Shchenkov S.V., Denisova S.A., Smirnova A.D., Shunatova N.N. 2019. [Mucoid glands of cercariae] // Invertebrate Zoology. Vol.16. No.4: 377–392 [in Russian, with English summary].
Department of Invertebrate Zoology, Saint Petersburg State University, Universitetskaya Emb., 7/9, St. Petersburg, 199034, Russia. E-mail: firstname.lastname@example.org
ABSTRACT: Though the mucoid glands of cercariae from different digenean families were discovered in the first half of the XX century, published data on their structure and development are very scarce and insufficient. Here we concentrate on a detailed description of the mucoid apparatus (a set of developing mucoid glands and their final products) in 13 species of cercariae from Plagiorchiidae, Microphallidae, Pleurogenidae, Lecithodendriidae, Renicolidae, Opisthorchiidae, Heterophyidae and Notocotylidae families. Our recent data together with previously published results on other cercaria’ species served the basis for comparative analysis of mucoid apparatus structure. Only four pairs of mucoid gland cytons were registered in different morphotypes of cercariae. They are formed at different stages of cercariae development, depending on the taxa. Traits of glands maturation, their final size and the pattern of their secretion into the tegumental plate vary across digenean families. New types of reservoirs for mucoid secretion were detected: acetabular vigulae of lecithodendriid cercaria and virgula-like structure of Metorchis sp. In addition to it, obtained data suggested that secretory cytons of notocotylid cercariae do not belong to the mucoid apparatus and thus abandon the previous concept. Revealed evolutionary trends in the mucoid apparatus organization, including plesiomorphic and apomorphic characters of studied families are in a good agreement with recent data on molecular phylogeny of digeneans.
KEY WORDS: mucoid glands, cercariae, digeneans, Trematoda.