For the past few days, I have been sorting and identifying macroinvertebrates from some samples collected from the decomposition bags. Doing so made me appreciate lugging a microscope to Costa Rica, since the scopes here are horrendous. The dishes pictured here contain macroinvertebrates, mostly insect larva, that I’ve sorted to family.
I don’t like being in the lab.
Here’s some photos of the apple snail eggs I mentioned that had been laid in one of my enclosures.
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I placed little bundles of dead Eichhornia and Neptunia on a string and then attached the strings to my competition enclosures. This will allow me to estimate decomposition of these two plants in artificial mats that vary in the density of the two plant species.
You might notice that the water is getting deeper – it’s over the first barb wire, which makes it difficult to slide through the fence. I may yet have to construct a door…
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Now there is plenty of Neptunia. I collected several bags for decomposition. The Neptunia appears to be reaching for the light.
Yesterday, I had the greatly appreciated help of several individuals that came along with the Tropical Biology OTS course. Pictured in the foreground are Abbie and Amanda, and in the background, Justin and Stevland. Not pictured is Mo Donnelly.
They fearlessly helped collect living Eichhornia at the crocodile-infested waters at the Catalina sector wetland for placement in competition enclosures in Palo Verde. The bags full of hyacinth are shown in the other picture.
Again, while photographing plants for a personal identification guide, I noticed there is much more going on in the photograph than plant identification.
I wonder what these flies are doing on this Echinodorus paniculatus flower. There is a pair for each petal; are they a breeding pair? If so, will they lay eggs and form a gull or otherwise use the Echinodorus has habitat/food? Are they simply attracted to the white?
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I’ve set out 200 mesh plastic bags to examine decomposition rates and changes in litter chemistry of four types of litter: freshly killed Eichhornia crassipes and Typha domingensis (or dominguensis depending on what paper you read), and the past seasons accumulated litter from both aforementioned species. The bags sit, baking in the sun, attached to 3-m poles of PVC, which actually may be too short given the height of Typha (cattail) around here. The two photographs of bags below show some test bags I set out a few days ago, with tadpoles skimming around the surface of the bag… potentially attempting to enter and process the litter themselves. The other photo is designated site E1. |
By the way, check out the excellent sewing job on the bags below… I can pump those out at a rate of 50 in 4 hrs now, although I started out at a much slower rate.
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Last updated:
23 May 2009
Figures 1 and 2 show a potential limpkin feeding site. I discovered 3 sites, one of which I had observed a limpkin fly away from. Before flying off, the limpkin was within 10 m of me, so I’m fairly confident that it had been standing at that location, but I was unable to observe a limpkin actually feeding at one of these locations. The shells are from a very thin-shelled aquatic snail that appear to be extremely abundant in a variety of vegetation types. I have encountered the snail in Pistia (Figure 3), an unknown emergent plant (see Massive herbivory; Figure 4), and Eichhornia.
The snail has no operculum and, when handled, doesn’t usually escape into its shell. I’m unsure whether or not the snail is a scraper, consuming epiphytic biofilm, or consumes macrophytes proper. If they snails are scrapers and are limpkin prey, there may be an interesting interaction occurring; Apple snails tend to consume macrophytic tissue and scraping snails have been shown to increase macrophyte growth. It may be far fetched, but could apple snail predation effectively farm these snails?
Reduced apple snail density = greater macrophyte biomass = more surface area for biofilm formation = great thinned-shelled snail densities
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Other than apple snails at snail kite perches, there was one other species of snail present. Figure 5 shows a snail shell found along with apple snail shells at a snail kite perch. Although this snail may also have been prey, several individuals were found lodged within apple snail shells, so these snails may have died while consuming left over apple snail tissue or attempting to escape drought. The shell is much thicker than the shells found at the limpkin sites discussed in this post, and is not likely the same species.
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In CSW, there is an abundant emergent macrophyte that I am unable to identify. It hasn’t flowered yet and the key in Crow’s Aquatic Plants of Palo Verde National Park and the Tempisque River Valley hasn’t been much help. If someone knows right away what this plant is, please let me know.
I’ve identified it to Thalia geniculata. Only the leaves are present currently.
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Today (23 May), while wading though the wetland, I noticed that this plant has been hammered by herbivory (Figure 2 and 3). The nearly complete consumption of the leaves of this plant throughout the entire wetland appears to have been a result of a caterpillar (Figure 4 and 5).
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I’ve found and have GPS coordinates of 4 Northern Jacana nests, three with four eggs and one with three eggs. I don’t know if they are from the same female, nor have I actually observe a Jacana incubating the eggs. The nests are fairly deep in the Catalina Sector Wetland (CSW) and are not observable from the road through the wetland, but I could observe them within the wetland itself. How is this usually done? The cattail is tall and basically impossible to see through or over.
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Is it possible to weigh or gently handle the eggs? I wonder if I can find more nest that are obviously from different females and monitor some measure of fitness for each: number of eggs, weight per egg, hatchling success, hatchling growth rate, etc. These could all vary by habitat perhaps. The two locations pictured in Figures 1 and 2 are dominated by Pistia and are open areas surrounded by cattail. One location is pure cattail, but is open and the nest rests on a bed of decomposing cattail.
