Herons!

I finally took a picture of a great blue heron (Ardea herodias) today!  I see them frequently when I first arrive at ponds, but they spook easily, so they’re usually long gone before I get my camera out.

“You’re interrupting my frog-eating.”

I also saw what might have been a green heron (Butorides virescens) yesterday.  I’m not a very good birder (yet), so I’ll have to see it again before I can be confident in my identification.  Here’s a photo of a green heron that someone else took:

Green Heron. Photo by Alex Lamoreaux.

And now, for the parasites!  One cool thing about having this blog is that I’m motivated to do things that I might not normally do, but that I probably should do.  For instance, I went to the Natural History Museum host-parasite database and looked up the parasites of the great blue heron.  There are a lot of potential parasites!

One of those parasites is the trematode Ribeiroia ondatrae.  You might have heard of this parasite because the metacercariae stage of the trematode encysts in larval amphibians, and is known to cause limb malformations in frogs.

A frog with limb malformations caused by the trematode parasite Ribeiroia ondatrae. Photo credit: Nature. 

Because Ribeiroia can cause these limb malformations, the parasite has been studied extensively to determine whether it is one partial cause of the worldwide decline in amphibian populations.  The jury is still out on that one!  I’ll probably talk more about Ribeiroia in the future, but for now, here’s a bit more information from the Parasite of the Day blog.

Any one else have heron pictures to share?  Or perhaps better yet, do you know of any other cool heron parasites?

When Parasites Invade: A Need for Hosts

When the host of a parasite invades new territory, the parasite species might invade with it.  In a recent Journal of Parasitology paper, Novak and Goater (2013) explored how the lung fluke Haematoloechus longiplexus invaded Vancouver Island when it’s definitive host bullfrog (Lithobates catesbeianus) was introduced in the 1930’s and subsequently established in the wild.

H. longiplexus has a complex life cycle that requires three hosts.  Therefore, in order for H. longiplexus to establish in new territory, the two intermediate hosts must be present along with the invading bullfrog.

This life cycle of Haematoloechus medioplexus is very similar to that of Haematoloechus longiplexus. Photo Credit: Graphic Images of Parasites.

Physa snails are geographically widespread, and occurred in Vancouver Island before the bullfrogs invaded.  Furthermore, Novak and Goater (2013) found H. longiplexus metacercariae in six damselfly species in sites along the East coast of Vancouver Island.  Therefore, H. longiplexus went to Vancouver Island with its bullfrog hosts, and was lucky enough to find functional intermediate hosts already present.  Invasion success!

Interesting note:  No dragonflies had H. longiplexus metacercariae, so H. longiplexus is a damselfly specialist in Vancouver Island.  One explanation for this host specificity might be that when dragonfly larvae undergo metamorphosis, they lose their metacercariae, but metacercariae in damselfly larvae aren’t lost.  So, if a bullfrog snacks on an adult dragonfly, it won’t get infected, but if snacks on an adult damselfly, it might!

Its a snack, its a hat…
Photo Credit: Today.com

Can you think of any other reasons for host specificity in H. longiplexus?

Source:

Novak, C.W. and T.M. Goater.  2013. Introduced Bullfrogs and Their Parasites: Haematoloechus longiplexus (Trematoda) Exploits Diverse Damselfly Intermediate Hosts on Vancouver Island. Journal of Parasitology, 99(1): 59-63.