helminth parasites of the steller sea lion, eumetopias...

Proc. Helminthol. Soc. Wash.53(2), 1986, pp. 194-197

Helminth Parasites of the Steller Sea Lion,Eumetopias jubatus, in Alaska

LARRY M. SHULTSDepartment of Zoology and Physiology, University of Wyoming, Laramie, Wyoming 82071

ABSTRACT: Sixty-seven Steller sea lions from the Gulf of Alaska and 7 from the Bering Sea were examined forhelminth parasites. The Gulf of Alaska sea lions harbored 11 species of helminths in the digestive tract:Diplogonoporus tetrapterus (von Seibold. 1848) Ariola, 1896, Diphyllobothrium pacificum (Nybelin, 1931) Mar-golis, 1956, Anophryocephalus ochotensis Delyamure and Krotov, 1955, Phocanema decipiens (Krabbe, 1878)Myers, 1959, Contracaccum osculatum (Rudolphi, 1802) Baylis, 1920, Anisakis similis (Baird, 1853) Baylis,1920, Pricetrema zalophi (Price, 1932)Ciurea, 1933, Phocitrema fusiforme Goto and Ozaki, 1930, Corynosomastrumosum (Rudolphi, 1802) Luhe, 1904, C. villosum Van Cleave, 1953, and Bolbosoma bobrovoi Krotov andDelyamure, 1952. The sea lions collected in the Bering Sea contained all of the above species except P. zalophi,P. fusiforme, C. strumosum, and B. bobrovoi. In addition, they harbored Corynosoma semerme (Forssell, 1904)Luhe, 1911, and C. validum Van Cleave, 1953. Phocitrema fusiforme, C. semerme, and C. validum are newhost records for the Steller sea lion.

In the course of lif e history investigations ofmarine mammals from areas of potential petro-leum development in the state of Alaska, per-sonnel of the Alaska Department of Fish andGame made available Steller sea lions collectedfrom hauling grounds throughout the Gulf ofAlaska (location 1) and from the southern edgeof the seasonal pack ice in the Bering Sea (lo-cation 2) (Fig. 1). Because reports of helminthsfrom Alaskan Steller sea lions are rare (Neiland,1962; Rausch, 1964) and because of the consid-erable sample size of these collections, the resultsof this study are reported here.

Materials and Methods

A total of 67 Steller sea lions from the Gulf of Alaskaand 7 from the Bering Sea were necropsied to deter-mine the kinds and incidence of helminths present.

The lungs, liver, heart, stomach, and intestine wereexamined for helminths. In order to determine strat-ification of helminth species within the intestine, 3.3-msections of the anterior, middle, and posterior parts ofthe small intestine, as well as the entire large intestinewere examined. Each section was split open and al-lowed to stand in a container of fresh water for severalhours before the helminths, freed from the mucosa,were decanted and relaxed in tap water containing sev-eral drops of pentabarbitol sodium (Nembutal). Afterrelaxation, the helminths were fixed in hot 10% for-malin. Cestodes, trematodes, and acanthocephalanswere stained in Semichon's acetocarmine, dehydratedin ethanol, cleared in terpineol, and mounted in per-mount. Nematodes were stained as above, destainedin 70% acetic ethanol, and mounted directly into Hoy-er's modified Berlese solution (Goldstein, 1955). Tis-sues were not checked for the presence of Trichinellaspiralis.

Results and Discussion

Helminths were found only in the stomach andthe small and large intestine. Gross visual ex-amination indicated that most of these appearedto have caused littl e or no pathological changesin those organs. The prevalence of each helminthspecies is summarized in Table 1. Representativespecimens of each have been deposited in theNational Parasite Collection, Agricultural Re-search Service, Beltsville, Maryland (USNMHelm. Coll. Nos. 74448, 76200-76211). The hel-minths recovered are summarized below.

Cestoda

1. Anophryocephalus ochotensis Delyamureand Krotov, 1955. This was the most frequentlyfound cestode in Steller sea lions and was themost abundant cestode in the individuals wherefound. It generally was represented only by scoli-ces with a short germinal portion and was locatedin the duodenal portion of the small intestine.Only a few individuals with gravid proglottidswere found. This cestode has been reported fromSteller sea lions in the Okhotsk Sea (Delyamure,1955) but had not been found previously in thishost in the eastern Pacific.

2. Diphyllobothrium pacificum (Nybelin, 1931)Margolis, 1956. Diphyllobothrium pacificum waspresent together with Diplogonoporus tetrapterusin sea lions from both areas of collection. It wasfound in the ilial portion of the small intestine.It has been reported from Steller sea lions inBritish Columbia, Canada (Margolis, 1956).

