Latreille, 1803
Adult members of the eumalacostracan Order Decapoda are crustaceans that are characterised by the carapace enclosing the branchial chambers and by the modification of the first three pairs of thoracopods as maxillipeds — the remaining five pairs of thoracopods are uniramous or weakly biramous leg-like limbs or pereiopods.
Decapods are highly diverse, occurring in all aquatic environments at all depths, a few species are (semi)terrestrial. Many decapods are pelagic, but most appear to be adapted to a life in, at, or close to the bottom. The Decapoda comprises the shrimps, prawns, lobsters, crayfish and crabs. The order is divided in two groups:
¥ Suborder Dendrobranchiata — a relatively small group, of which most species concerning the shrimps of the Superfamily Penaeoidea and Superfamily Sergestoidea
¥ Suborder Pleocyemata, a large group, with all remaining species.
The dendrobranchiate decapods are unique in that they have dendrobranchiate gills (one of the three basic decapod gill types) and the chelation of the first three pereiopods; furthermore, the females do not brood the eggs, but the eggs are shed in the water and fertilised externally, the larvae hatch from the egg as nauplius. In contrast, the pleocyemate decapods never possess dendrobranchiate gills and the females brood the fertilised eggs on their pleopods for some time and the larvae hatch at a stage later than nauplius, which stage has been passed within the egg membrane.
Larval development in Decapoda is metamorphic and includes nauplius, protozoa, mysis (or late zoea) and megalopa in the Suborder Dendrobranchiata, and zoea and megalopa in the Suborder Pleocyemata (see also Crustacean larval stages ).
The Suborder Pleocyemata holds seven infraorders all but one present in the North Sea. Those marked with an * asterisk do not contain species with pelagic adults.
¥ Infraorder Caridea
¥ Infraorder Stenopodidea* (not present in the area)
¥ Infraorder Astacidea*
¥ Infraorder Thalassinidea*
¥ Infraorder Palinura*
¥ Infraorder Anomura*
¥ Infraorder Brachyura
[Description after McLaughlin, 1980; Brusca and Brusca, 1990]
The present key is designed to identify either pelagic adult decapods that occur in the North Sea, or benthic and hyperbenthic adult decapods in this area, which may occur in the pelagic; this key starts at Page 330: Decapoda. In this volume larval stages of decapods are not keyed out to species. The following decapod species are included:
Order Decapoda
Suborder Dendrobranchiata
Family Sergestidae
Sergestes arcticus
Sergia robusta
Suborder Pleocyemata
Infraorder Caridea
Family Alpheidae
Athanas nitescens
Family Hippolytidae
Caridion gordoni
Caridion steveni
Eualus gaimardii
Eualus pusiolus
Hippolyte varians
Lebbeus polaris
Spirontocaris lilljeborgii
Spirontocaris phippsii
Spirontocaris spinus
Thoralus cranchii
Bythocaris simplicirostris
Cryptocheles pygmaea
Family Oplophoridae
Acanthephyra pelagica
Acanthephyra purpurea
Hymenodora glacialis
Systellapsis debilis
Family Nematocarcinidae
Nematocarcinus ensifer
Family Crangonidae
Crangon allmanni
Crangon crangon
Philocheras bispinosus
Philocheras echinulatus
Pontophilus norvegicus
Pontophilus spinosus
Sabinea sarsi
Sabinea septemcarinata
Family Palaemonidae
Palaemon adspersus
Palaemon elegans
Palaemon longirostris
Palaemon serratus
Palaemonetes varians
Family Pandalidae
Dichelopandalus bonnieri
Pandalina brevirostris
Pandalina profunda
Pandalus borealis
Pandalus montagui
Pandalus propinquus
Family Pasiphaeidae
Parapasiphae cristata
Parapasiphae sulcatifrons
Pasiphaea multidentata
Pasiphaea sivado
Pasiphaea tarda
Infraorder Astacidea
Family Nephropidae
Homarus gammarus [larva]
Nephrops norvegicus [larva]
Infraorder Palinura
Family Palinuridae
Palinurus elephas [larva]
Infraorder Brachyura
Family Portunidae
Polybius henslowii