Composition of Leukocytes in Blood of Goldfish Infected by Ligula (Digramma) Interrupta (Cestoda: Pseudophyllidea)

Abstract

The tapeworm Ligula interrupta of the genus Ligula (Digramma) (Cestoda: Pseudophyllidea) is a specific parasite of freshwater cyprinid fish; its plerocyrcoids are localized in the body cavity causing heavy parasitic pathology. With parasitosis, an important role in the regulation of the pathological process is assigned to the participants of the organism’s protective reactions, among which a special pool of immunocompetent cells – leukocytes – is distinguished. In the literature, there are single data on hemo- and immunopoiesis goldfish with digrammosis. In our work, new data were obtained on the leukocyte composition of the blood of goldfish Carassius auratus (Linnaeus, 1758), infected with Ligula interrupta in conditions of the native range (Shilen Lake and Cheremukhovoe Lake, Lake Baikal basin). All fish specimens caught with seine nets, both infested and noninfested with L. interrupta, were identical by the size and age composition (age +3…+5, body length 145–237 and 150–180 mm, respectively, weight 100–184 and 120–174 g). Hematological studies were carried out according to the Sbornik [2]. To quantify the individual types of leukocytes, the leukocyte profile, expressed in absolute terms, was calculated. Three groups of cells were revealed in the blood of all goldfish species: blast forms, granulocytes (neutrophils, pseudobasophils) and agranulocytes (lymphocytes, monocytes). The decrease in the blood of infected fish of the total number of leukocytes and their various types at all stages of development, the violation of the proliferation and differentiation of lymphoid and granulocytic elements in the studied organs, the formation of vacuolated and atypical cells, the absence of circulating basophils and eosinophils were established. It has been shown that in this parasitic system, partner relations are reduced to the launch of L. interrupta mechanisms that regulate the host's protective immunological processes by the type of inhibition of the acute inflammatory response and the development of mild chronic inflammation.