Pennella balaenopterae

P. balaenopterae is found around Antarctica, and in western and northern parts of the Pacific Ocean.^[3] It has also been recorded from the Mediterranean Sea.^[4]

The sei whale (Balaenoptera borealis) and the minke whale (Balaenoptera acutorostrata) are the main hosts of P. balaenopterae. Most species of Pennella have intermediate hosts which are important for the life cycle of the species, but the intermediate host of Pennella balaenopterae is not known. There have been recent records of this species parasitising pinnipeds, namely a northern elephant seal (Mirounga angustirostris) in the north Pacific^[5] and from fin whale, (Balaenoptera physalus)^[4] Cuvier's beaked whale (Ziphius cavirostris), Risso's dolphin (Grampus griseus), the bottlenose dolphin (Tursiops truncatus) in the Adriatic Sea^[6] and harbour porpoise Phocoena phocoena relicta in the Aegean Sea.^[7] The early development of the larvae takes place in the egg sac while it is still attached to the female until it is released into the water column possessing a full set of cephalic appendages and three pairs of thoracic legs. The larval form then finds an intermediate host where it remains and develops into the copepodid stages. After development of the attachment mouthparts, the female copepod finds its definitive host where it then permanently attaches. Females can produce from 300 to 700 eggs in each of her paired egg sacs while engorged and attached to her definitive host. Males remain as free swimming copepodids but the females have a distinctive anchoring processes that extend from its anterior end. After both sexes have reached full sexual maturity copulation occurs, after which the male dies. The female then loses all external segmentation and grows drastically in size. Both temperature and salinity are important factors to ensure successful reproduction.^[3]