A finding stemming from Josiah's masters research was published today in Biology Letters! The paper, "Maternal provisioning interacts with incubation temperature to affect hatchling exposure in an oviparous reptile," reports on the interesting observation that incubation temperature affects how maternal resources (aka, the egg) are used by the embryo and in turn influences contaminant concentrations.
In some of our earlier work (See Bock et al., 2021 Biological Bulletin!) we found that cooler incubation temperatures produce smaller and less heavy hatchlings when compared to warmer temperatures. This finding held even after accounting for differences in the size of the egg, suggesting that at cooler temperatures hatchlings must expend more of their energy reserves to develop and having less left-over 'body.' But sometimes moms living in contaminated environments will deposit contaminants in their eggs (not on purpose), and as a result the embryos are exposed. When these maternally derived contaminants occur in cooler nests, they essentially "distill" or concentrate these samples into a smaller hatchling and lead to elevated contaminant concentrations. In alligators, these cooler temperatures produce females and thus females have higher contaminant burdens relative to their male siblings, even though they were both given the same amount of contaminants! Not cool. We still are unsure of if the difference is big enough to have an effect on individual health and likely depends on how much moms are depositing, but I'm sure more studies will come out of this. You can find a link to the paper here and if you lack access, feel free to email email@example.com and I can send you a PDF.
Two powerhouses of the lab have successfully defended! Dr. Samantha Bock earned her PhD and is continuing as a postdoc leading a collaborative effort between our lab, Dr. Gavin Naylor's group at UF, and Dr. Kady Lyons at the Georgia Aquarium. Can't wait to see where 'THE BOCK' takes this work! Laura earned her masters and is heading to UC Davis to pursue a PhD-- we're going to miss her!
A slew of us recently headed to Georgetown, SC for the biannual symposium. We all had a great time getting to visit and meet colleagues doing all manner of cool things-- from managing populations of alligators, to rehoming American crocodiles, and even removing invasive Caimans from the Everglades. Samantha, Laura, Josiah, and Kristen gave great talks and Chris and I presented posters. Already looking forward to the next one.
This semester, Stacey Lance and I have been teaching the second iteration of our split-level EcoDevoToxo course. Despite meeting almost exclusively online, it has been enjoyable to talk all things EcoDevo with a super high-level group of graduate and undergraduate students. This semester, we were not able to do our workshop at the SREL, so instead we've experimented with several other activities, one of which is a course blog. I've been really impressed by several of the posts and if you're interested in these sorts of topics, feel free to visit (Ecodevotoxo.blogspot.com) and leave a comment or two while you're at it!
CONGRATULATIONS LAURA, WELL DESERVED!
The magnum opus chapter of Matthew’s dissertation reports on the mechanisms that underpin reproductive disorders in Lake Apopka female alligators (the paper can be found linked here). This lake is contaminated with endocrine disrupting chemicals that have the potential to interact with the estrogen receptor and the Lake Apopka alligator population has been used as a model for understanding environmental reproductive health since the early 90’s. We found that approximately ¾ of genes are differently expressed in Lake Apopka alligator ovaries when compared to a reference site. The big surprise was that exposing embryos from the reference site to a single dose of estrogen (prior to ovarian differentiation) was sufficient to overwhelmingly recapitulate these patterns. Also noteworthy is this estrogen treatment in reference animals also recapitulated the follicle abnormalities in Apopka ovaries. Our main conclusion is that estrogenic contaminants are likely disrupting the timing of estrogen signaling during ovarian differentiation, which leads to persistent changes to ovary structure and function that are apparent long after the initial exposure. Chris Smaga, a new graduate student in the lab, is following up on these questions, so stay tuned!
Samantha is tracing how climatic factors weave their way through developmental processes to influence organismal form, function, and survival. Her dissertation projects truly represent the integrative nature of our group and include monitoring/modelling alligator nest temperatures, investigating how thermal signals are integrated into sexually dimorphic epigenomes, and now trying to assess the influence of all these factors on survival! Like most of the projects in our lab, this takes a team effort and Samantha recently assembled a ‘super team’ to help with a hatchling roundup. This included grad students Emily, Laura and Kristen, along with SCDNR biologists Joseph and Mark, and of course, Thomas Rainwater from the Yawkey Wildlife Center and Clemson University. Good times!
We are thrilled to welcome Chris Smaga and Josiah Johnson to the lab! Chris earned his undergraduate degree from SIU where he studied snake fungal disease. In the Parrott Lab, Chris will be investigating the developmental origins and pathways underlying epigenetic variation across natural populations of alligators. Josiah hails from Colby College where he focused on advancing Northern black racer conservation. Josiah is planning to study how life history traits and reproductive development vary across amphibian communities along a contaminant gradient of Carolina Bays. Welcome guys!!
Yeraldi is doctoral student in Shane Campbell-Staton's lab at UCLA and is collaborating with us this summer. Samantha and Yeraldi are interested in discovering the determinants of alligator hatchling survival and how these traits are influenced by environment-by-embryo interactions during development. I don't want to give away any spoilers, but this project is HUGE! We are super excited to have Yeraldi at the lab-- welcome Yeraldi!!