Eggs to Adults: A Captive Rearing Program for an Endangered Dragonfly
Wow! Day 3 of the NABS/ASLO meeting is already over! It was a great day for me. There was a whole session on aquatic insects and that’s always a good thing, at least if you’re me. Day 3 was the day of the banquet, so I got to have a huge dinner of delicious Mexican foods. I love Mexican food! (Actually, I’ve had Mexican food for almost every meal since I’ve been here… I’m an addict!) I had a lovely dinner conversation with a professor from Wheaton College who has the exact sort of professorship that I hope to get. She was encouraging and had some very helpful advice for my impending job search that is going to be useful. She was incredibly nice as a bonus. And, I got second place in the photo contest for this photo:
There were over 50 entries, so I’m feeling pretty chuffed about it. My photo sold during the silent auction for the photos in the competition too. Excellent way to end an already good conference day.
Some things I learned:
— There is a research center in Minneapolis called the St. Anthony Falls Laboratory where researchers have built an artificial stream that can be precisely controlled, allowing researchers to do work that isn’t possible in natural streams.
— Iraq had an enormous marsh in the southern part of the country that has been used by people for thousands of years – until US soldiers used it as a hiding place during the first Gulf War. The Iraqi’s drained it and burned the vegetation to force the soldiers out. Locals in the area recently began breaking down the dams used to divert the water so that water is once again filling the marsh. Crazy!
— Freshwater clams and mussels are among the most highly endangered animals in the world.
And speaking of endangered species, I thought I would discuss a talk I heard today the relates to an endangered species. It was hard to choose a favorite talk today because I really loved several of them, but considering this blog is The Dragonfly Woman, I thought it appropriate to write about the dragonfly talk I heard. Behold Somatochlora hineana (also known as the Hine’s emerald dragonfly):
This is one of the most rare dragonflies in the world. It is in fact the only dragonfly on the endangered species list. According to the woman giving the talk, Rachel DeMots of the University of South Dakota, this species used to be found in several states in the U.S. In recent years, it has experienced a contraction in its home range so that it is currently found in only Wisconsin and Michigan. The populations in these two areas are at high risk of extinction and are of great concern for conservationists.
Endangered insect species often become the subjects of captive rearing programs. By capturing at least a few males and females in the field, researchers can bring them into the lab, mate them, and rear the eggs into new adults. Insects in captive rearing programs are kept safe while they are growing and are then released back into the wild as adults to augment the tiny populations left in the wild. (This has occurred in non-insect species as well, such as the California condor and the black footed ferret.) For a more detailed account of one of these programs, I highly recommend reading the section on the Lange’s metalmark butterfly (Chapter 11 – Butterfly Ressurection) in the excellent book The Dangerous Lives of Butterflies by Peter Laufur. It goes into detail about how the captive rearing program of the Lange’s metalmark, which had a total population size of only a handful of individuals living in a tiny area known as the Antioch Dunes in California, might help save this species from extinction.
But back to the dragonflies! The Hine’s emerald population isn’t quite as small as the Lange’s metalmark, but they’re still good candidates for captive rearing. They live in very a very specific habitat type – shallow, seasonally pooled streams – and those habitats are becoming degraded in the areas in which they still live. Rachel’s talk was about how the captive rearing program for the Hine’s emerald (of which she is a major part) works and demonstrated the successes of the program. The goal of the program is to allow researchers to bring populations of Hine’s emeralds into the lab, rescuing them from areas where their habitat has been degraded to the point that they can no longer survive there, and keep them safe until those habitats are restored to survivable conditions. If they do this, they allow the insects to survive periods of time when their habitats cannot support them. In essence, the dragonflies become refugees in the lab!
The captive rearing program at the University of South Dakota began in 2003. They originally collected nymphs in the field and brought them into the lab. Once in the lab, each dragonfly is given its own container, is kept at the same temperatures they would experience in the stream, and fed bloodworms in the amounts they naturally eat at any given point in the year. Basically, the team tried to mimic the field conditions as closely as possible. The dragonflies might be fed once a week during the winter and several times a week during the summer because that is how much they would eat if left in the field. When the nymphs are about to emerge as adults, they are transferred into emergence cages, allowed to emerge, and then released back into the field. They don’t keep adults because there really isn’t a good way to keep dragonfly adults in captivity for long periods of time.
Recently, the group has also begun to rear dragonflies from the egg stage. They collect eggs in the streams and bring them back to the lab, where the eggs are kept at the same temperature they would experience in the stream. After they hatch, each nymph is placed in its own container and fed brine shrimp (sea monkeys!) daily. Once they get bigger, they start eating the bloodworms, then emerge and are released as already described.
Rachel commented on the success of the program. The program currently reports an 80-90% survival rate for nymphs, which is pretty good. They have also placed some nymphs in cages (so they can’t be eaten) in their native streams so that they can compare the body size of individuals grown in the lab to those that would be found in the field. If they produce nymphs that are too small or too big, they can cause problems, so they wanted to be sure that their dragonflies were about the same size as ones produced in the field. Luckily, there is no difference between the body size of lab and field reared nymphs. Rachel also stated that, although it took some time to make it work, the egg rearing part of the program is currently boasting a survival rate of 85%. So, it looks like the captive rearing program is working!
Rachel ended her talk by discussing the benefits of the captive rearing program. First, it will augment the natural populations in areas where these dragonflies still exist, helping prevent extinction of the species. Second, they are able to use the insects they rear in the lab to test efforts to repair habitat in streams where these dragonflies live. By placing some lab reared nymphs in the stream and tracking their survival to adulthood, they can determine whether it is safe to reintroduce the dragonflies back into the area or not. And last, the team has a large number of the dragonflies that can be made available for other researchers to study. With endangered species, it’s generally impossible to do research in the field and it is illegal to remove them from their habitats. The lab reared population that Rachel and her colleagues maintain will allow researchers to do experiments without harming the natural populations of the dragonflies.
Check back tomorrow for a report on Day 4, the next to last day of the meeting. I’m going to a session on education in aquatic sciences, so I might report on one of those talks if they’re good. Until tomorrow!
Posts in this series:
Day 0 – Introduction to the Series
Day 1 – Invasive Crayfish
Day 2 – Giant Water Bug Dispersal
Day 3 – Dragonfly Captive Rearing
Day 4 – Integrating Service-Learning Programs into College Courses
Day 5 – Impact of a Small Preserve on Stream Health
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