Hey y’all, it’s Toni here! Now that the boys Burt and Tyrone are done telling you about their cool news, me and the gals have some even cooler updates for you! The scientists have been pretty busy learning some new things about the brains of us females. Sit back, grab some popcorn, and I’ll tell you 3 different short stories from the Geaux Girl Fish Power group!
Story #1: So you may remember that us females are mouthbrooders and we hold our developing babies inside our mouths for a couple of weeks. It’s kind of a drag because during this time, we can’t eat, because we’re such good mothers and we don’t want to eat our kids!, so we’re essentially in a starvation mode. But how do our brains control these behaviors of feeding and caring for our babies? Well, the researchers did an experiment to identify which regions of our brain were involved in feeding compared to maternal care. To do this, they used a neural activation marker called pS6 (they mentioned what that stood for, but it’s not really important for the story, plus, I forgot!). This marker shows which neurons in our brain were activated or ‘turned on’ when we were in different conditions. They compared groups of us females that were mouthbrooding (so starved and with a brood), ones that were starved without a brood, and ones that were fed without a brood, and then they looked at the patterns of neuron activation in like 16 different regions of the brain (I bet that’s why the paper they wrote about it has so many authors)! What they discovered was that some brain regions were more associated with the female’s energetic status (starved or fed), other regions were associated with maternal care, but the majority of regions showed involvement of both energetics and maternal care. This was pretty cool because it shows how complicated the regulation actually is and how tightly linked our feeding and mouthbrooding activities really are! The researchers say there’s evidence for both distinct and shared brain circuits involved in regulation of our maternal care, food intake, and energy balance. We’re excited about this too because it will help other scientists in the future to better understand the evolution of how the brain controls feeding and parenting, which is important for all animals that take care of their babies in some way!
Story #2: In this story, the researchers wanted to look at specific neurons in our brains called AVT cells. AVT stands for arginine vasotocin, which is a protein hormone that is involved in regulating many different behaviors, responses to stress, and salt and water balance in the body. Humans have this hormone also, but it’s called AVP, or arginine vasopressin (and sometimes also called antidiuretic hormone because it regulates how much water is in your body and how much you pee). We’ve already talked about peeing in the past, so you know that us girls and those boys are constantly peeing at each other, so yeah, we’re pretty much swimming around in a bunch of urine! – thank goodness for our wonderful filtration system! Anyway, back to this story, which is not about peeing. First, the researchers used several different staining techniques to label these AVT neurons in the brain (one method labels the AVT protein in the cell and another method labels the messenger RNA that will be made into the protein) and found them in several cell groups with funny names based on how big the cells are – gigantocellular (these are giant!), magnocellular (these are medium sized), and parvocellular (these are small). They also found another group of cells in a different brain region called the ventral hypothalamus, and these cells are larger in our brains when we are mouthbrooding compared to when we’re ready to mate. This result was pretty cool because it means that these neurons might help us with maternal care and taking care of those wriggly babies in our mouths – they are certainly a lot of work, and we have to starve ourselves while making them happy! Those gigantocellular cells I mentioned earlier are also even more gigantic as we get further into our mouthbrooding stage, so this may help us get ready to take care of our little kids once they’re ready to go out into the world and we let them out of our mouths – this is also lots of work for us mothers since we have to protect them from the hungry mouths of other fish by letting them back into our mouths for protection! Most previous studies on AVT were done in males (what else is new?!), but Wow, this study shows that these AVT neurons are pretty important in us females too!
Story #3: The researchers looked in our brains for a specific enzyme (proteins that help with chemical reactions in the body) called aromatase. Aromatase is important because it takes the hormone testosterone and converts it to estrogen, which is a very useful hormone for lots of body functions, particularly for us ladies. They found aromatase all over our brains!, and this make sense because fishes have the greatest ability to produce estrogen in their brains out of all animals! – pretty cool! And get this, it’s not found in neurons, but in glial cells! Glial cells are important for maintaining healthy neurons and brain function, and actually, there are way more glial cells in our brains (and your brains) than there are neurons! (we girls think that’s especially true for Burt, but that’s another story!). Anyway, the scientists also measured the levels of aromatase in different regions of our brains and found that it changes with our reproductive condition – in other words, my brain aromatase levels are higher when I’m looking for a mate, am gravid, and have large eggs in my ovaries, and then levels are lower when I’m brooding those babies in my mouth! While they saw changes in aromatase levels, there were no changes in the receptors that bind the newly made estrogen (called estrogen receptors). So, this local production of estrogen in specific regions of our brains may help us females in several ways: improve our ability to sense those crazy courtship displays from the boys, help us make decisions, prepare our brains for when we have to take care of our kids inside our mouths, and potentially lots of other things! Another awesome thing about this project was that there was an undergraduate researcher from another University (University of Louisiana, Monroe) that helped out with it – we love meeting and seeing new faces around the fish room!
Here’s the research papers that explain these experiments and results in detail:
Maruska, K.P., Butler, J.M., Field, K.E., Forester, C., and A. Augustus. 2020. Neural activation patterns related to energetic status and maternal mouthbrooding in an African cichlid fish. Neuroscience. link
Butler, J.M., Anselmo, C., and K.P. Maruska. 2020. Female reproductive state is associated with changes in distinct arginine vasotocin cell types in the preoptic area of Astatotilapia burtoni. J Comp Neurol. link
Maruska, K.P., Butler, J.M., Anselmo, C., and G. Tandukar. 2020. Distribution of aromatase in the brain of African cichlid fish Astatotilapia burtoni: Aromatase expression, but not estrogen receptors, varies with female reproductive state. J Comp Neurol. 528: 2499-2522. link