VARIATIONS IN THE MORPHOLOGY OF 



FISTULICOLA PLICATUS RUDOLPHI (1802) 



(CESTODA:PSEUDOPHYLLIDEA) FROM 



THE SWORDFISH, XIPHIAS GLADIUS L., 



IN THE NORTHWEST ATLANTIC OCEAN 



During the course of a survey of the helminth 

 parasites of the swordfish, Xiphias glasius L., from 

 the Northwest Atlantic Ocean, several morpholo- 

 gical variations were observed in specimens of the 

 pseudophyllidean tapeworm, Fistulicola plicatus. 

 The most notable of these variations were pseudo- 

 scolex form and proglottid shape and size. Methods 

 of scolex attachment to the organ wall, descriptions 

 of pseudoscolex structures, and organ specific varia- 

 tions in the morphology of F. plicatus are given. 



Materials and Methods 



A sample of 303 gills and gastrointestinal tracts 

 of swordfish was collected from four geographical 

 areas in the Northwest Atlantic Ocean in the late 

 summer and early fall of 1980. The areas sampled 

 and the number of swordfish collected from each 

 geographical area are as follows: Cape Hatteras (74), 

 Georges Bank (90), Scotian Shelf (69), and Grand 

 Bank (70); all collected by longline gear and frozen 

 at sea. The swordfish were later dissected and ex- 

 amined for helminth parasites in the laboratory. 



Pseudophyllidean cestodes were removed from 

 the infected organ and fixed whole in 70% alcohol 

 or 10% Formalin 1 . Several infected organs were 

 fixed whole in Bouin's fluid or 10% Formalin. Speci- 

 mens used for taxonomic examinations were stained 

 in Erlich's hematoxylin, Blachin's lactic acid car- 

 mine, or Semichon's aceto-carmine. Camera lucida 

 drawings were made from fixed, unstained speci- 

 mens. 



Results 



Fistulicola plicatus has been reported from the 

 swordfish by Linton (1901), Cooper (1918), Nigrelli 

 (1938), and lies (1970). In this study F. plicatus was 

 found in the intestines and recturns of swordfish 

 from all four sampling areas. Considerable morpho- 

 logical variation was found between individuals of 

 this species. Variations were in scolex form, overall 

 parasite length, and proglottid shape and size. About 

 50% of specimens recovered exhibited a scolex and 

 proglottid structure characteristic of specimens 



'Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



described by Yamaguti (1959). Scolices from these 

 were arrow-shaped and possessed two simple, leaf- 

 shaped bothridia (Fig. 1). Any variation from this 

 scolex form were considered to be pseudoscolices. 

 Proglottids from specimens described by Yamaguti 

 (1959) were short and broad with foliate lateral 

 edges. Internal proglottid morphology was not easily 

 seen in any of the specimens examined during the 

 present study, although nerve trunk location (near 

 lateral margins), cirrus-sac and vagina location (on 

 opposite lateral margins), and egg shell structure 

 (thick-shelled and operculate) were occasionally 

 observable. 



A total of 29 specimens recovered had penetrated 

 the wall of the infected organ. Occasionally the 

 tapeworms penetrated the organ wall and retained 

 typical scolex form, i.e., arrow-shaped with simple, 

 well-developed bothridia but, in the majority of 

 cases, complete perforation of the organ wall re- 

 sulted in the formation of a pseudoscolex. Attach- 

 ment to the organ wall (rectum and intestine) was 

 achieved in the following four ways: 



1) By complete perforation of the organ wall, the 

 scolex and a portion of the neck encapsulated 

 in a rounded, host-produced cyst attached to 

 the organ serosa. Scolices recovered from 

 these cysts were usually arrow-shaped with 

 typical bothridia, or occasionally found as a 

 round, transparent, fluid-filled bag, which pos- 

 sessed rudimentary or no apparent bothridia 

 (Fig. 2). 



2) By complete perforation of the organ wall, the 

 scolex and a portion of the neck encased in a 

 tubular, host-produced sheath, attached along 

 its entire length to the organ serosa. Occa- 

 sionally this sheath was entwined with the 

 mesenteries associated with the infected organ. 

 Pseudoscolices found within these sheaths 

 were long, rounded, and slender, and exhibited 

 no bothridia (Fig. 3). 



3) By complete penetration of the organ wall, the 

 scolex markedly enlarged (up to 6 cm in 

 length), lying free, and unencapsulated in the 

 peritoneal cavity. Pseudoscolices of this type 

 were long, broad, pseudosegmented, and pos- 

 sessed well-developed bothridia (Fig. 4). 



4) In this case the scolex did not fully penetrate 

 the organ wall, but perforated the wall to a 

 slight depth, and remained in that position. 

 Often specimens were found to exhibit this 

 slight organ wall penetration and re-emerge in- 

 to the lumen of the organ. In these cases the 



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FISHERY BULLETIN: VOL. 84, NO. 3, 1986. 



