The Blobs: Inquilines and Commensals in Sarracenia
The pitchers of Sarracenia capture a wide variety of prey, as the pencam shows. But they don’t do it alone. In the same way humans require a microbiome in our digestive tract, sarracenia employ an army of creatures that help it digest it's prey. Biologists refer to this army as commensals or inquilines. I have been calling what I can see broadly as “the blobs”, “worms” and “skippers” I believe “the blobs” are mites, the “worms” are midge larva and the “skippers” I still haven’t IDed them.
I will try to go into more detail about how i identified the many little monsters living in a pitcher. These identifications are meant to be preliminary, my expertise in plant ecology doesn’t extend beyond what’s available on the internet. And while the internet is an enormous resource, it can lead people astray (Just look at the rise of flat earthers). Hopefully, someone with some expertise will stop by and correct my work.
But until then….
The Blobs
The blobs were one of the first non prey animals i spotted inside a pitcher plant. I saw something, a white blob amongst the insect boneyard. And then it started moving. Then I noticed another, then another. The blobs are everywhere: from the graveyard in zone 4 sometimes in the hundreds as a roiling mass of mischief to the top of the pitcher if there’s food to be had.
The blobs are extremely small, nearly translucent animals. They can be nearly invisible in solution when illuminated with sunlight, but turn on the the pencam lights and there they are. They really light up, While they are easy to see, they are tiny and always moving which makes them difficult to get a good picture of. However with a little care I was able to get less “blobby” pictures
But what are the blobs? They appear to be a species of mites (aka. slime mites) They live symbiotically within the pitcher plant. Dahlem, Naczi and Linder describe the mites below
“Mites are one of the most species-rich groups of arthropods that inhabit pitchers. Two families of mites occur in this habitat, Histiostomatidae (suborder Astigmata) and Phytoseiidae (suborder Mesostigmata). The phytoseiids are represented by one species of fast-running predator, Macroseius biscutatus. The histiostomatids are a far larger group, with at least ten species of the genus Sarraceniopus living in pitcher plants. Sarraceniopus mites crawl slowly through prey remains in bases of pitchers, apparently filter-feeding on bacteria. Both Macroseius and Sarraceniopus are obligate symbionts of Sarraceniaceae, requiring pitchers to complete their life cycles. Our studies focus on the systematics of Sarraceniopus, since this genus is far less studied than Macroseius.
Macroseius are relatively large mites, with females (the largest stage of the life cycle) about the size of a pinhead. Sarraceniopus mites are much smaller, with the females only about 50% the length of Macroseius females. Macroseius are relatively easily seen with the naked eye, especially as they run on the interiors of pitchers. Sarraceniopus are just barely visible without magnification. Members of both genera are ivory-colored when alive, but transparent when cleared for microscopic study, as seen above and below.
Mites, like other arthropods, molt several times during their lifespan. Thus, an individual mite proceeds through several instars, including larva, various nymphs, and adults (males and females). For pitcher plant mites, the deutonymph (the second nymphal instar) is the usual dispersal stage. “
The authors have several pics of the Sarraceniopus below
I had trouble finding pictures of Macroseius biscutatus, what little I could find is shown below.
And from a over 50 years ago...
So it looks like I have both types of blobs/mites in my pitchers. These bloby mites are Macroseius biscutatus or a closely related species.
The Sarraceniopus is the other mite genus in the pitchers. It has a smoother body than the Macroseius It is nearly translucent. They are easy to miss. Here they are on lip of a S. Bugbat on "opening day"
and here is another Sarraceniopus rafting on the body of an ant. It gives relative scale of this animal.
Note: I have been trying to get a size on the various mites. Sarraceniopus looks to be around 0.5 mm (based on the diagram in the links below) I haven’t been able to get an accurate size of the Macroseius biscutatus. All I know is that it is larger than Sarraceniopus.
Midge and Mosquito Larva
The larva of midges and mosquitoes are the top of the food chain in sarracenia. When you see them in action, you can see why. The first time I spotted them they were (relatively) huge. They were slithering along the pitcher water’s edge, carrying a half dozen blob riders. (Like the sandworm riders in Dune) Both insect larva look similarly “wormy”, but I believe what I am seeing is midge (Metriocnemus knabi) not mosquito (Wyeomyia smithii) larva. I made this identification because the mosquito has a larger head and also because I see adult midges regularly. I could be wrong.
There is a mosquito, Wyeomyia smithii, whose larva live in pitcher plants as well. It, like the midge is the top of the food chain in the ecosystem inside pitcher plants. Unfortunately, I haven't spotted it, yet. And it would be hard to miss.
