King of All I Survey-Chapter 220: The Ceiba Tree’s Reaction to Injury
The view on the display shifted upward toward the green canopy, following the trunk up to the top where the fronds radiated outward from the trunk. Each frond had a prominent central vein running along its length tapering from larger to smaller as it got farther from the trunk and the frond itself narrowed to a point. The fronds were incredibly long, maybe sixty or seventy feet from tip to trunk. Rafael's gaze and the corresponding view on the display swept along the length of the frond, as if searching for something. Then, it snapped back to a position about 20 feet from the trunk. At first, I saw no reason for that spot to attract attention.
"There," Rafael said, "watch the movement. A piece of the frond is detaching. It's clear, almost completely transparent." I saw an area of the frond's central frond that looked a bit out of focus. As my eye found the pattern, I saw it. A flat gelatinous undulating, slug-like thing. It reminded me of a sea-slug more than anything else. It was flat-bodied and lacked any real distinguishing features. It crawled along the frond's central vein, the entire body rippling as it moved. Rafael must have adjusted the camera or viewing parameters of the recording he had made because my view zoomed in closer.
It was definitely separate from the tree, moving across its surface independently. Then the view backed up toward the direction where the creature came from. "That depression, the narrowing of the frond there is where this Sap Slug came from." He explained in his high-pitched, helium atmosphere voice. "Before I cut the tree and the sap leaked out, there was no indication that that spot was any different than any other part of the frond. Even deep scans showed nothing but the central vein itself. Somehow, when the sap was exposed, a piece of the tree, from the central vein of the frond, detached itself and became independently mobile. Its tissues changed, our analysis shows that a long protein chain reshaped itself from a straight, rigid form factor, into something like muscle fiber, expanding and contracting to form the undulations. The lower surface adheres to the Ceiba tree, or to any normal surface, and allows it to move or climb without falling. We've found that it forms a moving suction-cup like form factor over most of the contact surface. Several suction cup-like areas that flow, close and reform as the Ceiba Sap Slug moves." The view was now a close-up of the Ceiba sap slug, as Rafael called it, as it slid purposefully along the frond's central vein toward the injured tree trunk. The view then went back along its former path to a spot further out on the frond.
"See, there's another one, from the same frond. We've found that when a trunk generates more than one sap slug in response to a single event, they typically come from the same frond. If they are responding to an injury to the trunk, it'll be the frond whose origin most closely aligns with the injury along the vertical axis." Indeed, a second sap slug, to my eye identical to the previous one, was now sliding its way toward the trunk along the same frond.
The view raced ahead of the second sap slug to the first one. It was reaching the trunk and making a smooth transition from the frond to the Ceiba tree's trunk, clinging to the rougher outer surface with no apparent difficulty. "The underside of the slug, indeed all of its outer surface, is highly flexible, so it can mold itself perfectly to form a near-perfect seal for its suction-cup adherence regardless of the irregularities in the surface it crawls on. We've experimented with artificial surface textures with what should be very difficult geometries to create a good seal against. The Sap slug seems to be able to mold itself to fill gaps as small as 0.08 millimeters. Spaces smaller than that get filled with a fluid rather than with the flexible skin of the slug, allowing it to maintain the suction vacuum. The Sap Slug also excretes a very minute amount of a non-Newtonian fluid. I'm told that term is widely used by our scientists, so I trust you won't need it explained as I did," Rafael said. "Basically, this fluid allows the sap slug to stick to the surface when the portion of the slug in contact with it is under pressure from the muscular action of the slug pressing against it, compressing it against the surface on which it is travelling. When the same portion of the sap slug's undersurface pulls away from the underlying surface, however, it loses it's solid characteristics and behaves like a very thin, liquid lubricant. The edges of the suction cup area then adhere strongly to the surface with the glue-like solid properties of the sap-slug ooze, while the interior of the suction cup pulls away from the surface slides forward along with other portions of the underside that are not used for adhesion at any given moment." 𝐟𝕣𝕖𝐞𝐰𝕖𝚋𝐧𝗼𝚟𝐞𝕝.𝗰𝐨𝐦
