Brain-Encysting Trematodes (Euhaplorchis californiensis) Decrease Raphe Serotonergic Activity in California Killifish (Fundulus parvipinnis)

Authors

Siri H. Helland-Riise, Norwegian Academy of Sciences - Oslo
Marco A. Vindas, Norwegian University of Life Sciences - Oslo
Ida B. Johansen, Norwegian University of Life Sciences - Oslo
Lauren E. Nadler, Norwegian University of Life Sciences - Oslo; University of California - San DiegoFollow
Kelly L. Weinersmith, Rice University
Ryan F. Hechinger, University of California - San Diego
Øyvind Øverli, Norwegian University of Life Sciences - Oslo

ORCID

0000-0001-8225-8344

Document Type

Article

Publication Title

Biology Open

ISSN

2046-6390

Publication Date

7-8-2020

Keywords

Parasite density, Parasite intensity, Experimental infections, Neurobiology, Parasite alterations, Serotonin

Abstract

Modulation of brain serotonin (5-HT) signalling is associated with parasite-induced changes in host behaviour, potentially increasing parasite transmission to predatory final hosts. Such alterations could have substantial impact on host physiology and behaviour, as 5-HT serves multiple roles in neuroendocrine regulation. These effects, however, remain insufficiently understood, as parasites have been associated with both increased and decreased serotonergic activity. Here, we investigated effects of trematode Euhaplorchis californiensis metacercariae on post-stress serotonergic activity in the intermediate host California killifish (Fundulus parvipinnis). This parasite is associated with conspicuous behaviour and increased predation of killifish by avian end-hosts, as well as inhibition of post-stress raphe 5-HT activity. Until now, laboratory studies have only been able to achieve parasite densities (parasites/unit host body mass) well below those occurring in nature. Using laboratory infections yielding ecologically relevant parasite loads, we show that serotonergic activity indeed decreased with increasing parasite density, an association likely indicating changes in 5-HT neurotransmission while available transmitter stores remain constant. Contrary to most observations in the literature, 5-HT activity increased with body mass in infected fish, indicating that relationships between parasite load and body mass may in many cases be a real underlying factor for physiological correlates of body size. Our results suggest that parasites are capable of influencing brain serotonergic activity, which could have far-reaching effects beyond the neurophysiological parameters investigated here.

DOI

10.1242/bio.049551

Volume

9

Issue

bio049551

First Page

1

Last Page

8

Comments

©2020. Published by The Company of Biologists Ltd.

Additional Comments

Norges Forskningsrad project #s: 240116, 250048

NSUWorks Citation

Siri H. Helland-Riise, Marco A. Vindas, Ida B. Johansen, Lauren E. Nadler, Kelly L. Weinersmith, Ryan F. Hechinger, and Øyvind Øverli. 2020. Brain-Encysting Trematodes (Euhaplorchis californiensis) Decrease Raphe Serotonergic Activity in California Killifish (Fundulus parvipinnis) .Biology Open , (bio049551) : 1 -8. https://nsuworks.nova.edu/occ_facarticles/1113.