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Copyright © 2011, The Helminthological Society of Washington

195

0 100 200 300kmI 1 1 —I

Figure 1. Geographical locations of Steller sea lion collections. Circled numbers indicate sample size at eachcollecting locality.

3. Diplogonoporus tetrapterus (von Siebold,1848) Ariola, 1896. This cestode was found inthe ilial portion of the small intestine and largeintestine in sea lions from both locations. It hasbeen reported previously from this host byRausch (1964) and it exhibited morphologicvariations similar to those described by him inhaving from 1 to 4 sets of reproductive organsper proglottid.

Digenea4. Phocitrema fusiforme Goto and Ozaki,

1930. This trematode, found in the jejunal por-tion of the small intestine, occurred only in sealions from the Gulf of Alaska. It has been re-corded from Phoca vitulina collected at St. Law-rence Island in the Bering Sea (Rausch and Lock-er, 1951), and from Steller sea lions in northernJapan (Machida et al., 1981).

5. Pricetrema zalophi (Price, 1932) Ciurea,1933. Pricetrema zalophi was the most common

trematode encountered in this study. It was foundin hosts only from the Gulf of Alaska and oc-curred in the jejunal portion of the small intes-tine. This species has been reported from E. ju-batus in California (Dailey and Hill , 1970) andnorthern Japan (Machida et al., 1981).

Nematoda

6. Anisakis similis (Baird, 1853)Baylis, 1920.Nematodes of this species occurred in the stom-ach but were not associated with any pathologicallesions in the animals examined from either lo-cality. They have been reported previously fromthis host in California by Schroeder and Wege-forth (1935).

7. Contracaecum osculatum (Rudolphi, 1802)Baylis, 1920. Contracaecum osculatum was pres-ent in the stomach and pylorus of sea lions fromthe Gulf of Alaska. This species has been re-ported from E. jubatus in Canada (Margolis,1956).


196 PROCEEDINGS OF THE HELMINTHOLOGICAL SOCIETY

Table 1. Helminth parasites of Steller sea lions fromthe Gulf of Alaska and the Bering Sea.

Gulf ofAlaska

Species

Diplogonoporus tetrapterusDiphyllobothrium pacificumAnophryocephalus ochotensisPricetrema zalophiPhocitrema fusiformePhocanema decipiensAnisakis similisContracaecum osculatumCorynosoma semermeC. strumosumC. validumC. villosumBolbosoma bobrovoi

N =

No.inf

632164397

395150

—39—653

67

%inf

9431965810587675—58

—974

Bering SeaN =

No.inf

215

——5411

—17-

7

%inf

281471——71571414

—14

100-

8. Phocanema decipiens (Krabbe, 1878)Myers, 1959. In a few cases, clumps of thesenematodes caused ulcerations of the gastric mu-cosa in sea lions from both the Gulf of Alaskaand Bering Sea. It has been reported from Stellersea lions in British Columbia (Margolis, 1956)as well as the Commander Islands in the westernBering Sea by Delyamure (1955). Dailey and Hill(1970) did not find it in 9 E. jubatus examinedin California.

Acanthocephala

9. Bolbosoma bobrovoi Krotov and Delya-mure, 1952. This helminth was found in the ilialsegment of the small intestine of a small portionof Steller sea lions from the Gulf of Alaska. Ithas been previously reported from this host inthe Okhotsk Sea (Delyamure, 1955).

10. Corynosoma semerme (Forssell, 1904)Luhe, 1911. Corynosoma semerme occurred inthe ilial portion of the small intestine of Stellersea lions from the Bering Sea. This is the firstreport of this species from the Steller sea lionalthough it has been reported from spotted sealsPhoca largha Pallas, 1811 from the Bering Sea(Shults, 1982) and other phocid seals by Delya-mure (1955).

11. Corynosoma strumosum (Rudolphi, 1802)Luhe, 1904. This acanthocephalan was found inthe ilial portion of the small intestine of Stellersea lions from the Bering Sea. It has been re-ported in this host from California (Dailey and

Hill , 1970). Margolis and Dailey (1972) reportedit from Alaska, British Columbia, and Washing-ton in other pinnipeds as well as sea lions.

12. Corynosoma validum Van Cleave, 1953.This helminth was found only in hosts from theBering Sea where it also occurred in the ilial por-tion of the small intestine. It has been reportedfrom bearded seals Erignathus barbatus Erxle-ben, 1777 and walruses Odobenus rosmarus(Linnaeus, 1758) by Margolis and Dailey (1972)but is a new host record for the Steller sea lion.

13. Corynosoma villosum Van Cleave, 1953.This species also occurred in the ilial portion ofthe small intestine of Steller sea lions from boththe Gulf of Alaska and the Bering Sea. It was themost common helminth encountered from bothareas and has been reported previously in thishost from Canada by Margolis (1956).

