A common type of fish parasite can prevent the accumulation of heavy metals from pollution in the fish’s tissues, making the fish safer for humans to eat, a study by the Institute of Biological Sciences of the University of the Philippines Los Baños (UPLB) has found.
Species of Acanthocephala (namely Acanthogyrus sp.), also known as the thorny-headed worm, can infect fish but they bring more help than harm, the UPLB study, which was supported by the Department of Science and Technology (DOST), found.
Acanthocephalans are fish parasites that accumulate heavy metal concentration in their host’s tissues (gills and intestine).
The study found that fishes infected with parasites (parasitized) have lower levels of heavy metals compared with fishes not infected by parasites (non-parasitized).
The difference in the tissues of the parasitized and non-parasitized fish is “remarkable”, according to the study.
Acanthocephalan infection, according to the study, affects only the host’s (fish) size or weight and length but has no significant effect on the immediate health of the fish.
Vachel Gay V. Paller, NRCP biologist/researcher, said that as the number of parasites increases, the length of tilapia decreases.
“Smaller tilapia may not be so bad. Some may have parasites, but these parasites may just save the consumers from possible heavy metal intake. Besides, the parasites stay in those parts – gills and intestine – which the consumers most likely discard,” she explained.
Conducted in the seven lakes of San Pablo, Laguna (Bunot, Calibato, Mohicap, Palakpakin, Pandin, Sampaloc and Yambo), the study aimed to help farmers understand and control acanthocephalan infection among fishes in the lakes.
Acanthogyrus sp. were found in the following four species of fishes: O. niloticus (Tilapia), P. Managuensis, Vieja sp., and Red Nile Tilapia. The highest rate of
Acanthocephalan infection and intensity was recorded in Palakpakin Lake.
Among the heavy metal sources of pollutants in the Seven Lakes are vehicles (car exhaust, worn tires, engine parts, brake parts, rust or used antifreeze); and fish cages wherein the uneaten feeds that contain essential minerals for fish diet (copper, calcium, zinc, selenium, magnesium, potassium, phosphorous, manganese, iron and iodine) accumulate in the lake over the years. Other sources include untreated wastes from hospital, residential, commercial and industrial establishments; and pesticides from agricultural application in the nearby areas.
The study, funded by the National Research Council of the Philippines of the Department of Science and Technology (NRCP-DOST), is relevant at this time when the government is pushing for a cleaner environment, especially in the coastal areas where many people live and obtain their livelihood.
NRCP will be hosting the Science and Policy Forum for Sustainable Laguna Lake Management on November 22 and 23, 2016 in Days Hotel, Tagaytay. The forum will be a gathering of fishers, farmers, environmental experts in the academic, administrative and legislative sectors.
DEPARTMENT OF SCIENCE AND TECHNOLOGY