Nauplii and copepodids of Scottomyzon gibberum (Copepoda: Siphonostomatoida: Scottomyzontidae, a new family), a symbiont of Asterias rubens (Asteroidea)

Naupliar and copepodid stages of Scottomyzon gibberum associated with the starfish Asterias rubens Linnaeus, 1767 in the North and White Seas were collected from the host or reared in the laboratory. There are six copepodid stages and four naupliar stages. Changes in size and proportions of the prosome of adult females result from an expansion of unsclerotized integument along the margins of the shield of the cephalothorax and tergites of the second and third thoracic somites. The monotypic genus Scottomyzon Giesbrecht, 1897 is transferred to a new family Scottomyzontidae on the basis of a 3-segmented abdomen for adults of both sexes, paired dorsolateral gonopores near the posterior margin of somite, paired ventral copulatory pores near the middle of somite, and sexual dimorphism in oral siphon.