Thread by @BiolBulletin

It's #ReadAlong Day!

@AllenLabWM will #TakeOver our account at 12 pm ET.
Follow this thread for live tweets as we #ReadAlong:
E. E. Just, 1923 (journals.uchicago.edu/doi/pdf/10.230…)

Drop your questions and comments in this thread.

Happy Reading! 🧵(1/n)

@AllenLabWM: Hello Twitter! I'm excited to participate in the @BiolBulletin read along series. There have been two excellent examples for me to try and match from @wareslab and @BrackenGrissom. I am honored to have been asked to join them! (2/n)

For those who don't know me, I am a marine invertebrate biologist and larval ecologist fascinated by the complex life cycles of echinoderms and other marine invertebrates. My laboratory is primarily composed of the amazing undergraduate students who attend @williamandmary (3/n)

I'm very lucky to work with undergraduate students who share my natural curiosity about the animals that live in the ocean work and the way that they interact with their environment. (4/n)

I'm also incredibly lucky to have a long history publishing in @BiolBulletin, including my most-cited work on size-specific predation on marine invertebrate larvae: doi.org/10.2307/250666… (5/n)

I joined the editorial board of @BiolBulletin a couple of years ago, and have been impressed by the efforts of the other members of the editorial board and staff. It has really solidified for me what I always knew: this is a special journal! (6/n)

One reason I have always admired @BiolBulletin is its long history of publishing important scientific works. The journal has been in business for almost 125 years!! (7/n)

Today's #ReadAlong will take advantage of this long history by focusing on a classic set of papers by E.E. Just. In particular, we'll look closely at his 1923 paper on the effects of changing salinity on fertilization in the sand dollar Echinarachnius parma. (8/n)

I picked this paper because it is the last of the eight (!) papers in this series that E.E. Just published in @BiolBulletin and it is one of the first that I ever read. I was honestly largely ignorant of the personal story of Just when I read his old work... (9/n)

...and I just focused on the science. But today I will start with a bit of background on Just and his place in scientific history, and then dig into the science and why these papers were so influential. (10/n)

Background:
Like many people, I have an interest in the history of biology and selfishly the role that marine invertebrates played in influencing foundational figures in biology. (11/n)

For example, most folks know that Darwin developed theories on coral reef formation, but fewer know that one of Darwin's first research endeavors was to understand that the 'eggs' of bryozoans swim. (12/n)

Similarly, William Bateson is famous for first using the term 'genetics' and for describing homeotic mutations, but did you know he spent part of his career studying hemichordate embryos in Chesapeake Bay? (13/n)

Or that Thomas Hunt Morgan, another famous geneticist and the man most responsible for making Drosophila a model system for development, worked not only on hemichordates, but also sea spiders, sea urchins, sea squirts, ctenophores and mud snail embryos? (14/n)

I love to tell my students that all the best biologists got their start studying marine invertebrates! Given this pet interest of mine, to find famous biologists and find a way that marine invertebrates impacted their view of nature,(15/n)

...it is to my great shame that when I was co-authoring a paper (in @BiolBulletin) with Jan Pechenik (@SciSparkMan) that I was largely unaware of the life and history of E.E. Just. I didn't even know he was an African-American scientist.(16/n)

In our paper, Jan used the word 'remarkable' to describe Just and I felt we couldn't say that without a citation to support it. So I began reading @MalcolmByrnes and Bill Eckberg's excellent brief summary of Just's life and work (doi.org/10.1016/j.ydbi…) (17/n)

While there are longer and more complete descriptions of Just and his life and work, I am not sure there is a better summary of his scientific contributions to the field of #EcoDevo than that of @MalcolmByrnes and Eckberg 2006. Just truly is 'remarkable'. (18/n)

Beyond Just's contributions to #EcoDevo, in 2015 @MalcolmByrnes argued that Just is also best seen as 'The Forgotten Father of Epigenetics' (tinyurl.com/2787jwsj). (19/n)

That 2015 paper in American Scientist also places Just's work in the context of the social and cultural upheaval of his life and times. (20/n)

It's impossible for me, in my position of relative privilege, to do anything but marvel at what Just had to experience and how much easier my life has been than was his own. But beyond the remarkable life and times of Just is the remarkable nature of his science. (21/n)

That's what today's #ReadAlong is meant to focus on and that's why I selected the somewhat overlooked 1923 paper that marks the 8th and final chapter of his series on fertilization in Echinarachnius parma. (22/n)

I say that the 8th paper is overlooked, but really I could argue the entire series of papers has not gotten the attention it deserves. A quick search on Google Scholar suggests that, in sum, these papers have only been cited 222 times. (23/n)

Of those 222 cites, the majority are for the first paper in the series which has 123 citations. The first paper, which is *not* the focus of the #ReadAlong (!) is possibly Just's most impactful work where he describes the fast block to polyspermy (journals.uchicago.edu/doi/pdf/10.230…). (24/n)

