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Biology

Oceanbites at the Society for Integrative and Comparative Biology, Part I

Sources

Williams, Terrie. Society for Integrative and Comparative Biology, Portland, OR, 2016.  “The Biology of Big: Discovering the extraordinary costs of survival at the top of the food-chain”.

Urban et al., SICB, Portland, OR, 2016.  “An earful of jaw, then and now: insights from evolutionary developmental biology”.

Tulenko et al., SICB, Portland, OR, 2016.  “HoxD expression in the fin-fold compartment of paddlefish and catshark: implications for the evolution of gnathostome paired appendages”.

 

This month, I had the opportunity to travel to Portland, Oregon for the annual conference of the Society for Integrative and Comparative Biology (SICB).  I was able to present some of my own data, but even more importantly, I was able to listen to and interact with the other presenters and attendees.  These annual conferences are a hugely important component of the scientific/academic community – they are a chance to exchange ideas, inspire creativity, and renew or begin collaborations.  I am extremely lucky that my program provides yearly travel support to make such experiences financially feasible, but SICB itself provides over $200,000 yearly for student support, ensuring that as many students as possible have the ability to attend this important event.  Considering how awesome an experience it was, and how excited I am to talk about it with friends, family, and colleagues, I thought I’d share some of it with my Oceanbites audience as well by writing up summaries of my favorite talks from this meeting.

Reptile Jaws And Mammalian Ears – A Possum’s Tale of Recapitulation

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Figure One: A possum

            Ernst Haeckel, a 19th century German biologist and philosopher, is famous for having said “ontogeny recapitulates phylogeny”, meaning that he believed that ontogeny, or development across an individual’s lifetime, represents the entire evolutionary history of the organism that is developing.  For example, humans are descended from fish-like ancestors, and we show transitory gills while in the womb.  Haeckel believed that all such transitions are retained in some form during development.  While this is certainly not true in some instances, Australian possums (Figure 1) actually do develop in a way that retains an important evolutionary transition.  Dan Urban, competing for a Best Student Presentation award, provided a very comprehensive developmental series showing the growing inner ear bones in possums (Figure 2).  Before mammals evolved from a reptile-like ancestor, those same bones primarily formed part of the jaw.  The images showed quite convincingly that the bones in the youngest possums looked like fossil jaws of ancient reptile-like mammalian ancestors.  As they grew, those bones looked more and more like mammalian inner ear bones, and the jaw-like aspects completely disappeared.  Dan also looked into the underlying genetic mechanisms behind this transition.  When I asked him, he went on to explain that possums are born essentially deaf.  Their hearing begins to develop around the same time as the ear bones, and is essentially fully functional just after the final transition stage that he showed.  I cannot over-sell this talk.  It completely blew me away for a variety of reasons, including the speaker’s poise and charisma, the elegance of the system, and its potential for elucidating some of the mechanisms that cause congenital deafness in humans.

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Figure 2: Jaws and inner ears of mammals (top) and reptiles (bottom)

Insights from Paddlefish Fin Development

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Figure 3: A paddlefish, sometimes called a primitive fish because it has hardly changed over seventy five million years

            This talk focused on the role of Hox genes in paddlefish fin development (Figure 3).  Hox genes, sometimes called homeotic genes, are hugely important developmental genes that pattern the body at some of the earliest stages of development (Figure 4).  They set up the primary body axes (from snout to tail, for example) and are responsible for making sure that our body parts are built where they need to be built.  Frank Tulenko presented data showing that Hox genes are responsible for patterning the paddlefish fin, including the fin rays which make up the fin pad.  Expression patterns in paddlefish fins matched those known for mouse limbs.  The limbs of four-legged animals (tetrapods) are thought to have evolved from the paired fins of our fish-like ancestors, and many of the bones of our upper and lower arms and wrists are quite similar to those of the pectoral fins of fish. The fin rays which support the fin pad are not thought to be directly related to any bone in the forelimbs of tetrapods.  But Tulenko showed similar patterns of expression between mouse digits and the fin rays, which is a really cool finding because it may contradict our earlier belief that these bones are not related.

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Figure 4: A schematic of Hox genes across several major animal lineages. The genes are color coded based on where they are expressed in the developing embryo.

The Biology of Big – Life from a Top-Down Perspective

Figure 5: A male African lion

Figure 5: A male African lion

The plenary speaker, Terrie Williams, discussed the incredible opportunities she’s had to study some of the world’s biggest animals.  Dr. Williams’ research focuses on the costs of survival for large, meat-eating organisms, like lions and killer whales, which often have to spend large amounts of time hunting and rarely eat daily.  She uses this knowledge to further conservation efforts of these large, charismatic, and often-endangered species.  For example, lions in Africa often interact with shepherd’s flocks (Figure 5).   When the shepherd finds a member of the flock dead, the lions are often blamed for the killings, and the shepherds may kill the lion they believe to be responsible.  Dr. Williams, tracking lions with GPS collars equipped with accelerometers, is actually able to determine when and where one of her tracked lions made a kill – these animals hunt with characteristic movements (walking to find prey, slow stalking, a pounce followed by a short burst of rapid activity during which the kill is actually made).  Cross-referencing the tracking data with information about the dead animal can actually absolve the lions from the blame, and even save their lives. Dr. Williams ended her inspiring talk with a video she’s made about the impacts of scientific research on endangered species.  The video, shared below, speaks quite loudly for itself – I hope you’ll take a few minutes to watch it.

https://www.youtube.com/watch?v=J01XLuHIQMk&feature=youtu.be

Watching Evolution in Real Time with Threespine Stickleback

Evolution can occur on very, very short timescales – as little as fifty years is enough to see significant change between well-isolated populations!  Learn how we can watch stickleback invade and adapt new environments created by a major Alaskan earthquake in my February 2016 post.  Data from the same lab was presented at SICB, although it focused on a slightly different aspect of their research, and I’m looking forward to delving more deeply into the watery world of threespine stickleback next time.

Questions?  Comments?  Please sound off below!  I’d love to hear from you :)

Dina Navon
I am a doctoral candidate in the Organismic and Evolutionary Biology program at the University of Massachusetts Amherst. I’m interested in how an individual’s genes and the environment in which it grows come together to determine its physical traits. I study a group of closely related freshwater fish called cichlids which live in the African rift lakes like Victoria, Malawi, and Tanganyika.

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  1. […] to see them all. Luckily, there were two oceanbites authors present to report back. On Wednesday, Dina shared her favorite talks and gave a great introduction to the meeting. Today, I will share more of the exciting research we saw in Portland by reviewing my favorite […]

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