Crustacea interactive keys

There are currently more than 800 families of crustaceans and well over 40,000 species. Although some groups such as crabs and shrimps are reasonably well known on a world-wide basis, other groups, such as amphipods, are well known for only a few geographic areas.

Crustacea.net is an interactive key developed in 2000.

The method for producing this complex, illustrated, interactive keys was theDELTA system. This Windows based programs is a taxonomic data base which stores morphological information in such a way that it can be used to produce among other things, taxonomic keys and natural language descriptions.

The legacy website was developed by the Australian Museum, but is no longer maintained.

Visit the Australian Museum's crustacea.net

Difficulties in identification (particularly invertebrates) often make studies in ecology, conservation or environmental impact incomplete. Studies that include organisms identified at order or family level give little indication of species diversity. But these groups often provide the basic framework of whatever ecological system is under threat.

Crustaceans are particularly useful in aquatic environmental studies for several reasons. They are diverse and abundant in many habitats, play important roles in ecosystem processes, are often good indicators of stressed/polluted conditions, are relatively amenable to life history studies and frequently have commercial and cultural significance. They do, however, suffer the following difficulty.

Identification of crustaceans by non-experts is extremely difficult and time-consuming. Descriptive literature (including dichotomous keys) is often scattered and difficult to find. Terminology is jingoistic and often varies from one crustacean group to another. A non-expert, who wants to use crustaceans in his work must either, pay a taxonomist to identify his crustaceans or try to do the identifications himself. The problems are that there are not many experts and all of them are over committed and trying to identify without expert help is inefficient and often leads to inaccurate or inadequate identifications.

We think that if crustaceans were easier to identify and to learn about, then they would be used more often in survey work, in ecological studies and by young taxonomists. We also think that if they could be identified more efficiently and more accurately, then the quality of all studies using these animals would be greatly enhanced.

Please also refer to the Fauna databases and online resources, a free online public enquiry database that provides taxonomic and biological information on the Australian fauna.

The umbrella key (Crustacea, the Higher Taxa) identifies the higher taxa of the world Crustacea and leads into the keys to the crustacean families. There are 56 higher taxa (an arbitrary assignment which basically divides the crustaceans into familiar or natural groupings). Some of these are familiar, such as the brachyurans (crabs), the carideans (shrimps), the anostracans (fairy shrimps) and euphausiaceans (krill), and some are obscure, such as the monstrilloids (parasitic copepods) or mictaceans.

Once you know which group you have, then select the family or family/generic level key to that group. The first step is to accurately identify the higher taxon.

Interactive keys differ from traditional dichotomous keys in that you can select any available character for the identification and you can re-identify your taxon more than once using different sets of characters. As you make character state selections taxa are eliminated and the remaining taxa are listed on the screen until only one or none are left.

In interactive keys there are several kinds of characters:

1. Multistate characters are the most common and useful.
2. Integer characters define numbers, such as the number of articles in an antenna or the number of pairs of legs.
3. Real number characters, such as the ratio of the length of antenna 1 to antenna 2.
4. Text characters, such as synonymies, geographical distributions or remarks. These characters are used for information retrieval about an identified taxon.

Identification Procedures - Normal Mode