Altered Predation Susceptibility of Mosquitofish Infected With Eustrongylides Ignotus

Abstract

Eustrongylides ignotus is a parasitic nematode whose definitive hosts are often piscivorous wading birds (Ciconiiformes). Several species of small fishes are intermediate hosts, while larger predatory fish may be paratenic (transport) hosts. We examined predation susceptibility of infected mosquitofish (Gambusia holbrooki) to three species of predatory fishes, including juvenile largemouth bass (Micropterus salminoides), warmouth (Lepomis gulosus), and bluegill (Lepomis macrochirus). A 250 L aquarium with removable plexiglass divider and remote observation windows was constructed. Aquatic macrophytes were placed in the tank to provide refuge for the fishes. Predatory fish were allowed to acclimate to one half of the tank, while one infected and one uninfected mosquitofish were placed in the other. The divider was removed and an observer recorded the number of capture attempts and time required for capture. Predators were observed for behavioral alterations for 4 days after ingestion of infected mosquitofish, then examined at necropsy. Infected prey were selected preferentially in 31 of 38 (82%) trials. The number of capture attempts was 2.7+/-0.2 (x +/- SE) for infected fish and 3.9+/-0.4 for uninfected fish. Mean time of capture was 12.4+/-1.6 min for infected fish and 21.7+/-2.9 for uninfected fish. Because of these differences, infected mosquitofish were more susceptible to predation (P < 0.01) than uninfected fish. Aberrant behavior including lethargy, convulsions, and buoyancy abnormalities was observed in eight (67%) predatory fish. At necropsy, larvae of E. ignotus were found in the coelomic cavity, viscera, and swim bladders of predators. Parasite-induced behavior modification of intermediate hosts may predispose them to predation by wading birds and thereby facilitate the transmission of this nematode in natural populations.

Parasites: Small Players with Crucial Roles in the Ecological Theater

“…The avian definitive hosts become infected when they consume the fish, thus completing the life cycle. This parasite causes pathology in piscivorous fish hosts and renders smaller forage fish more susceptible to predation (Coyner et al, 2001). In addition, the parasite causes significant mortality among nestling birds.…”

Nematodes in Hoplerytrinus unitaeniatus, Hoplias malabaricus and Pygocentrus nattereri (pisces characiformes) in Marajó Island, Brazil

“…In both cases, fish may be a source of infection for piscivorous birds and marine mammals FAGERHOLM, 1995;ANDERSON, 2000). In parasitism involving Eustrongylides sp., the definitive hosts are piscivorous birds; while in infections with Contracaecum sp., fish participate as the second intermediate hosts and contamination occurs after ingestion of parasitized oligochaetes (COLE, 1999;COYNER et al, 2001).…”

Disease-Induced Chaotic Oscillations and its Possible Control in a Predator–Prey System with Disease in Predator

“…Holmes and Bethel [28] and Lafferty and Morris [31] studied that the parasitic infection reduces host stamina and locomotive efficiency. Coyner et al [9] showed that mosquitofish infected with parasite (Eustrongylides ignotus) and probably produce a physical and metabolic burden that may reduce and inhibit the fish's ability to avoid capture.…”