Characteristics of Penaeus (Fabricius, 1798)
Body integument always glabrous. Rostrum toothed dorsally and ventrally, length variable, adrostral carina extending well back on to the carapace. Carapace without longitudinal or transverse sutures; cervical and orbito-antennal sulci, antennal carina, hepatic and antennal spines, well defined; pterygostomial angle rounded. Dorsal carina on the 5th-6th abdominal somites, usually on the posterior part of the 4th as well; telson with deep median sulcus, without subapical fixed spines, with or without lateral movable spines. Antennular flagella shorter than the carapace. Maxillulary palp with two or three segments, usually three; 3rd maxilliped sexually dimorphic. Basial spines on 1st and 2nd pereopods; exopods on the 1st-4th pereopods, usually also on the 5th. Petasma pod-like and flexible with thin median lobes, usually with small thickened distal protuberances and forming a posterior tube-like projection; lateral lobes usually with thickened distal rounded margins. Thelycum with anterior plate between the coxae of the 4th pereopods variable in shape and smaller than the posterior part of the thelycum; seminal receptacle occupying the ventral surface of the last thoracic somite, usually closed by two flaps, or sometimes a single pocket, or sometimes open. Seventh and 8th thoracic somites with pleurobranchiae; a posterior arthrobranch only on the 7th. Epipods on 3rd-6th thoracic somites (Dall et al., 1990).

Females of all species of this genus grow to at least 50 g weight (over 200 mm length), and nearly all are commercially abundant, at least in the centre of their distribution. Penaeus spp. are the prime targets of capture fisheries and the favoured species for aquaculture. Because of their economic importance, most research has been done on Penaeus spp. as will be apparent in the subsequent chapters. The species are mostly easy to identify and many have distinctive colouring, which in the adults is fairly consistent (e.g. "tiger" prawns) (Dall et al., 1990).