Ciliates from Scandinavian molluscs
In: Ophelia: International Journal of Marine Biology. Ophelia Publications: Helsingør. ISSN 0078-5326, more
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| Abstract |
The present paper describes the ciliate fauna living on the ciliated epithelia of aquatic invertebrates, especially bivalves, from a systematical and an ecological point of view. In 64 Scandinavian invertebrate species, of which 57 were lamellibranchs, 47 morphologically distinct ciliate species were found of which 14 are new to science. The majority of these ciliates belongs to the order Thigmotrichida, the remainder being representatives of the families Urceolariidae, Licnophoridae and Euplotidae.A new family, Peniculistomatidae is created to contain Peniculistoma mytili (De Morgan), which possesses many characters in common with the pleuronematine hymenostomes and therefore must be considered as the most primitive thigmotrich. Conchophtheridae and Thigrnophryidae are considered to be specialized families.Three types of morphological adaptations were found within the ciliates of lamellibranchs. In all types, however, the organelles of attachment and a body shape giving minimum resistance to water currents are present.Although several ciliate species may occur in one lamellibranch species, the population sizes of the different species are independent and so are the infection frequencies. The problem of host specificity is discussed and it is shown that the rhynchodine thigmotrichs exhibit a higher host specificity than the other lamellibranch ciliates.It is shown that lamellibranchs are first infected by their ciliates at a certain age after metamorphosis. Experiments have demonstrated that infection normally takes place by freely swimming ciliates being passively imbibed by their hosts. The infection frequency is related to the population density of the hosts.The conjugation is shown to be an epidemic phenomenon. It is further shown that the tolerance limits of the ciliates to salinity changes are identical with those of their hosts.The distribution of the ciliates within the host group is discussed, and it is shown that the larnellibranchs with the highest number of ciliate species are those which form the densest populations. |
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