Examination of the jejunal, duodenal, and ilialportions of the small intestine of Steller sea lionsfrom the Gulf of Alaska and Bering Sea showedmarked stratification of helminths. Anophryo-cephalus ochotensis was found mainly in the an-terior (duodenal) part, and the jejunal portionwas the principal site for the trematodes Phoci-trema fusiforme and Pricetrema zalophi. Theacanthocephalans Corynosoma strumosum, C.villosum, C. semerme, C. validum, and Bolbo-soma bobrovoi were found primarily in the ilialportion of the small intestine. The ilial portionof the small intestine was also the usual site oc-cupied by Diphyllobothrium pacificum. Diplo-gonoporus tetrapterus was found with about equalfrequency in both the ilium and the large intes-tine.

The helminth fauna of Steller sea lions fromthe Gulf of Alaska was very similar to that re-ported from this host in the southwestern andnorthwestern parts of the Pacific (Delyamure,1955; Margolis and Dailey, 1972). Exceptionalwas the absence of nematodes of the genus Par-afilaroides in the Alaskan hosts and the presenceof Phocitrema fusiforme, Corynosoma semerme,and C. validum not previously reported from thishost. Steller sea lions collected in the Gulf ofAlaska harbored 4 species of helminths not foundin those from the Bering Sea and the Bering Seahosts had 2 species not found in the Gulf ofAlaska. Although the lif e histories of these hel-minths are generally not completely known, itwould seem that the different species composi-tion between the 2 localities is probably due tosea lions utilizing different intermediate hosts asfood items in each locality.


OF WASHINGTON, VOLUME 53, NUMBER 2, JULY 1986 197

Acknowledgments

I wish to thank members of the Alaska De-partment of Fish and Game, Anchorage andFairbanks for supplying the sea lion material.Special thanks is due to Dr. Francis H. Fay, In-stitute of Marine Science, University of Alaskawho directed the study. This study was supportedby the Bureau of Land Management throughinteragency agreement with the National Ocean-ic and Atmospheric Administration, under whicha multiyear program responding to needs of pe-troleum development of Alaskan continental shelfis managed by the Outer Continental Shelf En-vironmental Assessment Program (OCSEAP) Of-fice.

Literature Cited

Dailey, M. D, and B. L. Hill. 1970. A survey ofmetazoan parasites infecting the California (Zal-ophus californianus) and Steller (Eumetopias ju-batus) sea lion. Bulletin of the Southern CaliforniaAcademy of Sciences 69:126-132.

Delyamure, S. L. 1955. Helminthofauna of marinemammals (ecology and phylogeny). Izdatel'stvoAkademii Nauk SSSR, Moscow. 517 pp. IsraelProgram for Scientific Translations, Jerusalem. 552pp.

Goldstein, H. L. 1955. A novel medium for mountingnematodes. Journal of Agriculture of the Univer-sity of Puerto Rico 1:46-47.

Machida, M., N. Seki, and K. Yamaguchi. 1981.

Trematodes of Steller sea lions caught off Hok-kaido, northern Japan. Bulletin of the NationalScience Museum, Tokyo, Series A (Zoology) 7:147-154.

Margolis, L. 1956. Parasitic helminths and arthro-pods from pinnipeds of the Canadian Pacific Coast.Journal of the Fisheries Research Board of Canada13:489-505.

, and M. D. Dailey. 1972. Revised annotatedlist of parasites from sea mammals caught off thewest coast of North America. United States De-partment of Commerce Technical Report NMFSSSRF-647. 23 pp.

Neiland, K. A. 1962. Alaskan species of acantho-cephalan genus Corynosoma Luehe, 1904. Journalof Parasitology 48:69-75.

Rausch, R. L. 1964. Studies on the helminth faunaof Alaska. XLI . Observations on cestodes of thegenus Diplogonoporus Lonnberg, 1892 (Diphyl-lobothriidae). Canadian Journal of Zoology 42:1049-1069.

, and B. Locker. 1951. Studies on the helminthfauna of Alaska. II. On some helminths parasiticin the sea otter, Enhydra lutris (L.). Proceedingsof the Helminthological Society of Washington18:77-81.

Schroeder, C. R., and H. M. Wegeforth. 1935. Theoccurrence of gastric ulcers in sea mammals of theCalifornia coast, their etiology and pathology.Journal of the American Veterinary Medical As-sociation 87, N.S. 40:333-342.

Shults, L. M. 1982. Helminths of the spotted sealPhoca largha from the Bering Sea. Journal ofWildlif e Diseases 18:59-62.


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