Dendrobranchiata

Dendrobranchiata is a suborder of decapod shrimps, commonly known as prawns. There are 540 extant species in seven families, and a fossil record extending back to the Devonian. They differ from related animals, such as Caridea and Stenopodidea, by the branching form of the gills and by the fact that they do not brood their eggs, but release them directly into the water. They may reach a length of over 330 millimetres (13 in) and a mass of 450 grams (1.0 lb), and are widely fished and farmed for human consumption. While Dendrobranchiata and Caridea belong to different suborders of Decapoda, they are very similar in appearance, and in many contexts such as commercial farming and fisheries, they are both often referred to as 'shrimp' and 'prawn' interchangeably. In the United Kingdom, the word 'prawn' is more common on menus than 'shrimp', while the opposite is the case in North America. The term 'prawn' is also loosely used to describe any large shrimp, especially those that come 15 (or fewer) to the pound (such as 'king prawns', yet sometimes known as 'jumbo shrimp'). Australia and some other Commonwealth nations follow this British usage to an even greater extent, using the word 'prawn' almost exclusively. When Australian comedian Paul Hogan used the phrase, 'I'll slip an extra shrimp on the barbie for you' in an American television advertisement, it was intended to make what he was saying easier for his American audience to understand, and was thus a deliberate distortion of what an Australian would typically say. Together with other swimming Decapoda, Dendrobranchiata show the 'caridoid facies', or shrimp-like form. The body is typically robust, and can be divided into a cephalothorax (head and thorax fused together) and a pleon (abdomen). The body is generally slightly flattened side-to-side. The largest species, Penaeus monodon, can reach a mass of 450 grams (16 oz) and a length of 336 millimetres (13.2 in). The most conspicuous appendages arising from the head are the antennae. The first pair are biramous (having two flagella), except in Luciferidae, and are relatively small. The second pair can be 2–3 times the length of the body and are always uniramous (having a single flagellum). The mouthparts comprise pairs of mandibles, maxillules and maxillae, arising from the head, and three pairs of maxillipeds, arising from the thorax. A pair of stalked eyes points forwards from the head. The carapace grows from the thorax to cover the cephalothorax, and extends forwards between the eyes into a rostrum. This is only as long as the stalked eyes in Benthesicymidae, Luciferidae and Sergestidae, but considerably longer in Aristeidae. As well as the three pairs of maxillipeds, the thorax also bears five pairs of pereiopods, or walking legs; the first three of these end in small claws. The last two pereiopods are absent in Luciferidae and Acetes, but much longer than the preceding pereiopods in Hymenopenaeus and Xiphopenaeus. The thoracic appendages carry gills, which are protected beneath the carapace. The gills are typically branched, and so resemble trees, lending the group its scientific name, Dendrobranchiata, from the Greek words δένδρον (dendron, tree) and βράγχια (branchia, gill). The pleon, or abdomen, is similar in length to the cephalothorax. It has six segments, the first five bearing lamellar pleopods, and the last one bearing uropods. The pleopods are biramous, except in Sicyoniidae, where they are uniramous. The uropods and telson collectively form the tail fan; the uropods are not divided by a diaeresis, as they are in many other decapods. The telson is pointed and is usually armed with four pairs of setae or spines.