Gónadas, Contaminación

INTRODUCTION

Heavy metals are stable and persistent environmental contaminants. The range of metal concentration is generally below acute thresholds in coastal areas, where recognition of chronic sub lethal effects is more relevant. Evidence of long-term adverse effects such as cancer, due to heavy metals in marine animals comes from a number of field and experimental studies (Zauke et al. 1999; Mackey et al. 1996). The mechanism of metal carcinogenicity remain largely unknown, although several lines of experimental evidence suggest that a genotoxic effect may be involved (Ostapczuk et al. 1997; Morales y Ávila, 1999).

Vanadium is a steel-grey, corrosion-resistant metal, which exists in oxidation states ranging from –1 to +5. Metallic vanadium does not occur in nature, and the most common valence states are +3, +4 and +5. The vanadate form (VO^–3) predominates in extracellular body fluids whereas the form (VO⁺²) is the most common intracellular form. Because of its hardness and its ability to form alloy, vanadium (i,e., ferrovanadium) is a common component of hard steel alloy used in machines and tools (Barceloux, 1999).

Vanadium is probably an essential trace element. But a vanadium deficiency disease has not been identified in human. Most of the toxics effects of vanadium compounds result from local irritation of eyes and upper respiratory tract. The occupation exposure is mentioned like the main source of pollution in human, while the feeding and environmental exposure is not considered relevant. In marine organisms there is one report of linear correlation of hepatic vanadium with age (Mackey et al., 1996), and the transfer from one trophic level to a higher one in marine environment have been described already (Zorba et al., 1992).

Vanadium levels are at or below detection limits of 0.01 m g/g in liver tissue of marine mammals in USA east coast, and levels ranging from 0.02 to 1.2 m g/g of wet weight in the tissue of Alaskan marine mammals (Mackey et al., 1996). Nevertheless in our country, in spite of the importance of the fishery resources and the high content of this metal in our crude oil (main source), the levels of vanadium in marine organisms are not studied enough, specially in this area, where the input of differents chemical contaminants increases constantly (Arias, 1997; Bonilla, 1999). There is a lack of knowledge about vanadium level dynamic in relation to their accumulation in living organisms and their access to the marine environment of Cariaco Gulf.

The aim of this study was to evaluate the levels of vanadium in the gonadal tissue of the marine fish specie of wide distribution and big economic and social value in our country: the white mullet, Mugil curema (Pisces: Mugilidae, Osteichthyes, Perciforme), in the Cariaco Gulf, Venezuela. This study also look for the significance of this metal in the biota of this area, based on the reports by fishermen about notorious changes of head size by some specimens during the recruiting time.

MATERIALS AND METHODS

Adults of M. curema ( mean length 22.5 ± 2.5 cm), were obtained in the Cariaco Gulf, near of the small town of Chiguana (Figure 1). A pilot sample of 75 specimens were used that would be representative ( Keith et al., 1983). All specimens were dissected by surgical steel knife obtaining the gonad tissue. All glass and plastic material used were precleaned (UNEP, 1984)

All the samples were lyophilized and stored at – 20ºC. Between 0.5-1.0 g of this material was then soaked during 6 to 8 h in HNO₃ in a refrigerated system, heated during one hour at 40ºC, filtered through a filter paper and the filtrate made up to 20 ml with bidestilled water. Each sample was analyzed by triplicate.

Vanadium measurements were performed using a Perkin Elmer 3101 instrument with flame (FAA) and an AS 70 autosampler. V was measured at 318 nm with a limit of detection of 0.04 µg /l. Analytical procedures are referenced in AOAC(1996).

RESULTS AND DISCUSSION

Vanadium content in the gonads of white mullet was between 4.45 and 7.15 µg/g wet weigh. Vanadium mean was 5.91 ± 0.7 µg/g of wet weight. This value can be considered high when compared with the values reported earlier for marine mammals, with the values reported in for seafood, milk, potatoes and meat where vanadium was found in the range of 0.001 to 0.006 m g/g (Friberg et al., 1986). The Environment Organic Law of Veneuzela dictates that this metals should not be detected in marine ecosystems.

Nevertheless, the found values in this study can be discussed based on the toxicity risk in human by direct consumption (Alliot y Frenet, 1990; González, 1994), on the possibility of genotoxic effects of the same species (Bolognesi et al., 1999; Morales et al., 1999) and its correlation with the pollution of the marine environment (Arias, 1997). Generally, metal concentration in fishery resources is determined by age, feeding habits and by the trophic level to which the respective species belong to (Trucco et al., 1990). From these points of view, it is interesting to consider that the input of vanadium into the gonadal tissue can be related to the characteristics of this specie: M. curema is a migratory specie, omnivore, and filter feeding (specially during juvenile stage) from the bottom detritus, were the organic matter proteins are possibility contaminated and from suspended material of the water column. Also, the high fat content in the gonads due to its metabolic process allows to accumulate high levels of vanadium (Bridges and Andrews, 1961), and it may produce negative effects at genetic level.

Enrichment factors of vanadium in the studied zone, are related to the concentration in the marine environment. The presence of relatively high levels of this metal in the gonads may reflect a unique geochemical source of vanadium, or some anthropogenic input to the Cariaco Gulf. It can also depend on sampling location and time, but is also possible that natural occurrences (due to the significance of oil in the Paria Gulf), submarine streams, and vessels traffic can be involved. For the purpose of this study, the exchangeable, reducible, and organically bound fractions of the metal in the gonadal tissue of the white mullet would be considered as bioavailable forms (VO⁺², VO^-3). If an organism incorporate these forms through its digestive tract while feeding, probably this occurred during larval o juvenile stage, before white mullet reached Chiguana area for the spawning period. To define the vanadium bioavailable specific form would help to establish the origin of this metal in this environmet.

Although mobility of this specie in relation to the site of capture is an obvious concern when trying to establish associations of sampling locations and this particular toxic, no assessment of population mobility or migration pattern was addressed in this study. This exposure issue should also be studied in future research.

CONCLUSIONS

Results showed high concentration of vanadium in gonads of white mullet in the Cariaco Gulf. This could lead to some genotoxic effects on this species and its correlation with the marine pollution.

The results from this study are a contribution from the Regional Marine Environment and Fishery Resources Monitoring Project that is carried out in this country and this institution in order to preserve the human health and the marine environment.

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