In describing the slow block, Just notes that fertilization and specifically membrane elevation proceeds as a 'wave from the entrance point of the sperm'. (25/n)

Just continues to describe his discovery of the fast block: 'Moreover, what is more significant, before membrane elevation cortical changes blocking further sperm entry spread as a wave over the egg uniting finally at the point opposite the entrance point of the sperm'. (26/n)

This 'wave of negativity' that he couldn't directly observe but had to infer, is now accepted as the fast block. Quite the discovery! (27/n)

Amazingly, we still don't have a complete understanding of the mechanism underlying the fast block to polyspermy.But if you want some of the latest work, check out this short summary from... (28/n)

...Laurinda Jaffe that highlights work done most recently in frogs to analyze the molecular underpinnings (doi.org/10.1085/jgp.20…). More than 100 years after Just's paper and we are still working on this discovery! (29/n)

The rest of the papers in the series detail the effects of various aspects of egg/sperm physiology and the environment on fertilization. These include: the impacts of sperm/egg interactions and cross reactivity between E. parma and Arbacia punctulata (II), (30/n)

...the effects of Butryic acid as an egg activator that can lead to something resembling normal development (III and IV), the effects of hypotonic seawater in the time post sperm entry but before the fertilization membrane has 'hardened' (V), (31/n)

...the necessity of the egg cortex (but not the egg nucleus!) for fertilization (VI) and the inhibitory action of coelomic fluid on fertilization (VII). [See previous thread with Just's papers:

https://twitter.com/BiolBulletin/status/1385248426586116109?s=20

] (32/n)

Now (finally!) we come to the least appreciated of the 8 papers: Just's 1923 work on the effects of salinity on fertilization. (33/n)

I came to this topic thanks to discussions with @SciSparkMan who was interested in the effects of salinity on the polychaete Hydroides elegans (doi.org/10.1086/BBLv21…). (34/n)

Jan and I were aware of Just's explorations of the effects of salinity on development in echinoderms and we both felt that the presence of a fertilization envelope in echinoderms was a good reason to extend his prior work from polychaetes to sand dollars. (35/n)

We also knew that Just had really only scratched the surface of what was possible to explore in this system. Just's focus on fertilization meant that we could explore not only that time but also subsequent cleavage events, hatching and larval development... (36/n)

...all under low or fluctuating salinities. So what did Just demonstrate? Well, first he showed that eggs are robust to modest changes in salinity. One problem with the paper is that Just provides salinity data only as the percent of seawater. (37/n)

So we may never really know what salinities he used. For example, at 95% seawater, development was normal. If we assume a starting salinity of 32, then 95% would be a salinity of 30.5. At that level, eggs behave essentially normally. (38/n)

At 90% seawater (by my conversion this is a salinity of 28.8), fertilization and cleavage are normal but about 10% of the embryos form exogastrulae. This means the archenteron evaginates (moves outward) instead of invaginating (moving inward). (39/n)

I should probably mention I am more of an ecologist than a developmental biologist...so all of my 'knowledge' of development is rudimentary at best... (40/n)

Just proceeds moving through increasing dilutions of seawater until he gets to 75% below which point cleavage fails to occur. (41/n)

This result is confirmed by our work (Allen and Pechenik 2010) which shows in Figure 2B that cleavage falls off of a cliff below about 25 psu (roughly corresponding to Just's 75% dilution). (42/n)

Just also describes an experiment at lower salinities (as low as 50% or ~16 psu) to test how robust fertilization is to dilution of seawater. In Table 1, he shows the results of these trials. Basically you get very low fertilization below 75% dilution (~24 psu). (43/n)

But also of interest to me, you always get *some* fertilization at all salinities (albeit very low at 50% dilution). From the standpoint of selection, this may mean that under conditions of fluctuating salinity in nature, (44/n)

...you may have sufficient standing variation for some genotypes to survive (though most fail). Just is careful to point out that the data in Table 1 show that it is not fertilization that fails, but rather cleavage that fails at low salinity. (45/n)

For example, at 75% dilution, Just found about 80% fertilization and only about 8% cleavage. (46/n)

Just also describes his attempts to determine (as he did in part V of this series as well) if there is something special about the vulnerability to eggs/embryos just before, during or after fertilization (i.e. as the membrane is rising). (47/n)

And indeed he finds that there is increased cytolysis of the fertilized eggs if they are exposed to dilute seawater during the period of membrane separation rather than those exposed before or after. (48/n)

The paper, and indeed, the entire series, then ends without a discussion section or 'wrap up'. So where does this leave us? How can Just's discoveries in a paper that is only cited 4 (!!!) times be considered influential? (49/n)

I would argue that the influence of Just's early work on the influence of changing salinity on development is only beginning to be felt. (50/n)

Echinoderms have long been known to be sensitive to salinity changes (see Mike Russell's 2013 review for details: doi.org/10.1016/B978-0…)... (51/n)

