Steam Diversity Survey: Invertebrate ID's

Following on from doing the stream diversity in Brecon. We pickled the specimens we caught and then a week or two later we started trying to identify them.

I started with a stonefly (Plecoptera) larvae and a mayfly (Ephemeroptera) nymph.
Its easy to distinguish what is a mayfly or stonefly without using any keys however I did so the first time, just to check and its all good practice I guess. A stonefly will always have two tails whereas a mayfly will usually have three (although some have two). then the gills are the second easy detector to see which it is.

(Right: Stonefly specimen under the microscope)

Stonefly

I used a simple key to find out which family it was. which was the PERLIDAE family. The steps I took are as follows:

1. 3 tarsals not roughly equal lengths. 
2. The 3rd tarsal is obviously longer than the first two combined
3. it has obvious gills at the base of each leg ('hairy armpits')

I then got a stonefly book that goes further tan the family and tried to find the species. It was quite easy as there was only two species in this family and so I narrowed it down to:  Perla bipuncta. (left: My field notebook; rough diagrams of stonefly.)

Mayfly

The mayfly (photos below; under the microscope) was harder to identify than the stonefly. I narrowed it down to the family: HEPTAGENUDAE. It has a pronotum with flange-like extension and its eyes are dorsal. 

Im pretty sure that the species is Ecdyonurus insignis (eaton), however the book for the mayfly ID's wasnt as easy to understand and was harder to distinguish between species. However if you look closely at the underside of the body there are dark marking on the underside of the body (you can see this faintly in the picture to the right).

If you want to see more of these photos go to my flickr: Stream Diversity and Invertebrate ID's

(above: my field note book with 

notes and diagrams of the specimen)

Ecological Characteristics of Streams.

Today we went to Brecon (near Pen y Fan) to collect some invertebrate specimens from a stream; as well as looking at the physical and biological characteristics of the stream.

Typical Welsh weather; it was raining and even hailing for almost the entire duration of our time there. It was bitterly cold, made worse by the fact that we needed to get our hands wet (and for me, my feet). 

We took measurements of the stream:  width of the stream, bank heights, water heights and stone composition at different intervals across the stream. we also measured the speed of the current by using a leaf and a metre ruler. 

As well as the measurements we had to look at potential sources of pollution and how the area was managed. A lot of trees had been cut down near the stream and water ran through that area into the stream we were on.

Spaghum moss which is on the hill to the right of the stream is acidic and so this can wash down to the river. The red sandstone (mudstone) which is in the river, is also acidic (and contains silica). This all means that the stream will be slightly acidic. 

The area around the stream was sued for grazing of sheep, this means that along the hillside was a field. If the sheep did not graze her it would most likely be an oak forest. If it were than the stream may be different (for example what lives in it).

We looked for signs of flooding, for example plants had been pushed over. It seemed as though the stream had not flooded for a while, although some of the embankment had fallen in, but this could be due to general erosion.

We used nets to gather some invertebrates which we then put into a pot, ready to take back to the lab. 

These included web spinning caddis, cased caddis and large stoneflies.

 By this point the hail had really started to pick up and was starting to hurt as it hit and I knew that my wellies were definitely leaking now due to the lack of feeling in my toes. (The photos really don't show just how miserable the weather really was).

When we got back to the lab we had to pickle the specimens ready for our lab session next week. The water in the jar was emptied as much as possible (without loosing anything) and then methanol was added a 20% water to 80% methanol ratio.