Euhaplorchis californiensis
Encyclopedia
Euhaplorchis californiensis is a trophically transmitted parasite (TTP) that lives in the salt-water marshes of Southern California. Its lives in three hosts: shorebirds, horn snails
, and killifish
. As with many TTPs, E. californiensis modifies behavior of the prey to increase the likelihood of its transmission to the next host, the predator.
The parasite’s eggs are released in the droppings of shorebirds.
Horn snails consume the droppings and become sterile. Once the parasite has lived in the snail a couple of generations, the cercariae (the disk-shaped larva of flukes of the class Trematoda
, which have a tail-like appendage) swim out into the marsh.
The cercariae latch onto the gills of the killifish
and make their way along a nerve and into the brain cavity. The parasite forms a “carpet-like” layer over the brain.
According to Lafferty, infected killifish
are 4 times more likely to “shimmy, jerk, flash, and surface” than uninfected fish. This behavior makes the infected fish 30 times more likely to be caught and consumed by a bird.
Once the fish is consumed, the parasite lives in the bird’s gut and produces eggs to be released in the stool, which is spread into the marshes and ponds.
Lafferty did a study to observe how a population of un-parasitized snails performs in the absence of infected snails. He found that they released more eggs and became densely populated. He proposes that the snail population in the natural environment would be nearly double what it is if it weren’t for the parasite Euhaplorchis califoriensis.
Cerithidea californica
Cerithidea californica, common name the California hornsnail or the California horn snail, is a species of sea snail, a marine gastropod mollusk in the family Potamididae.-Distribution:...
, and killifish
Killifish
A killifish is any of various oviparous cyprinodontiform fish . Altogether, there are some 1270 different species of killifish, the biggest family being Rivulidae, containing more than 320 species...
. As with many TTPs, E. californiensis modifies behavior of the prey to increase the likelihood of its transmission to the next host, the predator.
Life cycle
The parasite’s eggs are released in the droppings of shorebirds.
Horn snails consume the droppings and become sterile. Once the parasite has lived in the snail a couple of generations, the cercariae (the disk-shaped larva of flukes of the class Trematoda
Trematoda
Trematoda is a class within the phylum Platyhelminthes that contains two groups of parasitic flatworms, commonly referred to as "flukes".-Taxonomy and biodiversity:...
, which have a tail-like appendage) swim out into the marsh.
The cercariae latch onto the gills of the killifish
Killifish
A killifish is any of various oviparous cyprinodontiform fish . Altogether, there are some 1270 different species of killifish, the biggest family being Rivulidae, containing more than 320 species...
and make their way along a nerve and into the brain cavity. The parasite forms a “carpet-like” layer over the brain.
According to Lafferty, infected killifish
Killifish
A killifish is any of various oviparous cyprinodontiform fish . Altogether, there are some 1270 different species of killifish, the biggest family being Rivulidae, containing more than 320 species...
are 4 times more likely to “shimmy, jerk, flash, and surface” than uninfected fish. This behavior makes the infected fish 30 times more likely to be caught and consumed by a bird.
Once the fish is consumed, the parasite lives in the bird’s gut and produces eggs to be released in the stool, which is spread into the marshes and ponds.
Effects on the Ecosystem
Armand Kuris speculates that the predator in this host-parasite interaction benefits by acquiring food easily. He also claims that the susceptibility of infected killifish to be picked-up by their avian predators has led to a diverse and abundant assemblage of piscivorous birds along the coasts.Lafferty did a study to observe how a population of un-parasitized snails performs in the absence of infected snails. He found that they released more eggs and became densely populated. He proposes that the snail population in the natural environment would be nearly double what it is if it weren’t for the parasite Euhaplorchis califoriensis.