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Molecular diet analysis of the marine fish-eating bat and potential mercury exposure

November 8, 2021 | 4 minute read

molecular analysis of the diet of a unique fish-eating bat,The following is an interview with Dr. Luis Gerardo Herrera Montalvo of the National Autonomous University of Mexico. He is the co author of a recent paper in the Canadian Journal of Zoology; the paper reports on a molecular analysis of the diet of a unique fish-eating bat, Myotis vivesi, found on islands in Mexico’s Gulf of California.

This study included a first-ever meta barcoding for this purpose done to identify multiple food sources simultaneously. It was undertaken as a step toward a better understanding of the relationship of foods and levels of mercury-induced toxicity in these rare animals.

Dr. Luis Gerardo Herrera Montalvo recently shared details with Dick Bourgeois-Doyle about his paper, Molecular diet analysis of the marine fish-eating bat (Myotis vivesi) and potential mercury exposure

Listen to the interview with Dr. Luis Gerardo Herrera Montalvo or read the interview below:

 

Canadian Science Publishing (CSP): Dr. Herrera Montalvo could you first describe a bit about the bats in their habitat.

Dr. Luis Gerardo Herrera Montalvo (GHM): They are medium-sized bats about 30 grams in body mass, they have big   teeth and claws to catch the fish and the shrimp.  They live under the rocks because there are no caves. And there are no trees in the islands. These are volcanic islands; the islands belong to an ecosystem that is very poor in resources. You know, it’s the Sonoran Desert. So, most of the year is dry. And then it gets some rain, and some of the nutrients that support these islands come from the sea. In order for bats to live in those islands in such big numbers, they need to take advantage of the rich sea that is around the islands. They adapted pretty well to life, fishing, catching shrimp as they don’t have many terrestrial insects available in those islands. So, they really flourish, adapting to these new conditions.

Myotis vivesi scaled

CSP: It sounds like a pretty important project when you think of the uniqueness of the bat and the specifics of the ecosystem. I wonder if you could explain the process of meta-barcoding and why it was important to this particular project?

GHM: Well, the problem with studying diets with these kinds of bats is that when they process the food, they destroy it. So, years ago, I was just looking at the content in the fishes, using a microscope with these bats; it’s almost impossible, identifying what they ate.  I did that with a student using a microscope, but she couldn’t get too much information about the taxonomic identification because the remains were destroyed.

There were pieces that were available, but that couldn’t prove much.  This metabarcoding is wonderful because it allows you to go farther than all the techniques can go.  You know, we can identify the species – quite possibly using these techniques. So, I think that that’s why we use this, this technique. It’s very useful in the case of bats that destroy the food.

And we also use the stable isotope. And the stable isotope is also a good technique, but it’s too general to describe the feeding habits of any animal; metabarcoding is nice because it allows us to go further than any other in terms of taxonomic identity. So that’s why we were eager. We have been dreaming of that for several years.

CSP: So, you were interested in what they were eating, but also the level of the contaminant?

GHM: Yes. Because of the diet, they may be exposed to these contaminants. So, it makes sense to combine both things in a single study.

CSP: I think the study showed that one of their primary food sources was California anchovies, is that correct? And some crustaceans or does that vary a lot from year to year?

GHM: Oh, they were found very consistently along the year and along several years. This fish – yeah, we think that that’s the main source of food. We have done some GPS work with these bats, and we know that they can fly for several kilometers to get their food, and they’re very consistent to the areas where they know they can find the food.

They just don’t go randomly. They have some areas where they know. I don’t know how they know but they know that those areas to catch the fish and the shrimp.

CSP: Do they drink sea water as well?

GHM: I don’t know –  we have never seen that. I think that they get the water from the food. I haven’t seen them drinking. It is not easy to see that of course in their natural habitat. And I suspect they get the water from the food because there are no freshwater sources in those islands. I suspect they get it from the food – they just metabolize it.

CSP:  So, would you classify them is a marine mammal?

GHM: Yeah, it’s, um, you know, sea lions, they spend half of their life on terrestrial systems.

CSP: They’re a small marine mammal, then maybe their study will illuminate our understanding of larger marine mammals. Do you plan to go back to the islands again?

GHM: We had to stop because of COVID. You know, we haven’t been able to go to the field last year, this year. Maybe, we hope we can go next year. There is always new things that we can do, you know. It’s a very, very interesting species. We have published several papers on these bats. It is a very nice bat to work with.

So hopefully we’ll go next year.

Banner and in-text images: Courtesy of Dr. Luis Gerardo Herrera Montalvo 

Podcast music is “Spring Cleaning” by Jay Man, www.Our-Music-Box.com

Canadian Science Publishing

Canada’s largest publisher of scientific journals and not-for-profit leader in mobilizing science.