Krøyer, 1878
Description
Cumacea are peracarid crustaceans with a carapace that is composed of the fused dorsal parts of the cephalon (head) and the first three thoracic somites. The body shape is very characteristic for the order, with two tagmata: an inflated cephalothorax and a very slender abdomen (pleon) with styliform uropods.
On either side of the carapace, the front is produced into a forward projecting so called pseudorostral lobe; both lobes together form the pseudorostrum. Dorsally behind the pseudorostrum is the bell-shaped frontal lobe from which the small ocular lobe projects forward, usually carrying the unpaired eyes. The eyes are sessile, compound, fused, but sometimes absent. Behind and to the sides of the frontal lobes are the branchial regions.
The last five thoracic somites together form the pereion and are usually free, although the first and rarely the second and third, may be combined with the carapace, while the fourth and fifth somite may be fused dorsally. Each of these five thoracic somites is called a pereionite.
The abdomen or pleon consists of six cylindriform somites, called pleonites and is prolonged by a telson in four of the families. Sometimes the telson is fused with the sixth pleonite into a pleotelson.
The body is covered with a chitinous epidermis, which is sometimes strongly calcified. Often the surface is sculptured with grooves, ridges, spines, tubercles or teeth, or is beset with setae and has a fine reticulated pitted or scaled appearance.
The antennules are uni- or biramous; the antennae are uniramous, short in female and juvenile, well developed in mature males. There are three pairs of maxillipedes (on the first three thoracic somites). The pereion has five pairs of pereiopods; the first two are directed forwards (the first normally reaching beyond the tip of the pseudorostrum), the last three are directed backwards. Abdominal appendages, the pleopods, are absent in females with the exception of a few species. Males may have one, two, three or five pairs of pleopods, or none at all. The uropods are elongate and styliform, the peduncle is single-segmented; the outer ramus (exopod) has two segments and the inner ramus (endopod) has one, two, or three segments.
Cumaceans display always some amount of sexual dimorphism, although more pronounced in some families than in others. In males the second antenna may be better developed, females have oostegites, i.e. flattened plates that are attached to the hind end of the coxa of the second maxilliped and are provided with long slender setae directed backwards into the brood chamber. Further, with a few exceptions females do not have pleopods; in males, the exopods of the pereiopods are more or better developed.
Larval development is epimorphic. After fertilisation, the female keeps the eggs in a brood chamber; the hatched larvae (manca stage) are retained there until they develop into a postlarva that much resembles the adult in morphology. An attempt could be made to identify juveniles at Page 220: Cumacea.
Ecology
Cumaceans are primarily marine; there are a few brackish and freshwater species. The majority of species occur on soft bottoms, burrowing in the sediment, but they also undertake frequently near-bottom swimming excursions. Adult males of many coastal species may form pelagic swarms, especially at night, then joined by the females, most likely to facilitate reproduction. Therefore, the occurrence of cumaceans in plankton samples is no exception.
[After Jones, 1976]
The key to the North Sea cumaceans starts at Page 220: Cumacea. The following species are included:
Order Cumacea
Family Bodotriidae
Vaunthompsonia cristata
Cumopsis goodsiri
Bodotria arenosa
Bodotria pulchella
Bodotria scorpioides
Iphinoe serrata
Iphinoe trispinosa
Cyclaspis longicaudata
Family Leuconidae
Leucon acutirostris
Leucon nasica
Leucon nasicoides
Leucon pallidus
Leucon fulvus
Eudorella emarginata
Eudorella hirsuta
Eudorella truncatula
Eudorellopsis deformis
Family Nannastacidae
Cumella pygmaea
Campylaspis rubicunda
Campylaspis glabra
Campylaspis costata
Campylaspis sulcata
Campylaspis horrida
Campylaspis verrucosa
Nannastacus unguiculatus
Family Lampropidae
Lamprops fasciata
Hemilamprops rosea
Family Pseudocumidae
Pseudocuma gilsoni
Pseudocuma longicornis
Pseudocuma similis
Petalosarsia declivis
Family Dyastylidae
Diastylis rathkei
Diastylis boecki
Diastylis bradyi
Diastylis cornuta
Diastylis echinata
Diastylis goodsiri
Diastylis laevis
Diastylis lucifera
Diastylis tumida
Diastylis rugosa
Brachydiastylis resima
Diastyloides biplicata
Diastyloides serrata
Leptostylis ampullacea
Leptostylis longimana
Leptostylis villosa