Distinct evolutionary lineages of Schistocephalus parasites infecting co-occurring sculpin and stickleback fishes in Alaska

• Published in: Parasitology
• Main Authors: David C. Heins, Kristine N. Moody, Martin C. Arostegui, Brian S. Harmon, Michael J. Blum, Thomas P. Quinn
• Format: Article
• Language: English
• Published: Cambridge University Press 2024-05-01
• Subjects: cryptic species; Diphyllobothriidea; molecular phylogeny; parasite; sculpin; stickleback; trophic transmission
• Online Access: https://www.cambridge.org/core/product/identifier/S0031182024000593/type/journal_article
• ISSN: 0031-1820; 1469-8161

Sculpins (coastrange and slimy) and sticklebacks (ninespine and threespine) are widely distributed fishes cohabiting 2 south-central Alaskan lakes (Aleknagik and Iliamna), and all these species are parasitized by cryptic diphyllobothriidean cestodes in the genus Schistocephalus. The goal of this investigation was to test for host-specific parasitic relationships between sculpins and sticklebacks based upon morphological traits (segment counts) and sequence variation across the NADH1 gene. A total of 446 plerocercoids was examined. Large, significant differences in mean segment counts were found between cestodes in sculpin (mean = 112; standard deviation [s.d.] = 15) and stickleback (mean = 86; s.d. = 9) hosts within and between lakes. Nucleotide sequence divergence between parasites from sculpin and stickleback hosts was 20.5%, and Bayesian phylogenetic analysis recovered 2 well-supported clades of cestodes reflecting intermediate host family (i.e. sculpin, Cottidae vs stickleback, Gasterosteidae). Our findings point to the presence of a distinct lineage of cryptic Schistocephalus in sculpins from Aleknagik and Iliamna lakes that warrants further investigation to determine appropriate evolutionary and taxonomic recognition.