Thursday, March 10, 2016

Another return from Trinidad

High-predation male guppy from Trinidad

For the last week and a half, Craig Marshall and Porsche Robison (graduate students), Travis Klee ("in-between" student), and Richard Evans (undergraduate) have been in Trinidad collecting fishes and working on several research projects. Craig and Richard are staying in Trinidad for long-term experiments, but Porsche and Travis just returned last night. If you follow me on Twitter (@Nautichthys) you may have seen some photos of the fish that returned with them. Though I wasn't able to join them on this trip, I thought I would post some updates on the research since people seem interested.

The lab set-up

For those of you who are probably wondering, "That sounds really cool and now I want to do research on fish in Trinidad, but how do you get all of those things back to Colorado?" You see those white bottles on the bottom shelf? That's how. Each bottle can fit 10-20 guppies (depending on size) or one predator. Then we pack the bottles into coolers, pack the coolers into large military duffel bags (to disguise them so that walking through the airport we are less conspicuous, though that probably doesn't help the "field" look/smell that we always come home with), then check them with our luggage. Then we get to say hi to our friends in US Fish and Wildlife upon re-entering the US. We try to call ahead so they expect us, and at this point, they are pretty used to us coming through a few times/year. Once the fish and researchers get back to Colorado, someone is usually waiting in the (pre-prepared) lab to help get all the fish into quarantine tanks, and if they're lucky, provide some dinner. This year that person was me.

So why did we need to go to Trinidad in the first place? One of the objectives of the trip was to collect fishes for me, for two projects. First, I have been involved in the guppy kit initiative and we had a recent disaster with water quality at the Education and Outreach Center that required obtaining more guppies. I have since solved that issue, so they brought back males from high and low predation rivers that we can use at the end of the month for our first STEM Friday event! Here are some videos of the two populations. See if you can spot the differences between the males!

High-predation males

Low predation males

The second project that I needed guppies for is my research. For my postdoc I am interested in local adaptation of the feeding and locomotor systems in guppies, and what that means for how they work together during prey capture. Right now I am working on describing the variation in natural high- and low-predation populations to see if there is even a difference between them. I am using live evasive Daphnia as prey currently to encourage the guppies to use suction to capture it because this feeding mode is extremely common in fishes and because I hypothesized that strong suction does not work with fast swimming based on what we know about suction-feeding fishes. At some point I also want to use a prey that they have to scrape because this is more likely what they are doing in the wild. Also, it has been shown by other researchers (for example, here and here) that biting may not be subject to the same constraints on morphology and function. So I would be interested in finding out what integration looks like across the predation gradient with an alternative feeding mode. Here's an example video of what prey capture looks like with Daphnia in guppies:

To find out what is happening with integration in guppies, we collected guppies from 2 replicate HP/LP sites (4 populations) last summer, brought them back to the lab, and I started filming them. However, several individuals didn't make it and my sample sizes have shrunk considerably. In fact, one population only has 5 fish left! This was due to a combination of a fungus that we think came from one of the sites and likely old age since they were all adult females when we collected them (and it took me so long to figure out the prey that would work for what I needed and I killed the 10 year old high-speed camera and had to figure out how to get another one). So Travis helped replenish the populations to increase my sample sizes back to the numbers I want (20-30 individuals). Here are some examples of those females from one of the population pairs:

Low-predation guppies collected from the Aripo River
(notice they are large and full of babies)
High-predation guppies collected from the Caroni River
(smaller but also full of babies,
less willing to come to the front of the tank)

That will keep me busy for the next several months.

Another project that is occurring both in Trinidad but also here in Colorado is Porsche's Master's thesis work. She came to us with professional interests in veterinary medicine and personal interests in everything fish, and has designed a project to examine the parasite loads plaguing guppies. This partly stemmed from the troubles we had after the last trip and our interest in learning more about what could go wrong. She is piggy-backing on the sites and species that Craig is utilizing for his study on the effect of salinity on metabolic and growth rates, and has become the local expert in guppy fecal smears. She did much of her work in the field but also brought a small number of guppies back alive to have fresh samples to dissect with the Parasitologists she is working with at the Veterinary Teaching Hospital here at CSU.

Porsche with her newly collected guppies
(also notice our awesome lab phone!)

Although Poecilia reticulata are the "famous" guppies, there are other species of Poecilia in Trinidad as well but their range is more limited to the brackish water interface closer to the mouth of the river. It will be interesting to know how well each of these species deals with parasites and the "nasties" they encounter.

Poecilia picta males (left) and females) right
collected from the Caroni swamp (brackish water) -
notice how the males are lined up on one side
Poecilia vivipara males collected
from the Caroni swamp (brackish water)

That will keep Porsche busy for a while.

The last project is one that Travis has undertaken in the past few months since he graduated from CSU. He decided to apply to grad school in the fall and wanted to get some independent research under his belt first. We have no shortage of questions and fish, so I'm helping him with the rest. He became interested in the predators rather than the guppies because guppy researchers always talk about how specialized pike cichlids are, but nobody has (to our knowledge) looked at what that means.

Photo of Travis attempting to catch pike cichlids by
hook-and-line from our trip last spring
(these attempts were unsuccessful)

Travis wants to compare several native guppy predators to look at differences in behavior, prey preference, capture success, and predator accuracy (right up my alley!) to get a better understanding of if/why pike cichlids are so formidable. Travis recently presented a poster at the CSU Front Range Student Ecology Symposium with some preliminary data and many ideas, and he won first place among undergraduates! Since we only had n=1 of some of the predators he was interested in, this trip to Trinidad was his chance to try to collect more predators to have replicate samples. He became an expert at catching pike cichlids using the butterfly nets that we catch guppies with! He was also successful in catching a few acara (which are also cichlids but probably only eat small guppies) and a small wolffish. I look forward to seeing how Travis' project turns out! 

Wolffish (Hoplias malabaricus) -
a guppy (and everything else) predator
Blue acara (Adinoacara pulcher)
Female (left) and male (right)
pike cichlids (Crenicichla frenata)

That will keep Travis busy for a while.

By the way, Travis is starting the search for graduate programs, *wink wink*

So although it was a short trip, I would say it was quite productive! I'll be sure to post updates as we begin to collect and analyze data. For now, I'll leave you with another image of the baby wolffish - just imagine this thing all grown up and the size of your arm!

They're cute when they're babies and
can't bite your fingers off!

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