Analysis Of Invertebrates In Kaaimans River

Introduction

On the 24th of August we went onto Nelson Mandela University, George Campus and down to the Kaaimans river. We then were split between three habitats, pools, sandy substrate and riffles and all this was done in the middle reaches of the Kaaimans River. After we were split, we had to find and identify invertebrates. My group and I worked in the riffles to see what invertebrates we could find. We found some worms, caddisflies, damselflies, mayflies and a beetle. When looking at these three different habitats, it can be found that in pools the water flow is not as fast as in riffles. The food source that is found in pools are the invertebrates, like mayflies, which feeds on the plant matter and these mayflies will be eaten by dragonflies. In riffles the water gets obstructed by rocks which speeds up the waterflow. Invertebrates uses these rocks to protect themselves against predators by seeking shelter and the water can be shallow or deep. In the sandy substrate it can be found that the water has a slow velocity or the water is not flowing.

Results

In the riffles there wasn’t a high abundance of invertebrates like in all the other habitats. The most abundant one was mayflies but there was also a lot of bugs and beetles that was found. In the sandy substrate the most abundant invertebrate was also mayflies and, in the pools, common flies and caddisflies. All the types of flies were seen mostly in all three habitats for the reason that they are able to fly, meaning they could be everywhere. The dragonflies feed on insects, flying insects, mayflies and common flies. This means that they were not really spotted at the riffles because they are more likely to find their food easier at the other two habitats for the reason that they have to search hard for food in riffles. The reason for the food being difficult to find is because in riffles, the water is fast flowing and the food hides between rocks or gets washed into the pools. The bugs and beetles that was found in the riffles were mostly larvae and one was an adult. The larvae are protected from predators because they are hidden in the riffles. Bugs and beetles were most abundant in the pools and sandy substrate, because they have easier access to insects and mayflies than in the riffles.

Dobsonflies feed on mayflies, stoneflies and caddisflies. They are mostly found near the riffles because they catch their prey in the middle of the riffles. They can be seen as predators and they can be found living under rocks most of their lives. Snipe flies are also predators which mostly feeds on blood. Some worms were found in the riffles and therefore some leeches were also found for the reason they feed on the worms and other insects but they also feed on plant matter. Leeches were found in the sandy substrate and in riffles. The reason for this is because they are mostly found in damp soil and in shallow water.

Caddisflies, Mayflies and Damselflies feed on plant matter, therefore they are mostly found in the pools where they can get some plant matter that is floating in the water. In the case of a beetle, they have small hairs underneath their body which keeps air in the middle of the water and their bodies this helps them to stay under the water for longer periods of time.

Conclusion

Invertebrates, that are found in water, usually have flattened bodies which helps them to stay under the water, on the soil surface, in fast flowing water. The velocity of the water that flows over the invertebrate is so great that it keeps it on the surface. The adaptation in this case is that these invertebrates know that they should keep their heads and tails (if they have) flat onto the surface and then they will not be washed away with the water. These invertebrates force their heads and the ends of their bodies, towards the surface and then the middle of their bodies raises and they will then go with the stream flow to where they want to go. The stream flow and food abundance had a big impact on where and how many invertebrates were found. Where the stream flow was fast, less invertebrates were found and therefore the food abundance in the pools and sandy substrate were more and as a result the most invertebrates were found in those two habitats.