Chromosome numbers for three species of medicinal leeches (Hirudo spp.).

Karyological preparations were made from the testisacs of three medicinal leech species Hirudo medicinalis Linnaeus, 1758, H. verbana Carena, 1820 and H. orientalis Utevsky & Trontelj, 2005 . The samples originated from different populations in Azerbaijan, Kazakhstan, Russian Federation, Ukraine and Uzbekistan. The chromosome numbers were determined both from mitotic and meiotic stages of spermatogenesis using the propionic haematoxylin staining technique. All three species were found to have different haploid chromosome numbers: H. medicinalis 14, H. verbana 13 and H. orientalis 12, thus corroborating the validity of these taxa. The chromosomes can be classified as meta-, submetacentric and acrocentric. The chromosome numbers obtained are similar to that of the related species Haemopis sanguisuga (Linnaeus, 1758), which has 13 pairs.

The medicinal leech as a convenient tool for water toxicity assessment.

Medicinal leeches previously were used in various toxicological and pharmacological studies because they are sensitive and easy to keep under laboratory conditions. Toxicological studies using leeches became restricted when their natural sources decreased dramatically. We breed medicinal leeches under laboratory conditions and have the possibility of using them for various investigations. The aim of the current study was to investigate changes in behavioral and physiological responses of leeches exposed to a heavy metal model mixture (HMMM). The composition of the HMMM was determined on the basis of the average annual amounts of representative metals (Zn, Mn, Cu, Cr, Ni, Cd, and Pb) in wastewater discharging from the Ignalina Nuclear Power Plant. An annual average was considered a concentration of 1%. Animals were exposed to 0.13%, 0.25%, 0.5%, 1%, and 2% concentrations of the HMMM. The avoidance responses, changes in body weight, feeding behavior, and excretion rates of the leeches were recorded. Avoidance response was observed in animals treated with 1% and 2% concentrations of the HMMM during the first 2 h of exposure. A decrease in body weight was recorded after a 4-week exposure to all tested concentrations. Disturbances in feeding behavior were observed after a 4-week exposure to 0.13%-2% concentrations. An increase in the defecation rate was observed during the 5-week exposure to 0.25%-2% concentrations. The excretion rate via nephridia was decreased during postfeeding period after exposure to 0.25%-2% concentrations. The avoidance response of medicinal leeches can be used as an express method for water quality assessment, whereas physiological responses may be used for the assessment of chronic toxicity of polluted environments.

Water and sediment toxicity assessment by use of behavioural responses of medicinal leeches.

Behaviour has been shown to be a sensitive indicator of chemically induced stress and pathology in aquatic organisms. However, ecotoxicological investigations on medicinal leech are restricted because of scarce leech resources in natural waters. We used artificially bred medicinal leech (Hirudo medicinalis L.) of two different ages: young (1-2 weeks old) and adult leeches (1 year old). Animals were exposed to: (1) waters of Lake Drukshiai-the cooler of Ignalina Nuclear Power Plant, (2) sediments of the river Nemunas and (3) solution of heavy metal model mixture (HMMM). The following behavioural responses of leech were investigated: mobility (number of moving individuals within certain periods of time), avoidance response (number of individuals escaping the tested water or sediments) changes in body shape (contractions of some muscles, abnormal position of suckers) and feeding activity (longevity of attachment process, interruptions of feeding bouts, size of blood meal). Mobility of young leeches was increased in the tested waters of Lake Drukshiai, whereas adult leeches showed no changes of this index. Avoidance response as well as impaired feeding activity (prolonged attachment process or completely suppressed attachment reflex, decreased size of blood meal) was observed in young leeches exposed to the waters from Lake Drukshiai and in adult animals exposed to all three kind of trials mentioned above. Avoidance response and changes in mobility were recorded during the first hour of exposure to tested samples; therefore, these responses can be used as an express method for water and sediment pollution assessment. Impaired feeding activity was recorded after 1-3-week exposure: this response may be used in assessing a chronic toxicity of pollution. Medicinal leech, due to its sensitivity, simplicity of measured indices and ease of laboratory maintenance, can be used as a test organism in ecotoxicity studies.