...but salinity is somewhat of a neglected topic in climate change research when compared with the effects of changing temperature and ocean acidification. (52/n)

Since I emphasized the effects of Just's work on my own career path, I thought I would highlight a couple of additional examples (in @BiolBulletin!) that continue his influence. (53/n)

First, I have already mentioned the 2010 paper that Jan Pechenik and I published extending Just's work in a pretty direct way. But that led us to make some new and (to me) very exciting discoveries about how coastal animals respond to changes in salinity. (54/n)

Second, in 2015 two students and I published a paper on the effect of salinity in inducing polyembryony (twins, triplets etc.) in Echinarachnius parma (doi.org/10.1086/BBLv22…). (55/n)

This paper came directly out of observations made by trying to replicate Just's 1923 work. That the number of offspring produced from a single egg could be affected simply by changing salinity was shocking to me. (56/n)

That it occurred within the realm of salinities that embryos normally experience was even more so. @slziegler220 and @armstrong_af deserve tons of credit for pushing that work through to publication. (57/n)

In many ways, that part of their careers derives directly from Just's perseverance in his own. (58/n)

Third, the observations we made about polyembryony in response to low salinity then led @armstrong_af and @Blackburn_HN (another lab alum from @williamandmary) to make key discoveries about the effects of low salinity on delaying hatching in E. parma. (59/n)

In fact, some embryos delay hatching for so long that they turn into larvae while still in the fertilization envelope. This would be like a baby bird staying inside its shell until it is ready to fly away from the nest. (60/n)

I would love to know what E.E. Just would make of these observations! Citation: doi.org/10.1086/668829. (61/n)

Fourth, another @STEM_at_WM alumna, Salma Abdel-Raheem @stabdelraheem extended many of our observations on Echinarachnius parma to a west coast sand dollar species, Dendraster excentricus. (62/n)

Dendraster has long been , like E. parma, a model system for developmental biologists interested in fertilization and larval ecology. But there are few details about how they respond to fluctuations in temperature and salinity. (63/n)

Both sand dollars on both coasts live in intertidal and shallow subtidal environments where changes in temperature and salinity occur seasonally and with the incoming/outgoing tides. (64/n)

Salma was able to show that the runoff from the Fraser River in Canada had the potential to radically alter the developmental phenotypes of Dendraster, (65/n)

...in much the same way that Shelby Ziegler, Frances Armstrong and Holly Blackburn showed that rain events on the east coast could influence Echinarachnius. (66/n)

Over the course of Dendraster's spawning season, you can see the radical changes in temperature and salinity that occur in the surface waters surrounding the San Juan Islands. (67/n)

This work, done by Salma while at Friday Harbor Labs @MarineBiol_FHL benefitted from the data collection and water monitoring provided by Emily Carrington
@EC_carrington. (68/n)

Figure 2 from Abdel-Raheem and Allen, published in @BiolBulletin in 2019 (doi.org/10.1086/706607) really demonstrates this nicely I think. This was Salma's first paper, based on her undergraduate honors thesis... (69/n)

...and, like Shelby, Frances and Holly before her, was built upon the observations E.E. Just began a hundred years before their time! (70/n)

Let’s bring this back around to Just and his accomplishments in that series of papers. As I noted, they don’t have a huge citation reach and that is a shame. (71/n)

The discovery of the fast block alone should generate dozens (or more) citations in developmental biology journals each year. Especially considering all that we don’t know about it *still*. (72/n)

The work that undergraduates from @williamandmary have done to extend the reach of Just's early discoveries is impressive. But it also highlights how little attention has been paid to salinity effects on development in free spawning marine invertebrates. (73/n)

If the experimental embryology of marine invertebrates is good enough for Darwin and Bateson and Morgan, then it is good enough for us all! (74/n)

I don’t know why Just’s scientific contributions don’t get more attention. But they should! As noted earlier in this thread, @BiolBulletin posted his many papers in the journal earlier this year at the excellent suggestion of @MalcolmByrnes:

https://twitter.com/BiolBulletin/status/1385248426586116109?s=20

(75/n)

Just's experiments are often simple for students to replicate and extend if they have access to artificial or flowing seawater. My own colleague, Shantá Hinton @williamandmary, and I...(76/n)

have used E.E. Just for years as an example of the kind of excellence that diversity in science can bring. We teach about him in our introductory and upper level courses and try to highlight his work that is accessible because of its simplicity. (77/n)

Yet that simplicity of approach belies the complex phenomena he describes and may obscure how little we truly understand about the interaction between cells and their environment. (78/n)

Every time I read Just's papers I find myself viewing cells and embryos in a new way. I guess that may be one of his most important legacies: giving biologists a new lens through which to view the process of development. (79/n)

I hope this tweetstorm will inspire you to dig through more of Just's works and find ways for him to inspire you and your students in the same way that he has me and mine. Thanks for reading along!! (fin)

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