Redescription of adults and description of copepodid development of Dermatomyzon nigripes (Brady & Robertson, 1876) and of Asterocheres lilljeborgi Boeck, 1859 (Copepoda: Siphonostomatoida: Asterocheridae)

摘要

Adult and immature copepodids of Dermatomyzon nigripes (Brady & Robertson, 1876) and Asterocheres lilljeborgi Boeck, 1859 were collected by SCUBA from the White Sea. All copepodids of D. nigripes were found on the bryozoan Flustra foliacea (Linnaeus, 1758); adults of D. nigripes also were washed out from the sponge Halichondria panicea (Pallas, 1766), the ophiuroid Ophiopholis aculeata (Linnaeus, 1767), and were collected among hydrozoans and other invertebrates from dead shells swept by tidal currents. Copepodids of A. lilljeborgi were washed from the starfish Henricia sanguinolenta (O. F. Miiller, 1776). Comparative analysis of development of D. nigripes and A. lilljeborgi with the related Scottomyzon gibberum (Scott & Scott, 1894) shows that both genders of A. lilljeborgi and S. gibberum suppress the formation of fourth abdominal somite. Females of A. lilljeborgi and D. nigripes develop a simple segmental complex when the arthrodial membrane separating the genital somite from the second abdominal somite fails to form; this arthrodial membrane develops on females of S. gibberum so that there is no genital complex. The antennule of A. lilljeborgi with a single, proximal complex of three segments appears most similar to the ancestral siphonostomatoid. The antennule of D. nigripes has a proximal complex of two segments and a distal complex of three segments; the antennule of S. gibberum has a proximal complex of three segments and a distal complex of four segments. Setation of the maxil-liped of D. nigripes and A. lilljeborgi are identical and appear similar to the ancestral siphonostomatoid; the maxilliped of S. gibberum differs in that it fails to add a seta to its syncoxa and loses a seta on the penultimate endopodal segment. Asterocheres lilljeborgi and S. gibberum share derived states of se-tation on the exopod of swimming legs 1-4, leg 5 and leg 6; D. nigripes and S. gibberum share derived states of setation on the endopod of swimming legs 3 and 4.