Water pollution is one of the major environmental problems of today and the aquatic biota is
one of the most affected by urban development. Fish are extremely sensitive animals, as they
can be contaminated through the direct absorption of substances from the environment by the
gills or food ingested. The objective of this research was to evaluate the mucous cells of
Hemigrammus levis collected in Lake Juá, Santarém, Pará, Brazil, as environmental
biomarkers, in addition to correlating the density of the cells with the physical-chemical
variables of lake water. The sampling points (1 and 2) were defined based on geographic
difference and based on previous environmental impact information and also used for water
collection. Point 1 was located near an anthropic area and point 2 was near the most preserved
area. Flona (Tapajós National Forest) was also used as the control environment. Samples were
collected for 12 months, from April 2017 to March 2018. Fish (n = 130, standard length (cm)
3.43 ± 4.2, weight (g) 0.73 ± 0.24) were placed in plastic bags with constant aeration before
biometry and anesthetized in eugenol solution (100 mg / L) to be submitted to the dissection
and histological procedure of the gills, in addition to marking the cells. The sections were
stained using Alcian Blue pH-2.5, Periodic Acid and Shiff React solution. The gill mucosa
cells were identified and quantified with the aid of a microscope coupled with an image
capture system and interactive measurement program, thus obtaining cell density in mm². The
water variables evaluated were pH, temperature, dissolved oxygen, electrical conductivity,
sodium, potassium, chloride, ammonia, hardness and alkalinity, submitted to Pearson
correlation analysis and regression. The mucosal cell density was analyzed from the MannWhitney Test. The analysis of water variables showed higher values of conductivity over a
year at point 1.Flona's variables approached point 2, with a higher concentration of dissolved
oxygen and lower electrical conductivity, suggesting a preserved environment. In the species
analyzed, it was observed that the density of acidic and neutral mucosal cells was modulated
by the changes that occurred in the physicochemical variables of water, especially in the low
water period. The data suggest that pH and potassium are the most important variables for this
purpose. Therefore, it is suggested that Hemigrammus levis is a potential species to be
visualized as an environmental quality bioindicator of Lake Juá, since it showed modulation
of mucous cells in the face of environmental changes.
Key words: anthropization, biomonitoring, gills, fish
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