Copepods and Branchiurans

Examples of at least four different genera once grouped together within the order Copepoda.  Now these genera diverge after the class level into too sub classes Branchiura and Copepoda as sister taxa to barnacles.  Care must be taken when analysing these Subclasses relatedness as the class Maxillopoda may not be a monophyletic group.

Freshwater Crayfish (Decapoda)

The freshwater crayfish genus Astacus is used to illustrate the internal anatomy of the now obsolete order Thoracostraca which comprised all shrimp, lobster and crayfish.  Internal structures are colour coded where red represents the open circulatory system, yellow the digestive system and blue the ventral nerve cord and associated ganglia.  Among the illustrations are an entire vertical longitudinal section (1), cross section through the thoracic region (2), the shape of various paired appendages (3), dorsal view of a dissected anterior region of alimentary canal (4), the network of vessels mixing the open circulatory system (5), the male (6) and female (7) reproductive organs, section of a compound eye (8) and structure of antennule with auditory structure labelled (9).

Decapod Larvae

Different larval stages of a range of different decapods.  Because of their complex life history many of the larval stages of different taxa were originally classified together as groups of their own.  Some lobster species have over twenty different larval stages.  Examples that are of note on this chart are the nauplius (1) of copepods, the zoea (10 & 11) of crabs, and the phyllosoma (3) of lobsters.