Periods of environmental sensitivity couple larval behavior and development
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Abstract
The typical life cycle in most animal phyla includes a larval period that bridges embryogenesis and adulthood 1 . Despite the great diversity of larval forms, all larvae grow, acquire adult morphology and function, while navigating their habitats to obtain resources necessary for development. How larval development is coordinated with behavior remains substantially unclear. Here, we describe features of the iterative organization of larval stages that serve to assess the environment and procure resources prior to costly developmental commitments. We found that male-excreted pheromones accelerate 2-4 the onset of adulthood in C. elegans hermaphrodites by coordinately advancing multiple developmental events and growth during the last larval stage. The larvae are sensitive to the accelerating male pheromones only at the end of the penultimate larval stage, just before the acceleration begins. Other larval stages also contain windows of sensitivity to environmental inputs. Importantly, behaviors associated with search and consumption of food are distinct between early and late portions of larval stages. We infer that each larval stage in C. elegans is subdivided into two epochs: A) global assessment of the environment to identify the most suitable patch and B) consumption of sufficient food and acquisition of salient information for developmental events in the next stage. We predict that in larvae of other species behavior is also divided into distinct epochs optimized either for assessing the habitat or obtaining the resources. Thus, a major role of larval behavior is to coordinate the orderly progression of development in variable environments.
“Life is what happens to you when you’re busy making other plans.”
Allen Saunders (popularized by John Lennon)
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The first sign of acceleration of the sequence of morphological transformations of the anchor cell on MCPs was evident around 36 hours
see my comment on the staging in the methods - i think it's important to stage AC invasion by multiple criteria - DIC showing the VPC stage is an excellent one in addition to any morphological changes you might see in the AC, which can be highly variable during invasion.
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Staging (see Figure S1D for representative images) was based primarily on the shape of the cell’s ventral side. AC1 = long curving ventral side not attached to P6 daughter cells. AC2 = flat and short ventral side indicates attachment. AC3 = invasive protrusion forms a V-shape. AC4 = invasive protrusion retracts forming an M-shape.
There is a well-established staging system for the timing of AC invasion based on the divisions of the underlying P6.p lineage (see Sherwood et al. 2003 or later papers from Sherwood lab). The shape of the AC is indicative but also highly variable. It is also worth pointing out that the AC breaches the underlying basement membrane during the mid-L3 stage, and that in wild-type the AC is in contact with the underlying vulval cells prior to the L3/L4 molt. The reason this is important, is that it appears from …
Staging (see Figure S1D for representative images) was based primarily on the shape of the cell’s ventral side. AC1 = long curving ventral side not attached to P6 daughter cells. AC2 = flat and short ventral side indicates attachment. AC3 = invasive protrusion forms a V-shape. AC4 = invasive protrusion retracts forming an M-shape.
There is a well-established staging system for the timing of AC invasion based on the divisions of the underlying P6.p lineage (see Sherwood et al. 2003 or later papers from Sherwood lab). The shape of the AC is indicative but also highly variable. It is also worth pointing out that the AC breaches the underlying basement membrane during the mid-L3 stage, and that in wild-type the AC is in contact with the underlying vulval cells prior to the L3/L4 molt. The reason this is important, is that it appears from your images that your AC4 image is younger (by VPC morphology) than your AC3 image (although I realize that the DIC image is quite small in the figure so I'm not 100% sure). Given that the effect you are seeing from the MCPs in relation to AC morphology (as a proxy for invasion status) is getting to "AC4" faster, I think it would be important to be careful with developmental staging here. I'd be happy to look at your images if that would be at all helpful!
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vulva anchor cell,
technically, the anchor cell is part of the somatic gonad, it just induces vulval fates (and forms the connection between the uterus and vulva)
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