Introduction

The crustaceans comprise economically important shrimps, crabs, lobsters and foulers, the barnacles as well as ‘fodder’ animals, branchiopods including Artemia, cladocerans, copepods and euphausiids. They also include biologically important groups, branchiopods, copepods and ostracods, which produce resting eggs/cysts that hatch after a short or long period of diapause. Commencing from the early Cambrian, they had ample time to undertake endless experimentation with form and function; today, “no other group of plants or animals on the planet Earth exhibits the range of morphological diversity seen among the extant Crustacea” (Martin and Davis, 2001). For example, the diversity within decapods alone ranges from shrimps with an elongated laterally compressed body, muscular pleon and limbs mainly adapted for swimming to crabs displaying dorso-ventrally †attened broad body with a reduced pleon and uniramous walking limbs. Among large decapods, there are species with limbs specialized for digging, cracking molluscan shell and all kinds and number of spines, pincers and scissors (Scholtz et al., 2009). In terms of overall species richness, the crustaceans, with more than 52,000 species, are placed fourth behind insects, molluscs and chelicerates. Considering the diverse morphological features as the base for classiŽcation, the superclass Crustacea is divided among six classes, 13 subclasses, 46 orders and 802 families (Martin and Davis, 2001). This crustacean extant may be compared with more or less equally successful 32,000 species of teleostean Žshes classiŽed under six subclasses, 64 orders and 563 families (FishBase, 2010, www.Žshbase.org). To familiarize the taxonomic status of the cited species, an introductory version of systematic resume of Martin and Davis (2001) is listed in Table 2.1.