Aquatic Invertebrate Identifications

Did you know that more than 95% of described animal’s species are invertebrates? We’re talking about 95% of the world’s animals not having a backbone! Owing to their huge numbers, invertebrates are a vital part of both aquatic and terrestrial ecosystems. They are important links in the food chain, passing nutrients from plants and algae to larger organisms such as fish, frogs, salamanders, reptiles, birds and mammals. They also tell us about the quality of the environment due to their sensitivity to factors such as sediment load, pollutants, pH and more.

In order to know what invertebrates are telling us, we need to be able to accurately identify them. One way to identify specimens is by using morphological features. This summer I will be using morphology in order to sort and identify aquatic invertebrates that were collected during last year’s BIObus trip. As I’ve learnt over the last several weeks, this is no easy task because aquatic invertebrates are extremely diverse. Aquatic invertebrates may live beneath the water, or they may live on the surface or on the plants surrounding it. Some breathe water, others breathe air. They may be able to walk, swim, float, skate, fly or glide on their bellies—or they might not move at all. On top of that, a large number of insects lead double lives. Dragonflies, mayflies, stoneflies, caddisflies, dobsonflies and more are aquatic as juveniles. Then, when they undergo their final molt, they leave the water and become winged adults that fly in the air. Other aquatic invertebrates remain aquatic their whole lives. Water boatmen, predaceous diving beetles, whirligig beetles, water striders, fishing spiders and others spend all their days hunting in and around water.

Essentially, the point I’m trying to get at is that there are a lot of animals that need to be identified, and it would take an expert to have them all memorized. Since I’m not an expert, I rely on an identification key. There are several different types of identification keys, but the one I’ve been using is similar to this one.

A simple aquatic invertebrate identification key that can be used in order to identify specimens using morphological features
A simple aquatic invertebrate identification key that can be used in order to identify specimens using morphological features

This type of key uses a fixed sequence of identification steps, each with multiple alternatives, the choice of which determines the next step. For example, if I have this specimen:

Crayfish can be found at many of the sampling locations we will be visiting this summer
Crayfish can be found at many of the sampling locations we will be visiting this summer

I would say that it has no shell, it has legs, it has 10+ legs, and it is lobster-like which leads us to the identification of crayfish.

An example of how to use an identification key, using a crayfish as the specimen
An example of how to use an identification key, using a crayfish as the specimen

We use keys similar to this one at BIO in order identify specimens accurately and quickly. This skill is called taxonomic identification, and we use it in combination with DNA barcoding. Many people believe that in order to identify a specimen, one must choose between taxonomy and DNA barcoding. However, both techniques are used for two different purposes and are integrated for optimum efficiency. Taxonomy gives names to species, define their limits and the diagnostic characters to recognize them. DNA barcoding use genetic data to assign a name given by taxonomy to an unidentified organism. The two approaches used together will help us continue to identify species and expand our knowledge.

-Kareina

 

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