General Structure
In the sub-class copepoda, there are two basic plans of body organization or tagmosis, gymnoplean and podoplean, differentiated by the position of the major body articulation. In the gymnoplean plan, this is behind the fifth pedigerous somite whereas in the podoplean plan (Harpacticoida) it is between the fourth and fifth pedigerous somites. The major articulation divides the body into an anterior prosome and a posterior urosome. The prosome is further into two sub-regions. Anteriorly is the cephalosome bearing the five head appendages and the maxillipeds and posterior to this are three free prosomites bearing the second to fourth swimming legs. The urosome comprises an anterior somite bearing the fifth pair of legs and five other somites (referred to as abdomen). In the males, all the usoromites are separated but, in the females, the second and third urosomites are usually fused to form the genital double-somite. The last urosomite or anal somite, in which the median anus opens either terminally or dorsally, bears two posterior caudal rami or furcal rami.
In the sub-class copepoda, there are two basic plans of body organization or tagmosis, gymnoplean and podoplean, differentiated by the position of the major body articulation. In the gymnoplean plan, this is behind the fifth pedigerous somite whereas in the podoplean plan (Harpacticoida) it is between the fourth and fifth pedigerous somites. The major articulation divides the body into an anterior prosome and a posterior urosome. The prosome is further into two sub-regions. Anteriorly is the cephalosome bearing the five head appendages and the maxillipeds and posterior to this are three free prosomites bearing the second to fourth swimming legs. The urosome comprises an anterior somite bearing the fifth pair of legs and five other somites (referred to as abdomen). In the males, all the usoromites are separated but, in the females, the second and third urosomites are usually fused to form the genital double-somite. The last urosomite or anal somite, in which the median anus opens either terminally or dorsally, bears two posterior caudal rami or furcal rami.
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