Day 14: 08:25 hours… It is our second day of unplanned exploration down a fast-flowing rocky stream. The view outside our windows is a rapid blur of white water bubbles and rocky stream bottom.
The speed of the current increases. I can see that we are being swept over a shallow flat surface, probably a stream-worn sheet of granite. And we are not alone!
Anchoring ourselves, we are treated to an outstanding view of the insects living here in the fast water. The smooth rock surface is crowded with hundreds of blackfly larvae.
A blackfly’s tube-like body sticks up into the current, gripping the rock with a claw-like foot pad. From the head end, the larva extends feather-like fans that catch tiny bits of food drifting by in the current.
10:20 hours… We have observed that these blackfly larvae prefer life in one of the most demanding habitats of the stream. Their adaptations for survival allow them to live in a place without any competition for food! Another insect would be whisked away by the powerful current.
As microscopic algae and other tiny organisms drift down stream, they are caught in a blackfly’s food-gathering fans. Every few seconds, the larva gathers in the fans and devours the accumulated snacks. There is no hunting for this aquatic insect – it just waits for the food to drift into its trap.
If fish or large animals disturb the water around the blackflies, the larvae respond instantly by releasing their hold on the bottom. As the insects drift downstream, they let out safety lines. When the disturbance passes, the larvae crawl up the safety line and reattach themselves in the best location for gathering food.
11:50 hours… I have ordered the anchor stowed – the Cyclops is once again on an unknown course down the stream.
Suddenly, Gyro shouts “Waterfall! Everybody hang on!”
There is no time to change course. The current is too strong. This may be the end of our bold adventure. We hang on as the Cyclops tumbles end over end – and is swept over the waterfall!
12:10 hours… We tumble through an explosion of thundering white water. I am certain that we will, at any moment, be smashed into the rocks. But that is not our fate!
Suddenly all is still. All is calm — how? A look outside reveals that by pure luck the Cyclops has washed over the waterfall and into a discarded bottle! Clinging to the outside of our transparent refuge, we see one of the strangest aquatic insects we have yet come across on our stream voyage – a water penny. The familiar insect body is protected by a flattened outer shell, a shape that is so perfectly streamlined that the fast current cannot wash the insect away. It appears to have found a perfect place on the bottle surface for scraping algae for food!
14:15 hours… Just when we were beginning to worry that we might never escape from this plastic bottle sanctuary, a flicker of bright light from above the surface catches our attention. It is our companion Tara! She is focusing sunlight through a lens in our direction. Tara is trying to help us with our problem, but how can focusing sunlight free us from the bottle?
By using a mirror we redirect Tara’s sunbeam through yet another lens. We focus the light into a very hot point at the bottom of the bottle. To our relief it works, and the plastic quickly melts. In no time we carve out an escape hatch. Not far from the waterfall the stream slows. We are able to navigate our way to shore where we reunite with Tara who is eager to expand our biological explorations into the nearby forest. It seems that the work of biological discovery is never done!
Different Adaptations, Same Habitat
The blackfly larva and the water penny show two sets of very different adaptations for living in fast-moving water.
The blackfly sticks up into the current and uses fans to catch small food organisms as they drift by. If disturbed the insect lets go and washes downstream, letting out a safety-line filament. When the disturbance has passed, the blackfly uses the safety-line to crawl back to its ideal feeding spot in the current.
The water penny is almost perfectly flat, and clings so tightly to the rock that the current passes smoothly over its protective streamlined shell. Under the shell the insect scours the surface of the rock, scraping off algae with its sharp mandibles. To be continued…
