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Abstract
A redescription of the caligid copepod Lepeophtheirus acutus Heegaard, Citation1943 is provided based on mature adults of both sexes collected from two new elasmobranch hosts, the Alfred manta Manta alfredi (Krefft, 1868) and the whale shark Rhincodon typus Smith, 1828, held in sea pens off Okinawa-jima Island, Japan. Lepeophtheirus acutus can be distinguished from other congeners by a combination of adult female characters that includes: (1) abdomen about one-third length of cephalothorax; (2) sternal furca with long, apically pointed tines; (3) leg 2 endopod with a row of large denticles and a spiniform projection on the distolateral corner of the first and second segments, respectively; (4) leg 3 endopod with six setae on the distal segment; and (5) leg 4 exopod with an armature of I-0; III. This report also confirms the observation of previous workers that L. acutus is a pathogen of elasmobranchs held in captivity.
Acknowledgements
We thank Karin S. Kronestedt (Swedish Museum of Natural History, Stockholm) for arranging the loan of type material, George Benz (Middle Tennessee State University) for sending us his unpublished illustrations of L. acutus, the staff of the Okinawa Churaumi Aquarium for assistance during sampling and two anonymous reviewers for their constructive comments. This research was made possible through financial support from the Japan Society for Promotion of Science Postdoctoral Fellowship (Grant No. 21-09117) to D.T., Korea Institute of Ocean Science and Technology Projects (PK08080, PE98747, PE98811) to B.A.V.M. and the Ocean Exposition Commemorative Park Management Foundation, Okinawa, to K.N.