Spatiotemporal and gender-specific parasitism in two species of gobiid fish.

Anssi Karvonen,Kai Lindström

doi:10.1002/ece3.4151

Abstract

Parasitism is considered a major selective force in natural host populations. Infections can decrease host condition and vigour, and potentially influence, for example, host population dynamics and behavior such as mate choice. We studied parasite infections of two common marine fish species, the sand goby (Pomatoschistus minutus) and the common goby (Pomatoschistus microps), in the brackish water Northern Baltic Sea. We were particularly interested in the occurrence of parasite taxa located in central sensory organs, such as eyes, potentially affecting fish behavior and mate choice. We found that both fish species harbored parasite communities dominated by taxa transmitted to fish through aquatic invertebrates. Infections also showed significant spatiotemporal variation. Trematodes in the eyes were very few in some locations, but infection levels were higher among females than males, suggesting differences in exposure or resistance between the sexes. To test between these hypotheses, we experimentally exposed male and female sand gobies to infection with the eye fluke Diplostomum pseudospathaceum. These trials showed that the fish became readily infected and females had higher parasite numbers, supporting higher susceptibility of females. Eye fluke infections also caused high cataract intensities among the fish in the wild. Our results demonstrate the potential of these parasites to influence host condition and visual abilities, which may have significant implications for survival and mate choice in goby populations.

Highlights

Parasitism is a potent source of selection in natural host populations and has recently been suggested to play a role in processes such as maintenance of sexual reproduction (Jokela, Dybdahl, & Lively, 2009; King, Delph, Jokela, & Lively, 2009) and divergence of host populations (Eizaguirre, Lenz, Kalbe, & Milinski, 2012; Karvonen & Seehausen, 2012)
In species where sexual selection is based on males displaying secondary sexual characteristics, the ability of females to judge male quality when infected with such parasites could be compromised
We explore parasitism and the infections in the eyes of gobiid fishes where females actively choose males based on secondary sexual characteristics

Summary

| INTRODUCTION

Parasitism is a potent source of selection in natural host populations and has recently been suggested to play a role in processes such as maintenance of sexual reproduction (Jokela, Dybdahl, & Lively, 2009; King, Delph, Jokela, & Lively, 2009) and divergence of host populations (Eizaguirre, Lenz, Kalbe, & Milinski, 2012; Karvonen & Seehausen, 2012). Several host species of parasites express secondary sexual characteristics through which they can advertise their vigour, as well as resistance to parasites (Hamilton & Zuk, 1982) Often these signals are visually perceived ornaments such as long tails or bright coloration, and commonly displayed by males. Reduction in host vision could impair the ability of individuals to perceive sexual signals It has been shown in cichlid fishes that visually perceived sexual signals advertised through male coloration can be blurred because of increased water turbidity, resulting in hybridization of species following the relaxation of color-based sexual selection (Seehausen, van Alphen, & Witte, 1997). Parasites found in the key sensory organs, such as the eyes, could impair host vision and the ability to perceive visual cues from potential mates (Karvonen & Seehausen, 2012). Differences in the abundance of these parasites between male and female fish under similar level of exposure would be consistent with the idea of differences in susceptibility between the sexes

| MATERIALS AND METHODS

Findings

| DISCUSSION