Pennella balaenoptera Koren & Danielssen 1877

Pennella balaenoptera Koren & Danielssen, 1877

(Figs. 4, 5)

Synonyms. P. antarctica (Quidor, 1912), P. anthonyi (Quidor, 1912), P. cetti (Quidor, 1912), P. charchoti (Quidor, 1912), P. crassicornis Steenstrup & Lutken, 1861

Type host and locality. Balaenoptera acutorostrata, North Sea.

Morphology. Size: 175–320 mm. Papillae: full or partial coverage, generally spherical, variable in size and shape, not found in organized groups. Holdfasts: usually three, laterals can be very long; dorsal horn shorter. First antenna with three segments, second with two segments. Plumes: dendritic, complex branching.

Remarks. A valid species. Pennella balaenoptera is the largest of all copepods and is the only Pennella found so far on marine mammals (Hogans 1987) and as such is unique amongst the mesoparasitic Copepoda in parasitizing warm-blooded hosts. Pennella balaenoptera is a pan-global parasite of whales (Balaenoptera acutorostrata, B. physalus and B. borealis; Hogans 1987 and references therein) and dolphins and porpoises (Rissos, Grampus griseus and bottlenose, Turisops truncatus; Vecchione & Aznar 2014; striped dolphin, Stenella coeruleoalba, Aznar et al., 2005; harbor porpoise, Phocaena phocaena, Danyer et al. 2014), but it has also been found on pinnipeds (northern elephant seal, Mirounga angustriostris; Dailey et al. 2002). Both the original description by Koren and Danielssen (1877) and a redescription by Turner (1905) were very well done; more recent reports on the morphology of P. balaenoptera, based on the entire parasite, including some details of the fine structure of the cephalothoracic appendages, have been completed (Hogans 1987; Abaunza et al. 2002; Hrvoje 2004).

In his review of Pennella on cetaceans (Hogans 1987) considered all previously described species from marine mammals to be synonyms of P. balaenoptera. Although another species, P. crassicornis, had been found on whales earlier (Steenstrup & Lutken 1861), and based on taxonomic priority was technically the oldest Pennella from mammals, P. crassicornis had also been reported from fish hosts in the same paper. Based on the host designations, P. balaenoptera was the oldest species to be found only on mammals and had priority over P. crassicornis.

Hogans (1987) reported on the morphological variability of P. balaenoptera reported from marine mammals. Based on examinations of the material reported on herein, the plasticity in P. balaenoptera has been further substantiated and is most evident in holdfast horn and neck structure.

Although P. balaenoptera has been previously reported from harbor porpoises (Aegean Sea; Danyer et al. 2014), it is here reported from this host in the Atlantic Ocean for the first time. To find P. balaenoptera on porpoises in a different locality is not unexpected considering the very wide known distribution of this parasite and the fact that minke whales and harbor porpoises live in close association and are common cetaceans in the lower Bay of Fundy (where the parasites were collected). There were no external morphological differences between the specimens collected from the minke whale and that found on the harbor porpoise reported on in this study. There was only one specimen from the porpoise to examine, however, it was identical in all aspects with the whale parasites except that it was 25mm shorter (178) than the average length (203) of the two specimens from the whale.