The larva of flesh flies, such as Sarcophaga sarraceniae, live and eat in the pitcher plant. I believe I have spotted one in the S. Yellow Jacket
According to Robert Zottoli at boginvertebrates it looks like the Fly Larva Blaesoxipha
Larvae of this species live exclusively in the fluid filled cup of the pitcher plant Sarracenia purpurea. I have never found more than one specimen in a single cup. They float near the liquid surface feeding on insects (mainly ants) that fall into the pitcher plant before the ants sink to the bottom. In one study, it was determined that Blaesoxipha consumed up to 50% of the insects that fell into pitcher plants. The larval head is incomplete. Note the black mandibles in the photograph and videos. They move parallel to one another as the animal feeds. Blaesoxipha floats, head down, with the deep, posterior, spiracular cavity extending slightly above the surface of the liquid. Two orange, raised ,spiracles lie within this cavity. Air is moved through the spiracles into two large tracheal tubes. The large white tubes, branch into smaller tubes (Visible) that deliver air, containing needed oxygen, to larval tissues. Larvae eventually crawl out of the pitcher plants and pupate on the bog surface.
What I haven’t identified.
There are a number of arthropods that live inside pitcher plants that have eluded identification. This not quite ant size insect is everywhere. It doesn't appear to be trapped prey. I suspect it's another commensal living off the food in the pitcher.
I also haven't identified the Halloween monster that showed up in Oct 2019. It is probably a fly larva. It's about the size of the midge and flesh fly larva, but it has these large paddle-like appendages. Spooky.
Also haven't identified what animal was "waving" at me.
More unidentified animals https://drmayhem12.wixsite.com/insidepitcherplants/blog/categories/not-yet-identified
Microorganisms in sarracenia
There are tons of microorganisms in the pitcher plant. Everything from fungi, rotifers, bacteria and cyanobacteria to name a few. They too help the plant digest prey, but they are the bottom of the food chain, Everything else eats them. These organisms and the ones previously described make up the complicated ecosystem inside the pitcher plant. But since they are smaller than the pencam can see, I am going to skip discussing them in detail and refer you to the references and let the experts go into more detail.
Books
The Revised Savage Garden My go to book on carnivorous plants. Get an autographed copy at California Carnivores. https://www.californiacarnivores.com/collections/books/products/the-revised-savage-garden-autographed
Pitcher Plants of the Americas by Stewart McPherson
A great book about all things pitcher plants.
Carnivorous Plants : Physiology, Ecology, and Evolution Aaron Ellison and Lubomir Adamec
The definitive academic book on carnivorous plants. Extremely detailed with extensive footnotes. (I’ve been Googling all the big words.)
Links to Sarracenia and their commensal animals
If you want to go deeper into mite biology, check out
http://idtools.org/id/mites/invasive_mite/Invasive_Mite_Identification/key/Mesostigmata/Media/Html/Macroseius.htm and in greater detail here https://etd.auburn.edu/bitstream/handle/10415/3533/Nathan%20Daniel%20Hall%20%28AUETD%20Revised%29.pdf?sequence=2&isAllowed=y
LIFE CYCLE OF SARRACENIOPUS NIPPONENSIS (HISTIOSTOMATIDAE: ASTIGMATA) FROM THE FLUID-FILLED PITCHERS OF SARRACENIA ALATA (SARRACENIACEAE)
A closer view of the mites (With an even better microscope than mine) https://www.youtube.com/watch?v=am2zOpr8Mfw
For more on mites, including the mites that live amongst us (and on us) click below.
It will creep you out. https://www2.palomar.edu/users/warmstrong/redmite7a.htm#mite
Acarologia a site dedicated to mites
Midges,Mosquitoes and Flies
On the ecosystem inside pitcher plants
Inquiline Food Web Assembly
Predicting Food-Web Structure with Metacommunity Model
Traps of carnivorous pitcher plants as a habitat: composition of the fluid, biodiversity and mutualistic activities
The Bacterial Composition within the Sarracenia purpurea Model System: Local Scale Differences and the Relationship with the Other Members of the Food Web
Pitcher plants build own communities
Small-scale patterns in community structure of Sarracenia purpurea inquilines
Fungal Endophyte Diversity in Sarracenia
The carnivorous pale pitcher plant harbors diverse, distinct, and time-dependent bacterial communities.
Inquiline diversity of the purple pitcher plant (Sarracenia purpurea) as a function of pitcher isolation: the role of dispersal in metacommunities
Biocomplexity Project: A Synthetic Approach to Phytotelmata Communities
An inside look at carnivorous plants: Researchers track the importance of microscopic inhabitants
Food-Web Models Predict Species Abundances in Response to Habitat Change
Predicting food-web structure with metacommunity models
Species Richness and Trophic Diversity Increase Decomposition in a Co-Evolved Food Web
Modelling the relationship between a pitcher plant (Sarracenia purpurea) and it’s phytotelma community:mutualism or parasitism?