Phenotypic Diversity of Population Groupings of Proteocephalus longicollis (Zeder 1800) (Cestoda: Proteocephalidae), a Parasite of Coregonus lavaretus (L.) Whitefish

Abstract

The phenotypic diversity of the population of Proteocephalus longicollis (Zeder 1800) cestode from Coregonus lavaretus (Linnaeus 1758) whitefish from Lake Kamennoe (Kostomukshsky Nature Reserve, North Karelia) was studied. The variability of intrapopulation groupings of P. longicollis (identified by discrete traits of the attachment and trophic–reproductive complexes) is described. The diversity, similarity, and difference of morphometric indices and the role of individual groupings in the phenotypic diversity of the population were estimated. It was demonstrated that the phenotype with a clavate scolex form the core of the P. longicollis population. Such a phenotype is well differentiated from the nucleus-like and lanceolate phenotypes by a larger size of the scolex and lower variability. It was concluded that the ecological type of the host’s behavior, which determines the niche occupied by a population, is an important factor shaping the phenotypic diversity and structure of the helminth population. The adaptive response of the P. longicollis population to a change in the host species is provided by a change in the frequencies of phenotypes that differ in the attachment traits.