STUDY OF MOVING REACTIONS
OF MEDICAL LEECH (HIRUDO MEDICINALIS)
DEPENDING ON THE CHARACTER OF WATER POLLUTION
N. V. Kovalinska, I.I. Kovalisnska, H. I. Falfushinska, O. B. Stolyar
Hnatyuk Ternopil National Pedagogical University, Ternopil, Ukraine, E-mail: firstname.lastname@example.org
Key words: Hirudo medicinalis, moving activity, mixed pollution
Н. В. Ковалінська, І. І. Ковалінська, Г. І. Фальфушинська, О. Б. Столяр
Тернопільський національний педагогічний університет ім. В. Гнатюка, м. Тернопіль, Україна,
Ключові слова: Hirudo medicinalis, рухова активність, комплексне забруднення
The traditional system of control of water pollution that is based on revealing by analytical methods of the certain substances is not effective. It caused by the absence of a plenty of analytical methods of revealing of all toxic combinations which can be the part of by-pass flow waters, diverse character of interaction of separate components of a mix and so on (Braginskiy, Linnik, 2003). The supplying of the effective control of small rivers pollution is especially difficult. The purpose of our research was the application of medical leech Hirudo medicinalis (Linnaeus, 1758) as a bioindicator for the estimation of water quality. The test-reaction was the change of the natural static state of leeches on a dynamic one at entering the water. We speculated that this is the first reaction of leeches to irritating and harmful action. The quality of water was estimated in the first 15–20 minutes of contact with it as the reduction of number of static state of experimental leeches.
The young leeches with the weight 30–20 mg were obtained from biofactories. The cups were half filled with distilled water, +18…+23°С. One hour before testing leeches were transferred in Petry cups for 3 leeches in everyone. The each group consists of nine individuals (in three cups). Before testing we convinced whether all the leeches were in a normal rest condition (a static state). If in one of the cups even one leech moves, both a cup with water and the leeches were replaced and the full motionless of a new leech was expected. Than all animals were in rest, the water from the cups with experimental and control leeches was merged. The control leeches were put again into the clean water (30 ml), and the experimental were put in a solution for testing (30 ml). It is necessary, that the quantity of water in all cups was identical because it can affect the accuracy of test performance. The average quantity of leeches in the state condition all over each 3 min in each group was calculated and expressed as means ±S.D. of 6 points analysed. In some cases the leeches have abandoned water and crept out on a cover of a Petry cup where they made a static pose. We considered such reaction as a dynamic one. Comparisons were made by applying of Fisher’s test.
The water from different sites of small river Hnizna (81 km length) passed through the territory of Ternopil region and model water systems were investigated. For the analysis water from the river Hnizna was selected on seven sites, which essentially differed with the character of drains. The first site for research was located near the beginning of the river as a spring. The second area was covered with the forest. The third one – agricultural zone; the fourths site (industrial zone) was a city zone of the town Terebovlya where the industrial targets, such as creamery and cannery, are located. The fifth and sixth zones were situated in the area of water purifying systems. The mouth of river was the seventh zone. In natural water we defined temperature, рН, hardness, oxidization, and the contents of phosphates and nitrite according to the standard techniques, iron, copper, zinc, manganese, cadmium and lead content. The water was tested in autumn (October, 2004) and spring (March, 2005).
Model systems were also investigated. They included the solutions of the mix of the ions of heavy metals, or phenol in ecologically realistic concentration and solutions of different acidity. The contents of metals in the mix were: Cu2+ (CuSO4) – 0,01 mg/l; Zn2+ (ZnSO4) – 0,1 mg/l; Mn2+ (MnCl2) – 0,12mg/l; Pb2+ (Pb(NO3)2) – 0,01mg/l counting upon cation. The contents of corresponding anions were much lower, than their allowed contents in fish-economy reservoirs and that causes sedimentation of ions. The content of phenol in water was 2 μg/l. The different acidity has made by applying of 0,1 mM sodium phosphate buffers with pH 5,8, 6,8, 8,0.
It was revealed that the water samples taken for testing in different areas of the river Hnizna provoke the great diversity of the answers of leech’s behavior. Less of all toxic for the leech was the water in the upper reaches of the river both in spring and in autumn. The water from wood or mouth of the river provoked less more high activity of leech. However in water taken from the river in the agricultural zone we observed symptoms of poisoning of leech. The water taken in the industrial zone and purifying constructions was mostly dangerous especially in the spring. The data revealed that only dilution in eight times in both seasons reduced the toxicity of water in industrial zone completely.
Generally, the carried out chemical analyses of water confirmed reaction of medical leeches to the contents of toxic substances in flow waters of the river Hnizna. But it didn’t reveal the significant level of pollution in the water of industrial zone according to measures of oxidization, metals and NO2- content. It was surprisingly at the first sight to observe the high level of pollution in water after purification plant, according to leech behavior and confirmed by chemical tests. These data reflect that the traditional municipal wastewater treatment plants are not effective and must be improved by additional chemical procedures for the sedimentation of heavy metals and for oxidation of organic pollutants to non dangerous compounds.
The significant destroying of the vital activity of leeches was observed in the experimental mix of metals (separate test–objects crept out on a cover of Petry cups). As known from our previous investigations the effect of the same metals mix on bivalve mollusk or fish carp didn’t provoke remarkable changes in general biochemical tests (Stolyar, 2004). Thus the medical leech is more sensitive and more suitable test–object for express analysis than bivalve and fish. The solution of phenol was less toxic. In the alkalescent рН environment all tests–objects occupy a natural static state, and in neutral acidic pH the leech occupies a corresponding pose only with increase in time.
According to our results we propose to separate three levels of water pollution and to use this classification in the estimation of water quality. It is accounted as the average percent of leech in a static state from six measurements during 15 min. I level of toxicity (0–35 %) is associated with most significant danger of water. It was observed in the industrial zone; in the surrounding of water purifying station in spring and in the experimental mix of metals. II level (35–70 %) characterizes the middle toxicity (observed for the water from agricultural zone and solution of phenol) and III level
(70–100 %) is due to comparatively clean water (start of the river).
The data taking together confirmed the high level of sensitivity of leech as bioindicator. It simple in application; it demands less financial expenses than then other methods of revealing of toxic in water. This test–object may be renewed. The carried out tests showed the high water impurity of comparable clean Ternopil region; nowadays the problem of biotesting is very actual.
Thus the test of water quality based on leech using may be recommend as not expensive and sensitive method for express–analysis of water quality in small rivers which not controlled effectively by government or municipal institution.
N. V. Kovalinska was the winner of Ukrainian National level of Stockholm Junior Water Prize in 2005 year for presentation of part of this investigation.
Zoocenosis — 2005
Біорізноманіття та роль зооценозу в природних і антропогенних екосистемах: Матеріали ІІІ Міжнародної наукової конференції. – Д.: Вид-во ДНУ, 2005. – С. 44-46.