Egg development, hatching and early life-history of Dissonus manteri (Copepoda), parasitic on the gills of coral trout, Plectropomus leopardus

The early life-history of Dissonus manteri differs markedly from that of Ca ligidae and from that of its congener Dissonus nudiventris. The uniseriate egg strings are of typical caligid form, but the stage hatching from the eg g is a pre-ecdysis nauplius which moults immediately to the copepodid. The empty naupliar cuticle remains tethered to the egg string by a pair of post erior threads which attach to the internal surface of the egg membrane. The duration of egg development is 112 h and the mean duration of hatching is 5.2 h at 25 degrees C. Aeration and water movement are important for succes sful hatching. Under these conditions, hatching success is 94.8%, but decre ases to 48.4% in static water with no aeration. Mean survival time of the c opepodid in the absence of a host is 41.4 h at 25 degrees C. The reduction of early free-living stages in the life-cycle and the high survival rate fr om egg to copepodid could be important in future coral trout aquaculture, s ince the potential for re-infection by this parasite is very high. (C) 1999 Australian Society for Parasitology. Published by Elsevier Science Ltd. Al l rights reserved.