HELMINTH PARASITES OF PORPOISES OF THE GENUS 



STENELLA IN THE EASTERN TROPICAL PACIFIC, 



WITH DESCRIPTIONS OF TWO NEW SPECIES: 



MASTIGONEMA STENELLAE GEN. ET SP. N. 



(NEMATODA: SPIRUROIDEA) AND ZALOPHOTREMA 



PACIFICUAl SP. N. (TREMATODA: DIGENEA) 



Murray D. Dailey' and William F. Perrin^ 



ABSTRACT 



Parasite frequencies in 72 spotted porpoise, Sienella graffniani (Lonnberg, 1934), and 

 19 spinner porpoise, S. cf. 5. longirostris (Gray, 1828), are reported and analyzed with 

 respect to age of host. In addition to the new nematode Mustigonema stenellae gen. 

 et sp. n. from the fore stomach of S. graffmani and the new fluke Zcilophotrema pacificum 

 sp. n. from the pancreatic duct of 5. graffniuni and S. cf. 5. longirosiris, parasites reported 

 include Anisukis simplex, Halocercus delphini, Crassicauda sp., Campula rochebruni, 

 Telrabothrium forsteri, Strobilocephalus triungidaris, Phyllobothrium delphini, and Mono- 

 rygiita grinialdii. Irreversible lesions in the ventral region of the skull due to infection 

 of the air sinuses by a Crassicaiida-Uke nematode were more frequent in skulls of 

 calves of S. graffmani than in skulls of subadults and adults (129 specimens total), 

 indicating that the parasite, or a condition correlated with its occurrence, is a significant 

 factor in natural mortality of the spotted porpoise in the eastern tropical Pacific. 



Porpoises of the genus Stenella are of great 

 importance to the U.S. tropical tuna fishery 

 (Perrin. 1969, 1970a). Yellowfin tuna associate 

 with porpoise schools in the eastern Pacific, 

 and the fishermen make use of this association 

 in locating and capturing the tuna. Despite 

 this economic importance, little is known of 

 the ecology of the porpoises. Parasites have 

 been previously reported from Stenella loiigi- 

 rostris, S. roseiventris, S. coeruleoalba, S. at- 

 tenuata, and S. graffmani (Dailey and Brownell, 

 1972). These reports have usually been from 

 a small sample and did not include numbers 

 of parasites per animal or percentage of sample 

 infected. This report deals with two members 

 of the genus in the eastern tropical Pacific: 

 the spotted porpoise and the spinner porpoise. 

 The taxonomy of the genus is currently in a 

 chaotic state. Spinner porpoises from the eastern 

 Pacific have been referred by recent authors 

 to Ste)iella Diicrops (Gray, 1846) and to S. 



' Department of Biology, California State University 

 at Long Beach, Long Beach, CA 90840. 



- Southwest Fisheries Center, National Marine Fisheries 

 Service, NOA A, La Jolla. CA 92037. 



Manuscript accepted September 1972. 

 FISHERY BULLETIN: VOL. 7K NO. 2, 1973. 



longirosiris (Gray, 1828) — Perrin and Hunter 

 (1972). The spotted porpoise S. graffma)ii 

 (Lonnberg, 1934) was described from Acapulco, 

 but Rice and Scheffer (1968) recently referred 

 all spotted porpoises to S. dubia (G. Cuvier, 

 1812), a decision that does not reflect a con- 

 census of current opinion (Perrin, 1970b; 

 Mitchell, 1970; Caldwell et al., 1971). We 

 here refer the spotted porpoise examined to 

 S. graffmani and the spinner porpoise tenta- 

 tively to S. longirosiris. The "eastern" and 

 "whitebelly" spinner porpoises (Perrin, 1972) 

 are considered to be geographical variants within 

 one species and are not treated separately. 

 This usage is provisional pending the results 

 of current taxonomic investigations. 



MATERIALS AND METHODS 



We examined 72 specimens of S. graffmani 

 and 19 of S. cf. S. longirostns (11 eastern 

 and 8 whitebelly). These were collected during 

 the course of investigations of morphology 

 and reproduction. We collected parasites as 

 we prepared skeletons of the animals for use 



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