At this point the slug was only about two feet away from the still leaking cut, Rafael's machete had opened in the tree trunk. "I want to focus on its action as it reaches the cut and the exposed sap, so for now, I'll summarize by saying that the sap slug is using both this adhesive/lubricant liquid and the mechanically generated physical vacuum suction to stick to vertical surfaces. As you see it now, either would be more than strong enough to hold it without the other system. It seems like overkill to use both where one system would do, but watch…"
The sap slug continued down the tree trunk to the injured section. It spread itself over the cut, not reorienting its length by physically turning to cover the lateral cut, but by changing its shape. Once the front edge of the slug crossed the damaged area and found uninjured bark on the other side, the front edge simply stopped moving forward. The back end continued its forward progress, however. The extra volume pushed out to the sides, the skin or surface layer flowing to accommodate it. The new front edge widened equally in both directions along the edge of the wound, covering it. It reached both ends of the cut, and the back edge continued downward until it also matched the upper edge shape of the cut in the tree bark which was now completely hidden. Once the ends of the cut were covered, the extra volume just thickened the portion of the slug that covered the cut. As I watched the view, I saw that it formed a shape exactly matching the cut, but extending, maybe a quarter inch beyond it onto the good, uninjured bark surface. A few sends after it had finished moving, the view zoomed in even closer, and Rafael's narration resumed.
"If you watch carefully at the very edge, the section where the sap slug overlaps the uninjured bark is thinning even more. The size of the overlap will vary depending upon size and depth of the injury to the main trunk." Indeed, this tiny overlapping area was thinning, it was almost paper thin, but still flexibly molded to the bark's surface. Like thin seal around the wound.
Rafael continued. "It has formed a tight, air-tight in fact, seal around the wound. Notice that the rest of the slug is still expanding slightly. When we scanned this process, we found that for a short time after the wound is covered, the sap still leaks out of the wounded Ceiba tree trunk. The sap is directly absorbed into the sap slug. Its underside becomes permeable to the sap, but only in one direction initially. It has no mouth or excretory openings of any sort, taking the sap directly through its skin. As this process continues the skin in contact with the sap and the wound presses outward until it exactly conforms to the injured surface, making an even more accurate fit that it can when traversing other surfaces. It matches the wounded surface down to the molecular level, as if the skin surface becomes a true liquid, seeming to lose its own shape entirely. Very quickly after that, our scans show no difference between the under surface of the sap slug and the outer surface of the wounded area. This is the same for both the cut edges of the outer bark-like surface and the exposed inner trunk tissue, which both have a different apparent cellular structure.
"At this point the outer exposed surface layer of the sap slug begins another action. The cells start to contract. It's almost like a muscular contraction, as the structural proteins shorten. This draws the our skin tighter and tighter exerting a pressure on the liquid sap that is both inside the slug and between it and the wounded trunk surface. The sap does not compress under the pressure. Instead it is forced through the semi-permeable tissue of the tree trunk. It is effectively reabsorbed by the Ceiba tree, merging with the sap that flows throughout the tree. Think of it as if a human had lost blood in an accident, and the blood could be collected and put back into the patient's veins. The exposed wounded surface allows the pressurized sap to flow back through its own cell membranes but does not allow anything else to pass through. Imagine that whatever caused the wound left some contaminant behind. Say by machete was coated in oil or even a poison, The trees cellular membranes open to the sap only, leaving the oil or poison or anything other than sap, trapped between the sap slug's top layer and the trunks internal tissues. At least until the sap is entirely absorbed. But the contaminant doesn't just sit there forever." The view shifted again, the second sap slug had now reached the first one.
"I'll talk more about that later. First, watch as the second slug arrives at the wound site."
